Dopamine D3 receptor ligands for drug addiction treatment: update on recent findings.

Science.gov (United States)

Le Foll, Bernard; Collo, Ginetta; Rabiner, Eugenii A; Boileau, Isabelle; Merlo Pich, Emilio; Sokoloff, Pierre

2014-01-01

The dopamine D3 receptor is located in the limbic area and apparently mediates selective effects on motivation to take drugs and drug-seeking behaviors, so that there has been considerable interest on the possible use of D3 receptor ligands to treat drug addiction. However, only recently selective tools allowing studying this receptor have been developed. This chapter presents an overview of findings that were presented at a symposium on the conference Dopamine 2013 in Sardinia in May 2013. Novel neurobiological findings indicate that drugs of abuse can lead to significant structural plasticity in rodent brain and that this is dependent on the availability of functional dopamine D3 autoreceptor, whose activation increased phosphorylation in the ERK pathway and in the Akt/mTORC1 pathway indicating the parallel engagement of a series of intracellular signaling pathways all involved in cell growth and survival. Preclinical findings using animal models of drug-seeking behaviors confirm that D3 antagonists have a promising profile to treat drug addiction across drugs of abuse type. Imaging the D3 is now feasible in human subjects. Notably, the development of (+)-4-propyl-9-hydroxynaphthoxazine ligand used in positron emission tomography (PET) studies in humans allows to measure D3 and D2 receptors based on the area of the brain under study. This PET ligand has been used to confirm up-regulation of D3 sites in psychostimulant users and to reveal that tobacco smoking produces elevation of dopamine at the level of D3 sites. There are now novel antagonists being developed, but also old drugs such as buspirone, that are available to test the D3 hypothesis in humans. The first results of clinical investigations are now being provided. Overall, those recent findings support further exploration of D3 ligands to treat drug addiction. © 2014 Elsevier B.V. All rights reserved.

The dopamine transporter: role in neurotoxicity and human disease

International Nuclear Information System (INIS)

Bannon, Michael J.

2005-01-01

The dopamine transporter (DAT) is a plasma membrane transport protein expressed exclusively within a small subset of CNS neurons. It plays a crucial role in controlling dopamine-mediated neurotransmission and a number of associated behaviors. This review focuses on recent data elucidating the role of the dopamine transporter in neurotoxicity and a number of CNS disorders, including Parkinson disease, drug abuse, and attention deficit hyperactivity disorder (ADHD)

The dopamine transporter: role in neurotoxicity and human disease

Energy Technology Data Exchange (ETDEWEB)

Bannon, Michael J [Department of Psychiatry and Behavioral Neuroscience, Pharmacology, and Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201 (United States)

2005-05-01

The dopamine transporter (DAT) is a plasma membrane transport protein expressed exclusively within a small subset of CNS neurons. It plays a crucial role in controlling dopamine-mediated neurotransmission and a number of associated behaviors. This review focuses on recent data elucidating the role of the dopamine transporter in neurotoxicity and a number of CNS disorders, including Parkinson disease, drug abuse, and attention deficit hyperactivity disorder (ADHD)

Presence and function of dopamine transporter (DAT in stallion sperm: dopamine modulates sperm motility and acrosomal integrity.

Directory of Open Access Journals (Sweden)

Javier A Urra

Full Text Available Dopamine is a catecholamine with multiple physiological functions, playing a key role in nervous system; however its participation in reproductive processes and sperm physiology is controversial. High dopamine concentrations have been reported in different portions of the feminine and masculine reproductive tract, although the role fulfilled by this catecholamine in reproductive physiology is as yet unknown. We have previously shown that dopamine type 2 receptor is functional in boar sperm, suggesting that dopamine acts as a physiological modulator of sperm viability, capacitation and motility. In the present study, using immunodetection methods, we revealed the presence of several proteins important for the dopamine uptake and signalling in mammalian sperm, specifically monoamine transporters as dopamine (DAT, serotonin (SERT and norepinephrine (NET transporters in equine sperm. We also demonstrated for the first time in equine sperm a functional dopamine transporter using 4-[4-(Dimethylaminostyryl]-N-methylpyridinium iodide (ASP(+, as substrate. In addition, we also showed that dopamine (1 mM treatment in vitro, does not affect sperm viability but decreases total and progressive sperm motility. This effect is reversed by blocking the dopamine transporter with the selective inhibitor vanoxerine (GBR12909 and non-selective inhibitors of dopamine reuptake such as nomifensine and bupropion. The effect of dopamine in sperm physiology was evaluated and we demonstrated that acrosome integrity and thyrosine phosphorylation in equine sperm is significantly reduced at high concentrations of this catecholamine. In summary, our results revealed the presence of monoamine transporter DAT, NET and SERT in equine sperm, and that the dopamine uptake by DAT can regulate sperm function, specifically acrosomal integrity and sperm motility.

Dopamine transporter-dependent and -independent striatal binding of the benztropine analog JHW 007, a cocaine antagonist with low abuse liability

Science.gov (United States)

The benztropine analog JHW 007 displays high affinity for the dopamine transporter (DAT), but unlike typical DAT ligands, has relatively low abuse liability and blocks effects of cocaine,including its self-administration. To determine sites responsible for the cocaine-antagonist effects of JHW 007, ...

Interactions of ligands with active and inactive conformations of the dopamine D2 receptor.

Science.gov (United States)

Malmberg, A; Mohell, N; Backlund Höök, B; Johansson, A M; Hacksell, U; Nordvall, G

1998-04-10

The affinities of 19 pharmacologically diverse dopamine D2 receptor ligands were determined for the active and inactive conformations of cloned human dopamine D2 receptors expressed in Ltk cells. The agonist [3H]quinpirole was used to selectively label the guanine nucleotide-binding protein-coupled, active receptor conformation. The antagonist [3H]raclopride, in the presence of the non-hydrolysable GTP-analogue Gpp(NH)p and sodium ions and in the absence of magnesium ions, was used to label the free inactive receptor conformation. The intrinsic activities of the ligands were determined in a forskolin-stimulated cyclic AMP assay using the same cells. An excellent correlation was shown between the affinity ratios (KR/KRG) of the ligands for the two receptor conformations and their intrinsic activity (r=0.96). The ligands included eight structurally related and enantiopure 2-aminotetralin derivatives; the enantiomers of 5-hydroxy-2-(dipropylamino)tetralin, 5-methoxy-2-(dipropylamino)tetralin, 5-fluoro-2-(dipropylamino)tetralin and 2-(dipropylamino)tetralin. The (S)-enantiomers behaved as full agonists in the cyclic AMP assay and displayed a large KR/KRG ratio. The (R)-enantiomers were classified as partial agonists and had lower ratios. The structure-affinity relationships of these compounds at the active and the inactive receptor conformations were analysed separately, and used in conjunction with a homology based receptor model of the dopamine D2 receptor. This led to proposed binding modes for agonists, antagonists and partial agonists in the 2-aminotetralin series. The concepts used in this study should be of value in the design of ligands with predetermined affinity and intrinsic activity.

Practical Approach for the Clinical Use of Dopamine Transporter Imaging

International Nuclear Information System (INIS)

Kim, Jae Seung

2008-01-01

Dopamine transporter imaging is useful in the diagnosis of Parkinson's disease and the most successful technique in the clinical use of neuroreceptor imaging. Recently, several radiopharmaceuticals including I-123 FP-CIT, Tc-99m TRODAT, and F-18 FP-CIT for dopamine transporter imaging have been approved for the routine clinical use in several European countries, Taiwan and Korea, respectively. This review summarized the practical issue for the routine clinical examination of dopamine transporter imaging

Reduced dopamine transporter binding predates impulse control disorders in Parkinson's disease.

Science.gov (United States)

Vriend, Chris; Nordbeck, Anna H; Booij, Jan; van der Werf, Ysbrand D; Pattij, Tommy; Voorn, Pieter; Raijmakers, Pieter; Foncke, Elisabeth M J; van de Giessen, Elsmarieke; Berendse, Henk W; van den Heuvel, Odile A

2014-06-01

Impulse control disorders (ICD) are relatively common in Parkinson's disease (PD) and generally are regarded as adverse effects of dopamine replacement therapy, although certain demographic and clinical risk factors are also involved. Previous single-photon emission computed tomography (SPECT) studies showed reduced ventral striatal dopamine transporter binding in Parkinson patients with ICD compared with patients without. Nevertheless, these studies were performed in patients with preexisting impulse control impairments, which impedes clear-cut interpretation of these findings. We retrospectively procured follow-up data from 31 medication-naïve PD patients who underwent dopamine transporter SPECT imaging at baseline and were subsequently treated with dopamine replacement therapy. We used questionnaires and a telephone interview to assess medication status and ICD symptom development during the follow-up period (31.5 ± 12.0 months). Eleven patients developed ICD symptoms during the follow-up period, eight of which were taking dopamine agonists. The PD patients with ICD symptoms at follow-up had higher baseline depressive scores and lower baseline dopamine transporter availability in the right ventral striatum, anterior-dorsal striatum, and posterior putamen compared with PD patients without ICD symptoms. No baseline between-group differences in age and disease stage or duration were found. The ICD symptom severity correlated negatively with baseline dopamine transporter availability in the right ventral and anterior-dorsal striatum. The results of this preliminary study show that reduced striatal dopamine transporter availability predates the development of ICD symptoms after dopamine replacement therapy and may constitute a neurobiological risk factor related to a lower premorbid dopamine transporter availability or a more pronounced dopamine denervation in PD patients susceptible to ICD. © 2014 International Parkinson and Movement Disorder Society.

Akinetic Crisis in Parkinson's Disease Is Associated with a Severe Loss of Striatal Dopamine Transporter Function: A Report of Two Cases

Directory of Open Access Journals (Sweden)

Valtteri Kaasinen

2014-11-01

Full Text Available Akinetic crisis or acute akinesia is a life-threatening complication of Parkinson's disease (PD with unknown pathophysiological mechanisms. Clinically, it resembles the neuroleptic malignant syndrome, and dopaminergic drugs are transiently ineffective in the acute phase of the condition. There are no published dopaminergic functional imaging studies on PD patients with akinetic crisis. Here we report 2 advanced PD patients with akinetic crisis who were scanned with SPECT using brain dopamine transporter ligand [123I]FP-CIT. The first patient was additionally scanned before the condition developed, and the second patient was scanned after recovery. Striatal dopamine transporter binding was lower during than before the crisis, and both patients showed a nearly complete loss of dopamine transporter binding during the crisis. Serial imaging showed that the uptake remained negligible despite an improvement in motor function after recovery. Akinetic crisis in PD appears to be associated with a particularly severe loss of presynaptic striatal dopamine function that does not improve after recovery. Apart from presynaptic dopaminergic function, other dopaminergic or nondopaminergic mechanisms are involved in the clinical improvement of motor functions after akinetic crisis in PD.

A C-terminal PDZ domain-binding sequence is required for striatal distribution of the dopamine transporter

DEFF Research Database (Denmark)

Rickhag, Karl Mattias; Hansen, Freja Herborg; Sørensen, Gunnar

2013-01-01

believed to bind synaptic scaffolding proteins, but its functional significance is uncertain. Here we demonstrate that two different dopamine transporter knock-in mice with disrupted PDZ-binding motifs (dopamine transporter-AAA and dopamine transporter+Ala) are characterized by dramatic loss of dopamine......The dopamine transporter mediates reuptake of dopamine from the synaptic cleft. The cellular mechanisms controlling dopamine transporter levels in striatal nerve terminals remain poorly understood. The dopamine transporters contain a C-terminal PDZ (PSD-95/Discs-large/ZO-1) domain-binding sequence...... transporter expression in the striatum, causing hyperlocomotion and attenuated response to amphetamine. In cultured dopaminergic neurons and striatal slices from dopamine transporter-AAA mice, we find markedly reduced dopamine transporter surface levels and evidence for enhanced constitutive internalization...

Toxicity, mutagenicity, and behavioral effects of β-CIT, a ligand for dopamine transporter exploration by SPECT

International Nuclear Information System (INIS)

Emond, P.; Farde, L.; Chalon, S.; Belzung, C.; Mauclaire, V.; Chiron, J. P.; Halldin, C.; Besnard, J.C.; Guilloteau, D.

1998-01-01

The cocaine analog β-CIT is one of the most used compounds for SPET examination of the dopamine transporter in drug abuse and Parkinson's disease. However, the toxicity of this agent has not yet been studied. We report here acute toxicity, mutagenicity, and effect on locomotor activity of β-CIT. Acute toxicity experiments were performed in mice and rats. The LD50 values were about 20 mg and 5 mg for mice and rats, respectively. There was no sex difference. The mutagenicity was evaluated using the Ames' test. No mutagenic effect was observed for β-CIT. Effects on locomotor activity were measured in mice using the open-field test. β-CIT increased locomotion (+65%) when injected at a dose of 0.312 mg/kg; the maximal increase (+205%) was observed at a dose of 1.25 mg/kg; at higher doses, the effect was decreased slightly. These pharmacological findings are in agreement with an inhibitory effect of β-CIT at the dopamine transporter. We conclude that with no mutagenic effects and LD50 more than 6 orders of magnitude higher than the routinely used doses in PET or SPET, it can be assumed that β-CIT can be safely used as a radioligand in humans

Toxicity, mutagenicity, and behavioral effects of {beta}-CIT, a ligand for dopamine transporter exploration by SPECT

Energy Technology Data Exchange (ETDEWEB)

Emond, P.; Farde, L.; Chalon, S.; Belzung, C.; Mauclaire, V.; Chiron, J. P.; Halldin, C.; Besnard, J.C.; Guilloteau, D

1998-05-01

The cocaine analog {beta}-CIT is one of the most used compounds for SPET examination of the dopamine transporter in drug abuse and Parkinson's disease. However, the toxicity of this agent has not yet been studied. We report here acute toxicity, mutagenicity, and effect on locomotor activity of {beta}-CIT. Acute toxicity experiments were performed in mice and rats. The LD50 values were about 20 mg and 5 mg for mice and rats, respectively. There was no sex difference. The mutagenicity was evaluated using the Ames' test. No mutagenic effect was observed for {beta}-CIT. Effects on locomotor activity were measured in mice using the open-field test. {beta}-CIT increased locomotion (+65%) when injected at a dose of 0.312 mg/kg; the maximal increase (+205%) was observed at a dose of 1.25 mg/kg; at higher doses, the effect was decreased slightly. These pharmacological findings are in agreement with an inhibitory effect of {beta}-CIT at the dopamine transporter. We conclude that with no mutagenic effects and LD50 more than 6 orders of magnitude higher than the routinely used doses in PET or SPET, it can be assumed that {beta}-CIT can be safely used as a radioligand in humans.

Novel and high affinity fluorescent ligands for the serotonin transporter based on (s)-citalopram

DEFF Research Database (Denmark)

Kumar, Vivek; Rahbek-Clemmensen, Troels; Billesbølle, Christian B

2014-01-01

Novel rhodamine-labeled ligands, based on (S)-citalopram, were synthesized and evaluated for uptake inhibition at the human serotonin, dopamine, and norepinephrine transporters (hSERT, hDAT, and hNET, respectively) and for binding at SERT, in transiently transfected COS7 cells. Compound 14 demons...... demonstrated high affinity binding and selectivity for SERT (K i = 3 nM). Visualization of SERT, using confocal laser scanning microscopy, validated compound 14 as a novel tool for studying SERT expression and distribution in living cells....

[99mTc[TRODAT-1: a novel technetium-99m complex as a dopamine transporter imaging agent

International Nuclear Information System (INIS)

Kung Meiping; Stevenson, D.A.; Ploessl, K.; Meegalla, S.K.; Beckwith, A.; Essman, W.D.; Mu, M.; Lucki, I.; Kung, H.F.

1997-01-01

Technetium-99m is the most commonly used radionuclide in routine nuclear medicine imaging procedures. Development of 99m Tc-labeled receptor-specific imaging agents for studying the central nervous system is potentially useful for evaluation of brain function in normal and disease states. A novel 99m Tc-labeled tropane derivative, [ 99m Tc[TRODAT-1, which is useful as a potential CNS dopamine transporter imaging agent, was evaluated and characterized. After i.v. injection into rats, [ 99m Tc[TRODAT-1 displayed specific brain uptake in the rat striatal region (striatum-cerebellum/cerebellum ratio 1.8 at 60 min), where dopamine neurons are concentrated. The specific striatal uptake could be blocked by pretreating rats with a dose of competing dopamine transporter ligand, β-CIT (or RTI-55, i.v., 1 mg/kg). However, the specific striatal uptake of [ 99m Tc[TRODAT-1 was not affected by co-injection of excess free ligand (TRODAT-1, up to 200 μg per rat) or by pretreating the rats with haloperidol (i.v., 1 mg/kg). The specific uptake in striatal regions of rats that had prior 6-hydroxydopamine lesion in the substantia nigra area showed a dramatic reduction. The radioactive material recovered from the rat striatal homogenates at 60 min after i.v. injection of [ 99m Tc[TRODAT-1 showed primarily the original compound (>95%), a good indication of in vivo stability in brain tissue. Similar and comparable organ distribution patterns and brain regional uptakes of [ 99m Tc[TRODAT-1 were obtained for male and female rats. (orig./AJ). With 4 figs., 6 tabs

Functional characterization of dopamine transporter in vivo using Drosophila melanogaster behavioral analysis.

Directory of Open Access Journals (Sweden)

Taro eUeno

2014-09-01

Full Text Available Dopamine mediates diverse functions such as motivation, reward, attention, learning/memory and sleep/arousal. Recent studies using model organisms including the fruit fly, have elucidated various physiological functions of dopamine, and identified specific neural circuits for these functions. Flies with mutations in the Drosophila dopamine transporter (dDAT gene show enhanced dopamine signaling, and short sleep and memory impairment phenotypes. However, understanding the mechanism by which dopamine signaling causes these phenotypes requires an understanding of the dynamics of dopamine release. Here we report the effects of dDAT expression on behavioral traits. We show that dDAT expression in a subset of dopaminergic neurons is sufficient for normal sleep. dDAT expression in other cell types such as Kenyon cells and glial cells can also rescue the short sleep phenotype of dDAT mutants. dDAT mutants also show a down-regulation of the D1-like dopamine receptor dDA1, and this phenotype is rescued when dDAT is expressed in the same cell types in which it rescues sleep. On the other hand, dDAT overexpression in mushroom bodies, which are the target of memory forming dopamine neurons, abolishes olfactory aversive memory. Our data demonstrate that expression of extrasynaptic dopamine transporters can rescue some aspects of dopamine signaling in dopamine transporter mutants. These results provide novel insights into regulatory systems that modulate dopamine signaling.

Intranasal dopamine reduces in vivo [123I]FP-CIT binding to striatal dopamine transporter: correlation with behavioral changes and evidence for Pavlovian conditioned dopamine response

OpenAIRE

Maria A de Souza Silva; C. eMattern; C. eMattern; C.I. eDecheva; Joseph P. Huston; A. eSadile; M. eBeu; H.W. eMüller; Susanne eNikolaus

2016-01-01

Purpose: Dopamine (DA), which does not cross the blood-brain barrier, has central and behavioral effects when administered via the nasal route. Neither the mechanisms of central action of intranasal dopamine (IN-DA), nor its mechanisms of diffusion and transport into the brain are well understood. We here examined whether IN-DA application influences dopamine transporter (DAT) binding in the dorsal striatum and assessed the extent of binding in relation to motor and exploratory behaviors. We ...

Design of a multi-dopamine-modified polymer ligand optimally suited for interfacing magnetic nanoparticles with biological systems.

Science.gov (United States)

Wang, Wentao; Ji, Xin; Na, Hyon Bin; Safi, Malak; Smith, Alexandra; Palui, Goutam; Perez, J Manuel; Mattoussi, Hedi

2014-06-03

We have designed a set of multifunctional and multicoordinating polymer ligands that are optimally suited for surface functionalizing iron oxide and potentially other magnetic nanoparticles (NPs) and promoting their integration into biological systems. The amphiphilic polymers are prepared by coupling (via nucleophilic addition) several amine-terminated dopamine anchoring groups, poly(ethylene glycol) moieties, and reactive groups onto a poly(isobutylene-alt-maleic anhydride) (PIMA) chain. This design greatly benefits from the highly efficient and reagent-free one-step reaction of maleic anhydride groups with amine-containing molecules. The availability of several dopamine groups in the same ligand greatly enhances the ligand affinity, via multiple coordination, to the magnetic NPs, while the hydrophilic and reactive groups promote colloidal stability in buffer media and allow subsequent conjugation with target biomolecules. Iron oxide nanoparticles ligand exchanged with these polymer ligands have a compact hydrodynamic size and exhibit enhanced long-term colloidal stability over the pH range of 4-12 and in the presence of excess electrolytes. Nanoparticles ligated with terminally reactive polymers have been easily coupled to target dyes and tested in live cell imaging with no measurable cytotoxicity. Finally, the resulting hydrophilic nanoparticles exhibit large and size-dependent r2 relaxivity values.

Blockade of dopamine D1-family receptors attenuates the mania-like hyperactive, risk-preferring, and high motivation behavioral profile of mice with low dopamine transporter levels.

Science.gov (United States)

Milienne-Petiot, Morgane; Groenink, Lucianne; Minassian, Arpi; Young, Jared W

2017-10-01

Patients with bipolar disorder mania exhibit poor cognition, impulsivity, risk-taking, and goal-directed activity that negatively impact their quality of life. To date, existing treatments for bipolar disorder do not adequately remediate cognitive dysfunction. Reducing dopamine transporter expression recreates many bipolar disorder mania-relevant behaviors (i.e. hyperactivity and risk-taking). The current study investigated whether dopamine D 1 -family receptor blockade would attenuate the risk-taking, hypermotivation, and hyperactivity of dopamine transporter knockdown mice. Dopamine transporter knockdown and wild-type littermate mice were tested in mouse versions of the Iowa Gambling Task (risk-taking), Progressive Ratio Breakpoint Test (effortful motivation), and Behavioral Pattern Monitor (activity). Prior to testing, the mice were treated with the dopamine D 1 -family receptor antagonist SCH 23390 hydrochloride (0.03, 0.1, or 0.3 mg/kg), or vehicle. Dopamine transporter knockdown mice exhibited hyperactivity and hyperexploration, hypermotivation, and risk-taking preference compared with wild-type littermates. SCH 23390 hydrochloride treatment decreased premature responding in dopamine transporter knockdown mice and attenuated their hypermotivation. SCH 23390 hydrochloride flattened the safe/risk preference, while reducing activity and exploratory levels of both genotypes similarly. Dopamine transporter knockdown mice exhibited mania-relevant behavior compared to wild-type mice. Systemic dopamine D 1 -family receptor antagonism attenuated these behaviors in dopamine transporter knockdown, but not all effects were specific to only the knockdown mice. The normalization of behavior via blockade of dopamine D 1 -family receptors supports the hypothesis that D 1 and/or D 5 receptors could contribute to the mania-relevant behaviors of dopamine transporter knockdown mice.

[{sup 99m}Tc]TRODAT-1: a novel technetium-99m complex as a dopamine transporter imaging agent

Energy Technology Data Exchange (ETDEWEB)

Meiping, Kung [Department of Radiology, University of Pennsylvania, Philadelphia (United States); Stevenson, D A [Department of Radiology, University of Pennsylvania, Philadelphia (United States); Ploessl, K [Department of Radiology, University of Pennsylvania, Philadelphia (United States); Meegalla, S K [Department of Radiology, University of Pennsylvania, Philadelphia (United States); Beckwith, A [Department of Radiology, University of Pennsylvania, Philadelphia (United States); Essman, W D [Department of Psychiatry, University of Pennsylvania, Philadelphia (United States); Mu, M [Department of Radiology, University of Pennsylvania, Philadelphia (United States); Lucki, I [Department of Psychiatry, University of Pennsylvania, Philadelphia (United States); [Department of Pharmacology, University of Pennsylvania, Philadelphia (United States); Kung, H F [Department of Radiology, University of Pennsylvania, Philadelphia (United States); [Department of Pharmacology, University of Pennsylvania, Philadelphia (United States)

1997-04-01

Technetium-99m is the most commonly used radionuclide in routine nuclear medicine imaging procedures. Development of {sup 99m}Tc-labeled receptor-specific imaging agents for studying the central nervous system is potentially useful for evaluation of brain function in normal and disease states. A novel {sup 99m}Tc-labeled tropane derivative, [{sup 99m}Tc]TRODAT-1, which is useful as a potential CNS dopamine transporter imaging agent, was evaluated and characterized. After i.v. injection into rats, [{sup 99m}Tc]TRODAT-1 displayed specific brain uptake in the rat striatal region (striatum-cerebellum/cerebellum ratio 1.8 at 60 min), where dopamine neurons are concentrated. The specific striatal uptake could be blocked by pretreating rats with a dose of competing dopamine transporter ligand, {beta}-CIT (or RTI-55, i.v., 1 mg/kg). However, the specific striatal uptake of [{sup 99m}Tc]TRODAT-1 was not affected by co-injection of excess free ligand (TRODAT-1, up to 200 {mu}g per rat) or by pretreating the rats with haloperidol (i.v., 1 mg/kg). The specific uptake in striatal regions of rats that had prior 6-hydroxydopamine lesion in the substantia nigra area showed a dramatic reduction. The radioactive material recovered from the rat striatal homogenates at 60 min after i.v. injection of [{sup 99m}Tc]TRODAT-1 showed primarily the original compound (>95%), a good indication of in vivo stability in brain tissue. Similar and comparable organ distribution patterns and brain regional uptakes of [{sup 99m}Tc]TRODAT-1 were obtained for male and female rats. (orig./AJ). With 4 figs., 6 tabs.

Serotonin transporters in dopamine transporter imaging: a head-to-head comparison of dopamine transporter SPECT radioligands 123I-FP-CIT and 123I-PE2I

DEFF Research Database (Denmark)

Ziebell, Morten; Holm-Hansen, Signe; Thomsen, Gerda

2010-01-01

Current SPECT radioligands available for in vivo imaging of the dopamine transporter (DAT) also show affinity for monoamine transporters other than DAT, especially the serotonin transporter (SERT). The effect of this lack of selectivity for in vivo imaging is unknown. In this study, we compared...

An Investigation of the Stoichiometry of Na+ Cotransport with Dopamine in Rat and Human Dopamine Transporters Expressed in Human Embryonic Kidney Cells

National Research Council Canada - National Science Library

Schumacher, Paul

2001-01-01

The neuronal membrane transporter for dopamine (DAT) is a member of the Na+ and Cl dependent family of transporters and concentrates dopamine intracellularly up to 106 fold over extracellular levels...

The binding sites for benztropines and dopamine in the dopamine transporter overlap

DEFF Research Database (Denmark)

Jensen, Heidi Bisgaard; Larsen, M Andreas B; Mazier, Sonia

2011-01-01

Analogs of benztropines (BZTs) are potent inhibitors of the dopamine transporter (DAT) but are less effective than cocaine as behavioral stimulants. As a result, there have been efforts to evaluate these compounds as leads for potential medication for cocaine addiction. Here we use computational...

Association of attention-deficit disorder and the dopamine transporter gene

Energy Technology Data Exchange (ETDEWEB)

Cook, E.H. Jr.; Stein, M.A.; Krasowski, M.D.; Cox, N.J.; Olkon, D.M.; Kieffer, J.E.; Leventhal, B.L. [Univ. of Chicago, IL (United States)

1995-04-01

Attention-deficit hyperactivity disorder (ADHD) has been shown to be familial and heritable, in previous studies. As with most psychiatric disorders, examination of pedigrees has not revealed a consistent Mendelian mode of transmission. The response of ADHD patients to medications that inhibit the dopamine transporter, including methylphenidate, amphetamine, pemoline, and bupropion, led us to consider the dopamine transporter as a primary candidate gene for ADHD. To avoid effects of population stratification and to avoid the problem of classification of relatives with other psychiatric disorders as affected or unaffected, we used the haplotype-based haplotype relative risk (HHRR) method to test for association between a VNTR polymorphism at the dopamine transporter locus (DAT1) and DSM-III-R-diagnosed ADHD (N = 49) and undifferentiated attention-deficit disorder (UADD) (N = 8) in trios composed of father, mother, and affected offspring. HHRR analysis revealed significant association between ADHS/UADD and the 480-bp DAT1 allele (X{sup 2} 7.51, 1 df, P = .006). When cases of UADD were dropped from the analysis, similar results were found (X{sup 2} 7.29, 1 df, P = .007). If these findings are replicated, molecular analysis of the dopamine transporter gene may identify mutations that increase susceptibility to ADHD/UADD. Biochemical analysis of such mutations may lead to development of more effective therapeutic interventions. 36 refs., 4 tabs.

Brain serotonin and dopamine transporter bindings in adults with high-functioning autism.

Science.gov (United States)

Nakamura, Kazuhiko; Sekine, Yoshimoto; Ouchi, Yasuomi; Tsujii, Masatsugu; Yoshikawa, Etsuji; Futatsubashi, Masami; Tsuchiya, Kenji J; Sugihara, Genichi; Iwata, Yasuhide; Suzuki, Katsuaki; Matsuzaki, Hideo; Suda, Shiro; Sugiyama, Toshiro; Takei, Nori; Mori, Norio

2010-01-01

Autism is a neurodevelopmental disorder that is characterized by repetitive and/or obsessive interests and behavior and by deficits in sociability and communication. Although its neurobiological underpinnings are postulated to lie in abnormalities of the serotoninergic and dopaminergic systems, the details remain unknown. To determine the occurrence of changes in the binding of serotonin and dopamine transporters, which are highly selective markers for their respective neuronal systems. Using positron emission tomography, we measured the binding of brain serotonin and dopamine transporters in each individual with the radioligands carbon 11 ((11)C)-labeled trans-1,2,3,5,6,10-beta-hexahydro-6-[4-(methylthio)phenyl]pyrrolo-[2,1-a]isoquinoline ([(11)C](+)McN-5652) and 2beta-carbomethoxy-3-beta-(4-fluorophenyl)tropane ([(11)C]WIN-35,428), respectively. Statistical parametric mapping was used for between-subject analysis and within-subject correlation analysis with respect to clinical variables. Participants recruited from the community. Twenty men (age range, 18-26 years; mean [SD] IQ, 99.3 [18.1]) with autism and 20 age- and IQ-matched control subjects. Serotonin transporter binding was significantly lower throughout the brain in autistic individuals compared with controls (P dopamine transporter binding was significantly higher in the orbitofrontal cortex of the autistic group (P dopamine transporter binding was significantly inversely correlated with serotonin transporter binding (r = -0.61; P = .004). The brains of autistic individuals have abnormalities in both serotonin transporter and dopamine transporter binding. The present findings indicate that the gross abnormalities in these neurotransmitter systems may underpin the neurophysiologic mechanism of autism. Our sample was not characteristic or representative of a typical sample of adults with autism in the community.

Functional Rescue of a Misfolded Drosophila melanogaster Dopamine Transporter Mutant Associated with a Sleepless Phenotype by Pharmacological Chaperones.

Science.gov (United States)

Kasture, Ameya; El-Kasaby, Ali; Szöllősi, Daniel; Asjad, H M Mazhar; Grimm, Alexandra; Stockner, Thomas; Hummel, Thomas; Freissmuth, Michael; Sucic, Sonja

2016-09-30

Folding-defective mutants of the human dopamine transporter (DAT) cause a syndrome of infantile dystonia/parkinsonism. Here, we provide a proof-of-principle that the folding deficit is amenable to correction in vivo by two means, the cognate DAT ligand noribogaine and the HSP70 inhibitor, pifithrin-μ. We examined the Drosophila melanogaster (d) mutant dDAT-G108Q, which leads to a sleepless phenotype in flies harboring this mutation. Molecular dynamics simulations suggested an unstable structure of dDAT-G108Q consistent with a folding defect. This conjecture was verified; heterologously expressed dDAT-G108Q and the human (h) equivalent hDAT-G140Q were retained in the endoplasmic reticulum in a complex with endogenous folding sensors (calnexin and HSP70-1A). Incubation of the cells with noribogaine (a DAT ligand selective for the inward-facing state) and/or pifithrin-μ (an HSP70 inhibitor) restored folding of, and hence dopamine transport by, dDAT-G108Q and hDAT-G140Q. The mutated versions of DAT were confined to the cell bodies of the dopaminergic neurons in the fly brain and failed to reach the axonal compartments. Axonal delivery was restored, and sleep time was increased to normal length (from 300 to 1000 min/day) if the dDAT-G108Q-expressing flies were treated with noribogaine and/or pifithrin-μ. Rescuing misfolded versions of DAT by pharmacochaperoning is of therapeutic interest; it may provide opportunities to remedy disorders arising from folding-defective mutants of human DAT and of other related SLC6 transporters. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

No association between striatal dopamine transporter binding and body mass index

DEFF Research Database (Denmark)

van de Giessen, Elsmarieke; Hesse, Swen; Caan, Matthan W A

2013-01-01

Dopamine is one among several neurotransmitters that regulate food intake and overeating. Thus, it has been linked to the pathophysiology of obesity and high body mass index (BMI). Striatal dopamine D(2) receptor availability is lower in obesity and there are indications that striatal dopamine...... transporter (DAT) availability is also decreased. In this study, we tested whether BMI and striatal DAT availability are associated....

Detection of dopamine neurotransmission in 'real time'

Directory of Open Access Journals (Sweden)

Rajendra D Badgaiyan

2013-07-01

Full Text Available Current imaging techniques have limited ability to detect neurotransmitters released during brain processing. It is a critical limitation because neurotransmitters have significant control over the brain activity. In this context, recent development of single-scan dynamic molecular imaging technique is important because it allows detection, mapping, and measurement of dopamine released in the brain during task performance. The technique exploits the competition between endogenously released dopamine and its receptor ligand for occupancy of receptor sites. Dopamine released during task performance is detected by dynamically measuring concentration of intravenously injected radiolabeled ligand using a positron emission tomography camera. Based on the ligand concentration, values of receptor kinetic parameters are estimated. These estimates allow detection of dopamine released in the human brain during task performance.

Novel aza-analogous ergoline derived scaffolds as potent serotonin 5-HT6 and dopamine D2 receptor ligands

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Krogsgaard-Larsen, Niels; Jensen, Anders A.; Schrøder, T.J.

2014-01-01

By introducing distal substituents on a tetracyclic scaffold resembling the ergoline structure, two series of analogues were achieved exhibiting subnanomolar receptor binding affinities for the dopamine D2 and serotonin 5-HT6 receptor subtype, respectively. While the 5-HT6 ligands were antagonists......, the D2 ligands displayed intrinsic activities ranging from full agonism to partial agonism with low intrinsic activity. These structures could potentially be interesting for treatment of neurological diseases such as schizophrenia, Parkinson’s disease, and cognitive deficits....

Interrogating the Molecular Basis for Substrate Recognition in Serotonin and Dopamine Transporters with High-Affinity Substrate-Based Bivalent Ligands

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Andersen, Jacob; Ladefoged, Lucy Kate; Kristensen, Trine N. Bjerre

2016-01-01

insight into substrate recognition in SERT and DAT. An optimized bivalent ligand comprising two serotonin moieties binds SERT with 3,800-fold increased affinity compared to that of serotonin, suggesting that the human transporters have two distinct substrate binding sites. We show that the bivalent...... ligands are inhibitors of SERT and an experimentally validated docking model suggests that the bivalent compounds bind with one substrate moiety in the central binding site (the S1 site), whereas the other substrate moiety binds in a distinct binding site (the S2 site). A systematic study of nonconserved...

Calmodulin kinase II interacts with the dopamine transporter C terminus to regulate amphetamine-induced reverse transport

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Fog, Jacob U; Khoshbouei, Habibeh; Holy, Marion

2006-01-01

Efflux of dopamine through the dopamine transporter (DAT) is critical for the psychostimulatory properties of amphetamines, but the underlying mechanism is unclear. Here we show that Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) plays a key role in this efflux. CaMKIIalpha bound to the d...

Clinical usefulness of dopamine transporter imaging

International Nuclear Information System (INIS)

Kim, Jong Min; Kim, Yu Kyeong; Kim, Sang Eun; Jeon, Beom S.

2007-01-01

Imaging of the dopamine transporter (DAT) provides a marker for the integrity of presynaptic nigrostriatal dopaminergic system. DAT density is reduced in Parkinson disease, multiple system atrophy, and progressive supranuclear palsy. In patients with suspicious parkinsonism, normal DAT imaging suggests an alternative diagnosis such as essential tremor, vascular parkinsonism, or drug-induced parkinsonism. DAT imaging is a useful tool to aid clinician's differential diagnosis in parkinsonism

Missense dopamine transporter mutations associate with adult parkinsonism and ADHD

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Hansen, Freja H; Skjørringe, Tina; Yasmeen, Saiqa

2014-01-01

experiments suggested that the disrupted function of the DAT-Asp421Asn mutant is the result of compromised sodium binding, in agreement with Asp421 coordinating sodium at the second sodium site. For DAT-Asp421Asn, substrate efflux experiments revealed a constitutive, anomalous efflux of dopamine......Parkinsonism and attention deficit hyperactivity disorder (ADHD) are widespread brain disorders that involve disturbances of dopaminergic signaling. The sodium-coupled dopamine transporter (DAT) controls dopamine homeostasis, but its contribution to disease remains poorly understood. Here, we......-deoxy-glucose-PET/MRI (FDG-PET/MRI) scan, the patient suffered from progressive dopaminergic neurodegeneration. In heterologous cells, both DAT variants exhibited markedly reduced dopamine uptake capacity but preserved membrane targeting, consistent with impaired catalytic activity. Computational simulations and uptake...

Syntaxin 1A interaction with the dopamine transporter promotes amphetamine-induced dopamine efflux

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Binda, Francesca; Dipace, Concetta; Bowton, Erica

2008-01-01

of the dopamine (DA) transporter (DAT) as the site of direct interaction with SYN1A. Amphetamine (AMPH) increases the association of SYN1A with human DAT (hDAT) in a heterologous expression system (hDAT cells) and with native DAT in murine striatal synaptosomes. Immunoprecipitation of DAT from the biotinylated...

Dopamine-transporter SPECT and Dopamine-D2-receptor SPECT in basal ganglia diseases

International Nuclear Information System (INIS)

Hesse, S.; Barthel, H.; Seese, A.; Sabri, O.

2007-01-01

The basal ganglia comprise a group of subcortical nuclei, which are essential for motor control. Dysfunction of these areas, especially in dopaminergic transmission, results in disordered movement and neurological diseases such as Parkinson's disease, Wilson's disease, or Huntington disease. Positron emission tomography and single photon emission computed tomography (SPECT) have enhanced the understanding of the underlying pathophysiology, but they much more contribute to the early differential diagnosis of patients suffering from Parkinsonian syndrome in routine care. The present article provides dopamine transporter and D 2 receptor SPECT findings in selected movement disorders. (orig.)

Intranasal dopamine reduces in vivo [123I]FP-CIT binding to striatal dopamine transporter: correlation with behavioral changes and evidence for Pavlovian conditioned dopamine response

Directory of Open Access Journals (Sweden)

Maria A de Souza Silva

2016-04-01

Full Text Available Purpose: Dopamine (DA, which does not cross the blood-brain barrier, has central and behavioral effects when administered via the nasal route. Neither the mechanisms of central action of intranasal dopamine (IN-DA, nor its mechanisms of diffusion and transport into the brain are well understood. We here examined whether IN-DA application influences dopamine transporter (DAT binding in the dorsal striatum and assessed the extent of binding in relation to motor and exploratory behaviors. We hypothesized that, based on the finding of increased extracellular DA in the striatum induced by application of IN-DA, binding of [123I]FP-CIT to the DAT should be decreased due to competition at the receptor.Methods: Rats were administered intranasal application of 3 mg/kg IN-DA and vehicle (VEH, with IN-DA injection either preceding or following VEH. Then motor and exploratory behaviors (traveled distance, velocity, center time, sitting, rearing, head-shoulder motility, grooming were assessed for 30 min in an open field prior to administration of [123I]FP-CIT. DAT binding after IN-DA and VEH was measured with small animal SPECT two hours following administration of the radioligand. Results: 1 After IN-DA application, striatal DAT binding was significantly lower as compared to VEH, indicating that the nasally delivered dopamine had central action and increased DA levels comparable to that found previously with L-DOPA administration. 2 DAT binding in response to intranasal VEH was lower when IN-DA application preceded VEH treatment. This finding is suggestive of Pavlovian conditioning of DA at the level of the DAT, since the DA treatment modified (decreased the binding in response to the subsequent VEH treatment. VEH treatment also reduced motor and exploratory behaviors more when applied before, as compared to when it followed IN-DA application, also indicative of behavioral Pavlovian conditioning akin to that found upon application of various psychostimulant

The second sodium site in the dopamine transporter controls cation permeability and is regulated by chloride

DEFF Research Database (Denmark)

Borre, Lars; Andreassen, Thorvald F; Shi, Lei

2014-01-01

The dopamine transporter (DAT) belongs to the family of neurotransmitter:sodium symporters (NSSs) and controls dopamine (DA) homeostasis by mediating Na(+)- and Cl(-)-dependent reuptake of DA. Here we used two-electrode voltage clamp measurements in Xenopus oocytes together with targeted mutagene......The dopamine transporter (DAT) belongs to the family of neurotransmitter:sodium symporters (NSSs) and controls dopamine (DA) homeostasis by mediating Na(+)- and Cl(-)-dependent reuptake of DA. Here we used two-electrode voltage clamp measurements in Xenopus oocytes together with targeted...

Pyrethroid pesticide-induced alterations in dopamine transporter function

International Nuclear Information System (INIS)

Elwan, Mohamed A.; Richardson, Jason R.; Guillot, Thomas S.; Caudle, W. Michael; Miller, Gary W.

2006-01-01

Parkinson's disease (PD) is a progressive neurodegenerative disease affecting the nigrostriatal dopaminergic pathway. Several epidemiological studies have demonstrated an association between pesticide exposure and the incidence of PD. Studies from our laboratory and others have demonstrated that certain pesticides increase levels of the dopamine transporter (DAT), an integral component of dopaminergic neurotransmission and a gateway for dopaminergic neurotoxins. Here, we report that repeated exposure (3 injections over 2 weeks) of mice to two commonly used pyrethroid pesticides, deltamethrin (3 mg/kg) and permethrin (0.8 mg/kg), increases DAT-mediated dopamine uptake by 31 and 28%, respectively. Using cells stably expressing DAT, we determined that exposure (10 min) to deltamethrin and permethrin (1 nM-100 μM) had no effect on DAT-mediated dopamine uptake. Extending exposures to both pesticides for 30 min (10 μM) or 24 h (1, 5, and 10 μM) resulted in significant decrease in dopamine uptake. This reduction was not the result of competitive inhibition, loss of DAT protein, or cytotoxicity. However, there was an increase in DNA fragmentation, an index of apoptosis, in cells exhibiting reduced uptake at 30 min and 24 h. These data suggest that up-regulation of DAT by in vivo pyrethroid exposure is an indirect effect and that longer-term exposure of cells results in apoptosis. Since DAT can greatly affect the vulnerability of dopamine neurons to neurotoxicants, up-regulation of DAT by deltamethrin and permethrin may increase the susceptibility of dopamine neurons to toxic insult, which may provide insight into the association between pesticide exposure and PD

Evidence for distinct sodium-, dopamine-, and cocaine-dependent conformational changes in transmembrane segments 7 and 8 of the dopamine transporter

DEFF Research Database (Denmark)

Norregaard, Lene; Loland, Claus Juul; Gether, Ulrik

2003-01-01

. Inhibitors such as cocaine did not alter the effect of MTSET in M371C. The protection of M371C inactivation by dopamine required Na+. Because dopamine binding is believed to be Na+-independent, this suggests that dopamine induces a transport-associated conformational change that decreases the reactivity of M......371C with MTSET. In contrast to M371C, cocaine decreased the reaction rate of A399C with MTSET, whereas dopamine had no effect. The protection by cocaine can either reflect that Ala-399 lines the cocaine binding crevice or that cocaine induces a conformational change that decreases the reactivity of A...

Structure-activity relationships for serotonin transporter and dopamine receptor selectivity.

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Agatonovic-Kustrin, Snezana; Davies, Paul; Turner, Joseph V

2009-05-01

Antipsychotic medications have a diverse pharmacology with affinity for serotonergic, dopaminergic, adrenergic, histaminergic and cholinergic receptors. Their clinical use now also includes the treatment of mood disorders, thought to be mediated by serotonergic receptor activity. The aim of our study was to characterise the molecular properties of antipsychotic agents, and to develop a model that would indicate molecular specificity for the dopamine (D(2)) receptor and the serotonin (5-HT) transporter. Back-propagation artificial neural networks (ANNs) were trained on a dataset of 47 ligands categorically assigned antidepressant or antipsychotic utility. The structure of each compound was encoded with 63 calculated molecular descriptors. ANN parameters including hidden neurons and input descriptors were optimised based on sensitivity analyses, with optimum models containing between four and 14 descriptors. Predicted binding preferences were in excellent agreement with clinical antipsychotic or antidepressant utility. Validated models were further tested by use of an external prediction set of five drugs with unknown mechanism of action. The SAR models developed revealed the importance of simple molecular characteristics for differential binding to the D(2) receptor and the 5-HT transporter. These included molecular size and shape, solubility parameters, hydrogen donating potential, electrostatic parameters, stereochemistry and presence of nitrogen. The developed models and techniques employed are expected to be useful in the rational design of future therapeutic agents.

Postendocytic sorting of constitutively internalized dopamine transporter in cell lines and dopaminergic neurons

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Eriksen, Jacob; Bjørn-Yoshimoto, Walden Emil; Jørgensen, Trine Nygaard

2010-01-01

The dopamine transporter (DAT) mediates reuptake of released dopamine and is the target for psychostimulants, such as cocaine and amphetamine. DAT undergoes marked constitutive endocytosis, but little is known about the fate and sorting of the endocytosed transporter. To study DAT sorting in cells...... lines, we fused the one-transmembrane segment protein Tac to DAT, thereby generating a transporter (TacDAT) with an extracellular antibody epitope suited for trafficking studies. TacDAT was functional and endocytosed constitutively in HEK293 cells. According to an ELISA-based assay, TacDAT intracellular...

De novo mutation in the dopamine transporter gene associates dopamine dysfunction with autism spectrum disorder.

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Hamilton, P J; Campbell, N G; Sharma, S; Erreger, K; Herborg Hansen, F; Saunders, C; Belovich, A N; Sahai, M A; Cook, E H; Gether, U; McHaourab, H S; Matthies, H J G; Sutcliffe, J S; Galli, A

2013-12-01

De novo genetic variation is an important class of risk factors for autism spectrum disorder (ASD). Recently, whole-exome sequencing of ASD families has identified a novel de novo missense mutation in the human dopamine (DA) transporter (hDAT) gene, which results in a Thr to Met substitution at site 356 (hDAT T356M). The dopamine transporter (DAT) is a presynaptic membrane protein that regulates dopaminergic tone in the central nervous system by mediating the high-affinity reuptake of synaptically released DA, making it a crucial regulator of DA homeostasis. Here, we report the first functional, structural and behavioral characterization of an ASD-associated de novo mutation in the hDAT. We demonstrate that the hDAT T356M displays anomalous function, characterized as a persistent reverse transport of DA (substrate efflux). Importantly, in the bacterial homolog leucine transporter, substitution of A289 (the homologous site to T356) with a Met promotes an outward-facing conformation upon substrate binding. In the substrate-bound state, an outward-facing transporter conformation is required for substrate efflux. In Drosophila melanogaster, the expression of hDAT T356M in DA neurons-lacking Drosophila DAT leads to hyperlocomotion, a trait associated with DA dysfunction and ASD. Taken together, our findings demonstrate that alterations in DA homeostasis, mediated by aberrant DAT function, may confer risk for ASD and related neuropsychiatric conditions.

Synthesis of the possible receptor Ligand [125I]-spiperone for D2-dopamine receptor and in-vivo biodistribution

International Nuclear Information System (INIS)

Amin, A.M.; Shoukry, M.; Abd EL-Bary, A.

2009-01-01

The spiperone is a selective D2-dopamine receptor antagonist radioiodination of spiperone is of interest for dopamine (DA) receptor studies both in vivo and in vitro. The labeling of spiperone with iodine-125 was extremely done in a neutral ph 7, using chloramine-T as oxidizing agent via heating the reaction mixture at 70 C (degree) for 10 - 15 minutes producing radiochemical yield of 97 %. In vivo biodistribution studies showed that the initial brain uptake correlated fairly well with the brain uptake index and that the kinetics of the radioactivity specifically bound to the striatum were strongly influenced by the dopamine receptor binding affinity of the compound. The brain uptake of 125 I-Spiperone was high and equal to 3.5, 3.25,2.75 and 1.7 % per gram tissue at 5, 30, 60 and 120 minutes post injection, respectively. 125 I-Spiperone binds with high affinity to dopamine receptors in vivo. Specific binding is about 65% of the total binding as is displaced stereo-specifically by clozapine. 125 I-spiperone may prove to be a useful ligand in studies examining D2-dopamine receptors. Furthermore iodinated spiperone may be useful in radioreceptor assays of neuroleptic drug levels and, in a 123 I-labeled form, for imaging of dopamine receptors, in vivo, using single photon tomography.

SPECT imaging of dopamine and serotonin transporters with [[sup 123]I][beta]-CIT. Binding kinetics in the human brain

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Bruecke, T; Asenbaum, S; Frassine, H; Podreka, I [Vienna Univ. (Austria). Neurologische Klinik; Kornhuber, J [Wuerzburg Univ. (Germany); Angelberger, P [Oesterreichisches Forschungszentrum Seibersdorf GmbH (Austria)

1993-01-01

Single photon emission computerized tomography (SPECT) studies in non-human primates have previously shown that the cocaine derivative [[sup 123]I]-2-[beta]-carbomethoxy-3-[beta]-(4-iodophenyl)-tropane ([[sup 123]I][beta]-CIT) labels dopamine transporters in the striatum and serotonin transporters in the hypothalamus-midbrain area. Here, we report on the regional kinetic uptake of [[sup 123]I][beta]-CIT in the brain of 4 normal volunteers and 2 patients with Parkinson's disease. In healthy subjects striatal activity increased slowly to reach peak values at about 20 hours post injection. In the hypothalamus-midbrain area peak activities were observed at about 4 hours with a slow decrease thereafter. Low activity was observed in cortical and cerebellar areas. The striatal to cerebellar ratio was about 4 after 5 hours and 9 after 20 hours. In 2 patients with idiopathic Parkinson's disease striatal activity was markedly decreased while the activity in hypothalamus-midbrain areas was only diminished. Uptake into cortical and cerebellar areas appeared to be unchanged in Parkinson's disease. Consequently, in Parkinson's disease the striatal to cerebellar ratio was decreased to values around 2.5 after 20 hours. These preliminary methodological studies suggest that [[sup 123]I][beta]-CIT is a useful SPECT ligand for studying dopamine and possibly also serotonin transporters in the living human brain.

MS-377, a novel selective sigma(1) receptor ligand, reverses phencyclidine-induced release of dopamine and serotonin in rat brain.

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Takahashi, S; Horikomi, K; Kato, T

2001-09-21

A novel selective sigma(1) receptor ligand, (R)-(+)-1-(4-chlorophenyl)-3-[4-(2-methoxyethyl)piperazin-1-yl]methyl-2-pyrrolidinone L-tartrate (MS-377), inhibits phencyclidine (1-(1-phenylcyclohexyl)piperidine; PCP)-induced behaviors in animal models. In this study, we measured extracellular dopamine and serotonin levels in the rat brain after treatment with MS-377 alone, using in vivo microdialysis. We also examined the effects of MS-377 on extracellular dopamine and serotonin levels in the rat medial prefrontal cortex after treatment with PCP. MS-377 itself had no significant effects on dopamine release in the striatum (10 mg/kg, p.o.) nor on dopamine or serotonin release in the medial prefrontal cortex (1 and 10 mg/kg, p.o.). PCP (3 mg/kg, i.p.) markedly increased dopamine and serotonin release in the medial prefrontal cortex. MS-377 (1 mg/kg, p.o.), when administered 60 min prior to PCP, significantly attenuated this effect of PCP. These results suggest that the inhibitory effects of MS-377 on PCP-induced behaviors are partly mediated by inhibition of the increase in dopamine and serotonin release in the rat medial prefrontal cortex caused by PCP.

Ascorbic acid and striatal transport of [3H]1-methyl-4-phenylpyridine (MPP+) and [3H]dopamine

International Nuclear Information System (INIS)

Debler, E.A.; Hashim, A.; Lajtha, A.; Sershen, H.

1988-01-01

The inhibition of uptake of [ 3 H]dopamine and [ 3 H]1-methyl-4-phenylpyridine (MPP + ) was examined in mouse striatal synaptosomal preparations. Kinetic analysis indicated that ascorbic acid is a noncompetitive inhibitor of [ 3 H]MPP + uptake. No inhibition of [ 3 H]dopamine uptake is observed. The dopamine uptake blockers, GBR-12909, cocaine, and mazindol strongly inhibit (IC 50 3 H]dopamine and [ 3 H]MPP + transport. Nicotine, its metabolites, and other tobacco alkaloids are weak inhibitors except 4-phenylpyridine and lobeline, which are moderate inhibitors of both [ 3 H]dopamine and [ 3 H]MPP + uptake. These similarities in potencies are in agreement with the suggestion that [ 3 H]MPP + and [ 3 H] are transported by the same carrier. The differences observed in the alteration of dopaminergic transport and mazindol binding by ascorbic acid suggest that ascorbic acid's effects on [ 3 H]MPP + transport are related to translocation and/or dissociation processes occurring subsequent to the initial binding event

Photoaffinity ligand for dopamine D2 receptors: azidoclebopride

International Nuclear Information System (INIS)

Niznik, H.B.; Guan, J.H.; Neumeyer, J.L.; Seeman, P.

1985-01-01

In order to label D2 dopamine receptors selectively and covalently by means of a photosensitive compound, azidoclebopride was synthesized directly from clebopride. The dissociation constant (KD) of clebopride for the D2 dopamine receptor (canine brain striatum) was 1.5 nM, while that for azidoclebopride was 21 nM. The affinities of both clebopride and azidoclebopride were markedly reduced in the absence of sodium chloride. In the presence of ultraviolet light, azidoclebopride inactivated D2 dopamine receptors irreversibly, as indicated by the inability of the receptors to bind [ 3 H]spiperone. Maximal photoinactivation of about 60% of the D2 dopamine receptors occurred at 1 microM azidoclebopride; 30% of the receptors were inactivated at 80 nM azidoclebopride (pseudo-IC50). Dopamine agonists selectively protected the D2 receptors from being inactivated by azidoclebopride, the order of potency being (-)-N-n-propylnorapomorphine greater than apomorphine greater than (+/-)-6,7-dihydroxy-2-aminotetralin greater than (+)-N-n-propylnorapomorphine greater than dopamine greater than noradrenaline greater than serotonin. Similarly, dopaminergic antagonists prevented the photoinactivation of D2 receptors by azidoclebopride with the following order of potency: spiperone greater than (+)-butaclamol greater than haloperidol greater than clebopride greater than (-)-sulpiride greater than (-)-butaclamol

Regulation of dopamine transporter activity by carboxypeptidase E

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Zhang Heping

2009-05-01

Full Text Available Abstract Background The dopamine transporter (DAT plays a critical role in terminating the action of dopamine by rapid reuptake into the presynaptic neuron. Previous studies have revealed that the DAT carboxyl terminus (DAT-CT can directly interact with other cellular proteins and regulate DAT function and trafficking. Results Here, we have identified that carboxypeptidase E (CPE, a prohormone processing exopeptidase and sorting receptor for the regulated secretory pathway, interacts with the DAT-CT and affects DAT function. Mammalian cell lines coexpressing CPE and DAT exhibited increased DAT-mediated dopamine uptake activity compared to cells expressing DAT alone. Moreover, coexpression of an interfering DAT-CT minigene inhibited the effects of CPE on DAT. Functional changes caused by CPE could be attributed to enhanced DAT expression and subsequent increase in DAT cell surface localization, due to decreased DAT degradation. In addition, CPE association could reduce the phosphorylation state of DAT on serine residues, potentially leading to reduced internalization, thus stabilizing plasmalemmal DAT localization. Conclusion Taken together, our results reveal a novel role for CPE in the regulation of DAT trafficking and DAT-mediated DA uptake, which may provide a novel target in the treatment of dopamine-governed diseases such as drug addiction and obesity.

De novo mutation in the dopamine transporter gene associates dopamine dysfunction with autism spectrum disorder

DEFF Research Database (Denmark)

Hamilton, P J; Campbell, N G; Sharma, S

2013-01-01

De novo genetic variation is an important class of risk factors for autism spectrum disorder (ASD). Recently, whole-exome sequencing of ASD families has identified a novel de novo missense mutation in the human dopamine (DA) transporter (hDAT) gene, which results in a Thr to Met substitution...

Zn(2+) site engineering at the oligomeric interface of the dopamine transporter.

Science.gov (United States)

Norgaard-Nielsen, Kristine; Norregaard, Lene; Hastrup, Hanne; Javitch, Jonathan A; Gether, Ulrik

2002-07-31

Increasing evidence suggests that Na(+)/Cl(-)-dependent neurotransmitter transporters exist as homo-oligomeric proteins. However, the functional implication of this oligomerization remains unclear. Here we demonstrate the engineering of a Zn(2+) binding site at the predicted dimeric interface of the dopamine transporter (DAT) corresponding to the external end of transmembrane segment 6. Upon binding to this site, which involves a histidine inserted in position 310 (V310H) and the endogenous Cys306 within the same DAT molecule, Zn(2+) potently inhibits [(3)H]dopamine uptake. These data provide indirect evidence that conformational changes critical for the translocation process may occur at the interface between two transporter molecules in the oligomeric structure.

Central serotonin and dopamine transporters in overeating, obesity and insulin resistance

NARCIS (Netherlands)

Koopman, K.E.M.

2014-01-01

The objectives of this thesis were to study cerebral serotonin transporters (SERT) in the diencephalon and striatal dopamine transporters (DAT) in humans in different metabolic conditions (i.e. lean, obese and insulin resistant state) in relation to feeding behavior and to investigate the early

Preparation of a potential positron emission tomographic radioligand for the dopamine transporter

International Nuclear Information System (INIS)

Mueller, L.; Halldin, C.; Foged, C.; Karlsson, P.; Hall, H.; Swahn, C.G.; Suzdak, P.D.; Hohlweg, R.; Nielsen, E.B.; Frade, L.

1994-01-01

NNC 12-0722 (1-[2-(bis(4-fluorophenyl)-methoxy)ethyl]-4-methyl piperazine) is a new selective inhibitor of the dopamine transporter. [ 11 C]NNC 12-0722 was prepared by N-methylation of the desmethyl compound with [ 11 C]methyl iodide. The total radiochemical yield of [ 11 C]NNC 12-0722 was 40%-50% with an overall synthesis time of 30-35 min. The radiochemical purity was higher than 99% and the specific radioactivity about 1500 Ci/mmol (55 GBq/μmol). Autoradiographic examination of [ 11 C]NNC 12-0722 binding on whole hemisphere cryosections from human brain post mortem demonstrated specific binding in the caudate nucleus and putamen. In a positron emission tomographic examination of [ 11 C]NNC 12-0722 in a cynomolgus monkey there was a rapid uptake of radioactivity in the brain. In the striatum, a region with a high density of dopamine transporters, the radioactivity was two times higher than in the cerebellum. These results indicate that [ 11 C]NNC 12-0722 may be a useful radioligand for labelling of the dopamine transporter in man. (orig.)

[Study of dopamine transporter imaging on the brain of children with autism].

Science.gov (United States)

Sun, Xiaomian; Yue, Jing; Zheng, Chongxun

2008-04-01

This study was conducted to evaluate the applicability of 99mTc-2beta-[ N, N'-bis (2-mercaptoethyl) ethylenediamino]methyl,3beta(4-chlorophenyl)tropane(TRODAT-1) dopamine transporter(DAT) SPECT imaging in children with autism, and thus to provide an academic basis for the etiology, mechanism and clinical therapy of autism. Ten autistic children and ten healthy controls were examined with 99mTc-TRODAT-1 DAT SPECT imaging. Striatal specific uptake of 99mTc-TRODAT-1 was calculated with region of interest analysis according to the ratics between striatum and cerebellum [(STR-BKG)/BKG]. There was no statistically significant difference in semiquantitative dopamine transporter between the bilateral striata of autistic children (P=0.562), and between those of normal controls (p=0.573); Dopamine transporter in the brain of patients with autism increased significantly as compared with that in the brain of normal controls (P=0.017). Dopaminergic nervous system is dysfunctioning in the brain of children with autism, and DAT 99mTc-TRODAT-1 SPECT imaging on the brain will help the imaging diagnosis of childhcod autism.

Effect of age and gender on dopamine transporter imaging with [123I]FP-CIT SPET in healthy volunteers

International Nuclear Information System (INIS)

Lavalaye, J.; Booij, J.; Reneman, L.; Habraken, J.B.A.; Royen, E.A. van

2000-01-01

Dopamine transporter imaging is a valuable tool to investigate the integrity of the dopaminergic neurons. To date, several reports have shown an age-associated decline in dopamine transporters in healthy volunteers. Although animal studies suggest an effect of gender on dopamine transporter density, this gender effect has not yet been confirmed in human studies. To study the influence of age and gender on dopamine transporter imaging in healthy volunteers, we performed single-photon emission tomography imaging with [ 123 I]FP-CIT to quantify dopamine transporters. Forty-five healthy volunteers (23 males and 22 females) were included, ranging in age from 18 to 83 years. SPET imaging was performed 3 h after injection of ±110 MBq [ 123 I]FP-CIT. An operator-independent volume of interest analysis was used for quantification of [ 123 I]FP-CIT binding in the striatum. The ratio of specific striatal to non-specific [ 123 I]FP-CIT binding was found to decrease significantly with age. Moreover, we found a high variance in [ 123 I]FP-CIT binding in young adults. Finally, females were found to have significantly higher [ 123 I]FP-CIT binding ratios than males. This effect of gender on [ 123 I]FP-CIT binding ratios was not related to age. The results of this study are consistent with findings from previous studies, which showed that dopamine transporter density declines with age. The intriguing finding of a higher dopamine transporter density in females than in males is in line with findings from animal studies. (orig.)

Regulator of G protein signaling-12 modulates the dopamine transporter in ventral striatum and locomotor responses to psychostimulants.

Science.gov (United States)

Gross, Joshua D; Kaski, Shane W; Schroer, Adam B; Wix, Kimberley A; Siderovski, David P; Setola, Vincent

2018-02-01

Regulators of G protein signaling are proteins that accelerate the termination of effector stimulation after G protein-coupled receptor activation. Many regulators of G protein signaling proteins are highly expressed in the brain and therefore considered potential drug discovery targets for central nervous system pathologies; for example, here we show that RGS12 is highly expressed in microdissected mouse ventral striatum. Given a role for the ventral striatum in psychostimulant-induced locomotor activity, we tested whether Rgs12 genetic ablation affected behavioral responses to amphetamine and cocaine. RGS12 loss significantly decreased hyperlocomotion to lower doses of both amphetamine and cocaine; however, other outcomes of administration (sensitization and conditioned place preference) were unaffected, suggesting that RGS12 does not function in support of the rewarding properties of these psychostimulants. To test whether observed response changes upon RGS12 loss were caused by changes to dopamine transporter expression and/or function, we prepared crude membranes from the brains of wild-type and RGS12-null mice and measured dopamine transporter-selective [ 3 H]WIN 35428 binding, revealing an increase in dopamine transporter levels in the ventral-but not dorsal-striatum of RGS12-null mice. To address dopamine transporter function, we prepared striatal synaptosomes and measured [ 3 H]dopamine uptake. Consistent with increased [ 3 H]WIN 35428 binding, dopamine transporter-specific [ 3 H]dopamine uptake in RGS12-null ventral striatal synaptosomes was found to be increased. Decreased amphetamine-induced locomotor activity and increased [ 3 H]WIN 35428 binding were recapitulated with an independent RGS12-null mouse strain. Thus, we propose that RGS12 regulates dopamine transporter expression and function in the ventral striatum, affecting amphetamine- and cocaine-induced increases in dopamine levels that specifically elicit acute hyperlocomotor responses.

EANM procedure guidelines for brain neurotransmission SPECT/PET using dopamine D2 receptor ligands, version 2

DEFF Research Database (Denmark)

Van Laere, Koen; Varrone, Andrea; Booij, Jan

2010-01-01

receptor SPECT or PET studies, and to achieve a high quality standard of dopamine D2 receptor imaging, which will increase the impact of this technique in neurological practice.The present document is an update of the first guidelines for SPECT using D2 receptor ligands labelled with (123)I [1......The guidelines summarize the current views of the European Association of Nuclear Medicine Neuroimaging Committee (ENC). The aims of the guidelines are to assist nuclear medicine practitioners in making recommendations, performing, interpreting and reporting the results of clinical dopamine D2......] and was guided by the views of the Society of Nuclear Medicine Brain Imaging Council [2], and the individual experience of experts in European countries. The guidelines intend to present information specifically adapted to European practice. The information provided should be taken in the context of local...

CA2+/CALMODULIN-DEPENDENT KINASE II- ASSOCIATES WITH THE C TERMINUS OF THE DOPAMINE TRANSPORTER AND INCREASES AMPHETAMINE-INDUCED DOPAMINE EFFLUX VIA PHOSPHORYLATION OF N-TERMINAL SERINES

DEFF Research Database (Denmark)

Fog, Jacob; Khoshbouei, H; Holy, M

The dopamine transporter(DAT) plays a key role in clearing extracellular dopamine(DA) from the synapse. Moreover DAT is a target for the action of widely abused psychostimulants such as cocaine and amphetamine(AMPH). AMPH is a substrate for the DAT and promotes the reversal of transport and thus...

Identification of rare high-risk copy number variants affecting the dopamine transporter gene in mental disorders

DEFF Research Database (Denmark)

Hoeffding, Louise Kristine Enggaard; Duong, Linh T T; Ingason, Andres

2016-01-01

BACKGROUND: The dopamine transporter, also known as solute carrier 6A3 (SLC6A3), plays an important role in synaptic transmission by regulating the reuptake of dopamine in the synapses. In line with this, variations in the gene encoding this transporter have been linked to both schizophrenia and ...

Diet-induced obesity: dopamine transporter function, impulsivity and motivation.

Science.gov (United States)

Narayanaswami, V; Thompson, A C; Cassis, L A; Bardo, M T; Dwoskin, L P

2013-08-01

A rat model of diet-induced obesity (DIO) was used to determine dopamine transporter (DAT) function, impulsivity and motivation as neurobehavioral outcomes and predictors of obesity. To evaluate neurobehavioral alterations following the development of DIO induced by an 8-week high-fat diet (HF) exposure, striatal D2-receptor density, DAT function and expression, extracellular dopamine concentrations, impulsivity, and motivation for high- and low-fat reinforcers were determined. To determine predictors of DIO, neurobehavioral antecedents including impulsivity, motivation for high-fat reinforcers, DAT function and extracellular dopamine were evaluated before the 8-week HF exposure. Striatal D2-receptor density was determined by in vitro kinetic analysis of [(3)H]raclopride binding. DAT function was determined using in vitro kinetic analysis of [(3)H]dopamine uptake, methamphetamine-evoked [(3)H]dopamine overflow and no-net flux in vivo microdialysis. DAT cell-surface expression was determined using biotinylation and western blotting. Impulsivity and food-motivated behavior were determined using a delay discounting task and progressive ratio schedule, respectively. Relative to obesity-resistant (OR) rats, obesity-prone (OP) rats exhibited 18% greater body weight following an 8-week HF-diet exposure, 42% lower striatal D2-receptor density, 30% lower total DAT expression, 40% lower in vitro and in vivo DAT function, 45% greater extracellular dopamine and twofold greater methamphetamine-evoked [(3)H]dopamine overflow. OP rats exhibited higher motivation for food, and surprisingly, were less impulsive relative to OR rats. Impulsivity, in vivo DAT function and extracellular dopamine concentration did not predict DIO. Importantly, motivation for high-fat reinforcers predicted the development of DIO. Human studies are limited by their ability to determine if impulsivity, motivation and DAT function are causes or consequences of DIO. The current animal model shows that

Altered neurocircuitry in the dopamine transporter knockout mouse brain.

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Xiaowei Zhang

2010-07-01

Full Text Available The plasma membrane transporters for the monoamine neurotransmitters dopamine, serotonin, and norepinephrine modulate the dynamics of these monoamine neurotransmitters. Thus, activity of these transporters has significant consequences for monoamine activity throughout the brain and for a number of neurological and psychiatric disorders. Gene knockout (KO mice that reduce or eliminate expression of each of these monoamine transporters have provided a wealth of new information about the function of these proteins at molecular, physiological and behavioral levels. In the present work we use the unique properties of magnetic resonance imaging (MRI to probe the effects of altered dopaminergic dynamics on meso-scale neuronal circuitry and overall brain morphology, since changes at these levels of organization might help to account for some of the extensive pharmacological and behavioral differences observed in dopamine transporter (DAT KO mice. Despite the smaller size of these animals, voxel-wise statistical comparison of high resolution structural MR images indicated little morphological change as a consequence of DAT KO. Likewise, proton magnetic resonance spectra recorded in the striatum indicated no significant changes in detectable metabolite concentrations between DAT KO and wild-type (WT mice. In contrast, alterations in the circuitry from the prefrontal cortex to the mesocortical limbic system, an important brain component intimately tied to function of mesolimbic/mesocortical dopamine reward pathways, were revealed by manganese-enhanced MRI (MEMRI. Analysis of co-registered MEMRI images taken over the 26 hours after introduction of Mn(2+ into the prefrontal cortex indicated that DAT KO mice have a truncated Mn(2+ distribution within this circuitry with little accumulation beyond the thalamus or contralateral to the injection site. By contrast, WT littermates exhibit Mn(2+ transport into more posterior midbrain nuclei and contralateral

Generation of an activating Zn(2+) switch in the dopamine transporter

DEFF Research Database (Denmark)

Loland, Claus Juul; Norregaard, Lene; Litman, Thomas

2002-01-01

Binding of Zn(2+) to the endogenous Zn(2+) binding site in the human dopamine transporter leads to potent inhibition of [(3)H]dopamine uptake. Here we show that mutation of an intracellular tyrosine to alanine (Y335A) converts this inhibitory Zn(2+) switch into an activating Zn(2+) switch, allowing...... Zn(2+)-dependent activation of the transporter. The tyrosine is part of a conserved YXX Phi trafficking motif (X is any residue and Phi is a residue with a bulky hydrophobic group), but Y335A did not show alterations in surface targeting or protein kinase C-mediated internalization. Despite wild...... for several substrates was increased. However, the presence of Zn(2+) in micromolar concentrations increased the V(max) up to 24-fold and partially restored the apparent affinities. The capability of Zn(2+) to restore transport is consistent with a reversible, constitutive shift in the distribution...

Exploration of the dopamine transporter: in vitro and in vivo characterization of a high-affinity and high-specificity iodinated tropane derivative (E)-N-(3-iodoprop-2-enyl)-2β-carbomethoxy- 3β-(4'-methylphenyl)nortropane (PE2I)

International Nuclear Information System (INIS)

Guilloteau, Denis; Emond, Patrick; Baulieu, Jean-Louis; Garreau, Lucette; Frangin, Yves; Pourcelot, Leandre; Mauclaire, Laurent; Besnard, Jean-Claude; Chalon, Sylvie

1998-01-01

For the diagnosis and follow-up of neurodegenerative diseases, many cocaine derivatives have been proposed as radioligands to explore the dopamine transporter. As none of them have all the criteria of specificity and kinetics for human use, we have developed a new derivative, (E)-N-(3-iodoprop-2-enyl)-2β-carbomethoxy-3β-(4'-methylphenyl)nortropane (PE2I), which displays promising properties. We report the characterization of PE2I in vitro on rat striatal membranes and in vivo in rats and in monkeys. PE2I had a high affinity (Kd=0.09±0.01 nM) and high specificity for the dopamine transporter. In rats we observed a high accumulation in the striatum; by contrast, a very low fixation was measured in the cortex. Moreover, a preinjection of a saturating dose of GBR 12909 prevented the striatal accumulation of PE2I by 74%. These results confirmed the specificity of PE2I for the dopamine transporter. In vivo in monkeys, SPECT studies showed a high accumulation in striatum. Moreover, an equilibrium state was obtained 1 h after injection. PE2I seemed to be the most promising ligand for the dopamine transporter exploration by SPECT using a single-day protocol.

Imaging of dopamine transporters in rats using high-resolution pinhole single-photon emission tomography

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Booij, Jan; Bruin, Kora de; Habraken, Jan B.A. [Department of Nuclear Medicine, F2N, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam (Netherlands); Voorn, Pieter [Department of Anatomy, Vrije Universiteit Medical Center, Amsterdam (Netherlands)

2002-09-01

To date, the vast majority of investigations on the dopaminergic system in small animals have been in vitro studies. In comparison with in vitro studies, single-photon emission tomography (SPET) or positron emission tomography (PET) imaging of the dopaminergic system in small animals has the advantage of permitting repeated studies within the same group of animals. Dopamine transporter imaging is a valuable non-invasive tool with which to investigate the integrity of dopaminergic neurons. The purpose of this study was to investigate the feasibility of assessing dopamine transporter density semi-quantitatively in rats using a recently developed high-resolution pinhole SPET system. This system was built exclusively for imaging of small animals. In this unique single-pinhole system, the animal rotates instead of the collimated detector. The system has proven to have a high spatial resolution. We performed SPET imaging with [{sup 123}I]FP-CIT to quantify striatal dopamine transporters in rat brain. In all seven studied control rats, symmetrical striatal binding to dopamine transporters was seen 2 h after injection of the radiotracer, with striatal-to-cerebellar binding ratios of approximately 3.5. In addition, test/retest variability of the striatal-to-cerebellar binding ratios was studied and found to be 14.5%. Finally, in unilaterally 6-hydroxydopamine-lesioned rats, striatal binding was only visible on the non-lesioned side. Quantitative analysis revealed that striatal-to-cerebellar SPET ratios were significantly lower on the lesioned (mean binding ratio 2.2{+-}0.2) than on the non-lesioned (mean ratio 3.1{+-}0.4) side. The preliminary results of this study indicate that semi-quantitative assessment of striatal dopamine transporter density using our recently developed high-resolution single-pinhole SPET system is feasible in living rat brain. (orig.)

Persistent Drug-Induced Parkinsonism in Patients with Normal Dopamine Transporter Imaging.

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Jin Yong Hong

Full Text Available Functional neuroimaging for the dopamine transporter (DAT is used to distinguish drug-induced parkinsonism (DIP from subclinical Parkinson's disease (PD. Although DIP patients who show a normal DAT image are expected to recover completely, some do not. We investigated whether these patients showed changes in striatal DAT activity using semi-quantitative analysis of 18F-FP-CIT PET data. DIP patients with visually normal DAT images were selected from medical records. The subjects were classified as patients who recovered partially (PR or completely within 12 months (CR. The 18F-FP-CIT uptake in each striatal subregion was compared between the CR and the PR groups. In total, 41 and 9 patients of the CR and PR groups were assessed, respectively. The two patient groups were comparable in terms of clinical characteristics including age, sex, and severity of parkinsonism. From semi-quantitative analysis of the PET image, the PR patients showed a relatively lower ligand uptake in the ventral striatum, the anterior putamen and the posterior putamen compared with the CR patients. This result suggests that persistent DIP in patients with visually normal DAT imaging may be associated with subtle decrement of DAT activity.

Dopamine transporter density in the basal ganglia assessed with 123I-IPT SPECT in children with Tourette's deosoder

International Nuclear Information System (INIS)

Yoo, Y. H.; Cheon, K. A.; Yoon, M. J.; Kim, C. H.; Lee, J. D.; Kim, H. H.; Choi, T. H.

2002-01-01

Previous studies in patients with Tourette's disorder (TD) provided evidences of presynaptic dopaminergic dysfunction, demonstrating increased dopamine transporter densities. We investigated dopamine transporter densities using 123 I-IPT SPECT in drug-naive children with TD and postulated that dopamine transporter density reflected dopamine concentrations. 9 drug-naive children with ADHD and 8 normal children were included in the study. We performed brain SPECT 2 hours after administration of 123 I-IPT and made both quantitative and qualitative analyses for assessment of specific/nonspecific DAT binding ratio in the BG. We then investigated correlation between the severity of tics in children with TD assessed with the YGTSS and specific/nonspecific binding ratio on BG. Drug-naive children with TD showed a significantly increased specific/nonspecific DAT binding ratio in the BG compared with normal children. We found no significant correlation between severity of tics assessed with YGTSS in children with TD and specific/nonspecific DAT binding ratio in BG. These findings support the hypothesis of dopamine dysregulation in presynaptic dopamine function of BG being involved in pathophysiology of TD

Super-resolution microscopy reveals functional organization of dopamine transporters into cholesterol and neuronal activity-dependent nanodomains

DEFF Research Database (Denmark)

Rahbek-Clemmensen, Troels; Lycas, Matthew D.; Erlendsson, Simon

2017-01-01

is dynamically sequestrated into cholesterol-dependent nanodomains in the plasma membrane of presynaptic varicosities and neuronal projections of dopaminergic neurons. Stochastic optical reconstruction microscopy reveals irregular dopamine transporter nanodomains (∼70 nm mean diameter) that were highly sensitive...... to cholesterol depletion. Live photoactivated localization microscopy shows a similar dopamine transporter membrane organization in live heterologous cells. In neurons, dual-color dSTORM shows that tyrosine hydroxylase and vesicular monoamine transporter-2 are distinctively localized adjacent to...

Atrial Natriuretic Peptide Stimulates Dopamine Tubular Transport by Organic Cation Transporters: A Novel Mechanism to Enhance Renal Sodium Excretion

Science.gov (United States)

Kouyoumdzian, Nicolás M.; Rukavina Mikusic, Natalia L.; Kravetz, María C.; Lee, Brenda M.; Carranza, Andrea; Del Mauro, Julieta S.; Pandolfo, Marcela; Gironacci, Mariela M.; Gorzalczany, Susana; Toblli, Jorge E.; Fernández, Belisario E.

2016-01-01

The aim of this study was to demonstrate the effects of atrial natriuretic peptide (ANP) on organic cation transporters (OCTs) expression and activity, and its consequences on dopamine urinary levels, Na+, K+-ATPase activity and renal function. Male Sprague Dawley rats were infused with isotonic saline solution during 120 minutes and randomized in nine different groups: control, pargyline plus tolcapone (P+T), ANP, dopamine (DA), D-22, DA+D-22, ANP+D-22, ANP+DA and ANP+DA+D-22. Renal functional parameters were determined and urinary dopamine concentration was quantified by HPLC. Expression of OCTs and D1-receptor in membrane preparations from renal cortex tissues were determined by western blot and Na+, K+-ATPase activity was determined using in vitro enzyme assay. 3H-DA renal uptake was determined in vitro. Compared to P+T group, ANP and dopamine infusion increased diuresis, urinary sodium and dopamine excretion significantly. These effects were more pronounced in ANP+DA group and reversed by OCTs blockade by D-22, demonstrating that OCTs are implied in ANP stimulated-DA uptake and transport in renal tissues. The activity of Na+, K+-ATPase exhibited a similar fashion when it was measured in the same experimental groups. Although OCTs and D1-receptor protein expression were not modified by ANP, OCTs-dependent-dopamine tubular uptake was increased by ANP through activation of NPR-A receptor and protein kinase G as signaling pathway. This effect was reflected by an increase in urinary dopamine excretion, natriuresis, diuresis and decreased Na+, K+-ATPase activity. OCTs represent a novel target that links the activity of ANP and dopamine together in a common mechanism to enhance their natriuretic and diuretic effects. PMID:27392042

Identification of intracellular residues in the dopamine transporter critical for regulation of transporter conformation and cocaine binding

DEFF Research Database (Denmark)

Loland, Claus Juul; Grånäs, Charlotta; Javitch, Jonathan A

2004-01-01

Recently we showed evidence that mutation of Tyr-335 to Ala (Y335A) in the human dopamine transporter (hDAT) alters the conformational equilibrium of the transport cycle. Here, by substituting, one at a time, 16 different bulky or charged intracellular residues, we identify three residues, Lys-26...

[11]Cocaine: PET studies of cocaine pharmacokinetics, dopamine transporter availability and dopamine transporter occupancy

International Nuclear Information System (INIS)

Fowler, Joanna S.; Volkow, Nora D.; Wang, Gene-Jack; Gatley, S. John; Logan, Jean

2001-01-01

Cocaine was initially labeled with carbon-11 in order to track the distribution and pharmacokinetics of this powerful stimulant and drug of abuse in the human brain and body. It was soon discovered that [ 11 C]cocaine was not only useful for measuring cocaine pharmacokinetics and its relationship to behavior but that it is also a sensitive radiotracer for dopamine transporter (DAT) availability. Measures of DAT availability were facilitated by the development of a graphical analysis method (Logan Plot) for reversible systems which streamlined kinetic analysis. This expanded the applications of [ 11 C]cocaine to studies of DAT availability in the human brain and allowed the first comparative measures of the degree of DAT occupancy by cocaine and another stimulant drug methylphenidate. This article will summarize preclinical and clinical research with [ 11 C]cocaine

Dopamine Transporters in Striatum Correlate with Deactivation in the Default Mode Network during Visuospatial Attention

International Nuclear Information System (INIS)

Tomasi, D.; Fowler, J.; Tomasi, D.; Volkow, N.D.; Wang, R.L.; Telang, F.; Wang, Chang L.; Ernst, T.; Fowler, J.S.

2009-01-01

Dopamine and dopamine transporters (DAT, which regulate extracellular dopamine in the brain) are implicated in the modulation of attention but their specific roles are not well understood. Here we hypothesized that dopamine modulates attention by facilitation of brain deactivation in the default mode network (DMN). Thus, higher striatal DAT levels, which would result in an enhanced clearance of dopamine and hence weaker dopamine signals, would be associated to lower deactivation in the DMN during an attention task. For this purpose we assessed the relationship between DAT in striatum (measured with positron emission tomography and [ 11 C]cocaine used as DAT radiotracer) and brain activation and deactivation during a parametric visual attention task (measured with blood oxygenation level dependent functional magnetic resonance imaging) in healthy controls. We show that DAT availability in caudate and putamen had a negative correlation with deactivation in ventral parietal regions of the DMN (precuneus, BA 7) and a positive correlation with deactivation in a small region in the ventral anterior cingulate gyrus (BA 24/32). With increasing attentional load, DAT in caudate showed a negative correlation with load-related deactivation increases in precuneus. These findings provide evidence that dopamine transporters modulate neural activity in the DMN and anterior cingulate gyrus during visuospatial attention. Our findings suggest that dopamine modulates attention in part by regulating neuronal activity in posterior parietal cortex including precuneus (region involved in alertness) and cingulate gyrus (region deactivated in proportion to emotional interference). These findings suggest that the beneficial effects of stimulant medications (increase dopamine by blocking DAT) in inattention reflect in part their ability to facilitate the deactivation of the DMN.

DELINEATING THE MOLECULAR BASIS FOR CONSTITUTIVE INTERNALIZATION AND DEGRADATION OF THE DOPAMINE TRANSPORTER

DEFF Research Database (Denmark)

Fog, Jacob; (Vægter), Christian Bjerggaard; Gether, Ulrik

The human dopamine transporter (hDAT) was transiently expressed in N2A neuroblastoma cells. Confocal fluorescence microscopy revealed efficient surface targeting of the transporter in undifferentiated cells as well as in differentiated cells. In the differentiated cells the hDAT displayed...

Pharmacological studies of dopamine transporter imaging agent 125/131I-β-CIT

International Nuclear Information System (INIS)

Ding Shiyu; Zhou Xiang; Chen Zhengping; Wu Chunying; Lin Yansong; Ji Shuren; Lu Chunxiong; Fang Ping; Tang Jun; Wang Feng

2001-01-01

To prepare 125/131 I-β-CIT (2β-carbomethoxy-3β-(4-iodophenyl) tropane) as an imaging agent for dopamine transporter (DAT), the labelling method from tributylstannyl precursor with peracetic acid has been reported. The radiochemical purity (RCP) of the labelled compound was over 95% determined by HPLC and TLC. The stability, partition coefficients were also determined. The pharmacological studies of the imaging agent were performed in rats, mice, rabbits and normal monkey. The ligand showed preferable uptake in brain (1.9% ID/organ in rats and 4.5% ID/organ in mice at 5 min). The ratios of striatum/cerebellum, hippocampus/cerebellum and cortex/cerebellum were 28.9, 3.97 and 4.75 at 6 h in rats, and 8.52, 2.99 and 3.06 at 6 h in mice, respectively. In monkey brain imaging the ratios of striatum/frontal cortex (ST/FC) and striatum/occipital cortex (ST/OC) were 5.14 and 5.97 at 4h, respectively. All of above showed the high affinity of the ligand to DAT. The compound was primarily metabolized in liver because the hepatic uptake was much higher than other organs (75.4% ID/organ at 18h). The half-life of blood elimination was 5 min. The dose received by mice was 2500 times as high as that received by human in the test of undue toxicity, which evaluated the safety of the agent. All the results suggest that β-CIT can be used as a potential DAT imaging agent

Methamphetamine Increases Locomotion and Dopamine Transporter Activity in Dopamine D5 Receptor-Deficient Mice

OpenAIRE

Hayashizaki, Seiji; Hirai, Shinobu; Ito, Yumi; Honda, Yoshiko; Arime, Yosefu; Sora, Ichiro; Okado, Haruo; Kodama, Tohru; Takada, Masahiko

2013-01-01

Dopamine regulates the psychomotor stimulant activities of amphetamine-like substances in the brain. The effects of dopamine are mediated through five known dopamine receptor subtypes in mammals. The functional relevance of D5 dopamine receptors in the central nervous system is not well understood. To determine the functional relevance of D5 dopamine receptors, we created D5 dopamine receptor-deficient mice and then used these mice to assess the roles of D5 dopamine receptors in the behaviora...

Cocaine Self-Administration Produces Long-Lasting Alterations in Dopamine Transporter Responses to Cocaine

Science.gov (United States)

Siciliano, Cody A.; Fordahl, Steve C.

2016-01-01

Cocaine addiction is a debilitating neuropsychiatric disorder characterized by uncontrolled cocaine intake, which is thought to be driven, at least in part, by cocaine-induced deficits in dopamine system function. A decreased ability of cocaine to elevate dopamine levels has been repeatedly observed as a consequence of cocaine use in humans, and preclinical work has highlighted tolerance to cocaine's effects as a primary determinant in the development of aberrant cocaine taking behaviors. Here we determined that cocaine self-administration in rats produced tolerance to the dopamine transporter-inhibiting effects of cocaine in the nucleus accumbens core, which was normalized following a 14 or 60 d abstinence period; however, although these rats appeared to be similar to controls, a single self-administered infusion of cocaine at the end of abstinence, even after 60 d, fully reinstated tolerance to cocaine's effects. A single cocaine infusion in a naive rat had no effect on cocaine potency, demonstrating that cocaine self-administration leaves the dopamine transporter in a “primed” state, which allows for cocaine-induced plasticity to be reinstated by a subthreshold cocaine exposure. Further, reinstatement of cocaine tolerance was accompanied by decreased cocaine-induced locomotion and escalated cocaine intake despite extended abstinence from cocaine. These data demonstrate that cocaine leaves a long-lasting imprint on the dopamine system that is activated by re-exposure to cocaine. Further, these results provide a potential mechanism for severe cocaine binge episodes, which occur even after sustained abstinence from cocaine, and suggest that treatments aimed at transporter sites may be efficacious in promoting binge termination following relapse. SIGNIFICANCE STATEMENT Tolerance is a DSM-V criterion for substance abuse disorders. Abusers consistently show reduced subjective effects of cocaine concomitant with reduced effects of cocaine at its main site of action

Structure-Guided Screening for Functionally Selective D2 Dopamine Receptor Ligands from a Virtual Chemical Library.

Science.gov (United States)

Männel, Barbara; Jaiteh, Mariama; Zeifman, Alexey; Randakova, Alena; Möller, Dorothee; Hübner, Harald; Gmeiner, Peter; Carlsson, Jens

2017-10-20

Functionally selective ligands stabilize conformations of G protein-coupled receptors (GPCRs) that induce a preference for signaling via a subset of the intracellular pathways activated by the endogenous agonists. The possibility to fine-tune the functional activity of a receptor provides opportunities to develop drugs that selectively signal via pathways associated with a therapeutic effect and avoid those causing side effects. Animal studies have indicated that ligands displaying functional selectivity at the D 2 dopamine receptor (D 2 R) could be safer and more efficacious drugs against neuropsychiatric diseases. In this work, computational design of functionally selective D 2 R ligands was explored using structure-based virtual screening. Molecular docking of known functionally selective ligands to a D 2 R homology model indicated that such compounds were anchored by interactions with the orthosteric site and extended into a common secondary pocket. A tailored virtual library with close to 13 000 compounds bearing 2,3-dichlorophenylpiperazine, a privileged orthosteric scaffold, connected to diverse chemical moieties via a linker was docked to the D 2 R model. Eighteen top-ranked compounds that occupied both the orthosteric and allosteric site were synthesized, leading to the discovery of 16 partial agonists. A majority of the ligands had comparable maximum effects in the G protein and β-arrestin recruitment assays, but a subset displayed preference for a single pathway. In particular, compound 4 stimulated β-arrestin recruitment (EC 50 = 320 nM, E max = 16%) but had no detectable G protein signaling. The use of structure-based screening and virtual libraries to discover GPCR ligands with tailored functional properties will be discussed.

Reversible Dopamine Transporter Modifications in Response to Methylphenidate Treatment of ADHD

Directory of Open Access Journals (Sweden)

J Gordon Millichap

2005-09-01

Full Text Available Single-photon emission computed tomography (SPECT was used to monitor the dopamine transporter activity in 5 males, ages 8 to 10, with ADHD, after cessation of methylphenidate (MPH treatment, in a study at the University Hospital Maastricht, The Netherlands.

Measuring dopamine release in the human brain with PET

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Volkow, N.D. [Brookhaven National Lab., Upton, NY (United States)]|[State Univ. of New York at Stony Brook, Stony Brook, NY (United States). Dept. of Psychiatry; Fowler, J.S.; Logan, J.; Wang, G.J. [Brookhaven National Lab., Upton, NY (United States)

1995-12-01

The dopamine system is involved in the regulation of brain regions that subserve motor, cognitive and motivational behaviors. Disruptions of dopamine (DA) function have ben implicated in neurological and psychiatric illnesses including substance abuse as well as on some of the deficits associated with aging of the human brain. This has made the DA system an important topic in research in the neurosciences and neuroimaging as well as an important molecular target for drug development. Positron Emission Tomography (PET), was the first technology that enabled direct measurement of components of the DA system in the living human brain. Imaging studies of DA in the living brain have been indirect, relying on the development of radiotracers to label DA receptors, DA transporters, compounds which have specificity for the enzymes which degrade synaptic DA. Additionally, through the use of tracers that provide information on regional brain activity (ie brain glucose metabolism and cerebral blood flow) and of appropriate pharmacological interventions, it has been possible to assess the functional consequences of changes in brain DA activity. DA specific ligands have been useful in the evaluation of patients with neuropsychiatric illnesses as well as to investigate receptor blockade by antipsychotic drugs. A limitation of strategies that rely on the use of DA specific ligands is that the measures do not necessarily reflect the functional state of the dopaminergic system and that there use to study the effects of drugs is limited to the investigation of receptor or transporter occupancy. Newer strategies have been developed in an attempt to provide with information on dopamine release and on the functional responsivity of the DA system in the human brain. This in turn allows to investigate the effects of pharmacological agent in an analogous way to what is done with microdialysis techniques.

Dopamine transporter polymorphism modulates oculomotor function and DAT1 mRNA expression in schizophrenia.

Science.gov (United States)

Wonodi, Ikwunga; Hong, L Elliot; Stine, O Colin; Mitchell, Braxton D; Elliott, Amie; Roberts, Rosalinda C; Conley, Robert R; McMahon, Robert P; Thaker, Gunvant K

2009-03-05

Smooth pursuit eye movement (SPEM) deficit is an established schizophrenia endophenotype with a similar neurocognitive construct to working memory. Frontal eye field (FEF) neurons controlling SPEM maintain firing when visual sensory information is removed, and their firing rates directly correlate with SPEM velocity. We previously demonstrated a paradoxical association between a functional polymorphism of dopamine signaling (COMT gene) and SPEM. Recent evidence implicates the dopamine transporter gene (DAT1) in modulating cortical dopamine and associated neurocognitive functions. We hypothesized that DAT1 10/10 genotype, which reduces dopamine transporter expression and increases extracellular dopamine, would affect SPEM. We examined the effects of DAT1 genotype on: Clinical diagnosis in the study sample (n = 418; 190 with schizophrenia), SPEM measures in a subgroup with completed oculomotor measures (n = 200; 87 schizophrenia), and DAT1 gene expression in FEF tissue obtained from postmortem brain samples (n = 32; 16 schizophrenia). DAT1 genotype was not associated with schizophrenia. DAT1 10/10 genotype was associated with better SPEM in healthy controls, intermediate SPEM in unaffected first-degree relatives of schizophrenia subjects, and worse SPEM in schizophrenia subjects. In the gene expression study, DAT1 10/10 genotype was associated with significantly reduced DAT1 mRNA transcript in FEF tissue from healthy control donors (P < 0.05), but higher expression in schizophrenia donors. Findings suggest regulatory effects of another gene(s) or etiological factor in schizophrenia, which modulate DAT1 gene function. 2008 Wiley-Liss, Inc.

Effects of Acute and Chronic Treatments with Dopamine D2 and D3 Receptor Ligands on Cocaine versus Food Choice in Rats.

Science.gov (United States)

Thomsen, Morgane; Barrett, Andrew C; Butler, Paul; Negus, S Stevens; Caine, S Barak

2017-07-01

Dopamine D 3 receptor ligands are potential medications for psychostimulant addiction. Medication assessment may benefit from preclinical studies that evaluate chronic medication effects on choice between an abused drug and an alternative, nondrug reinforcer. This study compared acute and chronic effects of dopamine D 2 - and D 3 -preferring ligands on choice between intravenous cocaine and palatable food in rats. Under baseline conditions, cocaine maintained dose-dependent increases in cocaine choice and reciprocal decreases in food choice. Acutely, the D 2 agonist R -(-)-norpropylapomorphine (NPA) and antagonist L-741,626 [3-[[4-(4-chlorophenyl)-4-hydroxypiperidin-l-yl]methyl-1 H -indole] produced leftward and rightward shifts in cocaine dose-effect curves, respectively, whereas the partial agonist terguride had no effect. All three drugs dose-dependently decreased food-maintained responding. Chronically, the effects of R -(-)-norpropylapomorphine and L-741,626 on cocaine self-administration showed marked tolerance, whereas suppression of food-reinforced behavior persisted. Acute effects of the D 3 ligands were less systematic and most consistent with nonselective decreases in cocaine- and food-maintained responding. Chronically, the D 3 agonist PF-592,379 [5-[(2 R ,5 S )-5-methyl-4-propylmorpholin-2-yl]pyridin-2-amine] increased cocaine choice, whereas an intermediate dose of the D 3 antagonist PG01037 [ N -[( E )-4-[4-(2,3-dichlorophenyl)piperazin-1-yl]but-2-enyl]-4-pyridin-2-ylbenzamide] produced a therapeutically desirable decrease in cocaine choice early in treatment; however, tolerance to this effect developed, and lower and higher doses were ineffective. D 3 ligands failed to significantly modify total cocaine intake but caused persistent decreases in food intake. Thus, D 2 -and D 3 -preferring ligands showed distinct profiles, consistent with different pharmacological actions. In addition, these results highlight the role of acute versus chronic treatment

Dopamine transporter density in the basal ganglia assessed with {sup 123}I-IPT SPECT in children with Tourette's deosoder

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Yoo, Y. H.; Cheon, K. A.; Yoon, M. J.; Kim, C. H.; Lee, J. D. [Yonsei University College of Medicine, Seoul (Korea, Republic of); Kim, H. H.; Choi, T. H. [Gachon Medical School, Incheon (Korea, Republic of)

2002-07-01

Previous studies in patients with Tourette's disorder (TD) provided evidences of presynaptic dopaminergic dysfunction, demonstrating increased dopamine transporter densities. We investigated dopamine transporter densities using {sup 123}I-IPT SPECT in drug-naive children with TD and postulated that dopamine transporter density reflected dopamine concentrations. 9 drug-naive children with ADHD and 8 normal children were included in the study. We performed brain SPECT 2 hours after administration of {sup 123}I-IPT and made both quantitative and qualitative analyses for assessment of specific/nonspecific DAT binding ratio in the BG. We then investigated correlation between the severity of tics in children with TD assessed with the YGTSS and specific/nonspecific binding ratio on BG. Drug-naive children with TD showed a significantly increased specific/nonspecific DAT binding ratio in the BG compared with normal children. We found no significant correlation between severity of tics assessed with YGTSS in children with TD and specific/nonspecific DAT binding ratio in BG. These findings support the hypothesis of dopamine dysregulation in presynaptic dopamine function of BG being involved in pathophysiology of TD.

Atypical dopamine transporter inhibitors R-modafinil and JHW 007 differentially affect D2 autoreceptor neurotransmission and the firing rate of midbrain dopamine neurons.

Science.gov (United States)

Avelar, Alicia J; Cao, Jianjing; Newman, Amy Hauck; Beckstead, Michael J

2017-09-01

Abuse of psychostimulants like cocaine that inhibit dopamine (DA) reuptake through the dopamine transporter (DAT) represents a major public health issue, however FDA-approved pharmacotherapies have yet to be developed. Recently a class of ligands termed "atypical DAT inhibitors" has gained attention due to their range of effectiveness in increasing extracellular DA levels without demonstrating significant abuse liability. These compounds not only hold promise as therapeutic agents to treat stimulant use disorders but also as experimental tools to improve our understanding of DAT function. Here we used patch clamp electrophysiology in mouse brain slices to explore the effects of two atypical DAT inhibitors (R-modafinil and JHW 007) on the physiology of single DA neurons in the substantia nigra and ventral tegmental area. Despite their commonalities of being DAT inhibitors that lack cocaine-like behavioral profiles, these compounds exhibited surprisingly divergent cellular effects. Similar to cocaine, R-modafinil slowed DA neuron firing in a D2 receptor-dependent manner and rapidly enhanced the amplitude and duration of D2 receptor-mediated currents in the midbrain. In contrast, JHW 007 exhibited little effect on firing, slow DAT blockade, and an unexpected inhibition of D2 receptor-mediated currents that may be due to direct D2 receptor antagonism. Furthermore, pretreatment with JHW 007 blunted the cellular effects of cocaine, suggesting that it may be valuable to investigate similar DAT inhibitors as potential therapeutic agents. Further exploration of these and other atypical DAT inhibitors may reveal important cellular effects of compounds that will have potential as pharmacotherapies for treating cocaine use disorders. Copyright © 2017 Elsevier Ltd. All rights reserved.

Equipment-independent reference values for dopamine transporter imaging with 123I-FP-CIT

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Koch, W.; Hornung, J.; Poepperl, G.; Tatsch, K.; Hamann, C.

2007-01-01

Aim: Reliable reference values are helpful to interpret and compare the results of dopamine transporter imaging with SPECT. Since semi-quantitative reference values cannot be easily transferred between imaging equipments, this study aimed to establish equipment independent normal values for the true striatal binding of 123 I-FP-CIT. Patients, methods: Specific striatal FP-CIT binding of 6 healthy volunteers and 26 patients with essential tremor were used to generate a reference range by applying an equipment specific resolution dependent factor to compensate for recovery effects. This factor has been determined previously by a series of standardized phantom measurements of an anthropomorphic basal ganglia phantom. Herewith, the resulting DAT binding values represent the expected true specific binding in the striatum. Results: On average, true specific striatal binding was 5.83 ± 0.96 in healthy controls, 5.25 ± 0.67 in patients with essential tremor and 5.36 ± 0.75 in the entire study cohort. Conclusion: These preliminary results may serve as a basis for the generation of a generally accepted equipment independent reference range for dopamine transporter imaging with 123 I-FP-CIT. By a simple phantom measurement that can be accomplished within one day factors related to specific imaging equipment and processing can be corrected for, resulting in specific binding values which may enable a more standardized interpretation of dopamine transporter scans. (orig.)

Development of molecular tools based on the dopamine D3 receptor ligand FAUC 329 showing inhibiting effects on drug and food maintained behavior.

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Stößel, Anne; Brox, Regine; Purkayastha, Nirupam; Hübner, Harald; Hocke, Carsten; Prante, Olaf; Gmeiner, Peter

2017-07-01

Dopamine D 3 receptor-mediated networks have been associated with a wide range of neuropsychiatric diseases, drug addiction and food maintained behavior, which makes D 3 a highly promising biological target. The previously described dopamine D 3 receptor ligand FAUC 329 (1) showed protective effects against dopamine depletion in a MPTP mouse model of Parkinson's disease. We used the radioligand [ 18 F]2, a [ 18 F]fluoroethoxy substituted analog of the lead compound 1 as a molecular tool for visualization of D 3 -rich brain regions including the islands of Calleja. Furthermore, structural modifications are reported leading to the pyrimidylpiperazine derivatives 3 and 9 displaying superior subtype selectivity and preference over serotonergic receptors. Evaluation of the lead compound 1 on cocaine-seeking behavior in non-human primates showed a substantial reduction in cocaine self-administration behavior and food intake. Copyright © 2017 Elsevier Ltd. All rights reserved.

Altered effect of dopamine transporter 3'UTR VNTR genotype on prefrontal and striatal function in schizophrenia.

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Prata, Diana P; Mechelli, Andrea; Picchioni, Marco M; Fu, Cynthia H Y; Toulopoulou, Timothea; Bramon, Elvira; Walshe, Muriel; Murray, Robin M; Collier, David A; McGuire, Philip

2009-11-01

The dopamine transporter plays a key role in the regulation of central dopaminergic transmission, which modulates cognitive processing. Disrupted dopamine function and impaired executive processing are robust features of schizophrenia. To examine the effect of a polymorphism in the dopamine transporter gene (the variable number of tandem repeats in the 3' untranslated region) on brain function during executive processing in healthy volunteers and patients with schizophrenia. We hypothesized that this variation would have a different effect on prefrontal and striatal activation in schizophrenia, reflecting altered dopamine function. Case-control study. Psychiatric research center. Eighty-five subjects, comprising 44 healthy volunteers (18 who were 9-repeat carriers and 26 who were 10-repeat homozygotes) and 41 patients with DSM-IV schizophrenia (18 who were 9-repeat carriers and 23 who were 10-repeat homozygotes). Regional brain activation during word generation relative to repetition in an overt verbal fluency task measured by functional magnetic resonance imaging. Main effects of genotype and diagnosis on activation and their interaction were estimated with analysis of variance in SPM5. Irrespective of diagnosis, the 10-repeat allele was associated with greater activation than the 9-repeat allele in the left anterior insula and right caudate nucleus. Trends for the same effect in the right insula and for greater deactivation in the rostral anterior cingulate cortex were also detected. There were diagnosis x genotype interactions in the left middle frontal gyrus and left nucleus accumbens, where the 9-repeat allele was associated with greater activation than the 10-repeat allele in patients but not controls. Insular, cingulate, and striatal function during an executive task is normally modulated by variation in the dopamine transporter gene. Its effect on activation in the dorsolateral prefrontal cortex and ventral striatum is altered in patients with schizophrenia

Imaging of striatal dopamine transporters in rat brain with single pinhole SPECT and co-aligned MRI is highly reproducible

International Nuclear Information System (INIS)

Booij, Jan; Bruin, Kora de; Win, Maartje M.L. de; Lavini, Cristina Mphil; Heeten, Gerard J. den; Habraken, Jan

2003-01-01

A recently developed pinhole high-resolution SPECT system was used to measure striatal to non-specific binding ratios in rats (n = 9), after injection of the dopamine transporter ligand 123 I-FP-CIT, and to assess its test/retest reproducibility. For co-alignment purposes, the rat brain was imaged on a 1.5 Tesla clinical MRI scanner using a specially developed surface coil. The SPECT images showed clear striatal uptake. On the MR images, cerebral and extra-cerebral structures could be easily delineated. The mean striatal to non-specific [ 123 I]FP-CIT binding ratios of the test/retest studies were 1.7 ± 0.2 and 1.6 ± 0.2, respectively. The test/retest variability was approximately 9%. We conclude that the assessment of striatal [ 123 I]FP-CIT binding ratios in rats is highly reproducible

Acute administration of haloperidol does not influence 123I-FP-CIT binding to the dopamine transporter

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Booij, Jan; van Loon, Guus; de Bruin, Kora; Voorn, Pieter

2014-01-01

A recent (123)I-FP-CIT ((123)-I-N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane) SPECT study on rats suggested that a single 1 mg/kg dose of the antipsychotic haloperidol induces enough dopamine release to compete with (123)I-FP-CIT for binding to the dopamine transporter. Taking into

Inhibition by sigma receptor ligand, MS-377, of N-methyl- D-aspartate-induced currents in dopamine neurons of the rat ventral tegmental area.

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Yamazaki, Yuu; Ishioka, Miwa; Matsubayashi, Hiroaki; Amano, Taku; Sasa, Masashi

2002-04-01

MS-377 [( R)-(+)-1-(4-chlorophenyl)-3-[4-(2-methoxyethyl) piperazin-1-yl]methyl-2-pyrrolidinone L-tartrate] is a novel anti-psychotic drug candidate with high affinity for sigma receptors but devoid of binding affinity for PCP binding site of NMDA receptor/ion channel complex. The effects of MS-377 on NMDA receptor and/or its ion channel complex were examined to elucidate the antipsychotic properties of MS-377. We examined the effect of MS-377 on NMDA ( N-methyl- D-aspartate)-induced current in acutely dissociated dopamine neurons of rat ventral tegmental area (VTA) using patch clamp whole cell recording. MS-377 applied in a bath inhibited the peak current evoked by NMDA applied via the U-tube method for 2 s in a concentration-dependent manner. Other sigma receptor ligands, BD-1063 (1-[2-(3,4-dichlorophenyl)ethyl]-4-methylpiperazine), NE-100 ( N, N-dipropyl-2-[4-methoxy-3-(2-phenylenoxy)-phenyl]-ethylamine monohydrochloride) and haloperidol also inhibited NMDA-induced current in a concentration-dependent manner. Interestingly, concomitant application of MS-377 with BD-1063, NE-100 or haloperidol at concentrations that had no effects on NMDA-induced current, potentiated the MS-377-induced inhibition. The results suggest that MS-377, as well as other sigma receptor ligands, indirectly acts on the sigma receptor to inhibit glutaminergic transmission mediated by NMDA receptor/ion channel complex in VTA dopamine neurons, thereby inhibiting dopamine release in target VTA areas.

A novel serotonin transporter ligand: (5-Iodo-2-(2-dimethylaminomethylphenoxy)-benzyl alcohol

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Zhuang, Z.-P.; Choi, S.-R.; Hou, Catherine; Mu Mu; Kung, M.-P. E-mail: kunghf@sunmac.spect.upenn.edu; Acton, Paul D.; Kung, Hank F

2000-02-01

The serotonin transporters (SERT) are the primary binding sites for selective serotonin reuptake inhibitors, commonly used antidepressants such as fluoxetine, sertraline, and paroxetine. Imaging of SERT with positron emission tomography and single photon emission computed tomography in humans would provide a useful tool for understanding how alterations of this system are related to depressive illnesses and other psychiatric disorders. In this article the synthesis and characterization of [{sup 125}I]ODAM [(5-iodo-2-(2-dimethylaminomethylphenoxy)-benzyl alcohol, 9)] as an imaging agent in the evaluation of central nervous system SERT are reported. A new reaction scheme was developed for the preparation of compound 9, ODAM, and the corresponding tri-n-butyltin derivative 10. Upon reacting 10 with hydrogen peroxide and sodium[{sup 125}I]iodide, the radiolabeled [{sup 125}I]9 was obtained in good yield (94% yield, radiochemical purity >95%). In an initial binding study using cortical membrane homogenates of rat brain, ODAM displayed a good binding affinity with a value of K{sub i}=2.8{+-}0.88 nM. Using LLC-PK{sub 1} cells specifically expressing the individual transporter (i.e. dopamine [DAT], norepinephrine [NET], and SERT, respectively), ODAM showed a strong inhibition on SERT (K{sub i}=0.12{+-}0.02 nM). Inhibition constants for the other two transporters were lower (K{sub i}=3.9{+-}0.7 {mu}M and 20.0 {+-} 1.9 nM for DAT and NET, respectively). Initial biodistribution study in rats after an intravenous (IV) injection of [{sup 125}I]ODAM showed a rapid brain uptake and washout (2.03, 1.49, 0.79, 0.27, and 0.07% dose/organ at 2, 30, 60, 120, and 240 min, respectively). The hypothalamus region where the serotonin neurons are located exhibited a high specific uptake. Ratios of hypothalamus-cerebellum/cerebellum based on percent dose per gram of these two regions showed values of 0.35, 0.86, 0.86, 0.63, and 0.34 at 2, 30, 60, 120, and 240 min, post-IV injection

A novel serotonin transporter ligand: (5-Iodo-2-(2-dimethylaminomethylphenoxy)-benzyl alcohol

International Nuclear Information System (INIS)

Zhuang, Z.-P.; Choi, S.-R.; Hou, Catherine; Mu Mu; Kung, M.-P.; Acton, Paul D.; Kung, Hank F.

2000-01-01

The serotonin transporters (SERT) are the primary binding sites for selective serotonin reuptake inhibitors, commonly used antidepressants such as fluoxetine, sertraline, and paroxetine. Imaging of SERT with positron emission tomography and single photon emission computed tomography in humans would provide a useful tool for understanding how alterations of this system are related to depressive illnesses and other psychiatric disorders. In this article the synthesis and characterization of [ 125 I]ODAM [(5-iodo-2-(2-dimethylaminomethylphenoxy)-benzyl alcohol, 9)] as an imaging agent in the evaluation of central nervous system SERT are reported. A new reaction scheme was developed for the preparation of compound 9, ODAM, and the corresponding tri-n-butyltin derivative 10. Upon reacting 10 with hydrogen peroxide and sodium[ 125 I]iodide, the radiolabeled [ 125 I]9 was obtained in good yield (94% yield, radiochemical purity >95%). In an initial binding study using cortical membrane homogenates of rat brain, ODAM displayed a good binding affinity with a value of K i =2.8±0.88 nM. Using LLC-PK 1 cells specifically expressing the individual transporter (i.e. dopamine [DAT], norepinephrine [NET], and SERT, respectively), ODAM showed a strong inhibition on SERT (K i =0.12±0.02 nM). Inhibition constants for the other two transporters were lower (K i =3.9±0.7 μM and 20.0 ± 1.9 nM for DAT and NET, respectively). Initial biodistribution study in rats after an intravenous (IV) injection of [ 125 I]ODAM showed a rapid brain uptake and washout (2.03, 1.49, 0.79, 0.27, and 0.07% dose/organ at 2, 30, 60, 120, and 240 min, respectively). The hypothalamus region where the serotonin neurons are located exhibited a high specific uptake. Ratios of hypothalamus-cerebellum/cerebellum based on percent dose per gram of these two regions showed values of 0.35, 0.86, 0.86, 0.63, and 0.34 at 2, 30, 60, 120, and 240 min, post-IV injection, respectively. The specific uptake in hypothalamus

Insertion of tetracysteine motifs into dopamine transporter extracellular domains.

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Deanna M Navaroli

Full Text Available The neuronal dopamine transporter (DAT is a major determinant of extracellular dopamine (DA levels and is the primary target for a variety of addictive and therapeutic psychoactive drugs. DAT is acutely regulated by protein kinase C (PKC activation and amphetamine exposure, both of which modulate DAT surface expression by endocytic trafficking. In order to use live imaging approaches to study DAT endocytosis, methods are needed to exclusively label the DAT surface pool. The use of membrane impermeant, sulfonated biarsenic dyes holds potential as one such approach, and requires introduction of an extracellular tetracysteine motif (tetraCys; CCPGCC to facilitate dye binding. In the current study, we took advantage of intrinsic proline-glycine (Pro-Gly dipeptides encoded in predicted DAT extracellular domains to introduce tetraCys motifs into DAT extracellular loops 2, 3, and 4. [(3H]DA uptake studies, surface biotinylation and fluorescence microscopy in PC12 cells indicate that tetraCys insertion into the DAT second extracellular loop results in a functional transporter that maintains PKC-mediated downregulation. Introduction of tetraCys into extracellular loops 3 and 4 yielded DATs with severely compromised function that failed to mature and traffic to the cell surface. This is the first demonstration of successful introduction of a tetracysteine motif into a DAT extracellular domain, and may hold promise for use of biarsenic dyes in live DAT imaging studies.

[123I]Iodobenzamide binding to the rat dopamine D2 receptor in competition with haloperidol and endogenous dopamine - an in vivo imaging study with a dedicated small animal SPECT

International Nuclear Information System (INIS)

Nikolaus, Susanne; Larisch, Rolf; Wirrwar, Andreas; Jamdjeu-Noune, Marlyse; Antke, Christina; Beu, Markus; Mueller, Hans-Wilhelm; Schramm, Nils

2005-01-01

This study assessed [ 123 I]iodobenzamide binding to the rat dopamine D 2 receptor in competition with haloperidol and endogenous dopamine using a high-resolution small animal SPECT. Subsequent to baseline quantifications of D 2 receptor binding, imaging studies were performed on the same animals after pre-treatment with haloperidol and methylphenidate, which block D 2 receptors and dopamine transporters, respectively. Striatal baseline equilibrium ratios (V 3 '' ) of [ 123 I]iodobenzamide binding were 1.42±0.31 (mean±SD). After pre-treatment with haloperidol and methylphenidate, V 3 '' values decreased to 0.54±0.46 (p 123 I]iodobenzamide binding induced by pre-treatment with haloperidol reflects D 2 receptor blockade, whereas the decrease in receptor binding induced by pre-treatment with methylphenidate can be interpreted in terms of competition between [ 123 I]IBZM and endogenous dopamine. Findings show that multiple in vivo measurements of [ 123 I]iodobenzamide binding to D 2 receptors in competition with exogenous and endogenous ligands are feasible in the same animal. This may be of future relevance for the in vivo evaluation of novel radioligands as well as for studying the interrelations between pre- and/or postsynaptic radioligand binding and different levels of endogenous dopamine. (orig.)

Development of 7TM receptor-ligand complex models using ligand-biased, semi-empirical helix-bundle repacking in torsion space: application to the agonist interaction of the human dopamine D2 receptor.

Science.gov (United States)

Malo, Marcus; Persson, Ronnie; Svensson, Peder; Luthman, Kristina; Brive, Lars

2013-03-01

Prediction of 3D structures of membrane proteins, and of G-protein coupled receptors (GPCRs) in particular, is motivated by their importance in biological systems and the difficulties associated with experimental structure determination. In the present study, a novel method for the prediction of 3D structures of the membrane-embedded region of helical membrane proteins is presented. A large pool of candidate models are produced by repacking of the helices of a homology model using Monte Carlo sampling in torsion space, followed by ranking based on their geometric and ligand-binding properties. The trajectory is directed by weak initial restraints to orient helices towards the original model to improve computation efficiency, and by a ligand to guide the receptor towards a chosen conformational state. The method was validated by construction of the β1 adrenergic receptor model in complex with (S)-cyanopindolol using bovine rhodopsin as template. In addition, models of the dopamine D2 receptor were produced with the selective and rigid agonist (R)-N-propylapomorphine ((R)-NPA) present. A second quality assessment was implemented by evaluating the results from docking of a library of 29 ligands with known activity, which further discriminated between receptor models. Agonist binding and recognition by the dopamine D2 receptor is interpreted using the 3D structure model resulting from the approach. This method has a potential for modeling of all types of helical transmembrane proteins for which a structural template with sequence homology sufficient for homology modeling is not available or is in an incorrect conformational state, but for which sufficient empirical information is accessible.

Brain dopamine-serotonin vesicular transport disease presenting as a severe infantile hypotonic parkinsonian disorder.

Science.gov (United States)

Jacobsen, Jessie C; Wilson, Callum; Cunningham, Vicki; Glamuzina, Emma; Prosser, Debra O; Love, Donald R; Burgess, Trent; Taylor, Juliet; Swan, Brendan; Hill, Rosamund; Robertson, Stephen P; Snell, Russell G; Lehnert, Klaus

2016-03-01

Two male siblings from a consanguineous union presented in early infancy with marked truncal hypotonia, a general paucity of movement, extrapyramidal signs and cognitive delay. By mid-childhood they had made little developmental progress and remained severely hypotonic and bradykinetic. They developed epilepsy and had problems with autonomic dysfunction and oculogyric crises. They had a number of orthopaedic problems secondary to their hypotonia. Cerebrospinal fluid (CSF) neurotransmitters were initially normal, apart from mildly elevated 5-hydroxyindolacetic acid, and the children did not respond favourably to a trial of levodopa-carbidopa. The youngest died from respiratory complications at 10 years of age. Repeat CSF neurotransmitters in the older sibling at eight years of age showed slightly low homovanillic acid and 5-hydroxyindoleacetic acid levels. Whole-exome sequencing revealed a novel mutation homozygous in both children in the monoamine transporter gene SLC18A2 (p.Pro237His), resulting in brain dopamine-serotonin vesicular transport disease. This is the second family to be described with a mutation in this gene. Treatment with the dopamine agonist pramipexole in the surviving child resulted in mild improvements in alertness, communication, and eye movements. This case supports the identification of the causal mutation in the original case, expands the clinical phenotype of brain dopamine-serotonin vesicular transport disease and confirms that pramipexole treatment may lead to symptomatic improvement in affected individuals.

Development of specific dopamine D-1 agonists and antagonists

International Nuclear Information System (INIS)

Sakolchai, S.

1987-01-01

To develop potentially selective dopamine D-1 agonists and to investigate on the structural requirement for D-1 activity, the derivatives of dibenzocycloheptadiene are synthesized and pharmacologically evaluated. The target compounds are 5-aminomethyl-10,11-dihydro-1,2-dihydroxy-5H-dibenzo[a,d]cycloheptene hydrobromide 10 and 9,10-dihydroxy-1,2,3,7,8,12b-hexahydrobenzo[1,2]cyclohepta[3,4,5d,e]isoquinoline hydrobromide 11. In a dopamine-sensitive rat retinal adenylate cyclase assay, a model for D-1 activity, compound 10 is essentially inert for both agonist and antagonist activity. In contrast, compound 11 is approximately equipotent to dopamine in activation of the D-1 receptor. Based on radioligand and binding data, IC 50 of compound 11 for displacement of 3 H-SCH 23390, a D-1 ligand, is about 7 fold less than that for displacement of 3 H-spiperone, a D-2 ligand. These data indicate that compound 11 is a potent selective dopamine D-1 agonist. This study provides a new structural class of dopamine D-1 acting agent: dihydroxy-benzocycloheptadiene analog which can serve as a lead compound for further drug development and as a probe for investigation on the nature of dopamine D-1 receptor

Dopamine receptors in human gastrointestinal mucosa

International Nuclear Information System (INIS)

Hernandez, D.E.; Mason, G.A.; Walker, C.H.; Valenzuela, J.E.

1987-01-01

Dopamine is a putative enteric neurotransmitter that has been implicated in exocrine secretory and motility functions of the gastrointestinal tract of several mammalian species including man. This study was designed to determine the presence of dopamine binding sites in human gastric and duodenal mucosa and to describe certain biochemical characteristics of these enteric receptor sites. The binding assay was performed in triplicate with tissue homogenates obtained from healthy volunteers of both sexes using 3 H-dopamine as a ligand. The extent of nonspecific binding was determined in the presence of a 100-fold excess of unlabeled dopamine. Scatchard analysis performed with increasing concentrations of 3 H-dopamine (20-500 nM) revealed a single class of saturable dopamine binding sites in gastric and duodenal mucosa. The results of this report demonstrate the presence of specific dopamine receptors in human gastric and duodenal mucosa. These biochemical data suggest that molecular abnormalities of these receptor sites may be operative in the pathogenesis of important gastrointestinal disorders. 33 references, 2 figures

The sigma-1 receptor modulates dopamine transporter conformation and cocaine binding and may thereby potentiate cocaine self-administration in rats.

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Hong, Weimin Conrad; Yano, Hideaki; Hiranita, Takato; Chin, Frederick T; McCurdy, Christopher R; Su, Tsung-Ping; Amara, Susan G; Katz, Jonathan L

2017-07-07

The dopamine transporter (DAT) regulates dopamine (DA) neurotransmission by recapturing DA into the presynaptic terminals and is a principal target of the psychostimulant cocaine. The sigma-1 receptor (σ 1 R) is a molecular chaperone, and its ligands have been shown to modulate DA neuronal signaling, although their effects on DAT activity are unclear. Here, we report that the prototypical σ 1 R agonist (+)-pentazocine potentiated the dose response of cocaine self-administration in rats, consistent with the effects of the σR agonists PRE-084 and DTG (1,3-di- o -tolylguanidine) reported previously. These behavioral effects appeared to be correlated with functional changes of DAT. Preincubation with (+)-pentazocine or PRE-084 increased the B max values of [ 3 H]WIN35428 binding to DAT in rat striatal synaptosomes and transfected cells. A specific interaction between σ 1 R and DAT was detected by co-immunoprecipitation and bioluminescence resonance energy transfer assays. Mutational analyses indicated that the transmembrane domain of σ 1 R likely mediated this interaction. Furthermore, cysteine accessibility assays showed that σ 1 R agonist preincubation potentiated cocaine-induced changes in DAT conformation, which were blocked by the specific σ 1 R antagonist CM304. Moreover, σ 1 R ligands had distinct effects on σ 1 R multimerization. CM304 increased the proportion of multimeric σ 1 Rs, whereas (+)-pentazocine increased monomeric σ 1 Rs. Together these results support the hypothesis that σ 1 R agonists promote dissociation of σ 1 R multimers into monomers, which then interact with DAT to stabilize an outward-facing DAT conformation and enhance cocaine binding. We propose that this novel molecular mechanism underlies the behavioral potentiation of cocaine self-administration by σ 1 R agonists in animal models. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Molecular dynamics of conformation-specific dopamine transporter-inhibitor complexes.

Science.gov (United States)

Jean, Bernandie; Surratt, Christopher K; Madura, Jeffry D

2017-09-01

The recreational psychostimulant cocaine inhibits dopamine reuptake from the synapse, resulting in excessive stimulation of postsynaptic dopamine receptors in brain areas associated with reward and addiction. Cocaine binds to and stabilizes the outward- (extracellular-) facing conformation of the dopamine transporter (DAT) protein, while the low abuse potential DAT inhibitor benztropine prefers the inward- (cytoplasmic-) facing conformation. A correlation has been previously postulated between psychostimulant abuse potential and preference for the outward-facing DAT conformation. The 3β-aryltropane cocaine analogs LX10 and LX11, however, differ only in stereochemistry and share a preference for the outward-facing DAT, yet are reported to vary widely in abuse potential in an animal model. In search of the molecular basis for DAT conformation preference, complexes of cocaine, benztropine, LX10 or LX11 bound to each DAT conformation were subjected to 100ns of all-atom molecular dynamics simulation. Results were consistent with previous findings from cysteine accessibility assays used to assess an inhibitor's DAT conformation preference. The respective 2β- and 2α-substituted phenyltropanes of LX10 and LX11 interacted with hydrophobic regions of the DAT S1 binding site that were inaccessible to cocaine. Solvent accessibility measurements also revealed subtle differences in inhibitor positioning within a given DAT conformation. This work serves to advance our understanding of the conformational selectivity of DAT inhibitors and suggests that MD may be useful in antipsychostimulant therapeutic design. Copyright © 2017 Elsevier Inc. All rights reserved.

5-Chloro-2-(2'-((dimethylamino)methyl)-4'-iodophenylthio)benzenamine: a new serotonin transporter ligand

International Nuclear Information System (INIS)

Oya, Shunichi; Choi, Seok-Rye; Kung, Mei-Ping; Kung, Hank F.

2007-01-01

Two novel ligands with 4' substitution on the Phenyl Ring B of biphenylthiol, 5-chloro-2-(2'-((dimethylamino)methyl)-4'-iodophenylthio)benzenamine (7) and 2-(2'-((dimethylamino)methyl)-4'-methoxyphenylthio)-5-iodobenzenamine (8), were prepared and tested as potential serotonin transporter (SERT) imaging agents. The new ligands displayed extremely high binding affinities to SERT (K i =0.22±0.09 and 0.11±0.04 nM, respectively), with very low binding affinities to dopamine and norepinephrine transporters (K i >1000 nM). The corresponding [ 125 I]7 and [ 125 I]8 were successfully prepared from tri-n-butyltin derivatives. They showed good brain uptakes and prolonged retention after intravenous injection in rats (brain uptake was 1.77% and 0.98% dose/g for [ 125 I]7, and 0.92% and 0.29% dose/g for [ 125 I]8, at 2 and 120 min, respectively). Significantly, [ 125 I]7 showed excellent uptake and prolonged retention in the hypothalamus, where SERT concentration was highest. The hypothalamus/cerebellum (HY/CB) ratios (target/background ratios) were 4.24, 7.10, 8.24 and 12.6 at 2, 4, 6 and 12 h, respectively. The HY/CB ratios for [ 125 I]8 were 3.97, 5.57 and 5.06 at 1, 2 and 4 h, respectively. Adding the 4'-iodo group to the Phenyl Ring B of Compound (7) appeared to reduce the rate of clearance from the brain, and kinetics favored uptake and retention in the hypothalamus. The localization of [ 125 I]7 in the hypothalamus region in the rat brain could be blocked by pretreatment with (+)McN5652, escitalopram and ADAM (2), which are all selective SERT ligands (at 2 mg/kg iv, 5 min pretreatment). Ex vivo autoradiograms of rat brain sections (at 4 h after intravenous injection of [ 125 I]7) showed intense labeling in regions of the brain known to have high SERT density. The excellent selective uptake and retention in the hypothalamus region suggest that [ 123 I]7 is a potential lead compound for developing new imaging agents targeting SERT-binding sites with single

Preclinical pharmacological studies of 99Tcm-TRODAT-1 as a dopamine transporter imaging agent

International Nuclear Information System (INIS)

Fang Ping; Wan Weixing; Liu Zhenguo; Wu Chunying; Chen Shengdi; Chen Zhengping; Zhou Xiang; Ji Shuren

2001-01-01

Objective: To develop a 99 Tc m labelled dopamine transporter (DAT) imaging agent, 99 Tc m -TRODAT-1 [TRODAT-1: 2β-([N,N'-bis(2-mercaptoethyl) ethylene diamino] methyl), 3β-(4-chlorophenyl) tropane], for evaluating the variation of DAT in patients with Parkinson's disease. Methods: 99 Tc m -TRODAT-1 was successfully prepared on a kit basis. Preclinical pharmacological studies were performed in rats, mice, rabbits, monkeys and a volunteer with diagnosed Parkinson disease (PD). Results: Radiochemical purity of 99 Tc m -TRODAT-1 was over 90%, and remained stable for 6 hours. The specific uptake in striatum was significantly diminished, from 3.45 to 0.12 at 2 h by pretreating rats with a dose of DAT competing ligand, β-CIT [1 mg/kg, 2β-carbomethoxy-3β-(4-iodophenyl) tropane]. Blood clearance kinetics was studied in rabbits, and the initial half-life was of 1.2 min, the elimination half-life was of 368 min. Images of normal monkey's brain exhibited an excellent accumulation in basal ganglia region, where dopamine neurons were concentrated. In hemi parkinsonism model monkeys, the ratio of normal ST/CB and lesioned ST/CB were 1.56 and 0.94, respectively. Brain imaging studies in volunteer indicated that uptake and retention in the basal ganglia, the ratio of normal striatal uptake to lesioned one's was 1.15 measured by SPECT imaging at 2 h. The result of imaging was conformable with his clinical symptoms. Conclusions: The stable, neutral and lipophilic complex, 99 Tc m -TRODAT-1, can be accumulated in the striatal area, where DAT is concentrated, high quality images can be obtained. It suggests that 99 Tc m -TRODAT-1 might be a safe and effective tracer for monitoring the variation in DAT which is associated with various neurodegenerative diseases

The preclinical pharmacological study of dopamine transporter imaging agnet (99mTc)trodat-1

International Nuclear Information System (INIS)

Fang, P.; Wan, W.; Wu, C.; Liu, Z.; Wang, T.; Chen, S.; Chen, Z.; Zhou, X.

2000-01-01

To develop 99m Tc labeled dopamine transporter (DAT) imaging agent 99m Tc-TRODAT-1 (TRODAT-1:2 β-[[N,N'-bis(2-mercaptoethyl)ethylenediamino]methl], 3 β-(4-chlorophenyl)tropane], used in SPECT, for evaluating changes of DAT in patients with Parkinson's disease(PD). Using Stannous as reducing agent, and the present of Na-glucoheptonate, 99m Tc-TRODAT-1 was successfully prepared. Preclinical pharmacological studies have been performed in rats. C57BL mice, normal and PD model monkeys and volunteers. Radiochemical purity of 99m Tc-TRODAT-1 was over 90%, and stable for 6 hours. The specific uptake in striatum was significantly diminished from 3.45 to 0.12 at 3 h by pretreated rats with a dose of competing DAT ligand β-CIT (1 mg/kg). Autoradiographic images in C57BL mice shows that the specific uptake has a good linear relationship with the quantity of neural-toxin (MPTP) which was given to the animals (r=0.9792). Images of normal monkey's brain exhibited excellent localization in basal ganglia region, where dopamine neurons were concentrated, and the ratios of ST/CB were 1.56-2.0. In hemiparkinsonian model monkeys, the ratio of normal ST/CB and lesioned ST/CB were 1.56 and 0.94, respectively. Brain image studies in volunteers indicated that uptake and retention in the basal ganglia, the ratio of normal striatal to lesioned one was 1.15 measured by SPECT imaging at 2 h. The result of images was consistent with the clinical symptoms. Above-mentioned results showed that 99m Tc-TRODAT-1 can be accumulated in the striatal area, where DAT are concentrated, high quality images were obtained. It is suggested that 99m Tc-TRODAT-1 might turn to be a safe and effective tracer for monitoring the change in DAT associated with various neurodegenerative diseases

Modeling and analysis of PET studies with norepinephrine transporter ligands: the search for a reference region

Energy Technology Data Exchange (ETDEWEB)

Logan, Jean [Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973 (United States)]. E-mail: logan@bnl.gov; Ding, Y.-S. [Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Lin, K.-S. [Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Pareto, Deborah [Medical Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Functional Imaging, Berkeley National Laboratory, Berkeley, CA 94720 (United States); Fowler, Joanna [Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Biegon, Anat [Medical Department, Brookhaven National Laboratory, Upton, NY 11973 (United States)

2005-07-01

The development of positron emission tomography (PET) ligands for the norepinephrine transporter (NET) has been slow compared to the development of radiotracers for others systems, such as the dopamine (DAT) or the serotonin transporters (SERT). The main reason for this appears to be the high nonspecific (non-NET) binding exhibited by many of these tracers, which makes the identification of a reference region difficult. With other PET ligands the use of a reference region increases the reproducibility of the outcome measure in test/retest studies. The focus of this work is to identify a suitable reference region or means of normalizing data for the NET ligands investigated. Methods: We have analyzed the results of PET studies in the baboon brain with labeled reboxetine derivatives (S,S)-[{sup 11}C]O-methyl reboxetine (SS-MRB), (S,S)-[{sup 18}F]fluororeboxetine (SS-FRB) as well as O-[{sup 11}C]nisoxetine and N-[{sup 11}C]nisoxetine (NIS), and, for comparison, the less active (R,R) enantiomers (RR-MRB, RR-FRB) in terms of the distribution volume (DV) using measured arterial input functions. Results: (1) For a given subject, a large variation in DV for successive baseline studies was observed in regions with both high and low NET density. (2) The occipital cortex and the basal ganglia were found to be the regions with the smallest change between baseline (SS-MRB) and pretreatment with cocaine, and were therefore used as a composite reference region for calculation of a distribution volume ratio (DVR). (3) The variability [as measured by the coefficient of variation (CV)=standard deviation/mean] in the distribution volume ratio (DVR) of thalamus (to reference region) was considerably reduced over that of the DV using this composite reference region. (4) Pretreatment with nisoxetine (1.0 mg/kg 10 min prior to tracer) in one study produced (in decreasing order) reductions in thalamus, cerebellum, cingulate and frontal cortex consistent with known NET densities. (5) [{sup

Modeling and analysis of PET studies with norepinephrine transporter ligands: the search for a reference region.

Science.gov (United States)

Logan, Jean; Ding, Yu-Shin; Lin, Kuo-Shyan; Pareto, Deborah; Fowler, Joanna; Biegon, Anat

2005-07-01

The development of positron emission tomography (PET) ligands for the norepinephrine transporter (NET) has been slow compared to the development of radiotracers for others systems, such as the dopamine (DAT) or the serotonin transporters (SERT). The main reason for this appears to be the high nonspecific (non-NET) binding exhibited by many of these tracers, which makes the identification of a reference region difficult. With other PET ligands the use of a reference region increases the reproducibility of the outcome measure in test/retest studies. The focus of this work is to identify a suitable reference region or means of normalizing data for the NET ligands investigated. We have analyzed the results of PET studies in the baboon brain with labeled reboxetine derivatives (S,S)-[(11)C]O-methyl reboxetine (SS-MRB), (S,S)-[(18)F]fluororeboxetine (SS-FRB) as well as O-[(11)C]nisoxetine and N-[(11)C]nisoxetine (NIS), and, for comparison, the less active (R,R) enantiomers (RR-MRB, RR-FRB) in terms of the distribution volume (DV) using measured arterial input functions. (1) For a given subject, a large variation in DV for successive baseline studies was observed in regions with both high and low NET density. (2) The occipital cortex and the basal ganglia were found to be the regions with the smallest change between baseline (SS-MRB) and pretreatment with cocaine, and were therefore used as a composite reference region for calculation of a distribution volume ratio (DVR). (3) The variability [as measured by the coefficient of variation (CV) = standard deviation/mean] in the distribution volume ratio (DVR) of thalamus (to reference region) was considerably reduced over that of the DV using this composite reference region. (4) Pretreatment with nisoxetine (1.0 mg/kg 10 min prior to tracer) in one study produced (in decreasing order) reductions in thalamus, cerebellum, cingulate and frontal cortex consistent with known NET densities. (5) [(11)C]Nisoxetine had a higher

Modeling and analysis of PET studies with norepinephrine transporter ligands: the search for a reference region

International Nuclear Information System (INIS)

Logan, Jean; Ding, Y.-S.; Lin, K.-S.; Pareto, Deborah; Fowler, Joanna; Biegon, Anat

2005-01-01

The development of positron emission tomography (PET) ligands for the norepinephrine transporter (NET) has been slow compared to the development of radiotracers for others systems, such as the dopamine (DAT) or the serotonin transporters (SERT). The main reason for this appears to be the high nonspecific (non-NET) binding exhibited by many of these tracers, which makes the identification of a reference region difficult. With other PET ligands the use of a reference region increases the reproducibility of the outcome measure in test/retest studies. The focus of this work is to identify a suitable reference region or means of normalizing data for the NET ligands investigated. Methods: We have analyzed the results of PET studies in the baboon brain with labeled reboxetine derivatives (S,S)-[ 11 C]O-methyl reboxetine (SS-MRB), (S,S)-[ 18 F]fluororeboxetine (SS-FRB) as well as O-[ 11 C]nisoxetine and N-[ 11 C]nisoxetine (NIS), and, for comparison, the less active (R,R) enantiomers (RR-MRB, RR-FRB) in terms of the distribution volume (DV) using measured arterial input functions. Results: (1) For a given subject, a large variation in DV for successive baseline studies was observed in regions with both high and low NET density. (2) The occipital cortex and the basal ganglia were found to be the regions with the smallest change between baseline (SS-MRB) and pretreatment with cocaine, and were therefore used as a composite reference region for calculation of a distribution volume ratio (DVR). (3) The variability [as measured by the coefficient of variation (CV)=standard deviation/mean] in the distribution volume ratio (DVR) of thalamus (to reference region) was considerably reduced over that of the DV using this composite reference region. (4) Pretreatment with nisoxetine (1.0 mg/kg 10 min prior to tracer) in one study produced (in decreasing order) reductions in thalamus, cerebellum, cingulate and frontal cortex consistent with known NET densities. (5) [ 11 C]Nisoxetine had

Atypical dopamine efflux caused by 3,4-methylenedioxypyrovalerone (MDPV) via the human dopamine transporter.

Science.gov (United States)

Shekar, Aparna; Aguilar, Jenny I; Galli, Greta; Cozzi, Nicholas V; Brandt, Simon D; Ruoho, Arnold E; Baumann, Michael H; Matthies, Heinrich J G; Galli, Aurelio

2017-10-01

Synthetic cathinones are similar in chemical structure to amphetamines, and their behavioral effects are associated with enhanced dopaminergic signaling. The past ten years of research on the common constituent of bath salts, MDPV (the synthetic cathinone 3,4-methylenedioxypyrovalerone), has aided the understanding of how synthetic cathinones act at the dopamine (DA) transporter (DAT). Several groups have described the ability of MDPV to block the DAT with high-affinity. In this study, we demonstrate for the first time a new mode of action of MDPV, namely its ability to promote DAT-mediated DA efflux. Using single cell amperometric assays, we determined that low concentrations of MDPV (1nM) can cause reverse transport of DA via DAT. Notably, administration of MDPV leads to hyperlocomotion in Drosophila melanogaster. These data describe further how MDPV acts at the DAT, possibly paving the way for novel treatment strategies for individuals who abuse bath salts. Copyright © 2017 Elsevier B.V. All rights reserved.

Attenuated Tonic and Enhanced Phasic Release of Dopamine in Attention Deficit Hyperactivity Disorder.

Directory of Open Access Journals (Sweden)

Rajendra D Badgaiyan

Full Text Available It is unclear whether attention deficit hyperactive disorder (ADHD is a hypodopaminergic or hyperdopaminergic condition. Different sets of data suggest either hyperactive or hypoactive dopamine system. Since indirect methods used in earlier studies have arrived at contradictory conclusions, we directly measured the tonic and phasic release of dopamine in ADHD volunteers. The tonic release in ADHD and healthy control volunteers was measured and compared using dynamic molecular imaging technique. The phasic release during performance of Eriksen's flanker task was measured in the two groups using single scan dynamic molecular imaging technique. In these experiments volunteers were positioned in a positron emission tomography (PET camera and administered a dopamine receptor ligand (11C-raclopride intravenously. After the injection PET data were acquired dynamically while volunteers either stayed still (tonic release experiments or performed the flanker task (phasic release experiments. PET data were analyzed to measure dynamic changes in ligand binding potential (BP and other receptor kinetic parameters. The analysis revealed that at rest the ligand BP was significantly higher in the right caudate of ADHD volunteers suggesting reduced tonic release. During task performance significantly lower ligand BP was observed in the same area, indicating increased phasic release. In ADHD tonic release of dopamine is attenuated and the phasic release is enhanced in the right caudate. By characterizing the nature of dysregulated dopamine neurotransmission in ADHD, the results explain earlier findings of reduced or increased dopaminergic activity.

Dopamine transporter imaging in clinically unclear cases of parkinsonism and the importance of Scans Without Evidence of Dopaminergic Deficit (SWEDDs

Directory of Open Access Journals (Sweden)

Marco A. T. Utiumi

2012-09-01

Full Text Available The clinical diagnosis of Parkinson's disease (PD is susceptible to misdiagnosis, especially in the earlier stages of the disease. Recently, in vivo imaging techniques assessing the presynaptic dopamine transporter (DAT have emerged as a useful tool in PD diagnosis, improving its accuracy. OBJECTIVE: It was to illustrate the clinical usefulness of a brain single-photon emission computed tomography (SPECT DAT ligand, and highlight relevant aspects of scans without evidence of dopaminergic deficit (SWEDDs in this context. CASES: We described four representative patients with clinically unclear parkinsonian syndromes who underwent [99mTc]-TRODAT-1 SPECT and reviewed the clinical implications. CONCLUSION: DAT-SPECT is an important, cost-effective, technique for the differential diagnosis of parkinsonian syndromes. Additionally, SWEDD cases present clinical and paraclinical peculiarities that may retrospectively identify them as essential/dystonic tremor. The lack of histopathological data limits further conclusions.

2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine (ADAM): an improved serotonin transporter ligand

International Nuclear Information System (INIS)

Oya, Shunichi; Choi, S.-R.; Hou, Catherine; Mu Mu; Kung, M.-P.; Acton, Paul D.; Siciliano, Michael; Kung, Hank F.

2000-01-01

Serotonin transporters (SERT) are target-sites for commonly used antidepressants, such as fluoxetine, paroxetine, sertraline, and so on. Imaging of these sites in the living human brain may provide an important tool to evaluate the mechanisms of action as well as to monitor the treatment of depressed patients. Synthesis and characterization of an improved SERT imaging agent, ADAM (2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine)(7) was achieved. The new compound, ADAM(7), displayed an extremely potent binding affinity toward SERT (K i =0.013 nM, in membrane preparations of LLC-PK 1 -cloned cell lines expressing the specific monoamine transporter). ADAM(7) also showed more than 1,000-fold selectivity for SERT over norepinephrine transporter (NET) and dopamine transporter (DAT) (K i =699 and 840 nM, for NET and DAT, respectively). The radiolabeled compound [ 125 I]ADAM(7) showed an excellent brain uptake in rats (1.41% dose at 2 min post intravenous [IV] injection), and consistently displayed the highest uptake (between 60-240 min post IV injection) in hypothalamus, a region with the highest density of SERT. The specific uptake of [ 125 I]ADAM(7) in the hypothalamus exhibited the highest target-to-nontarget ratio ([hypothalamus - cerebellum]/cerebellum was 3.97 at 120 min post IV injection). The preliminary imaging study of [ 123 I]ADAM in the brain of a baboon by single photon emission computed tomography (SPECT) at 180-240 min post IV injection indicated a specific uptake in midbrain region rich in SERT. These data suggest that the new ligand [ 123 I]ADAM(7) may be useful for SPECT imaging of SERT binding sites in the human brain

Dopamine transporter density of the basal ganglia assessed with I-123 IPT SPECT in methamphetamine abusers

International Nuclear Information System (INIS)

Lee, Joo Ryung; Ahn, Byeong Cheol; Kewm, Do Hun

2005-01-01

Functional imaging of dopamine transporter (DAT) defines integrity of the dopaminergic system, and DAT is the target site of drugs of abuse such as cocaine and methamphetamine. Functional imaging the DAT may be a sensitive and selective indicator of neurotoxic change by the drug. The aim of the present study is to evaluate the clinical implications of qualitative/quantitative analyses of dopamine transporter imaging in methamphetamine abusers. Six detoxified methamphetamine abusers (abuser group) and 4 volunteers (control group) were enrolled in this study. Brain MRI was performed in all of abuser group. Abuser group underwent psychiatric and depression assessment using brief psychiatric rating scale (BPRS) and Hamilton depression rating scale (HAMD), respectively. All of the subjects underwent I-123 IPT SPECT (IPT SPECT). IPT SPECT image was analysed with visual qualitative method and quantitative method using basal ganglia dopamine transporter (DAT) specific/non-specific binding ratio (SBR). Comparison of DAT SBR between abuser and control groups was performed. We also performed correlation tests between psychiatric and depression assessment results and DAT SBR in abuser group. All of abuser group showed normal MRI finding, but had residual psychiatric and depressive symptoms, and psychiatric and depressive symptom scores were exactly correlated (r=1.0, ρ =0.005) each other. Five of them showed abnormal finding on qualitative visual I-123 IPT SPECT. Abuser group had lower basal ganglia DAT SBR than that of control (2.38 ± 0.20 vs 3.04 ± 0.27, ρ =0.000). Psychiatric and depressive symptoms were negatively well correlated with basal ganglia DAT SBR (r=-0.908, ρ =0.012, r=-0.924, ρ =0.009) This results suggest that dopamine transporter imaging using I-123 IPT SPECT may be used to evaluate dopaminergic system of the basal ganglia and the clinical status in methamphetamine abusers

Dopamine transporter density of the basal ganglia assessed with I-123 IPT SPECT in methamphetamine abusers

Energy Technology Data Exchange (ETDEWEB)

Lee, Joo Ryung; Ahn, Byeong Cheol [Kyungpook National University Medical School, Daegu (Korea, Republic of); Kewm, Do Hun [National Bugok Mental Hospital, Changryung (Korea, Republic of)] (and others)

2005-10-15

Functional imaging of dopamine transporter (DAT) defines integrity of the dopaminergic system, and DAT is the target site of drugs of abuse such as cocaine and methamphetamine. Functional imaging the DAT may be a sensitive and selective indicator of neurotoxic change by the drug. The aim of the present study is to evaluate the clinical implications of qualitative/quantitative analyses of dopamine transporter imaging in methamphetamine abusers. Six detoxified methamphetamine abusers (abuser group) and 4 volunteers (control group) were enrolled in this study. Brain MRI was performed in all of abuser group. Abuser group underwent psychiatric and depression assessment using brief psychiatric rating scale (BPRS) and Hamilton depression rating scale (HAMD), respectively. All of the subjects underwent I-123 IPT SPECT (IPT SPECT). IPT SPECT image was analysed with visual qualitative method and quantitative method using basal ganglia dopamine transporter (DAT) specific/non-specific binding ratio (SBR). Comparison of DAT SBR between abuser and control groups was performed. We also performed correlation tests between psychiatric and depression assessment results and DAT SBR in abuser group. All of abuser group showed normal MRI finding, but had residual psychiatric and depressive symptoms, and psychiatric and depressive symptom scores were exactly correlated (r=1.0, {rho} =0.005) each other. Five of them showed abnormal finding on qualitative visual I-123 IPT SPECT. Abuser group had lower basal ganglia DAT SBR than that of control (2.38 {+-} 0.20 vs 3.04 {+-} 0.27, {rho} =0.000). Psychiatric and depressive symptoms were negatively well correlated with basal ganglia DAT SBR (r=-0.908, {rho} =0.012, r=-0.924, {rho} =0.009) This results suggest that dopamine transporter imaging using I-123 IPT SPECT may be used to evaluate dopaminergic system of the basal ganglia and the clinical status in methamphetamine abusers.

Amphetamine Paradoxically Augments Exocytotic Dopamine Release and Phasic Dopamine Signals

Science.gov (United States)

Daberkow, DP; Brown, HD; Bunner, KD; Kraniotis, SA; Doellman, MA; Ragozzino, ME; Garris, PA; Roitman, MF

2013-01-01

Drugs of abuse hijack brain reward circuitry during the addiction process by augmenting action potential-dependent phasic dopamine release events associated with learning and goal-directed behavior. One prominent exception to this notion would appear to be amphetamine (AMPH) and related analogs, which are proposed instead to disrupt normal patterns of dopamine neurotransmission by depleting vesicular stores and promoting non-exocytotic dopamine efflux via reverse transport. This mechanism of AMPH action, though, is inconsistent with its therapeutic effects and addictive properties - which are thought to be reliant on phasic dopamine signaling. Here we used fast-scan cyclic voltammetry in freely moving rats to interrogate principal neurochemical responses to AMPH in the striatum and relate these changes to behavior. First, we showed that AMPH dose-dependently enhanced evoked dopamine responses to phasic-like current pulse trains for up to two hours. Modeling the data revealed that AMPH inhibited dopamine uptake but also unexpectedly potentiated vesicular dopamine release. Second, we found that AMPH increased the amplitude, duration and frequency of spontaneous dopamine transients, the naturally occurring, non-electrically evoked, phasic increases in extracellular dopamine. Finally, using an operant sucrose reward paradigm, we showed that low-dose AMPH augmented dopamine transients elicited by sucrose-predictive cues. However, operant behavior failed at high-dose AMPH, which was due to phasic dopamine hyperactivity and the decoupling of dopamine transients from the reward predictive cue. These findings identify up-regulation of exocytotic dopamine release as a key AMPH action in behaving animals and support a unified mechanism of abused drugs to activate phasic dopamine signaling. PMID:23303926

FDG PET, Dopamine Transporter SPECT, and Olfaction: Combining Biomarkers in REM Sleep Behavior Disorder

NARCIS (Netherlands)

Meles, Sanne K.; Vadasz, David; Renken, Remco J.; Sittig-Wiegand, Elisabeth; Mayer, Geert; Depboylu, Candan; Reetz, Kathrin; Overeem, Sebastiaan; Pijpers, Angelique; Reesink, Fransje E.; van Laar, Teus; Heinen, Lisette; Teune, Laura K.; Höffken, Helmut; Luster, Marcus; Kesper, Karl; Adriaanse, Sofie M.; Booij, Jan; Leenders, Klaus L.; Oertel, Wolfgang H.

2017-01-01

Background: Idiopathic REM sleep behavior disorder is a prodromal stage of Parkinson's disease and dementia with Lewy bodies. Hyposmia, reduced dopamine transporter binding, and expression of the brain metabolic PD-related pattern were each associated with increased risk of conversion to PD. The

Tyrosine hydroxylase immunoreactivity and [3H]WIN 35,428 binding to the dopamine transporter in a hamster model of idiopathic paroxysmal dystonia

International Nuclear Information System (INIS)

Nobrega, J.N.; Gernert, M.; Loescher, W.; Raymond, R.; Belej, T.; Richter, A.

1999-01-01

Recent pharmacological studies and receptor analyses have suggested that dopamine neurotransmission is enhanced in mutant dystonic hamsters (dt sz ), a model of idiopathic paroxysmal dystonia which displays attacks of generalized dystonia in response to mild stress. In order to further characterize the nature of dopamine alterations, the present study investigated possible changes in the number of dopaminergic neurons, as defined by tyrosine hydroxylase immunohistochemistry, as well as binding to the dopamine transporter labelled with [ 3 H]WIN 35,428 in dystonic hamsters. No differences in the number of tyrosine hydroxylase-immunoreactive neurons were found within the substantia nigra and ventral tegmental area of mutant hamsters compared to non-dystonic control hamsters. Similarly, under basal conditions, i.e. in the absence of a dystonic episode, no significant changes in [ 3 H]WIN 35,428 binding were detected in dystonic brains. However, in animals killed during the expression of severe dystonia, significant decreases in dopamine transporter binding became evident in the nucleus accumbens and ventral tegmental area in comparison to controls exposed to the same external stimulation. Since stimulation tended to increase [ 3 H]WIN 35,428 binding in control brains, the observed decrease in the ventral tegmental area appeared to be due primarily to the fact that binding was increased less in dystonic brains than in similarly stimulated control animals.This finding could reflect a diminished ability of the dopamine transporter to undergo adaptive changes in response to external stressful stimulation in mutant hamsters. The selective dopamine uptake inhibitor GBR 12909 (20 mg/kg) aggravated dystonia in mutant hamsters, further suggesting that acute alterations in dopamine transporter function during stimulation may be an important component of dystonia in this model. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

Predictive value of dopamine transporter SPECT imaging with [123I]PE2I in patients with subtle parkinsonian symptoms

International Nuclear Information System (INIS)

Ziebell, Morten; Thomsen, Gerda; Knudsen, Gitte M.; Andersen, Birgitte B.; Pinborg, Lars H.; Karlsborg, Merete; Hasselbalch, Steen G.

2012-01-01

To examine the diagnostic sensitivity and specificity of dopamine transporter SPECT imaging with a highly dopamine transporter selective radioligand. The study included consecutively enrolled, drug-naive patients with an average short history of parkinsonian motor symptoms, referred for diagnostic scanning. The study group comprised 288 patients naive to antiparkinson treatment who were enrolled as they were admitted for a diagnostic SPECT scan with the radioligand [ 123 I]-N-(3-iodoprop-2E-enyl)-2-β-carbomethoxy-3β-(4-methylphenyl)n ortropane ( 123 I-PE2I). After the diagnostic scanning, patients were followed clinically with an average follow-up of 19.7 ± 12.5 months. A diagnosis could be clinically settled in 189 patients and among these patients, a dopamine transporter scan had a sensitivity of 88% and a specificity of 91% for discrimination between patients with and without striatal neurodegeneration. In cognitively impaired patients (Mini Mental State Examination 2 differentiated between idiopathic Parkinson's disease and atypical parkinsonian syndromes with a specificity of 84% and a sensitivity of 63%. In drug-naive patients with subtle clinical parkinsonian motor symptoms, dopamine transporter scan using 123 I-PE21 has a high sensitivity and specificity in distinguishing between patients with and without striatal neurodegeneration. The specificity is lower in patients who are also cognitively impaired. Calculation of the striatal APR can assist in differentiating between idiopathic Parkinson's disease and atypical parkinsonian syndromes. (orig.)

Dopamine transporter SPECT using fast kinetic ligands: 123I-FP-β-CIT versus 99mTc-TRODAT-1

International Nuclear Information System (INIS)

Laere, K. van; Ceuninck, L. de; Eynden, J. van den; Dupont, P.; Mortelmans, L.; Dom, R.; Vanbilloen, H.; Cleynhens, J.; Bormans, G.; Verbruggen, A.

2004-01-01

A comparative study was carried out on two promising presynaptic dopamine transporter single-photon emission tomography (SPECT) radioligands with a fast pharmacokinetic profile, 123 I-FP-β-CIT (FP) and 99m Tc-TRODAT-1 (TR), in order to assess their differential diagnostic power in early parkinsonism and their sensitivity for detection of disease progression. This cross-sectional study was conducted on 96 patients with early-stage parkinsonism referred in a tertiary clinical setting. Mean disease duration was 2.0±1.3 years, and patients had a modified Hoehn and Yahr (H and Y) stage of 1-2 (average 1.2). Forty-seven patients received TR, and 49 received FP. In both groups, ten patients with normal presynaptic function were included as a control population; all other patients were clinically diagnosed as having idiopathic Parkinson's disease. Groups were matched for gender, age, disease duration and modified H and Y stage. Triple-head gamma camera SPECT was analysed using a semiquantitative index of transporter binding (BI). Discriminant analysis with cross-validation resulted in a maximal classification accuracy for FP of 93% (sensitivity 95% and specificity 86%) for the contralateral putamen BI. For TR, the corresponding values were 87% accuracy, 92% sensitivity and 70% specificity. For FP, disease duration was correlated with both the putamen BI (-8.8%/year, ρ=-0.41, P=0.025) and the putamen/caudate ratio (-7.4%/year, ρ=-0.51, P=0.004), but for TR no significant correlation was found (all P values >0.5). In conclusion, both FP and TR show high sensitivity in a clinically relevant setting, but FP has superior accuracy for early differential diagnosis of idiopathic parkinsonism and non-degenerative extrapyramidal disorders, as well as better sensitivity for disease follow-up. (orig.)

SPECT imaging of D2 dopamine receptors and endogenous dopamine release in mice

NARCIS (Netherlands)

Jongen, C.; De Bruin, K.; Beekman, F.J.; Booij, J.

2008-01-01

Purpose: The dopamine D2 receptor (D2R) is important in the mediation of addiction. [123I]iodobenzamide (IBZM), a SPECT ligand for the D2R, has been used for in vivo studies of D2R availability in humans, monkeys, and rats. Although mouse models are important in the study of addiction, [123I]IBZM

Novel and High Affinity 2-[(Diphenylmethyl)sulfinyl]acetamide (Modafinil) Analogues as Atypical Dopamine Transporter Inhibitors

DEFF Research Database (Denmark)

Cao, Jianjing; Slack, Rachel D.; Bakare, Oluyomi M.

2016-01-01

The development of pharmacotherapeutic treatments of psychostimulant abuse has remained a challenge, despite significant efforts made toward relevant mechanistic targets, such as the dopamine transporter (DAT). The atypical DAT inhibitors have received attention due to their promising pharmacolog...

The effects of benzofury (5-APB) on the dopamine transporter and 5-HT2-dependent vasoconstriction in the rat.

Science.gov (United States)

Dawson, Patrick; Opacka-Juffry, Jolanta; Moffatt, James D; Daniju, Yusuf; Dutta, Neelakshi; Ramsey, John; Davidson, Colin

2014-01-03

5-APB, commonly marketed as 'benzofury' is a new psychoactive substance and erstwhile 'legal high' which has been implicated in 10 recent drug-related deaths in the UK. This drug was available on the internet and in 'head shops' and was one of the most commonly sold legal highs up until its recent UK temporary ban (UK Home Office). Despite its prominence, very little is known about its pharmacology. This study was undertaken to examine the pharmacology of 5-APB in vitro. We hypothesised that 5-APB would activate the dopamine and 5-HT systems which may underlie its putative stimulant and hallucinogenic effects. Autoradiographic studies showed that 5-APB displaced both [(125)I] RTI-121 and [(3)H] ketanserin from rat brain tissue suggesting affinity at the dopamine transporter and 5-HT2 receptor sites respectively. Voltammetric studies in rat accumbens brain slices revealed that 5-APB slowed dopamine reuptake, and at high concentrations caused reverse transport of dopamine. 5-APB also caused vasoconstriction of rat aorta, an effect antagonised by the 5-HT2A receptor antagonist ketanserin, and caused contraction of rat stomach fundus, which was reversed by the 5-HT2B receptor antagonist RS-127445. These data show that 5-APB interacts with the dopamine transporter and is an agonist at the 5-HT2A and 5-HT2B receptors in the rat. Thus 5-APB's pharmacology is consistent with it having both stimulant and hallucinogenic properties. In addition, 5-APB's activity at the 5-HT2B receptor may cause cardiotoxicity. © 2013.

Selective determination of dopamine using quantum-sized gold nanoparticles protected with charge selective ligands

Science.gov (United States)

Kwak, Kyuju; Kumar, S. Senthil; Lee, Dongil

2012-06-01

We report here the selective determination of dopamine (DA) using quantum-sized gold nanoparticles coated with charge selective ligands. Glutathione protected gold nanoparticles (GS-Au25) were synthesized and immobilized into a sol-gel matrix via thiol linkers. The GS-Au25 modified sol-gel electrode was found to show excellent electrocatalytic activity towards the oxidation of DA but no activity towards the oxidation of ascorbic acid. The role of electrostatic charge in the selective electrocatalytic activity of GS-Au25 was verified by voltammetry of redox markers carrying opposite charges. The pH dependent sensitivity for the determination of DA further confirmed the charge screening effect of GS-Au25. Mechanistic investigation revealed that the selectivity is attained by the selective formation of an electrostatic complex between the negatively charged GS-Au25 and DA cation. The GS-Au25 modified sol-gel electrode also showed excellent selectivity for DA in the presence of an interferent, ascorbic acid.We report here the selective determination of dopamine (DA) using quantum-sized gold nanoparticles coated with charge selective ligands. Glutathione protected gold nanoparticles (GS-Au25) were synthesized and immobilized into a sol-gel matrix via thiol linkers. The GS-Au25 modified sol-gel electrode was found to show excellent electrocatalytic activity towards the oxidation of DA but no activity towards the oxidation of ascorbic acid. The role of electrostatic charge in the selective electrocatalytic activity of GS-Au25 was verified by voltammetry of redox markers carrying opposite charges. The pH dependent sensitivity for the determination of DA further confirmed the charge screening effect of GS-Au25. Mechanistic investigation revealed that the selectivity is attained by the selective formation of an electrostatic complex between the negatively charged GS-Au25 and DA cation. The GS-Au25 modified sol-gel electrode also showed excellent selectivity for DA in the

2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine (ADAM): an improved serotonin transporter ligand

Energy Technology Data Exchange (ETDEWEB)

Oya, Shunichi; Choi, S.-R.; Hou, Catherine; Mu Mu; Kung, M.-P.; Acton, Paul D.; Siciliano, Michael; Kung, Hank F. E-mail: kunghf@sunmac.spect.upenn.edu

2000-04-01

Serotonin transporters (SERT) are target-sites for commonly used antidepressants, such as fluoxetine, paroxetine, sertraline, and so on. Imaging of these sites in the living human brain may provide an important tool to evaluate the mechanisms of action as well as to monitor the treatment of depressed patients. Synthesis and characterization of an improved SERT imaging agent, ADAM (2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine)(7) was achieved. The new compound, ADAM(7), displayed an extremely potent binding affinity toward SERT (K{sub i}=0.013 nM, in membrane preparations of LLC-PK{sub 1}-cloned cell lines expressing the specific monoamine transporter). ADAM(7) also showed more than 1,000-fold selectivity for SERT over norepinephrine transporter (NET) and dopamine transporter (DAT) (K{sub i}=699 and 840 nM, for NET and DAT, respectively). The radiolabeled compound [{sup 125}I]ADAM(7) showed an excellent brain uptake in rats (1.41% dose at 2 min post intravenous [IV] injection), and consistently displayed the highest uptake (between 60-240 min post IV injection) in hypothalamus, a region with the highest density of SERT. The specific uptake of [{sup 125}I]ADAM(7) in the hypothalamus exhibited the highest target-to-nontarget ratio ([hypothalamus - cerebellum]/cerebellum was 3.97 at 120 min post IV injection). The preliminary imaging study of [{sup 123}I]ADAM in the brain of a baboon by single photon emission computed tomography (SPECT) at 180-240 min post IV injection indicated a specific uptake in midbrain region rich in SERT. These data suggest that the new ligand [{sup 123}I]ADAM(7) may be useful for SPECT imaging of SERT binding sites in the human brain.

Serotonin and Dopamine Transporter Binding in Children with Autism Determined by SPECT

Science.gov (United States)

Makkonen, Ismo; Riikonen, Raili; Kokki, Hannu; Airaksinen, Mauno M.; Kuikka, Jyrki T.

2008-01-01

Disturbances in the serotonergic system have been recognized in autism. To investigate the association between serotonin and dopamine transporters and autism, we studied 15 children (14 males, one female; mean age 8y 8mo [SD 3y 10mo]) with autism and 10 non-autistic comparison children (five males, five females; mean age 9y 10mo [SD 2y 8mo]) using…

DIRECT VISUALIZATION OF THE DOPAMINE TRANSPORTER IN CULTURED NEWBORN RAT MIDBRAIN NEURONS USING THE FLUORESCENT COCAINE ANALOGUE JHC 1-64

DEFF Research Database (Denmark)

Rasmussen, Søren; Vægter, Christian Bjerggaard; Cha, J

In this study we have established methods for visualization and tracking of the dopamine transporter (DAT) in cultured dopaminergic neurons in real time using a fluorescent cocaine analogue JHC 1-64 and confocal fluorescence microscopy. The initial binding experiments in HEK 293 cells stably...... 1-64 was prevented by excess concentrations of dopamine, cocaine, mazindol, or RTI-55, whereas the norepinephrine and/or serotonin transporter specific inhibitors desmethylimipramine and citalopram did not affect fluorescent labeling of the neurons. This strongly supports that JHC 1-64 specifically...

Tyrosine hydroxylase immunoreactivity and [{sup 3}H]WIN 35,428 binding to the dopamine transporter in a hamster model of idiopathic paroxysmal dystonia

Energy Technology Data Exchange (ETDEWEB)

Nobrega, J.N. [Neuroimaging Research Section, Clarke Institute of Psychiatry, Toronto (Canada); Gernert, M.; Loescher, W. [Department of Pharmacology, Toxicology and Pharmacy, School of Veterinary Medicine, Buenteweg 17, D-30559 Hannover (Germany); Raymond, R.; Belej, T. [Neuroimaging Research Section, Clarke Institute of Psychiatry, Toronto (Canada); Richter, A. [Department of Pharmacology, Toxicology and Pharmacy, School of Veterinary Medicine, Buenteweg 17, D-30559 Hannover (Germany)

1999-08-01

Recent pharmacological studies and receptor analyses have suggested that dopamine neurotransmission is enhanced in mutant dystonic hamsters (dt{sup sz}), a model of idiopathic paroxysmal dystonia which displays attacks of generalized dystonia in response to mild stress. In order to further characterize the nature of dopamine alterations, the present study investigated possible changes in the number of dopaminergic neurons, as defined by tyrosine hydroxylase immunohistochemistry, as well as binding to the dopamine transporter labelled with [{sup 3}H]WIN 35,428 in dystonic hamsters. No differences in the number of tyrosine hydroxylase-immunoreactive neurons were found within the substantia nigra and ventral tegmental area of mutant hamsters compared to non-dystonic control hamsters. Similarly, under basal conditions, i.e. in the absence of a dystonic episode, no significant changes in [{sup 3}H]WIN 35,428 binding were detected in dystonic brains. However, in animals killed during the expression of severe dystonia, significant decreases in dopamine transporter binding became evident in the nucleus accumbens and ventral tegmental area in comparison to controls exposed to the same external stimulation. Since stimulation tended to increase [{sup 3}H]WIN 35,428 binding in control brains, the observed decrease in the ventral tegmental area appeared to be due primarily to the fact that binding was increased less in dystonic brains than in similarly stimulated control animals.This finding could reflect a diminished ability of the dopamine transporter to undergo adaptive changes in response to external stressful stimulation in mutant hamsters. The selective dopamine uptake inhibitor GBR 12909 (20 mg/kg) aggravated dystonia in mutant hamsters, further suggesting that acute alterations in dopamine transporter function during stimulation may be an important component of dystonia in this model. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved000.

Contribution of vesicular and cytosolic dopamine to the increased striatal dopamine efflux elicited by intrastriatal injection of SKF38393.

NARCIS (Netherlands)

Saigusa, T.; Aono, Y.; Sekino, R.; Uchida, T.; Takada, K.; Oi, Y.; Koshikawa, N.; Cools, A.R.

2009-01-01

Like dexamphetamine, SKF38393 induces an increase in striatal dopamine efflux which is insensitive for tetrodotoxin, Ca(2+) independent and prevented by a dopamine transporter inhibitor. The dexamphetamine-induced striatal dopamine efflux originates from both the reserpine-sensitive vesicular

Relationship between conformational changes in the dopamine transporter and cocaine-like subjective effects of uptake inhibitors

DEFF Research Database (Denmark)

Løland, Claus Juul; Desai, Rajeev I; Zou, Mu-Fa

2007-01-01

Cocaine exerts its stimulatory effect by inhibiting the dopamine transporter (DAT). However, novel benztropine- and rimcazole-based inhibitors show reduced stimulant effects compared with cocaine, despite higher affinity and selectivity for DAT. To investigate possible mechanisms, we compared...... the extracellular transporter gate is open but inaccessible when it is closed. The data indicated that cocaine analogs bind an open conformation, whereas benztropine and rimcazole analogs bind a closed conformation. Next, we investigated the changes in inhibition potency of [(3)H]dopamine uptake of the compounds...... at a mutant DAT (Y335A) characterized by a global change in the conformational equilibrium. We observed a close relationship between the decrease in potencies of inhibitors at this mutant and cocaine-like responding in rats trained to discriminate cocaine from saline injections. Our data suggest...

Potent haloperidol derivatives covalently binding to the dopamine D2 receptor.

Science.gov (United States)

Schwalbe, Tobias; Kaindl, Jonas; Hübner, Harald; Gmeiner, Peter

2017-10-01

The dopamine D 2 receptor (D 2 R) is a common drug target for the treatment of a variety of neurological disorders including schizophrenia. Structure based design of subtype selective D 2 R antagonists requires high resolution crystal structures of the receptor and pharmacological tools promoting a better understanding of the protein-ligand interactions. Recently, we reported the development of a chemically activated dopamine derivative (FAUC150) designed to covalently bind the L94C mutant of the dopamine D 2 receptor. Using FAUC150 as a template, we elaborated the design and synthesis of irreversible analogs of the potent antipsychotic drug haloperidol forming covalent D 2 R-ligand complexes. The disulfide- and Michael acceptor-functionalized compounds showed significant receptor affinity and an irreversible binding profile in radioligand depletion experiments. Copyright © 2017 Elsevier Ltd. All rights reserved.

5-Chloro-2-(2'-((dimethylamino)methyl)-4'-iodophenylthio)benzenamine: a new serotonin transporter ligand

Energy Technology Data Exchange (ETDEWEB)

Oya, Shunichi [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Choi, Seok-Rye [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Kung, Mei-Ping [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Kung, Hank F. [Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104 (United States); Department of Pharmacology, University of Pennsylvania, Philadelphia, PA 19104 (United States)

2007-02-15

Two novel ligands with 4' substitution on the Phenyl Ring B of biphenylthiol, 5-chloro-2-(2'-((dimethylamino)methyl)-4'-iodophenylthio)benzenamine (7) and 2-(2'-((dimethylamino)methyl)-4'-methoxyphenylthio)-5-iodobenzenamine (8), were prepared and tested as potential serotonin transporter (SERT) imaging agents. The new ligands displayed extremely high binding affinities to SERT (K {sub i}=0.22{+-}0.09 and 0.11{+-}0.04 nM, respectively), with very low binding affinities to dopamine and norepinephrine transporters (K {sub i}>1000 nM). The corresponding [{sup 125}I]7 and [{sup 125}I]8 were successfully prepared from tri-n-butyltin derivatives. They showed good brain uptakes and prolonged retention after intravenous injection in rats (brain uptake was 1.77% and 0.98% dose/g for [{sup 125}I]7, and 0.92% and 0.29% dose/g for [{sup 125}I]8, at 2 and 120 min, respectively). Significantly, [{sup 125}I]7 showed excellent uptake and prolonged retention in the hypothalamus, where SERT concentration was highest. The hypothalamus/cerebellum (HY/CB) ratios (target/background ratios) were 4.24, 7.10, 8.24 and 12.6 at 2, 4, 6 and 12 h, respectively. The HY/CB ratios for [{sup 125}I]8 were 3.97, 5.57 and 5.06 at 1, 2 and 4 h, respectively. Adding the 4'-iodo group to the Phenyl Ring B of Compound (7) appeared to reduce the rate of clearance from the brain, and kinetics favored uptake and retention in the hypothalamus. The localization of [{sup 125}I]7 in the hypothalamus region in the rat brain could be blocked by pretreatment with (+)McN5652, escitalopram and ADAM (2), which are all selective SERT ligands (at 2 mg/kg iv, 5 min pretreatment). Ex vivo autoradiograms of rat brain sections (at 4 h after intravenous injection of [{sup 125}I]7) showed intense labeling in regions of the brain known to have high SERT density. The excellent selective uptake and retention in the hypothalamus region suggest that [{sup 123}I]7 is a potential lead compound for

Nanodisc-Targeted STD NMR Spectroscopy Reveals Atomic Details of Ligand Binding to Lipid Environments.

Science.gov (United States)

Muñoz-García, Juan C; Inacio Dos Reis, Rosana; Taylor, Richard J; Henry, Alistair J; Watts, Anthony

2018-05-18

Saturation transfer difference (STD) NMR spectroscopy is one of the most popular ligand-based NMR techniques for the study of protein-ligand interactions. This is due to its robustness and the fact that it is focused on the signals of the ligand, without any need for NMR information on the macromolecular target. This technique is most commonly applied to systems involving different types of ligands (e.g., small organic molecules, carbohydrates or lipids) and a protein as the target, in which the latter is selectively saturated. However, only a few examples have been reported where membrane mimetics are the macromolecular binding partners. Here, we have employed STD NMR spectroscopy to investigate the interactions of the neurotransmitter dopamine with mimetics of lipid bilayers, such as nanodiscs, by saturation of the latter. In particular, the interactions between dopamine and model lipid nanodiscs formed either from charged or zwitterionic lipids have been resolved at the atomic level. The results, in agreement with previous isothermal titration calorimetry studies, show that dopamine preferentially binds to negatively charged model membranes, but also provide detailed atomic insights into the mode of interaction of dopamine with membrane mimetics. Our findings provide relevant structural information for the design of lipid-based drug carriers of dopamine and its structural analogues and are of general applicability to other systems. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Differences in striatal dopamine transporter density between tremor dominant and non-tremor Parkinson's disease

International Nuclear Information System (INIS)

Kaasinen, Valtteri; Kinos, Maija; Joutsa, Juho; Seppaenen, Marko; Noponen, Tommi

2014-01-01

Parkinson's disease (PD) can manifest with a tremor-dominant or a non-tremor (akinetic-rigid) phenotype. Although the tremor-dominant subtype may show a better prognosis, there is limited information on the phenotypic differences regarding the level of striatal dopamine transmission. The present study investigated striatal dopamine transporter (DAT) binding characteristics in a large sample of patients with and without tremor. [ 123 I]FP-CIT SPECT scans of 231 patients with a clinical diagnosis of PD and abnormal FP-CIT binding (157 with tremor, 74 without tremor) and 230 control patients with normal FP-CIT binding (148 with tremor, 82 without tremor) were analysed using an automated region-of-interest analysis of the scans (BRASS). Specific striatal binding ratios were compared between phenotypes and groups using age, sex, and symptom duration, predominant side of symptoms, dopaminergic medications and scanner as covariates. Patients with PD had 28.1 - 65.0 % lower binding in all striatal regions compared to controls (p < 0.001). The mean FP-CIT caudate nucleus uptake and the left caudate nucleus uptake were higher in PD patients with tremor than in PD patients without tremor (mean 9.0 % higher, left 10.5 % higher; p < 0.05), whereas there were no differences between tremor and non-tremor control patients. No significant effects of tremor on DAT binding were observed in the anterior or posterior putamen. The motor phenotype is associated with the extent of caudate dopamine terminal loss in PD, as dopamine function is relatively more preserved in tremor patients. Symptom type is related to caudate dopamine function only in association with Parkinsonian dopaminergic degeneration, not in intact dopamine systems in patients with non-PD tremor. (orig.)

Aberrant dopamine D2-like receptor function in a rodent model of schizophrenia.

Science.gov (United States)

Perez, Stephanie M; Lodge, Daniel J

2012-11-01

Based on the observation that antipsychotic medications display antagonist properties at dopamine D2-like receptors, aberrant dopamine signaling has been proposed to underlie psychosis in patients with schizophrenia. Thus, it is not surprising that considerable research has been devoted to understanding the mechanisms involved in the antipsychotic action of these compounds. It is important to note that the majority of these studies have been performed in "normal" experimental animals. Given that these animals do not possess the aberrant neuronal information processing typically associated with schizophrenia, the aim of the current study was to examine the dopamine D2 receptor system in a rodent model of schizophrenia. Here, we demonstrate that methylazoxymethanol acetate (MAM)-treated rats display an enhanced effect of quinpirole on dopamine neuron activity and an aberrant locomotor response to D2-like receptor activation, suggesting changes in postsynaptic D2-like receptor function. To better understand the mechanisms underlying the enhanced response to D2-like ligands in MAM-treated rats, we examined the expression of D2, D3, and dopamine transporter mRNA in the nucleus accumbens and ventral tegmental area by quantitative reverse transcription-polymerase chain reaction. MAM-treated rats displayed a significant increase in dopamine D3 receptor mRNA expression in the nucleus accumbens with no significant changes in the expression of the D2 receptor. Taken together, these data demonstrate robust alterations in dopamine D2-like receptor function in a rodent model of schizophrenia and provide evidence that preclinical studies examining the mechanisms of antipsychotic drug action should be performed in animal models that mirror aspects of the abnormal neuronal transmission thought to underlie symptoms of schizophrenia.

Radiation Absorbed Dose to the Basal Ganglia from Dopamine Transporter Radioligand 18F-FPCIT

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William Robeson

2014-01-01

Full Text Available Our previous dosimetry studies have demonstrated that for dopaminergic radiotracers, 18F-FDOPA and 18F-FPCIT, the urinary bladder is the critical organ. As these tracers accumulate in the basal ganglia (BG with high affinity and long residence times, radiation dose to the BG may become significant, especially in normal control subjects. We have performed dynamic PET measurements using 18F-FPCIT in 16 normal adult subjects to determine if in fact the BG, although not a whole organ, but a well-defined substructure, receives the highest dose. Regions of interest were drawn over left and right BG structures. Resultant time-activity curves were generated and used to determine residence times for dosimetry calculations. S-factors were computed using the MIRDOSE3 nodule model for each caudate and putamen. For 18F-FPCIT, BG dose ranged from 0.029 to 0.069 mGy/MBq. In half of all subjects, BG dose exceeded 85% of the published critical organ (bladder dose, and in three of those, the BG dose exceeded that for the bladder. The BG can become the dose-limiting organ in studies using dopamine transporter ligands. For some normal subjects studied with F-18 or long half-life radionuclide, the BG may exceed bladder dose and become the critical structure.

Progress of study on the dopamine D4 receptor imaging agent

International Nuclear Information System (INIS)

Tian Haibin; Zhang Lan; Zhang Chunfu; Li Junling; Yin Duanzhi

2001-01-01

Dopamine receptors were originally classified into five receptors subtypes, the dopamine D 4 receptor was included. Schizophrenic pathophysiology may be associated with expression and function of the dopamine D 4 receptor; it is of great importance to study the imaging agent of dopamine D 4 receptor. The study on radioactivity distribution and metabolize of radioligand remains hampered by the lack radioligand for the D 4 receptor which can be labeled using suitable nuclei. This paper reviews the progress of study on the dopamine D 4 receptor imaging agent, with particular emphasis vary nuclei, for example 11 C, 18 F, 123 I, labeled D 4 receptor ligands, antagonists and analogs as PET or SPECT imaging agents. Authors estimated affinity and selectivity of radioligands for the dopamine D 4 receptor in laboratory animal tests

Nature of rate-limiting steps in a compartmentalized enzyme system. Quantitation of dopamine transport and hydroxylation rates in resealed chromaffin granule ghosts

International Nuclear Information System (INIS)

Ahn, N.G.; Klinman, J.P.

1989-01-01

Using isolated chromaffin granule ghosts from bovine adrenal medullae, we have studied the kinetics of dopamine beta-monooxygenase (D beta M) activity as it is linked to dopamine transport. Measurements of the initial rates of transport and of transport-linked norepinephrine formation suggested that enzyme activity may be partially rate-limiting in the coupled carrier/enzyme system. This was confirmed by (i) measurements of initial rates of norepinephrine formation using deuterated substrate, which gave isotope effects greater than 2.0, and (ii) kinetic measurements using ghosts pulsed with varying concentrations of labeled dopamine, which indicated substantial substrate accumulation in the vesicle interior as a function of time. Initial rates of product formation, when combined with approximations of internal substrate concentrations, allowed estimates of Kcat and Km for intravesicular D beta M. Activation by external reductant was apparent in both initial rate parameters and the measurements of transients. Under conditions of optimal D beta M activity, the enzyme rate parameters (kcat = 0.31 nmol/s.mg and Km = 2 mM) indicated partial rate limitation compared to dopamine transport (kcat = 0.38 nmol/s.mg and Km = 32 microM). Compartmental analysis of the time curves, performed using numerical nonlinear least squares methods, gave least squares estimates of rate constants for a simple carrier mechanism and kcat values for D beta M which were consistent with estimates from initial rates

The effect of modafinil on the rat dopamine transporter and dopamine receptors D1-D3 paralleling cognitive enhancement in the radial arm maze

Directory of Open Access Journals (Sweden)

Yasemin eKarabacak

2015-08-01

Full Text Available A series of drugs have been reported to increase memory performance modulating the dopaminergic system and herein modafinil was tested for its working memory (WM enhancing properties. Reuptake inhibition of dopamine, serotonin (SERT and norepinephrine (NET by modafinil was tested. 60 male Sprague Dawley rats were divided into six groups (modafinil-treated 1-5-10 mg/kg body weight, trained and untrained and vehicle treated trained and untrained rats; daily injected intraperitoneally for a period of 10 days and tested in a radial arm maze (RAM, a paradigm for testing spatial WM. Hippocampi were taken six hours following the last day of training and complexes containing the unphosphorylated or phosphorylated dopamine transporter (DAT-CC and pDAT-CC and complexes containing the D1-3 dopamine receptor subunits (D1-D3-CC were determined. Modafinil was binding to the DAT but insignificantly to SERT or NET and dopamine reuptake was blocked specifically (IC50=11.11; SERT 1547; NET 182. From day 8 (day 9 for 1 mg/kg body weight modafinil was decreasing WM errors in the RAM significantly and remarkably at all doses tested as compared to the vehicle controls. WMEs were linked to the D2R-CC and the pDAT-CC. pDAT and D1-D3-CC levels were modulated significantly and modafinil was shown to enhance spatial WM in the rat in a well-documented paradigm at all the three doses and dopamine reuptake inhibition with subsequent modulation of D1-3-CC is proposed as a possible mechanism of action.

The Human Dopamine Transporter: Investigating the Role of the C Terminus in Surface Targeting

DEFF Research Database (Denmark)

Vægter, Christian Bjerggaard

2005-01-01

Dopaminergic neurotransmission is involved in the modulation of locomotor activity, emotional behavior, memory and cognition. Hence, imbalances in the dopaminergic system in humans have been hypothesized to contribute to the pathogenesis of a number of illnesses, including Parkinson's disease......, schizophrenia, ADHD (attention deficit hyperactivity disorder) and addiction. The dopamine transporter (DAT) is a presynaptic protein of dopaminergic nerve terminals that terminate dopaminergic signaling by rapidly sequestering released dopamine from the synaptic cleft. The DAT therefore plays an important role....... New data suggest a potential role of the PDZ interaction in the regulation of DAT internalization and recycling: we found that iv disrupting the PDZ domain-binding sequence affected the regulation of constitutive internalization, degradation and potentially also recycling of DAT in Neuro2A cells. We...

A role for accumbal glycine receptors in modulation of dopamine release by the glycine transporter-1 inhibitor Org25935

Directory of Open Access Journals (Sweden)

Helga eHöifödt Lidö

2011-03-01

Full Text Available AbstractAccumbal glycine modulates basal and ethanol-induced dopamine levels in the nucleus accumbens (nAc as well as voluntary ethanol consumption. Also, systemic administration of the glycine transporter-1 inhibitor Org25935 elevates dopamine levels in nAc, prevents a further ethanol-induced dopamine elevation and robustly and dose-dependently decreases ethanol consumption in rats. Here we investigated whether Org25935 applied locally in nAc modulates dopamine release, and whether accumbal glycine receptors or NMDA receptors are involved in this tentative effect. We also addressed whether Org25935 and ethanol applied locally in nAc interact with dopamine levels, as seen after systemic administration. We used in vivo microdialysis coupled to HPLC-ED in freely moving male Wistar rats to monitor dopamine output in nAc after local perfusion of Org25935 alone, with ethanol, or Org25935-perfusion after pre-treatment with the glycine receptor antagonist strychnine or the NMDA receptor glycine site antagonist L-701.324. Local Org25935 increased extracellular dopamine levels in a subpopulation of rats. Local strychnine, but not systemic L-701.324, antagonized the dopamine-activating effect of Org25935. Ethanol failed to induce a dopamine overflow in the subpopulation responding to Org25935 with a dopamine elevation. The study supports a role for accumbal glycine receptors rather than NMDA receptor signaling in the dopamine-activating effect of Org25935. The results further indicate that the previously reported systemic Org25935-ethanol interaction with regard to accumbal dopamine is localized to the nAc. This adds to the growing evidence for the glycine receptor as an important player in the dopamine reward circuitry and in ethanol’s effects within this system.

Synthesis of 3-[18F]fluoromethyl-BTCP and evaluation as a potential PET radioligand for the dopamine transporter in baboons

International Nuclear Information System (INIS)

Ponchant, M.; Crouzel, C.; Varastet, M.; Hantraye, P.;

1993-01-01

In an attempt to visualize in vivo the dopamine transporter and evaluate its potential as an imaging tool for monitoring dopamine fiber degeneration by positron emission tomography, the 18 F-positron-emitting analogue of 3-fluoromethyl-1-[2-benzothienyl)-cyclohexyl]-piperidine, [ 18 F]BTCP, was synthesized and tested in a primate model of hemiparkinsonism. When comparing binding ratios between the intact and the dopamine-denervated striatum, there was a modest loss of binding in denervated striatum, suggesting that degeneration of dopaminergic fibers could be detected using 3-[ 18 F]fluoromethyl-BTCP. However due to a high non-specific binding in vivo, the interest of 3-[ 18 F]fluoromethyl-BTCP to image the dopamine reuptake system in vivo appears limited. (author)

Interaction of Dopamine Transporter (DAT1) Genotype and Maltreatment for ADHD: A Latent Class Analysis

Science.gov (United States)

Li, James J.; Lee, Steve S.

2012-01-01

Background: Although the association of the dopamine transporter (DAT1) gene and attention-deficit/hyperactivity disorder (ADHD) has been widely studied, far less is known about its potential interaction with environmental risk factors. Given that maltreatment is a replicated risk factor for ADHD, we explored the interaction between DAT1 and…

Evaluating Dopamine Reward Pathway in ADHD; clinical implications

International Nuclear Information System (INIS)

Volkow, N.D.; Wang, G.; Volkow, N.D.; Wang, G.-J.; Kollins, S.H.; Wigal, T.L.; Newcorn, J.H.; Telang, F.; Fowler, J.S.; Zhu, W.; Logan, J.; Ma, Y.; Pradhan, K.; Wong, C.T.; Swanson, J.M.

2009-01-01

Attention-deficit/hyperactivity disorder (ADHD) - characterized by symptoms of inattention and hyperactivity-impulsivity - is the most prevalent childhood psychiatric disorder that frequently persists into adulthood, and there is increasing evidence of reward-motivation deficits in this disorder. To evaluate biological bases that might underlie a reward/motivation deficit by imaging key components of the brain dopamine reward pathway (mesoaccumbens). We used positron emission tomography to measure dopamine synaptic markers (transporters and D 2 /D 3 receptors) in 53 nonmedicated adults with ADHD and 44 healthy controls between 2001-2009 at Brookhaven National Laboratory. We measured specific binding of positron emission tomographic radioligands for dopamine transporters (DAT) using [ 11 C]cocaine and for D 2 /D 3 receptors using [ 11 C]raclopride, quantified as binding potential (distribution volume ratio -1). For both ligands, statistical parametric mapping showed that specific binding was lower in ADHD than in controls (threshold for significance set at P 2 /D 3 receptors, the mean accumbens for controls was 2.85 vs 2.68 for those with ADHD (95% CI, 0.06-0.30, P = .004); and in the midbrain, it was for controls 0.28 vs 0.18 for those with ADHD (95% CI, 0.02-0.17, P = .01). The analysis also corroborated differences in the left caudate: the mean DAT for controls was 0.66 vs 0.53 for those with ADHD (95% CI, 0.04-0.22; P = .003) and the mean D 2 /D 3 for controls was 2.80 vs 2.47 for those with ADHD (95% CI, 0.10-0.56; P = .005) and differences in D 2 /D 3 in the hypothalamic region, with controls having a mean of 0.12 vs 0.05 for those with ADHD (95% CI, 0.02-0.12; P = .004). Ratings of attention correlated with D 2 /D 3 in the accumbens (r = 0.35; 95% CI, 0.15-0.52; P = .001), midbrain (r = 0.35; 95% CI, 0.14-0.52; P = .001), caudate (r = 0.32; 95% CI, 0.11-0.50; P = .003), and hypothalamic (r = 0.31; CI, 0.10-0.49; P = .003) regions and with DAT in the midbrain

Dopamine Transporter Gene Moderates Response to Behavioral Parent Training in Children With ADHD : A Pilot Study

NARCIS (Netherlands)

van den Hoofdakker, Barbara J.; Dijck-Brouwer, D. A. Janneke; Nauta, Maaike H.; van der Veen-Mulders, Lianne; Sytema, Sjoerd; Emmelkamp, Paul M. G.; Minderaa, Ruud B.; Hoekstra, Pieter J.

There is great variability in the degree to which children with attention deficit/hyperactivity disorder (ADHD) improve through behavioral treatments. This study investigates the influence of the dopamine transporter gene (SCL6A3/DAT1) on outcome of behavioral parent training (BPT). Study subjects

Dopamine transporter gene moderates response to behavioral parent training in children with ADHD: A pilot study

NARCIS (Netherlands)

van den Hoofdakker, B.J.; Nauta, M.H.; Dijck-Brouwer, D.A.J.; van der Veen-Mulders, L.; Sytema, S.; Emmelkamp, P.M.G.; Minderaa, R.B.; Hoekstra, P.J.

2012-01-01

There is great variability in the degree to which children with attention deficit/hyperactivity disorder (ADHD) improve through behavioral treatments. This study investigates the influence of the dopamine transporter gene (SCL6A3/DAT1) on outcome of behavioral parent training (BPT). Study subjects

Intranasal Dopamine Reduces In Vivo [(123)I]FP-CIT Binding to Striatal Dopamine Transporter: Correlation with Behavioral Changes and Evidence for Pavlovian Conditioned Dopamine Response.

Science.gov (United States)

de Souza Silva, Maria A; Mattern, Claudia; Decheva, Cvetana; Huston, Joseph P; Sadile, Adolfo G; Beu, Markus; Müller, H-W; Nikolaus, Susanne

2016-01-01

Dopamine (DA), which does not cross the blood-brain barrier, has central and behavioral effects when administered via the nasal route. Neither the mechanisms of central action of intranasal dopamine (IN-DA), nor its mechanisms of diffusion and transport into the brain are well understood. We here examined whether IN-DA application influences dopamine transporter (DAT) binding in the dorsal striatum and assessed the extent of binding in relation to motor and exploratory behaviors. We hypothesized that, based on the finding of increased extracellular DA in the striatum induced by application of IN-DA, binding of [(123)I]FP-CIT to the DAT should be decreased due to competition at the receptor. Rats were administered 3 mg/kg IN-DA and vehicle (VEH), with IN-DA injection either preceding or following VEH. Then motor and exploratory behaviors (traveled distance, velocity, center time, sitting, rearing, head-shoulder motility, grooming) were assessed for 30 min in an open field prior to administration of [(123)I]FP-CIT. DAT binding after IN-DA and VEH was measured with small animal SPECT 2 h following administration of the radioligand. (1) After IN-DA application, striatal DAT binding was significantly lower as compared to VEH, indicating that the nasally delivered DA had central action and increased DA levels comparable to that found previously with L-DOPA administration; and (2) DAT binding in response to intranasal VEH was lower when IN-DA application preceded VEH treatment. This finding is suggestive of Pavlovian conditioning of DA at the level of the DAT, since the DA treatment modified (decreased) the binding in response to the subsequent VEH treatment. VEH treatment also reduced motor and exploratory behaviors more when applied before, as compared to when it followed IN-DA application, also indicative of behavioral Pavlovian conditioning akin to that found upon application of various psychostimulant drugs. (a) demonstrate a direct central action of intranasally

Clinical application of 99Tcm-TRODAT-1 SPECT imaging of dopamine transporter in monitoring the state of Parkinson's disease

International Nuclear Information System (INIS)

Deng Huaifu; Hu Ping

2005-01-01

To discuss the applicability of 99 Tc m -TRODAT-1 SPECT imaging of dopamine transporter in monitoring the state of Parkinson's disease (PD), 20 patients with PD and a control group of 14 healthy subjects were chosen to conduct dopamine transporter (DAT) imaging by SPECT with 99 Tc m -TRODAT-1. The radioactive ratio between bilateral striatum and cerebellum and the asymmetry index (Al) of bilateral striatum were computed by using the region of interest (ROI) technology. Meanwhile, the PD patients were classified by the improved Hoehn-Yahr Disability Score and then evaluated by Unified Parkinson's Disease Rating Scale (UPDRS). The findings show that there is a negative correlation between the bilateral ST/CB mean of the PD and the Hoehn-Yahr grading of the patients' state of illness, the UPDRS score, the patients' self-caring ability, the ability to move around. As for the asymmetry index AI PD , there was a positive correlation with the duration of disease, and a significant difference between the PD and the control group, with the former much higher than the latter. Therefore, the dopamine transporter imaging by SPECT with 99 Tc m -TRODAT-1 can monitor the state of Parkinson's disease, and show the symptom severity of Parkinson's disease. (authors)

Amphetamine activates Rho GTPase signaling to mediate dopamine transporter internalization and acute behavioral effects of amphetamine

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Wheeler, David S.; Underhill, Suzanne M.; Stolz, Donna B.; Murdoch, Geoffrey H.; Thiels, Edda; Romero, Guillermo; Amara, Susan G.

2015-01-01

Acute amphetamine (AMPH) exposure elevates extracellular dopamine through a variety of mechanisms that include inhibition of dopamine reuptake, depletion of vesicular stores, and facilitation of dopamine efflux across the plasma membrane. Recent work has shown that the DAT substrate AMPH, unlike cocaine and other nontransported blockers, can also stimulate endocytosis of the plasma membrane dopamine transporter (DAT). Here, we show that when AMPH enters the cytoplasm it rapidly stimulates DAT internalization through a dynamin-dependent, clathrin-independent process. This effect, which can be observed in transfected cells, cultured dopamine neurons, and midbrain slices, is mediated by activation of the small GTPase RhoA. Inhibition of RhoA activity with C3 exotoxin or a dominant-negative RhoA blocks AMPH-induced DAT internalization. These actions depend on AMPH entry into the cell and are blocked by the DAT inhibitor cocaine. AMPH also stimulates cAMP accumulation and PKA-dependent inactivation of RhoA, thus providing a mechanism whereby PKA- and RhoA-dependent signaling pathways can interact to regulate the timing and robustness of AMPH’s effects on DAT internalization. Consistent with this model, the activation of D1/D5 receptors that couple to PKA in dopamine neurons antagonizes RhoA activation, DAT internalization, and hyperlocomotion observed in mice after AMPH treatment. These observations support the existence of an unanticipated intracellular target that mediates the effects of AMPH on RhoA and cAMP signaling and suggest new pathways to target to disrupt AMPH action. PMID:26553986

Rare Autism-Associated Variants Implicate Syntaxin 1 (STX1 R26Q) Phosphorylation and the Dopamine Transporter (hDAT R51W) in Dopamine Neurotransmission and Behaviors

OpenAIRE

Cartier, Etienne; Hamilton, Peter J.; Belovich, Andrea N.; Shekar, Aparna; Campbell, Nicholas G.; Saunders, Christine; Andreassen, Thorvald F.; Gether, Ulrik; Veenstra-Vanderweele, Jeremy; Sutcliffe, James S.; Ulery-Reynolds, Paula G.; Erreger, Kevin; Matthies, Heinrich J.G.; Galli, Aurelio

2015-01-01

Background: Syntaxin 1 (STX1) is a presynaptic plasma membrane protein that coordinates synaptic vesicle fusion. STX1 also regulates the function of neurotransmitter transporters, including the dopamine (DA) transporter (DAT). The DAT is a membrane protein that controls DA homeostasis through the high-affinity re-uptake of synaptically released DA. Methods: We adopt newly developed animal models and state-of-the-art biophysical techniques to determine the contribution of the identified gen...

Impulse control disorders in Parkinson's disease: decreased striatal dopamine transporter levels.

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Voon, Valerie; Rizos, Alexandra; Chakravartty, Riddhika; Mulholland, Nicola; Robinson, Stephanie; Howell, Nicholas A; Harrison, Neil; Vivian, Gill; Ray Chaudhuri, K

2014-02-01

Impulse control disorders are commonly associated with dopaminergic therapy in Parkinson's disease (PD). PD patients with impulse control disorders demonstrate enhanced dopamine release to conditioned cues and a gambling task on [(11)C]raclopride positron emission tomography (PET) imaging and enhanced ventral striatal activity to reward on functional MRI. We compared PD patients with impulse control disorders and age-matched and gender-matched controls without impulse control disorders using [(123)I]FP-CIT (2β-carbomethoxy-3β-(4-iodophenyl)tropane) single photon emission computed tomography (SPECT), to assess striatal dopamine transporter (DAT) density. The [(123)I]FP-CIT binding data in the striatum were compared between 15 PD patients with and 15 without impulse control disorders using independent t tests. Those with impulse control disorders showed significantly lower DAT binding in the right striatum with a trend in the left (right: F(1,24)=5.93, p=0.02; left: F(1,24)=3.75, p=0.07) compared to controls. Our findings suggest that greater dopaminergic striatal activity in PD patients with impulse control disorders may be partly related to decreased uptake and clearance of dopamine from the synaptic cleft. Whether these findings are related to state or trait effects is not known. These findings dovetail with reports of lower DAT levels secondary to the effects of methamphetamine and alcohol. Although any regulation of DAT by antiparkinsonian medication appears to be modest, PD patients with impulse control disorders may be differentially sensitive to regulatory mechanisms of DAT expression by dopaminergic medications.

Molecular mechanism of ligand recognition by membrane transport protein, Mhp1

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Simmons, Katie J; Jackson, Scott M; Brueckner, Florian; Patching, Simon G; Beckstein, Oliver; Ivanova, Ekaterina; Geng, Tian; Weyand, Simone; Drew, David; Lanigan, Joseph; Sharples, David J; Sansom, Mark SP; Iwata, So; Fishwick, Colin WG; Johnson, A Peter; Cameron, Alexander D; Henderson, Peter JF

2014-01-01

The hydantoin transporter Mhp1 is a sodium-coupled secondary active transport protein of the nucleobase-cation-symport family and a member of the widespread 5-helix inverted repeat superfamily of transporters. The structure of Mhp1 was previously solved in three different conformations providing insight into the molecular basis of the alternating access mechanism. Here, we elucidate detailed events of substrate binding, through a combination of crystallography, molecular dynamics, site-directed mutagenesis, biochemical/biophysical assays, and the design and synthesis of novel ligands. We show precisely where 5-substituted hydantoin substrates bind in an extended configuration at the interface of the bundle and hash domains. They are recognised through hydrogen bonds to the hydantoin moiety and the complementarity of the 5-substituent for a hydrophobic pocket in the protein. Furthermore, we describe a novel structure of an intermediate state of the protein with the external thin gate locked open by an inhibitor, 5-(2-naphthylmethyl)-L-hydantoin, which becomes a substrate when leucine 363 is changed to an alanine. We deduce the molecular events that underlie acquisition and transport of a ligand by Mhp1. PMID:24952894

Behavioral Phenotyping of Dopamine Transporter Knockout Rats: Compulsive Traits, Motor Stereotypies, and Anhedonia

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Stefano Cinque

2018-02-01

Full Text Available Alterations in dopamine neurotransmission are generally associated with diseases such as attention-deficit/hyperactivity disorder (ADHD and obsessive-compulsive disorder (OCD. Such diseases typically feature poor decision making and lack of control on executive functions and have been studied through the years using many animal models. Dopamine transporter (DAT knockout (KO and heterozygous (HET mice, in particular, have been widely used to study ADHD. Recently, a strain of DAT KO rats has been developed (1. Here, we provide a phenotypic characterization of reward sensitivity and compulsive choice by adult rats born from DAT–HET dams bred with DAT–HET males, in order to further validate DAT KO rats as an animal model for preclinical research. We first tested DAT KO rats’ sensitivity to rewarding stimuli, provided by highly appetitive food or sweet water; then, we tested their choice behavior with an Intolerance-to-Delay Task (IDT. During these tests, DAT KO rats appeared less sensitive to rewarding stimuli than wild-type (WT and HET rats: they also showed a prominent hyperactive behavior with a rigid choice pattern and a wide number of compulsive stereotypies. Moreover, during the IDT, we tested the effects of amphetamine (AMPH and RO-5203648, a trace amine-associated receptor 1 (TAAR1 partial agonist. AMPH accentuated impulsive behaviors in WT and HET rats, while it had no effect in DAT KO rats. Finally, we measured the levels of tyrosine hydroxylase, dopamine receptor 2 (D2, serotonin transporter, and TAAR1 mRNA transcripts in samples of ventral striatum, finding no significant differences between WT and KO genotypes. Throughout this study, DAT KO rats showed alterations in decision-making processes and in motivational states, as well as prominent motor and oral stereotypies: more studies are warranted to fully characterize and efficiently use them in preclinical research.

Affinity Labeling of Membrane Receptors Using Tissue-Penetrating Radiations

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Franklin C. Wong

2013-01-01

Full Text Available Photoaffinity labeling, a useful in vivo biochemical tool, is limited when applied in vivo because of the poor tissue penetration by ultraviolet (UV photons. This study investigates affinity labeling using tissue-penetrating radiation to overcome the tissue attenuation and irreversibly label membrane receptor proteins. Using X-ray (115 kVp at low doses (<50 cGy or Rad, specific and irreversible binding was found on striatal dopamine transporters with 3 photoaffinity ligands for dopamine transporters, to different extents. Upon X-ray exposure (115 kVp, RTI-38 and RTI-78 ligands showed irreversible and specific binding to the dopamine transporter similar to those seen with UV exposure under other conditions. Similarly, gamma rays at higher energy (662 keV also affect irreversible binding of photoreactive ligands to peripheral benzodiazepine receptors (by PK14105 and to the dopamine (D2 membrane receptors (by azidoclebopride, respectively. This study reports that X-ray and gamma rays induced affinity labeling of membrane receptors in a manner similar to UV with photoreactive ligands of the dopamine transporter, D2 dopamine receptor (D2R, and peripheral benzodiazepine receptor (PBDZR. It may provide specific noninvasive irreversible block or stimulation of a receptor using tissue-penetrating radiation targeting selected anatomic sites.

Cell surface receptors for signal transduction and ligand transport: a design principles study.

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Harish Shankaran

2007-06-01

Full Text Available Receptors constitute the interface of cells to their external environment. These molecules bind specific ligands involved in multiple processes, such as signal transduction and nutrient transport. Although a variety of cell surface receptors undergo endocytosis, the systems-level design principles that govern the evolution of receptor trafficking dynamics are far from fully understood. We have constructed a generalized mathematical model of receptor-ligand binding and internalization to understand how receptor internalization dynamics encodes receptor function and regulation. A given signaling or transport receptor system represents a particular implementation of this module with a specific set of kinetic parameters. Parametric analysis of the response of receptor systems to ligand inputs reveals that receptor systems can be characterized as being: i avidity-controlled where the response control depends primarily on the extracellular ligand capture efficiency, ii consumption-controlled where the ability to internalize surface-bound ligand is the primary control parameter, and iii dual-sensitivity where both the avidity and consumption parameters are important. We show that the transferrin and low-density lipoprotein receptors are avidity-controlled, the vitellogenin receptor is consumption-controlled, and the epidermal growth factor receptor is a dual-sensitivity receptor. Significantly, we show that ligand-induced endocytosis is a mechanism to enhance the accuracy of signaling receptors rather than merely serving to attenuate signaling. Our analysis reveals that the location of a receptor system in the avidity-consumption parameter space can be used to understand both its function and its regulation.

Dopamine-independent locomotor actions of amphetamines in a novel acute mouse model of Parkinson disease.

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2005-08-01

Full Text Available Brain dopamine is critically involved in movement control, and its deficiency is the primary cause of motor symptoms in Parkinson disease. Here we report development of an animal model of acute severe dopamine deficiency by using mice lacking the dopamine transporter. In the absence of transporter-mediated recycling mechanisms, dopamine levels become entirely dependent on de novo synthesis. Acute pharmacological inhibition of dopamine synthesis in these mice induces transient elimination of striatal dopamine accompanied by the development of a striking behavioral phenotype manifested as severe akinesia, rigidity, tremor, and ptosis. This phenotype can be reversed by administration of the dopamine precursor, L-DOPA, or by nonselective dopamine agonists. Surprisingly, several amphetamine derivatives were also effective in reversing these behavioral abnormalities in a dopamine-independent manner. Identification of dopamine transporter- and dopamine-independent locomotor actions of amphetamines suggests a novel paradigm in the search for prospective anti-Parkinsonian drugs.

Dopamine transporter imaging in rapid eye movement sleep behavior disorder

International Nuclear Information System (INIS)

Kim, Yu Kyeong; Yoon, In Young; Kim, Jong Min; Jeong, Seok Hoon; Kim, Ji Sun; Lee, Byung Chul; Lee, Won Woo; Kim, Sang Eun

2007-01-01

The pathogenesis of rapid eye movement (REM) sleep behavior disorder (RBD) is still unknown. However, involvement of dopaminergic system in RBD has been hypothesized because of frequent association with degenerative movement disorders such as Parkinson's disease. The purpose of this study was to examine the extent and pattern of loss of dopamine transporter in RBD using FP-CIT SPECT. Fourteen patient with idiopathic RBD (mean age:665 yrs, M:F=10:3) participated in this study. Polysonmography confirmed loss of REM atonia and determined RBD severities by amount of tonic/phasic muscle activity during REM sleep in all cases. To compare with RBD, 14 early idiopathic Parkinson's disease rated as Hoehn and Yahr stage 1 (IPD) and 12 healthy controls were also selected. All participants performed single-photon emission computed tomography (SPECT) imaging 3 hours after injection of [123I]FP-CIT. Regions of interest were drawn on bilateral caudate and putamen, whole striatum and occipital cortex. Specific binding for dopamine transporters (DAT) were calculated using region to occipital uptake ratio based on the transient equilibrium method. Overall mean of DAT density in the striatum was lower in RBD group than controls, and higher than IPD group, However, DAT density in most individual RBD was still within normal range, and total striatal DAT density was not correlated with severity of RBD. Meanwhile, the caudate to putamen uptake ratio (C/P ratio) in RBD group was insignificantly higher than those in healthy controls. Nevertheless, C/P ratio within RBD group was reversely correlated with the RBD severity. Our study suggested that nigrostriatal dopaminergic degeneration could be a part of the pathogenesis of RBD, but not essential for the development of RBD. Further longitudinal evaluation of presynaptic dopaminergic system in idiopathic RBD may guarantee the more understanding for RBD and associated neurodegenerative disease

Dopamine transporter imaging in rapid eye movement sleep behavior disorder

Energy Technology Data Exchange (ETDEWEB)

Kim, Yu Kyeong; Yoon, In Young; Kim, Jong Min; Jeong, Seok Hoon; Kim, Ji Sun; Lee, Byung Chul; Lee, Won Woo; Kim, Sang Eun [Seoul National Univ. College of Medicine, Seoul (Korea, Republic of)

2007-07-01

The pathogenesis of rapid eye movement (REM) sleep behavior disorder (RBD) is still unknown. However, involvement of dopaminergic system in RBD has been hypothesized because of frequent association with degenerative movement disorders such as Parkinson's disease. The purpose of this study was to examine the extent and pattern of loss of dopamine transporter in RBD using FP-CIT SPECT. Fourteen patient with idiopathic RBD (mean age:665 yrs, M:F=10:3) participated in this study. Polysonmography confirmed loss of REM atonia and determined RBD severities by amount of tonic/phasic muscle activity during REM sleep in all cases. To compare with RBD, 14 early idiopathic Parkinson's disease rated as Hoehn and Yahr stage 1 (IPD) and 12 healthy controls were also selected. All participants performed single-photon emission computed tomography (SPECT) imaging 3 hours after injection of [123I]FP-CIT. Regions of interest were drawn on bilateral caudate and putamen, whole striatum and occipital cortex. Specific binding for dopamine transporters (DAT) were calculated using region to occipital uptake ratio based on the transient equilibrium method. Overall mean of DAT density in the striatum was lower in RBD group than controls, and higher than IPD group, However, DAT density in most individual RBD was still within normal range, and total striatal DAT density was not correlated with severity of RBD. Meanwhile, the caudate to putamen uptake ratio (C/P ratio) in RBD group was insignificantly higher than those in healthy controls. Nevertheless, C/P ratio within RBD group was reversely correlated with the RBD severity. Our study suggested that nigrostriatal dopaminergic degeneration could be a part of the pathogenesis of RBD, but not essential for the development of RBD. Further longitudinal evaluation of presynaptic dopaminergic system in idiopathic RBD may guarantee the more understanding for RBD and associated neurodegenerative disease.

Essential Oils from the Medicinal Herbs Upregulate Dopamine Transporter in Rat Pheochromocytoma Cells.

Science.gov (United States)

Choi, Min Sun; Choi, Bang-sub; Kim, Sang Heon; Pak, Sok Cheon; Jang, Chul Ho; Chin, Young-Won; Kim, Young-Mi; Kim, Dong-il; Jeon, Songhee; Koo, Byung-Soo

2015-10-01

The dopamine transporter (DAT) protein, a component of the dopamine system, undergoes adaptive neurobiological changes from drug abuse. Prevention of relapse and reduction of withdrawal symptoms are still the major limitations in the current pharmacological treatments of drug addiction. The present study aimed to investigate the effects of essential oils extracted from Elsholtzia ciliata, Shinchim, Angelicae gigantis Radix, and Eugenia caryophyllata, well-known traditional Korean medicines for addiction, on the modulation of dopamine system in amphetamine-treated cells and to explore the possible mechanism underlying its therapeutic effect. The potential cytotoxic effect of essential oils was evaluated in PC12 rat pheochromocytoma cells using cell viability assays. Quantification of DAT, p-CREB, p-MAPK, and p-Akt was done by immunoblotting. DAT was significantly reduced in cells treated with 50 μM of amphetamine in a time-dependent manner. No significant toxicity of essential oils from Elsholtzia ciliata and Shinchim was observed at doses of 10, 25, and 50 μg/mL. However, essential oils from A. gigantis Radix at a dose of 100 μg/mL and E. caryophyllata at doses of 50 and 100 μg/mL showed cytotoxicity. Treatment with GBR 12909, a highly selective DAT inhibitor, significantly increased DAT expression compared with that of amphetamine only by enhancing phosphorylation of mitogen-activated protein kinases (MAPK) and Akt. In addition, essential oils effectively induced hyperphosphorylation of cyclic-AMP response element-binding protein (CREB), MAPK, and Akt, which resulted in DAT upregulation. Our study implies that the essential oils may rehabilitate brain dopamine function through increased DAT availability in abstinent former drug users.

Effects of acute and chronic treatments with dopamine D₂ and D₃ receptor ligands on cocaine versus food choice in rats

DEFF Research Database (Denmark)

Thomsen, Morgane; Barrett, Andrew C.; Butler, Paul

2017-01-01

effects of dopamine D2- and D3-preferring ligands on choice between intravenous cocaine and palatable food in rats. Under baseline conditions, cocaine maintained dose-dependent increases in cocaine choice and reciprocal decreases in food choice. Acutely, the D2 agonist R-(2)-norpropylapomorphine (NPA......) and antagonist L-741,626 [3-[[4-(4-chlorophenyl)-4-hydroxypiperidin-lyl] methyl-1H-indole] produced leftward and rightward shifts in cocaine dose-effect curves, respectively, whereas the partial agonist terguride had no effect. All three drugs dose-dependently decreased food-maintained responding. Chronically......, the effects of R-(2)-norpropylapomorphine and L-741,626 on cocaine selfadministration showed marked tolerance, whereas suppression of food-reinforced behavior persisted. Acute effects of the D3 ligands were less systematic and most consistent with nonselective decreases in cocaine- and food-maintained...

Striatal dopamine in Parkinson disease: A meta-analysis of imaging studies.

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Kaasinen, Valtteri; Vahlberg, Tero

2017-12-01

A meta-analysis of 142 positron emission tomography and single photon emission computed tomography studies that have investigated striatal presynaptic dopamine function in Parkinson disease (PD) was performed. Subregional estimates of striatal dopamine metabolism are presented. The aromatic L-amino-acid decarboxylase (AADC) defect appears to be consistently smaller than the dopamine transporter and vesicular monoamine transporter 2 defects, suggesting upregulation of AADC function in PD. The correlation between disease severity and dopamine loss appears linear, but the majority of longitudinal studies point to a negative exponential progression pattern of dopamine loss in PD. Ann Neurol 2017;82:873-882. © 2017 American Neurological Association.

Distinct Roles of Opioid and Dopamine Systems in Lateral Hypothalamic Intracranial Self-Stimulation.

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Ide, Soichiro; Takahashi, Takehiro; Takamatsu, Yukio; Uhl, George R; Niki, Hiroaki; Sora, Ichiro; Ikeda, Kazutaka

2017-05-01

Opioid and dopamine systems play crucial roles in reward. Similarities and differences in the neural mechanisms of reward that are mediated by these 2 systems have remained largely unknown. Thus, in the present study, we investigated the differences in reward function in both µ-opioid receptor knockout mice and dopamine transporter knockout mice, important molecules in the opioid and dopamine systems. Mice were implanted with electrodes into the right lateral hypothalamus (l hour). Mice were then trained to put their muzzle into the hole in the head-dipping chamber for intracranial electrical stimulation, and the influences of gene knockout were assessed. Significant differences are observed between opioid and dopamine systems in reward function. µ-Opioid receptor knockout mice exhibited enhanced intracranial electrical stimulation, which induced dopamine release. They also exhibited greater motility under conditions of "despair" in both the tail suspension test and water wheel test. In contrast, dopamine transporter knockout mice maintained intracranial electrical stimulation responding even when more active efforts were required to obtain the reward. The absence of µ-opioid receptor or dopamine transporter did not lead to the absence of intracranial electrical stimulation responsiveness but rather differentially altered it. The present results in µ-opioid receptor knockout mice are consistent with the suppressive involvement of µ-opioid receptors in both positive incentive motivation associated with intracranial electrical stimulation and negative incentive motivation associated with depressive states. In contrast, the results in dopamine transporter knockout mice are consistent with the involvement of dopamine transporters in positive incentive motivation, especially its persistence. Differences in intracranial electrical stimulation in µ-opioid receptor and dopamine transporter knockout mice underscore the multidimensional nature of reward. © The Author

Differences in striatal dopamine transporter density between tremor dominant and non-tremor Parkinson's disease

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Kaasinen, Valtteri; Kinos, Maija; Joutsa, Juho [University of Turku and Turku University Hospital, Division of Clinical Neurosciences, Turku (Finland); University of Turku and Turku University Hospital, Turku PET Centre, Turku (Finland); Seppaenen, Marko [University of Turku and Turku University Hospital, Turku PET Centre, Turku (Finland); University of Turku and Turku University Hospital, Department of Clinical Physiology and Nuclear Medicine, Turku (Finland); Noponen, Tommi [University of Turku and Turku University Hospital, Department of Clinical Physiology and Nuclear Medicine, Turku (Finland)

2014-10-15

Parkinson's disease (PD) can manifest with a tremor-dominant or a non-tremor (akinetic-rigid) phenotype. Although the tremor-dominant subtype may show a better prognosis, there is limited information on the phenotypic differences regarding the level of striatal dopamine transmission. The present study investigated striatal dopamine transporter (DAT) binding characteristics in a large sample of patients with and without tremor. [{sup 123}I]FP-CIT SPECT scans of 231 patients with a clinical diagnosis of PD and abnormal FP-CIT binding (157 with tremor, 74 without tremor) and 230 control patients with normal FP-CIT binding (148 with tremor, 82 without tremor) were analysed using an automated region-of-interest analysis of the scans (BRASS). Specific striatal binding ratios were compared between phenotypes and groups using age, sex, and symptom duration, predominant side of symptoms, dopaminergic medications and scanner as covariates. Patients with PD had 28.1 - 65.0 % lower binding in all striatal regions compared to controls (p < 0.001). The mean FP-CIT caudate nucleus uptake and the left caudate nucleus uptake were higher in PD patients with tremor than in PD patients without tremor (mean 9.0 % higher, left 10.5 % higher; p < 0.05), whereas there were no differences between tremor and non-tremor control patients. No significant effects of tremor on DAT binding were observed in the anterior or posterior putamen. The motor phenotype is associated with the extent of caudate dopamine terminal loss in PD, as dopamine function is relatively more preserved in tremor patients. Symptom type is related to caudate dopamine function only in association with Parkinsonian dopaminergic degeneration, not in intact dopamine systems in patients with non-PD tremor. (orig.)

Dopamine transporter SPECT in patients with Parkinson's disease

International Nuclear Information System (INIS)

Hamano, Tadanori; Tsuchida, Tatsuro; Hirayama, Mikio; Fujiyama, Jiro; Mutoh, Tatsuro; Yonekura, Yoshiharu; Kuriyama, Masaru

2000-01-01

The major neuropathological feature in Parkinson's disease (PD) is severe degeneration of the dopamine (DA) neurons in the substantia nigra. Dopamine transporter (DAT) is an important protein in the regulation of DA neurotransmission. It has been reported that PD patients show a loss of DAT in striatum. We report here the findings of single photon emission computed tomography (SPECT) of the DAT with 2β-carboxymethoxy-3β-(4[ 123 I]iodophenyl)tropane ([ 123 I]β-CIT) to investigate striatal DAT in 10 patients with PD, one patient with vascular parkinsonism (VP), and one patient with dystonia syndrome. Patients were evaluated using the Webster rating scale. Specific/nondisplaceable striatal binding ratio (V3'') was obtained in each case. In PD patients, the uptake of [ 123 I]β-CIT was reduced, especially in the tail of putamen compared with caudate nucleus. Even in the early stage of PD, the uptake of β-CIT was reduced not only in the severely affected side, but also in the mildly disturbed side of the brain. Putamen caudate ratio was generally low in PD patients. In VP patient, the uptake was reduced, but putamen caudate ratio was not decreased. V3'' values showed significant correlation with the severity of clinical symptoms such as self-care, facies, posture, gait, speech, and Hoehn-Yahr's stage. On the other hand, V3'' values were not significantly correlated with the degree of tremor, seborrhea, and duration of the illness. In conclusion, we found that SPECT of the [ 123 I]β-CIT is a useful method for the diagnosis in the patients presenting parkinsonism, and for the clinico-physiological estimation of parkinsonian symptoms such as self-care, facies, posture, gait, and speech. (author)

Ab initio calculation of transport properties between PbSe quantum dots facets with iodide ligands

Science.gov (United States)

Wang, B.; Patterson, R.; Chen, W.; Zhang, Z.; Yang, J.; Huang, S.; Shrestha, S.; Conibeer, G.

2018-01-01

The transport properties between Lead Selenide (PbSe) quantum dots decorated with iodide ligands has been studied using density functional theory (DFT). Quantum conductance at each selected energy levels has been calculated along with total density of states and projected density of states. The DFT calculation is carried on using a grid-based planar augmented wave (GPAW) code incorporated with the linear combination of atomic orbital (LCAO) mode and Perdew Burke Ernzerhof (PBE) exchange-correlation functional. Three iodide ligand attached low index facets including (001), (011), (111) are investigated in this work. P-orbital of iodide ligand majorly contributes to density of state (DOS) at near top valence band resulting a significant quantum conductance, whereas DOS of Pb p-orbital shows minor influence. Various values of quantum conductance observed along different planes are possibly reasoned from a combined effect electrical field over topmost surface and total distance between adjacent facets. Ligands attached to (001) and (011) planes possess similar bond length whereas it is significantly shortened in (111) plane, whereas transport between (011) has an overall low value due to newly formed electric field. On the other hand, (111) plane with a net surface dipole perpendicular to surface layers leading to stronger electron coupling suggests an apparent increase of transport probability. Apart from previously mentioned, the maximum transport energy levels located several eVs (1 2 eVs) from the edge of valence band top.

Homeostatic mechanisms in dopamine synthesis and release: a mathematical model

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Nijhout H Frederik

2009-09-01

Full Text Available Abstract Background Dopamine is a catecholamine that is used as a neurotransmitter both in the periphery and in the central nervous system. Dysfunction in various dopaminergic systems is known to be associated with various disorders, including schizophrenia, Parkinson's disease, and Tourette's syndrome. Furthermore, microdialysis studies have shown that addictive drugs increase extracellular dopamine and brain imaging has shown a correlation between euphoria and psycho-stimulant-induced increases in extracellular dopamine 1. These consequences of dopamine dysfunction indicate the importance of maintaining dopamine functionality through homeostatic mechanisms that have been attributed to the delicate balance between synthesis, storage, release, metabolism, and reuptake. Methods We construct a mathematical model of dopamine synthesis, release, and reuptake and use it to study homeostasis in single dopaminergic neuron terminals. We investigate the substrate inhibition of tyrosine hydroxylase by tyrosine, the consequences of the rapid uptake of extracellular dopamine by the dopamine transporters, and the effects of the autoreceoptors on dopaminergic function. The main focus is to understand the regulation and control of synthesis and release and to explicate and interpret experimental findings. Results We show that the substrate inhibition of tyrosine hydroxylase by tyrosine stabilizes cytosolic and vesicular dopamine against changes in tyrosine availability due to meals. We find that the autoreceptors dampen the fluctuations in extracellular dopamine caused by changes in tyrosine hydroxylase expression and changes in the rate of firing. We show that short bursts of action potentials create significant dopamine signals against the background of tonic firing. We explain the observed time courses of extracellular dopamine responses to stimulation in wild type mice and mice that have genetically altered dopamine transporter densities and the observed

PRESYNAPTIC DOPAMINE MODULATION BY STIMULANT SELF ADMINISTRATION

Science.gov (United States)

España, Rodrigo A.; Jones, Sara R.

2013-01-01

The mesolimbic dopamine system is an essential participant in the initiation and modulation of various forms of goal-directed behavior, including drug reinforcement and addiction processes. Dopamine neurotransmission is increased by acute administration of all drugs of abuse, including the stimulants cocaine and amphetamine. Chronic exposure to these drugs via voluntary self-administration provides a model of stimulant abuse that is useful in evaluating potential behavioral and neurochemical adaptations that occur during addiction. This review describes commonly used methodologies to measure dopamine and baseline parameters of presynaptic dopamine regulation, including exocytotic release and reuptake through the dopamine transporter in the nucleus accumbens core, as well as dramatic adaptations in dopamine neurotransmission and drug sensitivity that occur with acute non-contingent and chronic, contingent self-administration of cocaine and amphetamine. PMID:23277050

Evaluation of dopamine transporters and D2 receptors in hemiparkinsonian rat brains in vivo using consecutive PET scans of [18F]FPCIT and [18F]fallypride

International Nuclear Information System (INIS)

Choi, Jae Yong; Kim, Chul Hoon; Jeon, Tae Joo; Cho, Won Gil; Lee, Jin Suk; Lee, Soo Jin; Choi, Tae Hyun; Kim, Byoung Soo; Yi, Chi Hoon; Seo, Youngbeom; Yi, Dae Ik; Han, Sang Jin; Lee, Minkyung; Kim, Dong Goo; Lee, Jong Doo; An, Gwangil

2012-01-01

The aim of this study was to investigate dopaminergic function in unilaterally lesioned 6-OHDA rats by dual PET radioligands: [ 18 F]FPCIT (a dopamine transporter imaging radioligand) and [ 18 F]fallypride (a dopamine D2 receptors imaging radioligand). As a result, the brain uptake of [ 18 F]FPCIT was significantly reduced and that of [ 18 F]fallypride was increased in the ipsilateral striatum (lesion side) of the 6-OHDA rats. These findings implicated that dopamine transporter is down-regulated and dopamine D2 receptor is up-regulated in this hemiparkinsonian rat model. - Highlights: ► The dopaminergic integrity in unilateral 6-OHDA was evaluated by dual PET tracers. ► The brain uptake and BP ND of [ 18 F]FPCIT was greatly decreased. ► The brain uptake and BP ND [ 18 F]fallypride was slightly increased. ► DAT are down-regulated and D2R are up-regulated.

ILLICIT DOPAMINE TRANSIENTS: RECONCILING ACTIONS OF ABUSED DRUGS

OpenAIRE

Covey, Dan P.; Roitman, Mitchell F.; Garris, Paul A.

2014-01-01

Phasic increases in brain dopamine are required for cue-directed reward seeking. While compelling within the framework of appetitive behavior, the view that illicit drugs hijack reward circuits by hyper-activating these dopamine transients is inconsistent with established psychostimulant pharmacology. However, recent work reclassifying amphetamine (AMPH), cocaine, and other addictive dopamine-transporter inhibitors (DAT-Is) supports transient hyper-activation as a unifying hypothesis of abuse...

Inhibitor mechanisms in the S1 binding site of the dopamine transporter defined by multi-site molecular tethering of photoactive cocaine analogs.

Science.gov (United States)

Krout, Danielle; Pramod, Akula Bala; Dahal, Rejwi Acharya; Tomlinson, Michael J; Sharma, Babita; Foster, James D; Zou, Mu-Fa; Boatang, Comfort; Newman, Amy Hauck; Lever, John R; Vaughan, Roxanne A; Henry, L Keith

2017-10-15

Dopamine transporter (DAT) blockers like cocaine and many other abused and therapeutic drugs bind and stabilize an inactive form of the transporter inhibiting reuptake of extracellular dopamine (DA). The resulting increases in DA lead to the ability of these drugs to induce psychomotor alterations and addiction, but paradoxical findings in animal models indicate that not all DAT antagonists induce cocaine-like behavioral outcomes. How this occurs is not known, but one possibility is that uptake inhibitors may bind at multiple locations or in different poses to stabilize distinct conformational transporter states associated with differential neurochemical endpoints. Understanding the molecular mechanisms governing the pharmacological inhibition of DAT is therefore key for understanding the requisite interactions for behavioral modulation and addiction. Previously, we leveraged complementary computational docking, mutagenesis, peptide mapping, and substituted cysteine accessibility strategies to identify the specific adduction site and binding pose for the crosslinkable, photoactive cocaine analog, RTI 82, which contains a photoactive azide attached at the 2β position of the tropane pharmacophore. Here, we utilize similar methodology with a different cocaine analog N-[4-(4-azido-3-I-iodophenyl)-butyl]-2-carbomethoxy-3-(4-chlorophenyl)tropane, MFZ 2-24, where the photoactive azide is attached to the tropane nitrogen. In contrast to RTI 82, which crosslinked into residue Phe319 of transmembrane domain (TM) 6, our findings show that MFZ 2-24 adducts to Leu80 in TM1 with modeling and biochemical data indicating that MFZ 2-24, like RTI 82, occupies the central S1 binding pocket with the (+)-charged tropane ring nitrogen coordinating with the (-)-charged carboxyl side chain of Asp79. The superimposition of the tropane ring in the three-dimensional binding poses of these two distinct ligands provides strong experimental evidence for cocaine binding to DAT in the S1 site

The Role of the Dopamine Transporter (DAT) in the Development of PTSD in Preschool Children

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Drury, Stacy S.; Theall, Katherine P.; Keats, Bronya J.B.; Scheeringa, Michael

2015-01-01

Population-based association studies have supported the heritability of posttraumatic stress disorder (PTSD). This study explored the influence of genetic variation in the dopamine transporter (DAT) 3′ untranslated region variable number tandem repeat on the development of PTSD in preschool children exposed to Hurricane Katrina, diagnosed using a developmentally appropriate semistructured interview. A diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV; American Psychiatric Association, 1994), total symptoms, and specifically Criterion D symptoms were significantly more likely to be found in children with the 9 allele. This study replicates a previous finding in adults with PTSD. The specificity of this finding to the increased arousal symptoms of Criterion D suggests that dopamine and the DAT allele may contribute to one heritable path in a multifinality model of the development of PTSD. PMID:19960520

Neuronal Depolarization Drives Increased Dopamine Synaptic Vesicle Loading via VGLUT.

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Aguilar, Jenny I; Dunn, Matthew; Mingote, Susana; Karam, Caline S; Farino, Zachary J; Sonders, Mark S; Choi, Se Joon; Grygoruk, Anna; Zhang, Yuchao; Cela, Carolina; Choi, Ben Jiwon; Flores, Jorge; Freyberg, Robin J; McCabe, Brian D; Mosharov, Eugene V; Krantz, David E; Javitch, Jonathan A; Sulzer, David; Sames, Dalibor; Rayport, Stephen; Freyberg, Zachary

2017-08-30

The ability of presynaptic dopamine terminals to tune neurotransmitter release to meet the demands of neuronal activity is critical to neurotransmission. Although vesicle content has been assumed to be static, in vitro data increasingly suggest that cell activity modulates vesicle content. Here, we use a coordinated genetic, pharmacological, and imaging approach in Drosophila to study the presynaptic machinery responsible for these vesicular processes in vivo. We show that cell depolarization increases synaptic vesicle dopamine content prior to release via vesicular hyperacidification. This depolarization-induced hyperacidification is mediated by the vesicular glutamate transporter (VGLUT). Remarkably, both depolarization-induced dopamine vesicle hyperacidification and its dependence on VGLUT2 are seen in ventral midbrain dopamine neurons in the mouse. Together, these data suggest that in response to depolarization, dopamine vesicles utilize a cascade of vesicular transporters to dynamically increase the vesicular pH gradient, thereby increasing dopamine vesicle content. Copyright © 2017 Elsevier Inc. All rights reserved.

Photoaffinity labelling of high affinity dopamine binding proteins

International Nuclear Information System (INIS)

Ross, G.M.; McCarry, B.E.; Mishra, R.K.

1986-01-01

A photoactive analogue of the dopamine agonist 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronapthalene (ADTN) has been synthesized and used to photoaffinity label dopamine binding proteins prepared from bovine caudate nucleus. N-(3-]N'-4-azidobenzamidol]-aminopropyl)-aminopropyl)-ADTN (AzB-AP-ADTN) was incubated with caudate membranes and irradiated with UV light. Membranes were then repeatedly washed by centrifugation to remove excess photolabel. A binding assay, using ( 3 H)-SCH 23390 (a D 1 specific antagonist), was then performed to evaluate the loss of receptor density in the photolyzed preparation. AzB-AP-ADTN irreversibly blocked ( 3 H)-SCH 23390 binding in a dose-dependent manner. Scatchard analysis revealed a decrease in the B/sub max/, with no significant change in the K/sub d/, of ( 3 H)-SCH 23390 binding. Compounds which compete for D 1 receptor binding (such as dopamine, SKF 38393 or apomorphine), proteted the SCH 23390 binding site from inactivation. This data would suggest that the novel photoaffinity ligand, AzB-AP-ADTN, can covalently label the D 1 (adenylate cyclase linked) dopamine receptor

Methylphenidate and cocaine have a similar in vivo potency to block dopamine transporters in the human brain

International Nuclear Information System (INIS)

Volkow, N.D.

1999-01-01

The reinforcing effects of cocaine and methylphenidate have been linked to their ability to block dopamine transporters (DAT). Though cocaine and methylphenidate have similar in vitro affinities for DAT the abuse of methylphenidate in humans is substantially lower than of cocaine. To test if differences in in vivo potency at the DAT between these two drugs could account for the differences in their abuse liability the authors compared the levels of DAT occupancies that they had previously reported separately for intravenous methylphenidate in controls and for intravenous cocaine in cocaine abusers. DAT occupancies were measured with Positron Emission Tomography using [ 11 C]cocaine, as a DAT ligand, in 8 normal controls for the methylphenidate study and in 17 active cocaine abusers for the cocaine study. The ratio of the distribution volume of [ 11 C]cocaine in striatum to that in cerebellum, which corresponds to Bmax/Kd+1, was used as measure of DAT availability. Parallel measures were obtained to assess the cardiovascular effects of these two drugs. Methylphenidate and cocaine produced comparable dose-dependent blockage of DAT with an estimated ED 50 for methylphenidate of 0.07 mg/kg and for cocaine of 0.13 mg/kg. Both drugs induced similar increases in heart rate and blood pressure but the duration of the effects were significantly longer for methylphenidate than for cocaine

New detection of brain dopamine receptors with [3H]dihydroergocryptine

International Nuclear Information System (INIS)

Tittler, M.; Weinreich, P.; Seeman, P.

1977-01-01

Because dihydroergocryptine (DHE) and closely related ergots are dopamine-mimetic agonists, we tested [ 3 H]DHE as a possible ligand for [ 3 H]dopamine receptors in the calf caudate. In order to avoid [ 3 H]DHE from tagging α-adrenergic receptors, an excess of 500 nM phentolamine was used to block these sites, permitting the dopamine receptors to be measured separately. Specific binding of [ 3 H]DHE was defined as total binding minus that occurring in the presence of 1 μM (+)-butaclamol. Excess phentolamine reduced the specific binding of [ 3 H]DHE from 328 down to 138 fmol/mg, the difference presumably representing α-receptors. The K/sub D/ for [ 3 H]DHE was 0.55 nM (with or without phentolamine), and this high affinity site was blocked (in the presence of phentolamine) by 250 nM apomorphine, 650 nM dopamine, and 1200 nM (-)-norepinephrine, indicating that [ 3 H]DHE was binding to dopamine receptors. All neuroleptics blocked specific [ 3 H]DHE binding in direct relation to the clinical potency of the neuroleptic. The displacement of specific [ 3 H]DHE binding by dopamine or by norepinephrine (in the presence of phentolamine) revealed two subsets of dopamine receptors

Validation of a method for accurate and highly reproducible quantification of brain dopamine transporter SPECT studies

DEFF Research Database (Denmark)

Jensen, Peter S; Ziebell, Morten; Skouboe, Glenna

2011-01-01

In nuclear medicine brain imaging, it is important to delineate regions of interest (ROIs) so that the outcome is both accurate and reproducible. The purpose of this study was to validate a new time-saving algorithm (DATquan) for accurate and reproducible quantification of the striatal dopamine t...... transporter (DAT) with appropriate radioligands and SPECT and without the need for structural brain scanning....

The serotonin transporter: Examination of the changes in transporter affinity induced by ligand binding

International Nuclear Information System (INIS)

Humphreys, C.J.

1989-01-01

The plasmalemmal serotonin transporter uses transmembrane gradients of Na + , Cl - and K + to accumulate serotonin within blood platelets. Transport is competitively inhibited by the antidepressant imipramine. Like serotonin transport, imipramine binding requires Na + . Unlike serotonin, however, imipramine does not appear to be transported. To gain insight into the mechanism of serotonin transport the author have analyzed the influences of Na + and Cl - , the two ions cotransported with serotonin, on both serotonin transport and the interaction of imipramine and other antidepressant drugs with the plasmalemmal serotonin transporter of human platelets. Additionally, the author have synthesized, purified and characterized the binding of 2-iodoimipramine to the serotonin transporter. Finally, the author have conducted a preliminary study of the inhibition of serotonin transport and imipramine binding produced by dicyclohexylcarbodiimide. My results reveal many instances of positive heterotropic cooperativity in ligand binding to the serotonin transporter. Na + binding enhances the transporters affinity for imipramine and several other antidepressant drugs, and also increases the affinity for Cl - . Cl - enhances the transporters affinity for imipramine, as well as for Na + . At concentrations in the range of its K M for transport serotonin is a competitive inhibitor of imipramine binding. At much higher concentrations, however, serotonin also inhibits imipramines dissociation rate constant. This latter effect which is Na + -independent and species specific, is apparently produced by serotonin binding at a second, low affinity site on, or near, the transporter complex. Iodoimipramine competitively inhibit both [ 3 H]imipramine binding and [ 3 H]serotonin transport

Ligand binding and crystal structures of the substrate-binding domain of the ABC transporter OpuA.

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Justina C Wolters

2010-04-01

Full Text Available The ABC transporter OpuA from Lactococcus lactis transports glycine betaine upon activation by threshold values of ionic strength. In this study, the ligand binding characteristics of purified OpuA in a detergent-solubilized state and of its substrate-binding domain produced as soluble protein (OpuAC was characterized.The binding of glycine betaine to purified OpuA and OpuAC (K(D = 4-6 microM did not show any salt dependence or cooperative effects, in contrast to the transport activity. OpuAC is highly specific for glycine betaine and the related proline betaine. Other compatible solutes like proline and carnitine bound with affinities that were 3 to 4 orders of magnitude lower. The low affinity substrates were not noticeably transported by membrane-reconstituted OpuA. OpuAC was crystallized in an open (1.9 A and closed-liganded (2.3 A conformation. The binding pocket is formed by three tryptophans (Trp-prism coordinating the quaternary ammonium group of glycine betaine in the closed-liganded structure. Even though the binding site of OpuAC is identical to that of its B. subtilis homolog, the affinity for glycine betaine is 4-fold higher.Ionic strength did not affect substrate binding to OpuA, indicating that regulation of transport is not at the level of substrate binding, but rather at the level of translocation. The overlap between the crystal structures of OpuAC from L.lactis and B.subtilis, comprising the classical Trp-prism, show that the differences observed in the binding affinities originate from outside of the ligand binding site.

Ligand-Receptor Interaction-Mediated Transmembrane Transport of Dendrimer-like Soft Nanoparticles: Mechanisms and Complicated Diffusive Dynamics.

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Liang, Junshi; Chen, Pengyu; Dong, Bojun; Huang, Zihan; Zhao, Kongyin; Yan, Li-Tang

2016-05-09

Nearly all nanomedical applications of dendrimer-like soft nanoparticles rely on the functionality of attached ligands. Understanding how the ligands interact with the receptors in cell membrane and its further effect on the cellular uptake of dendrimer-like soft nanoparticles is thereby a key issue for their better application in nanomedicine. However, the essential mechanism and detailed kinetics for the ligand-receptor interaction-mediated transmembrane transport of such unconventional nanoparticles remain poorly elucidated. Here, using coarse-grained simulations, we present the very first study of molecular mechanism and kinetics behaviors for the transmembrane transport of dendrimer-like soft nanoparticles conjugated with ligands. A phase diagram of interaction states is constructed through examining ligand densities and membrane tensions that allows us to identify novel endocytosis mechanisms featured by the direct wrapping and the penetration-extraction vesiculation. The results provide an in-depth insight into the diffusivity of receptors and dendrimer in the membrane plane and demonstrate how the ligand density influences receptor diffusion and uptake kinetics. It is interesting to find that the ligand-conjugated dendrimers present superdiffusive behaviors on a membrane, which is revealed to be driven by the random fluctuation dynamics of the membrane. The findings facilitate our understanding of some recent experimental observations and could establish fundamental principles for the future development of such important nanomaterials for widespread nanomedical applications.

Dual-isotope single-photon emission computed tomography for dopamine and serotonin transporters in normal and parkinsonian monkey brains

International Nuclear Information System (INIS)

Li, I-H.; Huang, W.-S.; Yeh, C.-B.; Liao, M.-H.; Chen, C.-C.; Shen, L.-H.; Liu, J.-C.; Ma, K.-H.

2009-01-01

Introduction: Parkinson's disease (PD) affects both dopaminergic and serotonergic systems. In this study, we simultaneously evaluated dopamine and serotonin transporters in primates using dual-isotope single-photon emission computed tomography (SPECT) imaging and compared the results with traditional single-isotope imaging. Methods: Four healthy and one 6-OHDA-induced PD monkeys were used for this study. SPECT was performed over 4 h after individual or simultaneous injection of [ 99m Tc]TRODAT-1 (a dopamine transporter imaging agent) and [ 123 I]ADAM (a serotonin transporter imaging agent). Results: The results showed that the image quality and uptake ratios in different brain regions were comparable between single- and dual-isotope studies. The striatal [ 99m Tc]TRODAT-1 uptake in the PD monkey was markedly lower than that in normal monkeys. The uptake of [ 123 I]ADAM in the midbrain of the PD monkey was comparable to that in the normal monkeys, but there were decreased uptakes in the thalamus and striatum of the PD monkey. Conclusions: Our results suggest that dual-isotope SPECT using [ 99m Tc]TRODAT-1 and [ 123 I]ADAM can simultaneously evaluate changes in dopaminergic and serotonergic systems in a PD model.

Dopamine

International Nuclear Information System (INIS)

Walters, L.

1983-01-01

Dopamine is an important neurotransmittor in the central nervous system. The physiological function of the peripheral dopamine receptors is unknown, but they are of therapeutic importance as dopamine is used to improve renal blood flow in shocked patients. There are 4 dopamine receptors. The classification of these dopamine receptors has been made possible by research with radiopharmaceuticals. Dopamine sensitive adenylate cyclase is an inherent part of the dopamine-1-receptor. Dopamine-1-receptors are stimulated by micromolar (physiological) concentrations of dopamine and inhibited by micromolar (supratherapeutic) concentrations of the antipsychotic drugs. The vascular effect of dopamine is mediated through the dopamine-1-receptors. Dopamine-2-receptors are responsible for the effect of dopamine at the mesolimbic, nigrostriatal and chemoreceptortrigger areas. It is activated by micromolar concentrations of dopamine and blocked by nanomolar (therapeutic) concentrations of the anti-psychotic drugs. Dopamine-3-receptors are activated by nanomolar concentrations of dopamine and inhibited by micromolar concentrations of the antipsychotic drugs. They occur on presynaptic nerve terminals and have a negative feedback effect on the liberation of dopamine, noradrenaline and serotonin. The dopamine-4-receptors are activated by nanomolar concentrations of dopamine. These are the only dopamine receptors that could be responsible for effects in the hypophysis as only nanomolar concentrations of dopamine occur there. These receptors are blocked by nanomolar concentrations of the antipsychotic drugs

A Conserved Salt Bridge between Transmembrane Segment 1 and 10 Constitutes an Extracellular Gate in the Dopamine Transporter

DEFF Research Database (Denmark)

Pedersen, Anders Vingborg; Andreassen, Thorvald Faurschou; Løland, Claus Juul

2014-01-01

into the structural and dynamic requirements for substrate transport. These structures support the existence of gating domains controlling access to a central binding site. On the extracellular side, access is controlled by the "thin gate" formed by an interaction between Arg-30 and Asp-404. In the human dopamine...

Maternal separation affects dopamine transporter function in the Spontaneously Hypertensive Rat: An in vivo electrochemical study

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Womersley Jacqueline S

2011-12-01

Full Text Available Abstract Background Attention-deficit/hyperactivity disorder (ADHD is a developmental disorder characterised by symptoms of inattention, impulsivity and hyperactivity. The spontaneously hypertensive rat (SHR is a well-characterised model of this disorder and has been shown to exhibit dopamine dysregulation, one of the hypothesised causes of ADHD. Since stress experienced in the early stages of life can have long-lasting effects on behaviour, it was considered that early life stress may alter development of the dopaminergic system and thereby contribute to the behavioural characteristics of SHR. It was hypothesized that maternal separation would alter dopamine regulation by the transporter (DAT in ways that distinguish SHR from control rat strains. Methods SHR and control Wistar-Kyoto (WKY rats were subjected to maternal separation for 3 hours per day from postnatal day 2 to 14. Rats were tested for separation-induced anxiety-like behaviour followed by in vivo chronoamperometry to determine whether changes had occurred in striatal clearance of dopamine by DAT. The rate of disappearance of ejected dopamine was used as a measure of DAT function. Results Consistent with a model for ADHD, SHR were more active than WKY in the open field. SHR entered the inner zone more frequently and covered a significantly greater distance than WKY. Maternal separation increased the time that WKY spent in the closed arms and latency to enter the open arms of the elevated plus maze, consistent with other rat strains. Of note is that, maternal separation failed to produce anxiety-like behaviour in SHR. Analysis of the chronoamperometric data revealed that there was no difference in DAT function in the striatum of non-separated SHR and WKY. Maternal separation decreased the rate of dopamine clearance (k-1 in SHR striatum. Consistent with this observation, the dopamine clearance time (T100 was increased in SHR. These results suggest that the chronic mild stress of

Molecular Imaging of Transporters with Positron Emission Tomography

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Antoni, Gunnar; Sörensen, Jens; Hall, Håkan

Positron emission tomography (PET) visualization of brain components in vivo is a rapidly growing field. Molecular imaging with PET is also increasingly used in drug development, especially for the determination of drug receptor interaction for CNS-active drugs. This gives the opportunity to relate clinical efficacy to per cent receptor occupancy of a drug on a certain targeted receptor and to relate drug pharmacokinetics in plasma to interaction with target protein. In the present review we will focus on the study of transporters, such as the monoamine transporters, the P-glycoprotein (Pgp) transporter, the vesicular monoamine transporter type 2, and the glucose transporter using PET radioligands. Neurotransmitter transporters are presynaptically located and in vivo imaging using PET can therefore be used for the determination of the density of afferent neurons. Several promising PET ligands for the noradrenaline transporter (NET) have been labeled and evaluated in vivo including in man, but a really useful PET ligand for NET still remains to be identified. The most promising tracer to date is (S,S)-[18F]FMeNER-D2. The in vivo visualization of the dopamine transporter (DAT) may give clues in the evaluation of conditions related to dopamine, such as Parkinson's disease and drug abuse. The first PET radioligands based on cocaine were not selective, but more recently several selective tracers such as [11C]PE2I have been characterized and shown to be suitable as PET radioligands. Although there are a large number of serotonin transporter inhibitors used today as SSRIs, it was not until very recently, when [11C]McN5652 was synthesized, that this transporter was studied using PET. New candidates as PET radioligands for the SERT have subsequently been developed and [11C]DASB and [11C]MADAM and their analogues are today the most promising ligands. The existing radioligands for Pgp transporters seem to be suitable tools for the study of both peripheral and central drug

Dopamine Gene Profiling to Predict Impulse Control and Effects of Dopamine Agonist Ropinirole.

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MacDonald, Hayley J; Stinear, Cathy M; Ren, April; Coxon, James P; Kao, Justin; Macdonald, Lorraine; Snow, Barry; Cramer, Steven C; Byblow, Winston D

2016-07-01

Dopamine agonists can impair inhibitory control and cause impulse control disorders for those with Parkinson disease (PD), although mechanistically this is not well understood. In this study, we hypothesized that the extent of such drug effects on impulse control is related to specific dopamine gene polymorphisms. This double-blind, placebo-controlled study aimed to examine the effect of single doses of 0.5 and 1.0 mg of the dopamine agonist ropinirole on impulse control in healthy adults of typical age for PD onset. Impulse control was measured by stop signal RT on a response inhibition task and by an index of impulsive decision-making on the Balloon Analogue Risk Task. A dopamine genetic risk score quantified basal dopamine neurotransmission from the influence of five genes: catechol-O-methyltransferase, dopamine transporter, and those encoding receptors D1, D2, and D3. With placebo, impulse control was better for the high versus low genetic risk score groups. Ropinirole modulated impulse control in a manner dependent on genetic risk score. For the lower score group, both doses improved response inhibition (decreased stop signal RT) whereas the lower dose reduced impulsiveness in decision-making. Conversely, the higher score group showed a trend for worsened response inhibition on the lower dose whereas both doses increased impulsiveness in decision-making. The implications of the present findings are that genotyping can be used to predict impulse control and whether it will improve or worsen with the administration of dopamine agonists.

The Mechanistic Basis for Noncompetitive Ibogaine Inhibition of Serotonin and Dopamine Transporters*

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Bulling, Simon; Schicker, Klaus; Zhang, Yuan-Wei; Steinkellner, Thomas; Stockner, Thomas; Gruber, Christian W.; Boehm, Stefan; Freissmuth, Michael; Rudnick, Gary; Sitte, Harald H.; Sandtner, Walter

2012-01-01

Ibogaine, a hallucinogenic alkaloid proposed as a treatment for opiate withdrawal, has been shown to inhibit serotonin transporter (SERT) noncompetitively, in contrast to all other known inhibitors, which are competitive with substrate. Ibogaine binding to SERT increases accessibility in the permeation pathway connecting the substrate-binding site with the cytoplasm. Because of the structural similarity between ibogaine and serotonin, it had been suggested that ibogaine binds to the substrate site of SERT. The results presented here show that ibogaine binds to a distinct site, accessible from the cell exterior, to inhibit both serotonin transport and serotonin-induced ionic currents. Ibogaine noncompetitively inhibited transport by both SERT and the homologous dopamine transporter (DAT). Ibogaine blocked substrate-induced currents also in DAT and increased accessibility of the DAT cytoplasmic permeation pathway. When present on the cell exterior, ibogaine inhibited SERT substrate-induced currents, but not when it was introduced into the cytoplasm through the patch electrode. Similar to noncompetitive transport inhibition, the current block was not reversed by increasing substrate concentration. The kinetics of inhibitor binding and dissociation, as determined by their effect on SERT currents, indicated that ibogaine does not inhibit by forming a long-lived complex with SERT, but rather binds directly to the transporter in an inward-open conformation. A kinetic model for transport describing the noncompetitive action of ibogaine and the competitive action of cocaine accounts well for the results of the present study. PMID:22451652

The mechanistic basis for noncompetitive ibogaine inhibition of serotonin and dopamine transporters.

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Bulling, Simon; Schicker, Klaus; Zhang, Yuan-Wei; Steinkellner, Thomas; Stockner, Thomas; Gruber, Christian W; Boehm, Stefan; Freissmuth, Michael; Rudnick, Gary; Sitte, Harald H; Sandtner, Walter

2012-05-25

Ibogaine, a hallucinogenic alkaloid proposed as a treatment for opiate withdrawal, has been shown to inhibit serotonin transporter (SERT) noncompetitively, in contrast to all other known inhibitors, which are competitive with substrate. Ibogaine binding to SERT increases accessibility in the permeation pathway connecting the substrate-binding site with the cytoplasm. Because of the structural similarity between ibogaine and serotonin, it had been suggested that ibogaine binds to the substrate site of SERT. The results presented here show that ibogaine binds to a distinct site, accessible from the cell exterior, to inhibit both serotonin transport and serotonin-induced ionic currents. Ibogaine noncompetitively inhibited transport by both SERT and the homologous dopamine transporter (DAT). Ibogaine blocked substrate-induced currents also in DAT and increased accessibility of the DAT cytoplasmic permeation pathway. When present on the cell exterior, ibogaine inhibited SERT substrate-induced currents, but not when it was introduced into the cytoplasm through the patch electrode. Similar to noncompetitive transport inhibition, the current block was not reversed by increasing substrate concentration. The kinetics of inhibitor binding and dissociation, as determined by their effect on SERT currents, indicated that ibogaine does not inhibit by forming a long-lived complex with SERT, but rather binds directly to the transporter in an inward-open conformation. A kinetic model for transport describing the noncompetitive action of ibogaine and the competitive action of cocaine accounts well for the results of the present study.

NEUROTRANSMITTERS AND IMMUNITY: 1. DOPAMINE

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Lucian Hritcu

2007-08-01

Full Text Available Dopamine is one of the principal neurotransmitters in the central nervous system (CNC, and its neuronal pathways are involved in several key functions such as behavior (Hefco et al., 2003a,b, control of movement, endocrine regulation, immune response (Fiserova et al., 2002; Levite et al., 2001, Hritcu et al., 2006a,b,c, and cardiovascular function. Dopamine has at least five G-protein, coupled receptor subtypes, D1-D5, each arising from a different gene (Sibley et al., 1993. Traditionally, these receptors have been classified into D1-like (the D1 and D5 and D2-like (D2, D3 and D4 receptors subtypes, primarily according to their ability to stimulate or inhibit adenylate cyclase, respectively, and to their pharmacological characteristics (Seeman et al., 1993. Receptors for dopamine (particularly of D2 subclass are the primary therapeutic target in a number of neuropathological disorders including schizophrenia, Parkinson’s disease and Huntington’s chorea (Seeman et al., 1987. Neither dopamine by itself, nor dopaminergic agonists by themselves, has been shown to activate T cell function. Nevertheless, lymphocytes are most probably exposed to dopamine since the primary and secondary lymphoid organs of various mammals are markedly innervated, and contain nerve fibers which stain for tyrosine hydroxylase (Weihe et al., 1991, the enzyme responsible for dopamine synthesis. Moreover, cathecolamines and their metabolites are present in single lymphocytes and in extracts of T and B cell clones, and pharmacological inhibition of tyrosine hydroxylase reduces catecholamine levels, suggesting catecholamine synthesis by lymphocytes (Bergquist et al., 1994. The existence of putative dopamine receptors of D2, D3, D4 and D5 subtypes on immune cells has been proposed of several authors, primarily on the basis of dopaminergic ligand binding assays and specific mRNA expression as monitored by reverse transcription-PCR. Several experiments evoked the idea of a

Central actions of a novel and selective dopamine antagonist

International Nuclear Information System (INIS)

Schulz, D.W.

1985-01-01

Receptors for the neurotransmitter dopamine traditionally have been divided into two subgroups: the D 1 class, which is linked to the stimulation of adenylate cyclase-activity, and the D 2 class which is not. There is much evidence suggesting that it is the D 2 class which is not. There is much evidence suggesting that it is the D 2 dopamine receptor that mediates the physiological and behavioral actions of dopamine in the intact animal. However, the benzazepine SCH23390 is a dopamine antagonist which has potent behavioral actions while displaying apparent neurochemical selectivity for the D 1 class of dopamine receptors. The purpose of this dissertation was to (1) confirm and characterize this selectivity, and (2) test certain hypothesis related to possible modes of action of SCH233390. The inhibition of adenylate cyclase by SCH23390 occurred via an action at the dopamine receptor only. A radiolabeled analog of SCH23390 displayed the receptor binding properties of a specific high-affinity ligand, and regional receptor densities were highly correlated with dopamine levels. The subcellular distribution of [ 3 H]-SCH23390 binding did not correspond completely with that of dopamine-stimulated adenylate cyclase. The neurochemical potency of SCH23390 as a D 1 receptor antagonist was preserved following parental administration. A variety of dopamine agonists and antagonists displayed a high correlation between their abilities to compete for [ 3 H]-SCH23390 binding in vitro and to act at an adenylate cyclase-linked receptor. Finally, the relative affinities of dopamine and SCH23390 for both D 1 receptors and [ 3 H]-SCH23390 binding sites were comparable. It is concluded that the behavioral effects of SCH23390 are mediated by actions at D 1 dopamine receptors only, and that the physiological importance of this class of receptors should be reevaluated

Return of D4 Dopamine Receptor Antagonists in Drug Discovery.

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Lindsley, Craig W; Hopkins, Corey R

2017-09-14

The dopamine D 4 receptor garnered a great deal of interest in the early 1990s when studies showed the atypical antipsychotic clozapine possessed higher affinity for D 4 , relative to other dopamine receptor subtypes, and that this activity might underlie the unique clinical efficacy of clozapine. Unfortunately, D 4 antagonists that were developed for schizophrenia failed in the clinic. Thus, D 4 fell out of favor as a therapeutic target, and work in this area was silent for decades. Recently, D 4 ligands with improved selectivity for D 4 against not only D 1-3,5 but also other biogenic amine targets have emerged, and D 4 is once again in the spotlight as a novel target for both addiction and Parkinson's disease (PD), as well as other emerging diseases. This report will review the historical data for D 4 , review the known D 4 ligands, and then highlight new data supporting a role for D 4 inhibition in addiction, PD, and cancer.

Evaluating Dopamine Reward Pathway in ADHD; clinical implications

Energy Technology Data Exchange (ETDEWEB)

Volkow, N.D.; Wang, G.; Volkow, N.D.; Wang, G.-J.; Kollins, S.H., Wigal, t.L.; Newcorn, J.H.; Telang, F.; Fowler, J.S.; Zhu, W.; Logan, J.; Ma, Y.; Pradhan, K.; Wong, C.T.; Swanson, J.M.

2009-09-09

Attention-deficit/hyperactivity disorder (ADHD) - characterized by symptoms of inattention and hyperactivity-impulsivity - is the most prevalent childhood psychiatric disorder that frequently persists into adulthood, and there is increasing evidence of reward-motivation deficits in this disorder. To evaluate biological bases that might underlie a reward/motivation deficit by imaging key components of the brain dopamine reward pathway (mesoaccumbens). We used positron emission tomography to measure dopamine synaptic markers (transporters and D{sub 2}/D{sub 3} receptors) in 53 nonmedicated adults with ADHD and 44 healthy controls between 2001-2009 at Brookhaven National Laboratory. We measured specific binding of positron emission tomographic radioligands for dopamine transporters (DAT) using [{sup 11}C]cocaine and for D{sub 2}/D{sub 3} receptors using [{sup 11}C]raclopride, quantified as binding potential (distribution volume ratio -1). For both ligands, statistical parametric mapping showed that specific binding was lower in ADHD than in controls (threshold for significance set at P < .005) in regions of the dopamine reward pathway in the left side of the brain. Region-of-interest analyses corroborated these findings. The mean (95% confidence interval [CI] of mean difference) for DAT in the nucleus accumbens for controls was 0.71 vs 0.63 for those with ADHD (95% CI, 0.03-0.13, P = .004) and in the midbrain for controls was 0.16 vs 0.09 for those with ADHD (95% CI, 0.03-0.12; P {le} .001); for D{sub 2}/D{sub 3} receptors, the mean accumbens for controls was 2.85 vs 2.68 for those with ADHD (95% CI, 0.06-0.30, P = .004); and in the midbrain, it was for controls 0.28 vs 0.18 for those with ADHD (95% CI, 0.02-0.17, P = .01). The analysis also corroborated differences in the left caudate: the mean DAT for controls was 0.66 vs 0.53 for those with ADHD (95% CI, 0.04-0.22; P = .003) and the mean D{sub 2}/D{sub 3} for controls was 2.80 vs 2.47 for those with ADHD (95% CI, 0

In vivo neurochemical characterization of clothianidin induced striatal dopamine release.

Science.gov (United States)

Faro, L R F; Oliveira, I M; Durán, R; Alfonso, M

2012-12-16

Clothianidin (CLO) is a neonicotinoid insecticide with selective action on nicotinic acetylcholine receptors. The aim of this study was to determine the neurochemical basis for CLO-induced striatal dopamine release using the microdialysis technique in freely moving and conscious rats. Intrastriatal administration of CLO (3.5mM), produced an increase in both spontaneous (2462 ± 627% with respect to basal values) and KCl-evoked (4672 ± 706% with respect to basal values) dopamine release. This effect was attenuated in Ca(2+)-free medium, and was prevented in reserpine pre-treated animals or in presence of tetrodotoxin (TTX). To investigate the involvement of dopamine transporter (DAT), the effect of CLO was observed in presence of nomifensine. The coadministration of CLO and nomifensine produced an additive effect on striatal dopamine release. The results suggest that the effect of CLO on striatal dopamine release is predominantly mediated by an exocytotic mechanism, Ca(2+), vesicular and TTX-dependent and not by a mechanism mediated by dopamine transporter. Published by Elsevier Ireland Ltd.

Low dopamine transporter occupancy by methylphenidate as a possible reason for reduced treatment effectiveness in ADHD patients with cocaine dependence

NARCIS (Netherlands)

Crunelle, Cleo L.; van den Brink, Wim; Veltman, Dick J.; van Emmerik-van Oortmerssen, Katelijne; Dom, Geert; Schoevers, Robert A.; Booij, Jan

2013-01-01

Methylphenidate (MPH) occupies brain striatal dopamine transporters (DATs) and is an effective treatment for attention deficit hyperactivity disorder (ADHD). However, patients with ADHD and comorbid cocaine dependence do not benefit significantly from treatment with MPH. To better understand the

Bitropic D3 Dopamine Receptor Selective Compounds as Potential Antipsychotics.

Science.gov (United States)

Luedtke, Robert R; Rangel-Barajas, Claudia; Malik, Mahinder; Reichert, David E; Mach, R H

2015-01-01

modified to develop bivalent ligands capable of interacting with receptor dimers or oligomers are also provided. Preclinical studies using bitropic D3 dopamine receptor selective ligands are also discussed as strategy to pharmacologically dissect the role of the D2 and D3 dopamine receptor subtypes in animal models of neuropsychiatric, neurological and substance abuse disorders. This research has the potential to a) advance the understanding of the role of the D2 and D3 dopamine receptor subtypes in neuropsychiatric disorders and b) lead to new treatment strategies for neuropsychiatric disorders.

Evaluation of striatal dopamine transporter density using ({sup 123}I)-{beta}-CIT SPECT in schizophrenic patients treated with olanzapine: pilot study

Energy Technology Data Exchange (ETDEWEB)

Kim, Chul Eung; Moon, Hey Won; Choe, Won Sick; Kim, Chang Ho; Chi, Dae Yoon [Inha Univ., Incheon (Korea, Republic of)

2002-08-01

This pilot study was performed to understand the pharmacological effect of olanzapine, an atypical antipsychotic agent, on dopamine transporter in schizophrenic patients. Six patients (3 male, 3 female) with schizophrenia, who had not taken any psychotropic drugs for at least four weeks, were studied. Nuclear imaging using ({sup 123}I)-{beta}-CIT SPECT was obtained before and after 4-week treatment with olanzapine. Analysis of ROI on the striatum, caudate nucleus, and putamen was performed. Post-treatment uptake was significantly increased in all the ROIs compared with pre-treatment uptake. This preliminary study with the small number of schizophrenic patients suggested an increase in uptake of dopamine transporter in the striatum, caudate nucleus, and putamen after 4-week treatment with olanzapine, which warrants a large-scaled controlled study to confirm the current findings.

TFH-derived dopamine accelerates productive synapses in germinal centres.

Science.gov (United States)

Papa, Ilenia; Saliba, David; Ponzoni, Maurilio; Bustamante, Sonia; Canete, Pablo F; Gonzalez-Figueroa, Paula; McNamara, Hayley A; Valvo, Salvatore; Grimbaldeston, Michele; Sweet, Rebecca A; Vohra, Harpreet; Cockburn, Ian A; Meyer-Hermann, Michael; Dustin, Michael L; Doglioni, Claudio; Vinuesa, Carola G

2017-07-20

Protective high-affinity antibody responses depend on competitive selection of B cells carrying somatically mutated B-cell receptors by follicular helper T (T FH ) cells in germinal centres. The rapid T-B-cell interactions that occur during this process are reminiscent of neural synaptic transmission pathways. Here we show that a proportion of human T FH cells contain dense-core granules marked by chromogranin B, which are normally found in neuronal presynaptic terminals storing catecholamines such as dopamine. T FH cells produce high amounts of dopamine and release it upon cognate interaction with B cells. Dopamine causes rapid translocation of intracellular ICOSL (inducible T-cell co-stimulator ligand, also known as ICOSLG) to the B-cell surface, which enhances accumulation of CD40L and chromogranin B granules at the human T FH cell synapse and increases the synapse area. Mathematical modelling suggests that faster dopamine-induced T-B-cell interactions increase total germinal centre output and accelerate it by days. Delivery of neurotransmitters across the T-B-cell synapse may be advantageous in the face of infection.

Decreased lymphocyte dopamine transporter in romantic lovers.

Science.gov (United States)

Marazziti, Donatella; Baroni, Stefano; Giannaccini, Gino; Piccinni, Armando; Mucci, Federico; Catena-Dell'Osso, Mario; Rutigliano, Grazia; Massimetti, Gabriele; Dell'Osso, Liliana

2017-06-01

The role of dopamine (DA) in romantic love is suggested by different evidence and is supported by the findings of some brain imaging studies. The DA transporter (DAT) is a key structure in regulating the concentration of the neurotransmitter in the synaptic cleft. Given the presence of DAT in blood cells, the present study aimed to explore it in resting lymphocytes of 30 healthy subjects of both sexes in the early stage of romantic love (no longer than 6 months), as compared with 30 subjects involved in a long-lasting relationship. All subjects had no physical or psychiatric illness. The DAT was measured by means of the [3H]-WIN 35,428 binding and the [3H]-DA reuptake to resting lymphocytes membranes. Romantic love was assessed by a specific questionnaire developed by us. The results showed that the subjects in the early phase of romantic love had a global alteration of the lymphocyte DAT involving both a decreased number of proteins (Bmax) and a reduced functionality (Vmax). Taken together, these findings would indicate the presence of increased levels of DA in romantic love that, if paralleled by similar concentrations in the brain, would explain some peculiar features of this human feeling.

Dopamine1 receptors in rat kidneys identified with 125I-Sch 23982

International Nuclear Information System (INIS)

Felder, R.A.; Jose, P.A.

1988-01-01

Dopamine1 receptors were studied in rat kidney using the selective dopamine1 antagonist 125I-labeled Sch 23982. The specific binding of 125I-Sch 23982 (defined by 5 microM Sch 23390) to renal cortical homogenates incubated at room temperature was rapid, saturable with time and ligand concentration, and reversible. Analysis of Rosenthal plots revealed a single class of receptors with an apparent dissociation constant of 12.2 +/- 1.9 nM and maximum receptor density of 1.03 +/- 0.15 pmol/mg protein (n = 6). However, competition experiments with the dopamine1 antagonist Sch 23390 revealed a low- and high-affinity binding site with inhibition constants of 1 x 10(-6) and 1 x 10(-8) M, respectively. The competition experiments were also indicative of dopamine1 receptors with stereoselectivity noted for dopamine1 but not for dopamine2 antagonists. The inhibition constants for dopamine1 antagonists and agonists were two orders of magnitude greater in renal cortical than striatal homogenates. Different buffers affected striatal but not renal cortical binding. Autoradiographic studies revealed 125I-Sch 23982 binding in renal cortical but not medullary tissue. These studies confirm the presence of dopamine1 receptors in the cortex of the rat kidney

Cross-talk between an activator of nuclear receptors-mediated transcription and the D1 dopamine receptor signaling pathway.

Science.gov (United States)

Schmidt, Azriel; Vogel, Robert; Rutledge, Su Jane; Opas, Evan E; Rodan, Gideon A; Friedman, Eitan

2005-03-01

Nuclear receptors are transcription factors that usually interact, in a ligand-dependent manner, with specific DNA sequences located within promoters of target genes. The nuclear receptors can also be controlled in a ligand-independent manner via the action of membrane receptors and cellular signaling pathways. 5-Tetradecyloxy-2-furancarboxylic acid (TOFA) was shown to stimulate transcription from the MMTV promoter via chimeric receptors that consist of the DNA binding domain of GR and the ligand binding regions of the PPARbeta or LXRbeta nuclear receptors (GR/PPARbeta and GR/LXRbeta). TOFA and hydroxycholesterols also modulate transcription from NF-kappaB- and AP-1-controlled reporter genes and induce neurite differentiation in PC12 cells. In CV-1 cells that express D(1) dopamine receptors, D(1) dopamine receptor stimulation was found to inhibit TOFA-stimulated transcription from the MMTV promoter that is under the control of chimeric GR/PPARbeta and GR/LXRbeta receptors. Treatment with the D(1) dopamine receptor antagonist, SCH23390, prevented dopamine-mediated suppression of transcription, and by itself increased transcription controlled by GR/LXRbeta. Furthermore, combined treatment of CV-1 cells with TOFA and SCH23390 increased transcription controlled by the GR/LXRbeta chimeric receptor synergistically. The significance of this in vitro synergy was demonstrated in vivo, by the observation that SCH23390 (but not haloperidol)-mediated catalepsy in rats was potentiated by TOFA, thus showing that an agent that mimics the in vitro activities of compounds that activate members of the LXR and PPAR receptor families can influence D1 dopamine receptor elicited responses.

Lack of effect of polymorphisms in dopamine metabolism related genes on imaging of TRODAT-1 in striatum of asymptomatic volunteers and patients with Parkinson's disease.

Science.gov (United States)

Lynch, David R; Mozley, P David; Sokol, Set; Maas, Nicole M C; Balcer, Laura J; Siderowf, Andrew D

2003-07-01

SPECT scanning using (99)Tc-TRODAT-1, a ligand that binds to dopamine transporters, may be useful for detection of early Parkinson's disease (PD), diagnosis of presymptomatic individuals, and monitoring disease progression. Understanding whether genetic factors contribute to inter-individual variability is crucial for interpreting imaging results in the context of disease pathophysiology. We tested whether polymorphisms in the genes for catechol-O-methyltransferase (COMT), monoamine-oxidase B (MAO-B), and the dopamine transporter (DAT) influence dopamine uptake parameters in the striatum in vivo in asymptomatic volunteers and patients with PD as measured with (99)Tc-TRODAT-1. (99)Tc-TRODAT-1 binding declined with age in both asymptomatic volunteers and PD patients, and depended on disease duration in PD patients. We found no significant association between COMT, MAO-B, and DAT polymorphisms and results of (99)Tc-TRODAT-1 testing in asymptomatic volunteers or patients with PD. In PD patients, the age of disease onset and speed of progression did not differ based on these polymorphisms. These results demonstrate that these specific genetic variations do not alter the fidelity of (99)Tc-TRODAT-1 as a measure of dopaminergic function in asymptomatic volunteer individuals or patients with PD. Copyright 2003 Movement Disorder Society

Early diagnosis of Parkinson's disease: neurospect by trodat-1Tc99m, dopamine transporter marker

International Nuclear Information System (INIS)

Mena, Ismael; Diaz, Fernando; Gomez, Ariel

2001-01-01

Information: We have recently preliminarily reported that NeuroSPECT (NSP) of the Dopamine Transporter (DAT) is a highly sensitive method for early diagnosis of Parkinson disease (27). Objectives: To evaluate the sensitivity of NSP of DAT in patients with de novo hemiparkinsonism and compare the contralateral Vs ipsilateral to the symptomatic side results and also Vs. normal controls, in order to assess the sensitivity to detect pre symptomatic and symptomatic impairment of concentration of DAT (Au)

Synthesis of symmetrical and non-symmetrical bivalent neurotransmitter ligands

DEFF Research Database (Denmark)

Stuhr-Hansen, Nicolai; Andersen, Jacob; Thygesen, Mikkel Boas

2016-01-01

A novel procedure for synthesis of bivalent neurotransmitter ligands was developed by reacting O-benzyl protected N-nosylated dopamine and serotonin with alkyl- or PEG-linked diols under Fukuyama-Mitsunobu conditions in the presence of DIAD/PPh3 generating three different bivalent neurotransmitte...

Structural and Functional Effect of an Oscillating Electric Field on the Dopamine-D3 Receptor: A Molecular Dynamics Simulation Study.

Directory of Open Access Journals (Sweden)

Zohreh Fallah

Full Text Available Dopamine as a neurotransmitter plays a critical role in the functioning of the central nervous system. The structure of D3 receptor as a member of class A G-protein coupled receptors (GPCRs has been reported. We used MD simulation to investigate the effect of an oscillating electric field, with frequencies in the range 0.6-800 GHz applied along the z-direction, on the dopamine-D3R complex. The simulations showed that at some frequencies, the application of an external oscillating electric field along the z-direction has a considerable effect on the dopamine-D3R. However, there is no enough evidence for prediction of changes in specific frequency, implying that there is no order in changes. Computing the correlation coefficient parameter showed that increasing the field frequency can weaken the interaction between dopamine and D3R and may decrease the Arg128{3.50}-Glu324{6.30} distance. Because of high stability of α helices along the z-direction, applying an oscillating electric field in this direction with an amplitude 10-time higher did not have a considerable effect. However, applying the oscillating field at the frequency of 0.6 GHz along other directions, such as X-Y and Y-Z planes, could change the energy between the dopamine and the D3R, and the number of internal hydrogen bonds of the protein. This can be due to the effect of the direction of the electric field vis-à-vis the ligands orientation and the interaction of the oscillating electric field with the dipole moment of the protein.

ILLICIT DOPAMINE TRANSIENTS: RECONCILING ACTIONS OF ABUSED DRUGS

Science.gov (United States)

Covey, Dan P.; Roitman, Mitchell F.; Garris, Paul A.

2014-01-01

Phasic increases in brain dopamine are required for cue-directed reward seeking. While compelling within the framework of appetitive behavior, the view that illicit drugs hijack reward circuits by hyper-activating these dopamine transients is inconsistent with established psychostimulant pharmacology. However, recent work reclassifying amphetamine (AMPH), cocaine, and other addictive dopamine-transporter inhibitors (DAT-Is) supports transient hyper-activation as a unifying hypothesis of abused drugs. We argue here that reclassification also identifies generating burst firing by dopamine neurons as a keystone action. Unlike natural rewards, which are processed by sensory systems, drugs act directly on the brain. Consequently, to mimic natural reward and exploit reward circuits, dopamine transients must be elicited de novo. Of available drug targets, only burst firing achieves this essential outcome. PMID:24656971

Dual-isotope single-photon emission computed tomography for dopamine and serotonin transporters in normal and parkinsonian monkey brains

Energy Technology Data Exchange (ETDEWEB)

Li, I-H. [Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 114, Taiwan (China); Huang, W.-S. [Department of Nuclear Medicine, Tri-Service General Hospital, Taipei, 114, Taiwan (China); Yeh, C.-B. [Department of Psychiatry, Tri-Service General Hospital, Taipei, 114, Taiwan (China); Liao, M.-H.; Chen, C.-C.; Shen, L.-H. [Division of Isotope Application, Institute of Nuclear Energy Research, Taoyaun, 325 Taiwan (China); Liu, J.-C. [Department of Biology and Anatomy, National Defense Medical Center, Taipei 114, Taiwan (China); Ma, K.-H. [Department of Biology and Anatomy, National Defense Medical Center, Taipei 114, Taiwan (China)], E-mail: kuohsing91@yahoo.com.tw

2009-08-15

Introduction: Parkinson's disease (PD) affects both dopaminergic and serotonergic systems. In this study, we simultaneously evaluated dopamine and serotonin transporters in primates using dual-isotope single-photon emission computed tomography (SPECT) imaging and compared the results with traditional single-isotope imaging. Methods: Four healthy and one 6-OHDA-induced PD monkeys were used for this study. SPECT was performed over 4 h after individual or simultaneous injection of [{sup 99m}Tc]TRODAT-1 (a dopamine transporter imaging agent) and [{sup 123}I]ADAM (a serotonin transporter imaging agent). Results: The results showed that the image quality and uptake ratios in different brain regions were comparable between single- and dual-isotope studies. The striatal [{sup 99m}Tc]TRODAT-1 uptake in the PD monkey was markedly lower than that in normal monkeys. The uptake of [{sup 123}I]ADAM in the midbrain of the PD monkey was comparable to that in the normal monkeys, but there were decreased uptakes in the thalamus and striatum of the PD monkey. Conclusions: Our results suggest that dual-isotope SPECT using [{sup 99m}Tc]TRODAT-1 and [{sup 123}I]ADAM can simultaneously evaluate changes in dopaminergic and serotonergic systems in a PD model.

Regulation of the Dopamine and Vesicular Monoamine Transporters: Pharmacological Targets and Implications for Disease.

Science.gov (United States)

German, Christopher L; Baladi, Michelle G; McFadden, Lisa M; Hanson, Glen R; Fleckenstein, Annette E

2015-10-01

Dopamine (DA) plays a well recognized role in a variety of physiologic functions such as movement, cognition, mood, and reward. Consequently, many human disorders are due, in part, to dysfunctional dopaminergic systems, including Parkinson's disease, attention deficit hyperactivity disorder, and substance abuse. Drugs that modify the DA system are clinically effective in treating symptoms of these diseases or are involved in their manifestation, implicating DA in their etiology. DA signaling and distribution are primarily modulated by the DA transporter (DAT) and by vesicular monoamine transporter (VMAT)-2, which transport DA into presynaptic terminals and synaptic vesicles, respectively. These transporters are regulated by complex processes such as phosphorylation, protein-protein interactions, and changes in intracellular localization. This review provides an overview of 1) the current understanding of DAT and VMAT2 neurobiology, including discussion of studies ranging from those conducted in vitro to those involving human subjects; 2) the role of these transporters in disease and how these transporters are affected by disease; and 3) and how selected drugs alter the function and expression of these transporters. Understanding the regulatory processes and the pathologic consequences of DAT and VMAT2 dysfunction underlies the evolution of therapeutic development for the treatment of DA-related disorders. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

[mRNA expression of dopamine receptor D2 and dopamine transporter in peripheral blood lymphocytes before and after treatment in children with tic disorder].

Science.gov (United States)

Ji, Xiao-Yi; Wu, Min

2016-04-01

To investigate the mRNA expression of dopamine receptor D2 (DRD2) and dopamine transporter (DAT) in peripheral blood lymphocytes before and after treatment in children with tic disorder (TD). RT-PCR was used to measure the mRNA expression of DRD2 and DAT in peripheral blood lymphocytes before and after treatment in 60 children with TD. The correlations between mRNA expression of DRD2 and DAT and the severity of TD were analyzed. Sixty healthy children served as the control group. Before treatment, the children with TD had a significant increase in the mRNA expression of DRD2 and DAT compared with the control group (PTic Severity Scale (YGTSS) score (P<0.05). In the children with moderate TD, the mRNA expression of DAT was positively correlated with YGTSS score (P<0.05). In children with TD, the mRNA expression of DRD2 in peripheral blood lymphocytes can be used as one of the indicators for diagnosing TD, assessing the severity of TD, and evaluating clinical outcomes.

Dopamine transporter gene variation modulates activation of striatum in youth with ADHD.

Science.gov (United States)

Bédard, Anne-Claude; Schulz, Kurt P; Cook, Edwin H; Fan, Jin; Clerkin, Suzanne M; Ivanov, Iliyan; Halperin, Jeffrey M; Newcorn, Jeffrey H

2010-11-15

Polymorphisms in the 3'UTR variable number tandem repeat (VNTR) of exon 15 of the dopamine transporter gene (DAT1) have been linked to attention-deficit hyperactivity disorder (ADHD); moreover, variability in DAT1 3'UTR genotype may contribute to both heterogeneity of the ADHD phenotype and differences in response to stimulant medications. The impact of this VNTR on neuronal function in individuals with ADHD remains unclear despite evidence that the polymorphisms influence dopamine transporter expression. Thus, we used event-related functional magnetic resonance imaging to examine the impact of DAT1 3'UTR genotype on brain activation during response inhibition in unmedicated children and adolescents with ADHD. Twenty-one youth with ADHD who were homozygous for the 10-repeat (10R) allele of the DAT1 3'UTR and 12 youth who were carriers of the 9-repeat (9R) allele were scanned while they performed a Go/No-Go task. Response inhibition was modeled by contrasting activation during correct No-Go trials versus correct Go trials. Participants who were homozygous for the DAT1 3'UTR 10R allele and those who had a single 9R allele did not differ on percent of trials with successful inhibition, which was the primary measure of inhibitory control. Yet, youth with the DAT1 3'UTR 10R/10R genotype had significantly greater inhibitory control-related activation than those with one 9R allele in the left striatum, right dorsal premotor cortex, and bilaterally in the temporoparietal cortical junction. These findings provide preliminary evidence that neural activity related to inhibitory control may differ as a function of DAT1 3'UTR genotype in youth with ADHD. Copyright 2009 Elsevier Inc. All rights reserved.

MDMA-evoked changes in the binding of dopamine D(2) receptor ligands in striatum of rats with unilateral serotonin depletion

DEFF Research Database (Denmark)

Ostergaard, Søren Dinesen; Alstrup, Aage Kristian Olsen; Gramsbergen, Jan Bert

2010-01-01

We earlier reported an anomalous 50% decrease in [(11)C]N-methylspiperone ([(11)C]NMSP) binding to dopamine D(2)-like receptors in living pig striatum after challenge with 3,4-methylenedioxymethamphetamine (MDMA, "Ecstasy"), suggesting either (1) a species peculiarity in the vulnerability...... lesions, later verified by [(125)I]RTI-55 autoradiography. Baseline [(11)C]NMSP microPET recordings were followed by either saline or MDMA-HCl (4 mg/kg) injections (i.v.), and a second [(11)C]NMSP recording, culminating with injection of [(3)H]raclopride for autoradiography ex vivo. Neither MDMA......-challenge nor serotonin lesion had any detectable effect on [(11)C]NMSP binding. In contrast, MDMA challenge increased receptor occupancy by [(3)H]raclopride ex vivo (relative to the B(max) in vitro) from 8% to 12%, and doubled the free ligand concentration in cerebral cortex, apparently by blocking hepatic CYP...

Change of striatum dopaminergic transporter and content of dopamine in rats with experimental hyperthyroidism

International Nuclear Information System (INIS)

Lin Yansong; Wang Huicheng; Zhao Zhiying; Zhu Li; Zhang Yingqiang; Chen Zhengping

2009-01-01

Objective: The central dopamine system plays an important role in regulating movement and mood. In our routine clinical practice,we found that patients with hyperthyroidism often show tremor of their hands or legs. Meanwhile they also experienced emotional problems such as anxiety and depression. These reminded us that there might be close relationship between thyroid hormone and dopamine system. Based on our previous works, in this study we evaluated the change of striatum dopamine transporter (DAT) by using 99 Tc m -2β- [N, N'-bis (2-merecaptoethyl) ethylenediamino]methyl, 3β- (4-chlorophenyl) tropane (TRODAT-1) brain biodistribution, and the content of striatum dopamine and its metabolites 3.4-di-hydroxyphenylacetic (DOPAC) by high performace liquid chromatograph-electrochemical detection (HPLC-ECD) in rats with experimental hyperthyroidism. Methods: All 24 rats were randomly divided into two groups, thyroxin group were induced by daily thyroxin infusion for 14 d to be experimental hyperthyroidism, the others were control group which received saline infusion. The blood samples were randomly taken from thyroxine group and control group, and the concentration of TT 3 and TT 4 were detected by radioimmunoassay. After 14 d,both experimental (thyroxine group) and control group were further divided into 2 sub-groups. One was for evaluation of the function of striatum DAT by 99 Tc m -TRODAT-1 biodistribution study and the other was for HPIJC-ECD measurement of the concentration of dopamine and its metabolites DOPAC. Results: Significantly hyperactivity and weight loss [(223.90 ± 8.40) VS (261.60 ± 14.20)g, t=6.98. P 3 and TT 4 after thyroxin infusion was significantly elevated than that of before thyroxin infusion [(2.72 ± 0.29) V8(1.46 ± 0.17) nmol/L, t=10.51, P 3 , and TT 4 after saline infusion showed no statistical significance as compared with before saline infusion [(1.71 ± 0.20) vs (1.54 ± O.09) nmol/L, t=1.68. P>0.05 and (88.38 ± 6.76) vs (98.38 ± 9

Dopamine denervation does not alter in vivo 3H-spiperone binding in rat striatum: implications for external imaging of dopamine receptors in Parkinson's disease

International Nuclear Information System (INIS)

Bennett, J.P. Jr.; Wooten, G.F.

1986-01-01

Striatal particulate preparations, both from rats with lesion-induced striatal dopamine (DA) loss and from some striatal dopamine (DA) loss and from some patients with Parkinson's disease, exhibit increased 3 H-neuroleptic binding, which is interpreted to be the mechanism of denervation-induced behavioral supersensitivity to dopaminergic compounds. After intravenous 3 H-spiperone ( 3 H-SP) administration to rats with unilateral nigral lesions, we found no differences in accumulation of total or particulate-bound 3 H-SP in dopamine-denervated compared with intact striata. 3 H-SP in vivo binds to less than 10% of striatal sites labeled by 3 H-SP incubated with striatal particulate preparations in vitro. Quantitative autoradiography of 3 H-SP binding to striatal sections in vitro also failed to reveal any effects of dopamine denervation. 3 H-SP bound to striatal sites in vivo dissociates more slowly than that bound to striatal particulate preparations labeled in vitro. Striatal binding properties of 3 H-SP administered in vivo are quite different from the same kinetic binding parameters estimated in vitro using crude membrane preparations of striatum. In addition, striatal binding of in vivo-administered 3H-SP is not affected by prior lesion of the substantia nigra, which results in profound ipsilateral striatal dopamine depletion. Thus, behavioral supersensitivity to dopaminergic compounds may not be associated with altered striatal binding properties for dopamine receptor ligands in vivo

Illicit dopamine transients: reconciling actions of abused drugs.

Science.gov (United States)

Covey, Dan P; Roitman, Mitchell F; Garris, Paul A

2014-04-01

Phasic increases in brain dopamine are required for cue-directed reward seeking. Although compelling within the framework of appetitive behavior, the view that illicit drugs hijack reward circuits by hyperactivating these dopamine transients is inconsistent with established psychostimulant pharmacology. However, recent work reclassifying amphetamine (AMPH), cocaine, and other addictive dopamine-transporter inhibitors (DAT-Is) supports transient hyperactivation as a unifying hypothesis of abused drugs. We argue here that reclassification also identifies generating burst firing by dopamine neurons as a keystone action. Unlike natural rewards, which are processed by sensory systems, drugs act directly on the brain. Consequently, to mimic natural rewards and exploit reward circuits, dopamine transients must be elicited de novo. Of available drug targets, only burst firing achieves this essential outcome. Copyright © 2014 Elsevier Ltd. All rights reserved.

Rare autism-associated variants implicate syntaxin 1 (STX1 R26Q) phosphorylation and the dopamine transporter (hDAT R51W) in dopamine neurotransmission and behaviors

DEFF Research Database (Denmark)

Cartier, Etienne; Hamilton, Peter J; Belovich, Andrea N

2015-01-01

BACKGROUND: Syntaxin 1 (STX1) is a presynaptic plasma membrane protein that coordinates synaptic vesicle fusion. STX1 also regulates the function of neurotransmitter transporters, including the dopamine (DA) transporter (DAT). The DAT is a membrane protein that controls DA homeostasis through...... the high-affinity re-uptake of synaptically released DA. METHODS: We adopt newly developed animal models and state-of-the-art biophysical techniques to determine the contribution of the identified gene variants to impairments in DA neurotransmission observed in autism spectrum disorder (ASD). OUTCOMES......: Here, we characterize two independent autism-associated variants in the genes that encode STX1 and the DAT. We demonstrate that each variant dramatically alters DAT function. We identify molecular mechanisms that converge to inhibit reverse transport of DA and DA-associated behaviors. These mechanisms...

Ligand Binding and Crystal Structures of the Substrate-Binding Domain of the ABC Transporter OpuA

NARCIS (Netherlands)

Wolters, Justina C.; Berntsson, Ronnie P-A.; Gul, Nadia; Karasawa, Akira; Thunnissen, Andy-Mark W. H.; Slotboom, Dirk-Jan; Poolman, Bert

2010-01-01

The ABC transporter OpuA from Lactococcus lactis transports glycine betaine upon activation by threshold values of ionic strength. In this study, the ligand binding characteristics of purified OpuA in a detergent-solubilized state and of its substrate-binding domain produced as soluble protein

An inquiry into the semiquantitative parameters of striatal dopamine receptor imaging

International Nuclear Information System (INIS)

Cao Guoxiang; Tan Tianzhi; Kuang Anren; Liang Zhenglu

1998-01-01

Purpose: To inquire into the optimal striatal reference region for nonspecific IBZM uptake in brain dopamine receptor imaging. Methods: Using in vivo data from rats, the authors compared the results of 125 I-iodobenzamide ( 125 I-IBZM) striatal specific binding that were respectively obtained taking cerebellum and frontal cortex as striatal reference region of nonspecific uptake of ligand. Results: Radioiodination labelled IBZM bound stereoselectively and reversibly to striatal D2 receptors. Frontal cortex and cerebellum showed rapid uptake and rapid washout of ligand. When cerebellar uptake was used as a reference of nonspecific uptake in striatum, IBZM saturation could not be demonstrated. But when the frontal cortex was used as reference region, saturation could be demonstrated with B max = 44 pmol/g striatum tissue. The percentage of haloperidol replacement and the percentage of uptake difference between striatum and other brain regions which were derived from competitive inhibition experiments with a large does of spiperone or haloperidol, suggested that the cerebellar uptake underestimated nonspecific uptake in the striatum while frontal cortex was an appropriate reference region for nonspecific uptake of ligand in striatum. Conclusions: For the calculation of specific IBZM binding and other semiquantitative parameters of striatal dopamine D2 receptor imaging, frontal cortex would be the nonspecific reference region of choice

Dopamine modulates metabolic rate and temperature sensitivity in Drosophila melanogaster.

Directory of Open Access Journals (Sweden)

Taro Ueno

Full Text Available Homeothermal animals, such as mammals, maintain their body temperature by heat generation and heat dissipation, while poikilothermal animals, such as insects, accomplish it by relocating to an environment of their favored temperature. Catecholamines are known to regulate thermogenesis and metabolic rate in mammals, but their roles in other animals are poorly understood. The fruit fly, Drosophila melanogaster, has been used as a model system for the genetic studies of temperature preference behavior. Here, we demonstrate that metabolic rate and temperature sensitivity of some temperature sensitive behaviors are regulated by dopamine in Drosophila. Temperature-sensitive molecules like dTrpA1 and shi(ts induce temperature-dependent behavioral changes, and the temperature at which the changes are induced were lowered in the dopamine transporter-defective mutant, fumin. The mutant also displays a preference for lower temperatures. This thermophobic phenotype was rescued by the genetic recovery of the dopamine transporter in dopamine neurons. Flies fed with a dopamine biosynthesis inhibitor (3-iodo-L-tyrosine, which diminishes dopamine signaling, exhibited preference for a higher temperature. Furthermore, we found that the metabolic rate is up-regulated in the fumin mutant. Taken together, dopamine has functions in the temperature sensitivity of behavioral changes and metabolic rate regulation in Drosophila, as well as its previously reported functions in arousal/sleep regulation.

Phenyl Ring-Substituted Lobelane Analogs: Inhibition of [3H]Dopamine Uptake at the Vesicular Monoamine Transporter-2

OpenAIRE

Nickell, Justin R.; Zheng, Guangrong; Deaciuc, Agripina G.; Crooks, Peter A.; Dwoskin, Linda P.

2011-01-01

Lobeline attenuates the behavioral effects of methamphetamine via inhibition of the vesicular monoamine transporter (VMAT2). To increase selectivity for VMAT2, chemically defunctionalized lobeline analogs, including lobelane, were designed to eliminate nicotinic acetylcholine receptor affinity. The current study evaluated the ability of lobelane analogs to inhibit [3H]dihydrotetrabenazine (DTBZ) binding to VMAT2 and [3H]dopamine (DA) uptake into isolated synaptic vesicles and determined the m...

Sex-Dependent Changes in Striatal Dopamine Transport in Preadolescent Rats Exposed Prenatally and/or Postnatally to Methamphetamine

Czech Academy of Sciences Publication Activity Database

Šírová, J.; Krištofíková, Z.; Vrajová, M.; Fujakova-Lipski, M.; Řípová, D.; Klaschka, Jan; Šlamberová, R.

2016-01-01

Roč. 41, č. 8 (2016), s. 1911-1923 ISSN 0364-3190 Grant - others:GA MŠk(CZ) ED2.1.00/03.0078; GA ČR(CZ) GA14-03708S; Univerzita Karlova(CZ) Prvouk P34; GA UK(CZ) 88315; SVV(CZ) 260277/2016 Institutional support: RVO:67985807 Keywords : methamphetamine * dopamine transporte * sex differences * membrane fluidity Subject RIV: FH - Neurology Impact factor: 2.581, year: 2016

Study and development of retinal dopamine nervous system in experimental myopia

International Nuclear Information System (INIS)

Zhao Juan; Liu Xingdang

2007-01-01

Myopia is the most familiar ametropia. Animal experimental models include form deprivation myopia and defocus myopia. Experimental animals we often use are chicken and mammals. The retinal dopamine system and vision experience have close relations with the regulation of eyeball's growth after birth, while the change of dopamine transporter may reflect the change of dopamine in the synaptic cleft more directly. (authors)

Testosterone induces molecular changes in dopamine signaling pathway molecules in the adolescent male rat nigrostriatal pathway.

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Tertia D Purves-Tyson

Full Text Available Adolescent males have an increased risk of developing schizophrenia, implicating testosterone in the precipitation of dopamine-related psychopathology. Evidence from adult rodent brain indicates that testosterone can modulate nigrostriatal dopamine. However, studies are required to understand the role testosterone plays in maturation of dopamine pathways during adolescence and to elucidate the molecular mechanism(s by which testosterone exerts its effects. We hypothesized that molecular indices of dopamine neurotransmission [synthesis (tyrosine hydroxylase, breakdown (catechol-O-methyl transferase; monoamine oxygenase, transport [vesicular monoamine transporter (VMAT, dopamine transporter (DAT] and receptors (DRD1-D5] would be changed by testosterone or its metabolites, dihydrotestosterone and 17β-estradiol, in the nigrostriatal pathway of adolescent male rats. We found that testosterone and dihydrotestosterone increased DAT and VMAT mRNAs in the substantia nigra and that testosterone increased DAT protein at the region of the cell bodies, but not in target regions in the striatum. Dopamine receptor D2 mRNA was increased and D3 mRNA was decreased in substantia nigra and/or striatum by androgens. These data suggest that increased testosterone at adolescence may change dopamine responsivity of the nigrostriatal pathway by modulating, at a molecular level, the capacity of neurons to transport and respond to dopamine. Further, dopamine turnover was increased in the dorsal striatum following gonadectomy and this was prevented by testosterone replacement. Gene expression changes in the dopaminergic cell body region may serve to modulate both dendritic dopamine feedback inhibition and reuptake in the dopaminergic somatodendritic field as well as dopamine release and re-uptake dynamics at the presynaptic terminals in the striatum. These testosterone-induced changes of molecular indices of dopamine neurotransmission in males are primarily androgen

Serotonin/dopamine interactions in a hyperactive mouse: reduced serotonin receptor 1B activity reverses effects of dopamine transporter knockout.

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Frank Scott Hall

Full Text Available Knockout (KO mice that lack the dopamine transporter (SL6A3; DAT display increased locomotion that can be attenuated, under some circumstances, by administration of drugs that normally produce psychostimulant-like effects, such as amphetamine and methylphenidate. These results have led to suggestions that DAT KO mice may model features of attention deficit hyperactivity disorder (ADHD and that these drugs may act upon serotonin (5-HT systems to produce these unusual locomotor decreasing effects. Evidence from patterns of brain expression and initial pharmacologic studies led us to use genetic and pharmacologic approaches to examine the influence of altered 5-HT1B receptor activity on hyperactivity in DAT KO mice. Heterozygous 5-HT1B KO and pharmacologic 5-HT1B antagonism both attenuated locomotor hyperactivity in DAT KO mice. Furthermore, DAT KO mice with reduced, but not eliminated, 5-HT1B receptor expression regained cocaine-stimulated locomotion, which was absent in DAT KO mice with normal levels of 5-HT1B receptor expression. Further experiments demonstrated that the degree of habituation to the testing apparatus determined whether cocaine had no effect on locomotion in DAT KO or reduced locomotion, helping to resolve differences among prior reports. These findings of complementation of the locomotor effects of DAT KO by reducing 5-HT1B receptor activity underscore roles for interactions between specific 5-HT receptors and dopamine (DA systems in basal and cocaine-stimulated locomotion and support evaluation of 5-HT1B antagonists as potential, non-stimulant ADHD therapeutics.

A Markov State-based Quantitative Kinetic Model of Sodium Release from the Dopamine Transporter

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Razavi, Asghar M.; Khelashvili, George; Weinstein, Harel

2017-01-01

The dopamine transporter (DAT) belongs to the neurotransmitter:sodium symporter (NSS) family of membrane proteins that are responsible for reuptake of neurotransmitters from the synaptic cleft to terminate a neuronal signal and enable subsequent neurotransmitter release from the presynaptic neuron. The release of one sodium ion from the crystallographically determined sodium binding site Na2 had been identified as an initial step in the transport cycle which prepares the transporter for substrate translocation by stabilizing an inward-open conformation. We have constructed Markov State Models (MSMs) from extensive molecular dynamics simulations of human DAT (hDAT) to explore the mechanism of this sodium release. Our results quantify the release process triggered by hydration of the Na2 site that occurs concomitantly with a conformational transition from an outward-facing to an inward-facing state of the transporter. The kinetics of the release process are computed from the MSM, and transition path theory is used to identify the most probable sodium release pathways. An intermediate state is discovered on the sodium release pathway, and the results reveal the importance of various modes of interaction of the N-terminus of hDAT in controlling the pathways of release.

A DNA sequence obtained by replacement of the dopamine RNA aptamer bases is not an aptamer.

Science.gov (United States)

Álvarez-Martos, Isabel; Ferapontova, Elena E

2017-08-05

A unique specificity of the aptamer-ligand biorecognition and binding facilitates bioanalysis and biosensor development, contributing to discrimination of structurally related molecules, such as dopamine and other catecholamine neurotransmitters. The aptamer sequence capable of specific binding of dopamine is a 57 nucleotides long RNA sequence reported in 1997 (Biochemistry, 1997, 36, 9726). Later, it was suggested that the DNA homologue of the RNA aptamer retains the specificity of dopamine binding (Biochem. Biophys. Res. Commun., 2009, 388, 732). Here, we show that the DNA sequence obtained by the replacement of the RNA aptamer bases for their DNA analogues is not able of specific biorecognition of dopamine, in contrast to the original RNA aptamer sequence. This DNA sequence binds dopamine and structurally related catecholamine neurotransmitters non-specifically, as any DNA sequence, and, thus, is not an aptamer and cannot be used neither for in vivo nor in situ analysis of dopamine in the presence of structurally related neurotransmitters. Copyright © 2017 Elsevier Inc. All rights reserved.

Genetically determined interaction between the dopamine transporter and the D2 receptor on prefronto-striatal activity and volume in humans.

Science.gov (United States)

Bertolino, Alessandro; Fazio, Leonardo; Di Giorgio, Annabella; Blasi, Giuseppe; Romano, Raffaella; Taurisano, Paolo; Caforio, Grazia; Sinibaldi, Lorenzo; Ursini, Gianluca; Popolizio, Teresa; Tirotta, Emanuele; Papp, Audrey; Dallapiccola, Bruno; Borrelli, Emiliana; Sadee, Wolfgang

2009-01-28

Dopamine modulation of neuronal activity during memory tasks identifies a nonlinear inverted-U shaped function. Both the dopamine transporter (DAT) and dopamine D(2) receptors (encoded by DRD(2)) critically regulate dopamine signaling in the striatum and in prefrontal cortex during memory. Moreover, in vitro studies have demonstrated that DAT and D(2) proteins reciprocally regulate each other presynaptically. Therefore, we have evaluated the genetic interaction between a DRD(2) polymorphism (rs1076560) causing reduced presynaptic D(2) receptor expression and the DAT 3'-VNTR variant (affecting DAT expression) in a large sample of healthy subjects undergoing blood oxygenation level-dependent (BOLD)-functional magnetic resonance imaging (MRI) during memory tasks and structural MRI. Results indicated a significant DRD(2)/DAT interaction in prefrontal cortex and striatum BOLD activity during both working memory and encoding of recognition memory. The differential effect on BOLD activity of the DAT variant was mostly manifest in the context of the DRD(2) allele associated with lower presynaptic expression. Similar results were also evident for gray matter volume in caudate. These interactions describe a nonlinear relationship between compound genotypes and brain activity or gray matter volume. Complementary data from striatal protein extracts from wild-type and D(2) knock-out animals (D2R(-/-)) indicate that DAT and D(2) proteins interact in vivo. Together, our results demonstrate that the interaction between genetic variants in DRD(2) and DAT critically modulates the nonlinear relationship between dopamine and neuronal activity during memory processing.

Striatal dopamine D1 and D2 receptors: widespread influences on methamphetamine-induced dopamine and serotonin neurotoxicity.

Science.gov (United States)

Gross, Noah B; Duncker, Patrick C; Marshall, John F

2011-11-01

Methamphetamine (mAMPH) is an addictive psychostimulant drug that releases monoamines through nonexocytotic mechanisms. In animals, binge mAMPH dosing regimens deplete markers for monoamine nerve terminals, for example, dopamine and serotonin transporters (DAT and SERT), in striatum and cerebral cortex. Although the precise mechanism of mAMPH-induced damage to monoaminergic nerve terminals is uncertain, both dopamine D1 and D2 receptors are known to be important. Systemic administration of dopamine D1 or D2 receptor antagonists to rodents prevents mAMPH-induced damage to striatal dopamine nerve terminals. Because these studies employed systemic antagonist administration, the specific brain regions involved remain to be elucidated. The present study examined the contribution of dopamine D1 and D2 receptors in striatum to mAMPH-induced DAT and SERT neurotoxicities. In this experiment, either the dopamine D1 antagonist, SCH23390, or the dopamine D2 receptor antagonist, sulpiride, was intrastriatally infused during a binge mAMPH regimen. Striatal DAT and cortical, hippocampal, and amygdalar SERT were assessed as markers of mAMPH-induced neurotoxicity 1 week following binge mAMPH administration. Blockade of striatal dopamine D1 or D2 receptors during an otherwise neurotoxic binge mAMPH regimen produced widespread protection against mAMPH-induced striatal DAT loss and cortical, hippocampal, and amygdalar SERT loss. This study demonstrates that (1) dopamine D1 and D2 receptors in striatum, like nigral D1 receptors, are needed for mAMPH-induced striatal DAT reductions, (2) these same receptors are needed for mAMPH-induced SERT loss, and (3) these widespread influences of striatal dopamine receptor antagonists are likely attributable to circuits connecting basal ganglia to thalamus and cortex. Copyright © 2011 Wiley-Liss, Inc.

Interactions of dopaminergic agonists and antagonists with dopaminergic D3 binding sites in rat striatum. Evidence that [3H]dopamine can label a high affinity agonist-binding state of the D1 dopamine receptor

International Nuclear Information System (INIS)

Leff, S.E.; Creese, I.

1985-01-01

The interactions of dopaminergic agonists and antagonists with 3 H-agonist labeled D3 dopaminergic binding sites of rat striatum have been characterized by radioligand-binding techniques. When the binding of [ 3 H]dopamine and [ 3 H]apomorphine to D2 dopamine receptors is blocked by the inclusion of D2 selective concentrations of unlabeled spiroperidol or domperidone, these ligands appear to label selectively the previously termed D3 binding site. Antagonist/[ 3 H]dopamine competition curves are of uniformly steep slope (nH . 1.0), suggesting the presence of a single D3 binding site. The relative potencies of antagonists to inhibit D3 specific [ 3 H]dopamine binding are significantly correlated with their potencies to block D1 dopamine receptors as measured by the inhibition of both dopamine-stimulated adenylate cyclase and [ 3 H]flupentixol-binding activities. The affinities of agonists to inhibit D3 specific [ 3 H]dopamine binding are also correlated with estimates of these agonists affinities for the high affinity binding component of agonist/[ 3 H]flupentixol competition curves. Both D3 specific [ 3 H] dopamine binding and the high affinity agonist-binding component of dopamine/[ 3 H]flupentixol competition curves show a similar sensitivity to guanine nucleotides. Taken together, these data strongly suggest that the D3 binding site is related to a high affinity agonist-binding state of the D1 dopamine receptor

Dopamine transporter SPECT imaging of the peroral addicts of compound codeine phosphate solution

International Nuclear Information System (INIS)

Sun Taotao; Hu Shu; Jia Shaowei; Chen Qing; Fan Rong

2010-01-01

Objective: To study the damage to striatum in patients perorally addicted to compound codeine phosphate solution by using the brain dopamine transporter SPECT imaging. Methods: Patients perorally addicted to compound codeine phosphate solution (n = 29) and addicted to heroin (n = 27), as well as healthy volunteers (n = 31) were included in the study. Each of them underwent dopamine transporter (DAT) SPECT imaging with 99 Tc m -2β-[N, N'-bis-( 2- mercaptoethyl ) ethylenediamino] methyl, 3β-(4-chlorophenyl)tropane ( 99 Tc m -TRODAT-1). The striatum volume (V, cm 3 ), mass (m, g) and radioactivity ratio (Ra) of striatum to whole brain were calculated using physio-mathematical modeling method. Results: Bilateral striatum of healthy volunteers showed typical 'panda eyes' pattern and the distribution of DAT was uniform and symmetrical. Bilateral striatum of patients addicted to compound codeine phosphate showed impaired tracer uptake, similar to those addicted to heroin. The V, m and Ra of bilateral striatum of patients addicted to compound codeine phosphate were (23.68±4.94) cm 3 , (24.87±5.19) g and (5.01±0.88) %, respectively, which were significantly lower than those of healthy controls: (35.39 ±4.42) cm 3 ,(37.16±4.64) g and (7.93±0.86)% (t =-9.69, -9.69, - 13.01, all P =0.000), but significantly higher than those addicted to heroin: (18.87±4.66) cm 3 , (19.81±4.90) g and (4.26±1.02) % (t =3.74, 3.74, 2.96, P = 0.000, 0.000, 0.005). Conclusion: Long-term peroral intake of compound codeine phosphate solution may damage the function of cerebral striatum, which is someway similar to though less severe than, the impairment caused by heroin. (authors)

Effect of nerve activity on transport of nerve growth factor and dopamine β-hydroxylase antibodies in sympathetic neurones

International Nuclear Information System (INIS)

Lees, G.; Chubb, I.; Freeman, C.; Geffen, L.; Rush, R.

1981-01-01

The effect of nerve activity on the uptake and retrograde transport of nerve growth factor (NGF) and dopamine β-hydroxylase (DBH) antibodies was studied by injecting 125 I-labelled NGF and anti-DBH into the anterior eye chamber of guinea-pigs. Decentralization of the ipsilateral superior cervical ganglion (SCG) had no significant effect on the retrograde transport of either NGF or anti-DBH. Phenoxybenzamine produced a 50% increase in anti-DBH but not NGF accumulation and this effect was prevented by prior decentralization. This demonstrates that NGF is taken up independently of the retrieval of synaptic vesicle components. (Auth.)

Dopamine transporter SPECT in patients with Parkinson's disease

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Hamano, Tadanori; Tsuchida, Tatsuro; Hirayama, Mikio; Fujiyama, Jiro; Mutoh, Tatsuro; Yonekura, Yoshiharu; Kuriyama, Masaru [Fukui Medical Univ., Matsuoka (Japan)

2000-03-01

The major neuropathological feature in Parkinson's disease (PD) is severe degeneration of the dopamine (DA) neurons in the substantia nigra. Dopamine transporter (DAT) is an important protein in the regulation of DA neurotransmission. It has been reported that PD patients show a loss of DAT in striatum. We report here the findings of single photon emission computed tomography (SPECT) of the DAT with 2{beta}-carboxymethoxy-3{beta}-(4[{sup 123}I]iodophenyl)tropane ([{sup 123}I]{beta}-CIT) to investigate striatal DAT in 10 patients with PD, one patient with vascular parkinsonism (VP), and one patient with dystonia syndrome. Patients were evaluated using the Webster rating scale. Specific/nondisplaceable striatal binding ratio (V3'') was obtained in each case. In PD patients, the uptake of [{sup 123}I]{beta}-CIT was reduced, especially in the tail of putamen compared with caudate nucleus. Even in the early stage of PD, the uptake of {beta}-CIT was reduced not only in the severely affected side, but also in the mildly disturbed side of the brain. Putamen caudate ratio was generally low in PD patients. In VP patient, the uptake was reduced, but putamen caudate ratio was not decreased. V3'' values showed significant correlation with the severity of clinical symptoms such as self-care, facies, posture, gait, speech, and Hoehn-Yahr's stage. On the other hand, V3'' values were not significantly correlated with the degree of tremor, seborrhea, and duration of the illness. In conclusion, we found that SPECT of the [{sup 123}I]{beta}-CIT is a useful method for the diagnosis in the patients presenting parkinsonism, and for the clinico-physiological estimation of parkinsonian symptoms such as self-care, facies, posture, gait, and speech. (author)

Cerebral kinetics of the dopamine D{sub 2} receptor ligand [{sup 123}I]IBZM in mice

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Meyer, Philipp T. [Department of Neurology, University Hospital Aachen, 52074 Aachen (Germany); Department of Nuclear Medicine, University Hospital Aachen, 52074 Aachen (Germany)], E-mail: pmeyer@ukaachen.de; Salber, Dagmar [C. and O. Vogt Institute of Brain Research, University Hospital Duesseldorf, 40225 Duesseldorf (Germany); Schiefer, Johannes [Department of Neurology, University Hospital Aachen, 52074 Aachen (Germany); Cremer, Markus [Institute of Neurosciences and Biophysics, Research Center Juelich, 52425 Juelich (Germany); Schaefer, Wolfgang M. [Department of Nuclear Medicine, University Hospital Aachen, 52074 Aachen (Germany); Kosinski, Christoph M. [Department of Neurology, University Hospital Aachen, 52074 Aachen (Germany); Langen, Karl-Josef [Institute of Neurosciences and Biophysics, Research Center Juelich, 52425 Juelich (Germany)

2008-05-15

Introduction: In vivo small animal imaging of the dopaminergic system is of great interest for basic and applied neurosciences, especially in transgenic mice. Small animal SPECT is particularly attractive because of its superior spatial resolution and tracer availability. We investigated the kinetics of the commercial dopamine D{sub 2} receptor (DZR) ligand [{sup 123}I]IBZM in mice as a prerequisite for an appropriate design of translational SPECT imaging between mice and humans. Methods: Cerebral kinetics of [{sup 123}I]IBZM under isoflurane anaesthesia were assessed by autoradiography in mice sacrificed at 30, 60, 120 and 200 min after iv injection. To explore the possible effects of isoflurane anaesthesia, an additional mice group was only anaesthetized for 20 min before being sacrificed at 140 min (putative time of single-scan SPECT analysis). Results: Maximum [{sup 123}I]IBZM uptake in the striatum (D{sub 2}R-rich; 10.5{+-}2.7 %ID/g) and cerebellum (D{sub 2}R-devoid; 2.4{+-}0.7 %ID/g) was observed at 30 min after injection. Thereafter, [{sup 123}I]IBZM uptake decreased slowly in striatum and rapidly in the cerebellum (200 min: 5.3{+-}1.9 and 0.4{+-}0.2 %ID/g, respectively). The striatum-to-cerebellum (S/C) [{sup 123}I]IBZM uptake ratio increased from 4.6{+-}1.2 at 30 min to 11.6{+-}2.6 at 120 min. The S/C ratio at 200 min was highly variable (17.8{+-}10.1), possibly indicating pseudo-equilibration in some animals. In mice, which were only anaesthetized between 120 and 140 min, a higher S/C ratio of 17.0{+-}5.1 was observed. Conclusions: The present study suggests that [{sup 123}I]IBZM is a suitable ligand for D{sub 2}R-SPECT in mice. Although a single-scan analysis may be a pragmatic semi-quantitative approach, tracer kinetic analyses on dynamic SPECT data should be pursued. The interfering effects of isoflurane anaesthesia need to be considered.

Effects of unilateral 6-OHDA lesions on [3H]-N-propylnorapomorphine binding in striatum ex vivo and vulnerability to amphetamine-evoked dopamine release in rat

DEFF Research Database (Denmark)

Palner, Mikael; Kjaerby, Celia; Knudsen, Gitte M

2011-01-01

It has been argued that agonist ligands for dopamine D(2/3) receptors recognize a privileged subset of the receptors in living striatum, those which are functionally coupled to intracellular G-proteins. In support of this claim, the D(2/3) agonist [(3)H]-N-propylnorapomorphine ([(3)H]NPA) proved...... to be more vulnerable to competition from endogenous dopamine than was the antagonist ligand [(11)C]raclopride, measured ex vivo in mouse striatum, and subsequently in multi-tracer PET studies of analogous design. Based on these results, we predicted that prolonged dopamine depletion would result...... in a preferential increase in agonist binding, and a lesser competition from residual dopamine to the agonist binding. To test this hypothesis we used autoradiography to measure [(3)H]NPA and [(3)H]raclopride binding sites in hemi-parkinsonian rats with unilateral 6-OHDA lesions, with and without amphetamine...

Effects of dopamine D1-like and D2-like antagonists on cocaine discrimination in muscarinic receptor knockout mice.

Science.gov (United States)

Thomsen, Morgane; Caine, Simon Barak

2016-04-05

Muscarinic and dopamine brain systems interact intimately, and muscarinic receptor ligands, like dopamine ligands, can modulate the reinforcing and discriminative stimulus (S(D)) effects of cocaine. To enlighten the dopamine/muscarinic interactions as they pertain to the S(D) effects of cocaine, we evaluated whether muscarinic M1, M2 or M4 receptors are necessary for dopamine D1 and/or D2 antagonist mediated modulation of the S(D) effects of cocaine. Knockout mice lacking M1, M2, or M4 receptors, as well as control wild-type mice and outbred Swiss-Webster mice, were trained to discriminate 10mg/kg cocaine from saline in a food-reinforced drug discrimination procedure. Effects of pretreatments with the dopamine D1 antagonist SCH 23390 and the dopamine D2 antagonist eticlopride were evaluated. In intact mice, both SCH 23390 and eticlopride attenuated the cocaine discriminative stimulus effect, as expected. SCH 23390 similarly attenuated the cocaine discriminative stimulus effect in M1 knockout mice, but not in mice lacking M2 or M4 receptors. The effects of eticlopride were comparable in each knockout strain. These findings demonstrate differences in the way that D1 and D2 antagonists modulate the S(D) effects of cocaine, D1 modulation being at least partially dependent upon activity at the inhibitory M2/M4 muscarinic subtypes, while D2 modulation appeared independent of these systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Delta-9-tetrahydrocannabinol-induced dopamine release as a function of psychosis risk: 18F-fallypride positron emission tomography study.

Directory of Open Access Journals (Sweden)

Rebecca Kuepper

Full Text Available Cannabis use is associated with psychosis, particularly in those with expression of, or vulnerability for, psychotic illness. The biological underpinnings of these differential associations, however, remain largely unknown. We used Positron Emission Tomography and (18F-fallypride to test the hypothesis that genetic risk for psychosis is expressed by differential induction of dopamine release by Δ(9-THC (delta-9-tetrahydrocannabinol, the main psychoactive ingredient of cannabis. In a single dynamic PET scanning session, striatal dopamine release after pulmonary administration of Δ(9-THC was measured in 9 healthy cannabis users (average risk psychotic disorder, 8 patients with psychotic disorder (high risk psychotic disorder and 7 un-related first-degree relatives (intermediate risk psychotic disorder. PET data were analyzed applying the linear extension of the simplified reference region model (LSRRM, which accounts for time-dependent changes in (18F-fallypride displacement. Voxel-based statistical maps, representing specific D2/3 binding changes, were computed to localize areas with increased ligand displacement after Δ(9-THC administration, reflecting dopamine release. While Δ(9-THC was not associated with dopamine release in the control group, significant ligand displacement induced by Δ(9-THC in striatal subregions, indicative of dopamine release, was detected in both patients and relatives. This was most pronounced in caudate nucleus. This is the first study to demonstrate differential sensitivity to Δ(9-THC in terms of increased endogenous dopamine release in individuals at risk for psychosis.

Clinical impact of diagnostic SPET investigations with a dopamine re-uptake ligand

International Nuclear Information System (INIS)

Loekkegaard, Annemette; Werdelin, Lene M.; Friberg, Lars

2002-01-01

The diagnosis of Parkinson's disease is based on clinical features with pathological verification. However, autopsy has been found to confirm a specialist diagnosis in only about 75% of cases. Especially early in the course of the disease, the clinical diagnosis can be difficult. Imaging of presynaptic dopamine transporters (DAT receptors) has provided a possible diagnostic probe in the evaluation of Parkinson's disease. The cocaine analogue [ 123 I]-2-β-carboxymethoxy-3-β(4-iodophenyl)tropane ([ 123 I]-β-CIT) is one of several radioligands that have been developed for single-photon emission tomography (SPET). The purpose of this study was to evaluate the impact of [ 123 I]-β-CIT SPET on the diagnosis and clinical management of patients with a primary, tentative diagnosis of parkinsonism. We undertook a retrospective evaluation of the clinical records of 90 consecutive patients referred to [ 123 I]-β-CIT SPET from the neurological department, Bispebjerg Hospital. In 58 subjects the scans revealed altered tracer uptake consistent with Parkinson's disease, progressive supranuclear palsy and multiple system atrophy. A significant change in the management or treatment because of the scan was found in 25 patients (28%). The sensitivity of the examination was 97% and the specificity 83%. In conclusion, a significant clinical impact of DAT receptor SPET imaging was found. DAT receptor imaging is a useful diagnostic probe in patients with a possible diagnosis of parkinsonism. (orig.)

Single photon emission tomography (SPET) imaging of dopamine D2 receptors in the course of dopamine replacement therapy in patients with nocturnal myoclonus syndrome (NMS)

International Nuclear Information System (INIS)

Staedt, J.; Stoppe, G.; Riemann, H.; Hajak, G.; Ruether, E.; Koegler, A.; Emrich, D.

1995-01-01

Single photon emission tomography (SPET) permits the in vivo measurements of regional cerebral radioactivity in the human brain following the administration of compounds labeled with photon-emitting isotopes. According to our SPET findings of a reduced binding of [ 123 I]labeled (S)-2-hydroxy-3-iodo-6-methoxy-([1-ethyl-2-pyrrolidinyl]methyl) benzamide (IBZM) (a highly selective CNS D 2 dopamine receptor ligand) to D 2 dopamine receptors in striatal structures in untreated patients with nocturnal myoclonus syndrome (NMS) it seemed to be of interest to investigate whether there are changes in D 2 receptor binding under dopamine replacement therapy or not. We studied the uptake and distribution of [ 123 I]IBZM before and in the course of dopamine replacement therapy in four patients with severe insomnia caused by nocturnal myoclonus syndrome (NMS). We found an increase of the IBZM binding to D 2 receptors in the course of treatment, which was associated with an improvement of sleep quality. Reasons for this are discussed. The [ 123 I]IBZM SPET technique in conclusion offers an interesting tool for in vivo investigations of functional changes in the dopaminergic neurotransmitter system in longitudinal studies. (author)

Automated preparation of the dopamine D{sub 2/3} receptor agonist ligand [{sup 11}C]-(+)-PHNO for human PET imaging studies

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Plisson, Christophe, E-mail: Christophe.2.plisson@gsk.com [GlaxoSmithKline, Clinical Imaging Centre, Hammersmith Hospital, London W12 0NN (United Kingdom); Huiban, Mickael; Pampols-Maso, Sabina; Singleton, Goerkem; Hill, Samuel P.; Passchier, Jan [GlaxoSmithKline, Clinical Imaging Centre, Hammersmith Hospital, London W12 0NN (United Kingdom)

2012-02-15

Carbon-11 labelled (+)-4-Propyl-3,4,4a,5,6,10b-hexahydro-2H-naphtho[1,2-b][1,4]oxazin-9-ol ([{sup 11}C]-(+)-PHNO) is used as a high-affinity state, dopamine D{sub 2/3} receptor ligand in clinical PET studies. To facilitate its use, robust, rapid, efficient and GMP compliant methods are required for the manufacturing and QC testing processes. Additionally, to allow for full quantification of the resulting signal in the CNS, a reliable method is required to establish the parent plasma concentration over the course of the scan. This paper provides high-quality methods to support clinical application of [{sup 11}C]-(+)-PHNO. - Highlights: Black-Right-Pointing-Pointer Fully automated synthesis of [{sup 11}C]-(+)-PHNO. Black-Right-Pointing-Pointer Rapid multi-step synthesis and QC analysis. Black-Right-Pointing-Pointer Reproducible synthesis process typically yielding more than 3 GBq of [{sup 11}C]-(+)-PHNO. Black-Right-Pointing-Pointer Very low failure rate.

Synthesis, resolution and radioiodination of S(-)trans-5-hydroxy-2-[N-n-propyl-N-(3'-iodo-2'-propenyl)amino]tet ralin-S(-)trans-5-OH-PIPAT: a new dopamine D2-like receptor ligand

International Nuclear Information System (INIS)

Chumpradit, Sumalee; Meiping Kung; Vessotskie, Janet; Kung, H.F.

1995-01-01

A new dopamine D2-like receptor ligand, (R,S)trans-5-hydroxy-2-[N-n0propyl-N-(3'-iodo-2'-propeny)amino]tet ralin ((R,S)trans-5-OH-PIPAT,3), based on high affinity dopamine receptor agonist 5-hydroxy-2-[N,N-(di-n-propyl)-2-amino]tetralin (5-OH-DPAT,1), was prepared. The synthesis was achieved by a reductive amination of 5-methoxy-2-tetralone with n-propylamine, followed by N-alkylation, to afford 5-methoxy-N-propyl-N-2'-aminotetralin,7. Reduction of 7 with tributyltin hydride gave the tri-n-butyl tin derivative,8, which was converted to 9 by an iododemetalation reaction. Demethylation of 9 gave the desired compound, (R,S)trans-5-OH-PIPAT,3. The resolved (R) and (S)trans-5-OH-PIPAT,3 were also quantitatively prepared. (author)

VMAT2 and Parkinson’s disease: harnessing the dopamine vesicle

OpenAIRE

Lohr, Kelly M; Miller, Gary W

2014-01-01

Despite a movement away from dopamine-focused Parkinson’s disease (PD) research, a recent surge of evidence now suggests that altered vesicular storage of dopamine may contribute to the demise of the nigral neurons in this disease. Human studies demonstrate that the vesicular monoamine transporter 2 (VMAT2; SLC18A2) is dysfunctional in PD brain. Moreover, studies with transgenic mice suggest that there is an untapped reserve capacity of the dopamine vesicle that could be unbridled by increasi...

Differential up-regulation of striatal dopamine transporter and α-synuclein by the pyrethroid insecticide permethrin

International Nuclear Information System (INIS)

Gillette, Jeffrey S.; Bloomquist, Jeffrey R.

2003-01-01

The effects of permethrin on striatal dopaminergic biomarkers were assessed in this study. Retired breeder male C57 B1/6 mice were given an ip dose of permethrin (0.1-200 mg/kg) at 7-day intervals, over a 2-week period (Days 0, 7, and 14). Animals were then sacrificed 1 day (t = 1), 14 days (t 14), or 28 days after the last treatment (t = 28). Dopamine transporter (DAT) protein as assayed by Western blotting was increased to 115% in the 0.8 mg/kg group over that of control mice at t = 1 (P 3 H]GBR 12935, used to assay DAT binding, followed the same trend as that for the Western blotting data for 0.8 and 1.5 mg/kg doses of permethrin over the 4 weeks posttreatment. At 200 mg/kg permethrin, DAT protein was unchanged vs controls (t = 1), but had significantly increased by t = 14 and continued to increase at t = 28, suggesting that the reduced dopamine transport at this dose was due to nerve terminal stress and that recovery had occurred. The protein α-synuclein was also significantly induced at the 1.5 mg/kg dose at t = 1; however, unlike DAT up-regulation, this effect had declined to control values by t 14. Maximal induction of α-synuclein protein occurred at a dose of 50 mg/kg permethrin. These data provide evidence that the pyrethroid class of insecticides can modulate the dopaminergic system at low doses, in a persistent manner, which may render neurons more vulnerable to toxicant injury

Dopamine synapse is a neuroligin-2–mediated contact between dopaminergic presynaptic and GABAergic postsynaptic structures

Science.gov (United States)

Uchigashima, Motokazu; Ohtsuka, Toshihisa; Kobayashi, Kazuto; Watanabe, Masahiko

2016-01-01

Midbrain dopamine neurons project densely to the striatum and form so-called dopamine synapses on medium spiny neurons (MSNs), principal neurons in the striatum. Because dopamine receptors are widely expressed away from dopamine synapses, it remains unclear how dopamine synapses are involved in dopaminergic transmission. Here we demonstrate that dopamine synapses are contacts formed between dopaminergic presynaptic and GABAergic postsynaptic structures. The presynaptic structure expressed tyrosine hydroxylase, vesicular monoamine transporter-2, and plasmalemmal dopamine transporter, which are essential for dopamine synthesis, vesicular filling, and recycling, but was below the detection threshold for molecules involving GABA synthesis and vesicular filling or for GABA itself. In contrast, the postsynaptic structure of dopamine synapses expressed GABAergic molecules, including postsynaptic adhesion molecule neuroligin-2, postsynaptic scaffolding molecule gephyrin, and GABAA receptor α1, without any specific clustering of dopamine receptors. Of these, neuroligin-2 promoted presynaptic differentiation in axons of midbrain dopamine neurons and striatal GABAergic neurons in culture. After neuroligin-2 knockdown in the striatum, a significant decrease of dopamine synapses coupled with a reciprocal increase of GABAergic synapses was observed on MSN dendrites. This finding suggests that neuroligin-2 controls striatal synapse formation by giving competitive advantage to heterologous dopamine synapses over conventional GABAergic synapses. Considering that MSN dendrites are preferential targets of dopamine synapses and express high levels of dopamine receptors, dopamine synapse formation may serve to increase the specificity and potency of dopaminergic modulation of striatal outputs by anchoring dopamine release sites to dopamine-sensing targets. PMID:27035941

Dopamine transporter and vesicular monoamine transporter knockout mice : implications for Parkinson's disease.

Science.gov (United States)

Miller, G W; Wang, Y M; Gainetdinov, R R; Caron, M G

2001-01-01

One of the most valuable methods for understanding the function of a particular protein is the generation of animals that have had the gene encoding for the protein of interest disrupted, commonly known as a "quo;knockout"quo; or null mutant. By incorporating a sequence of DNA (typically encoding antibiotic resistance to aid in the selection of the mutant gene) into embryonic stem cells by homologous recombination, the normal transcription of the gene is effectively blocked (Fig. 1). Since a particular protein is encoded by two copies of a gene, it is necessary to have the gene on both alleles "quo;knocked out."quo; This is performed by cross-breeding animals with one affected allele (heterozygote) to generate offspring that have inherited two mutant alleles (homozygote). This procedure has been used to generate animals lacking either the plasma membrane dopamine transporter (DAT; Fig. 2) or the vesicular monoamine transporter (VMAT2; Fig. 3). Both DAT and VMAT2 are essential for dopamine homeostasis and are thought to participate in the pathogenesis of Parkinson's disease (1-5). Fig. 1. Maps of the targeting vector and the mock construct. The mouse genomic fragment (clone 11) was isolated from a Stratagene 129 SvJ library by standard colony hybridization using a PCR probe from the 5' end of rat cDNA. The restriction site abbreviations are as follows: H, HindIII; N, NotI; Sc, SacI; Sn, SnaI; X, XbaI; and Xh, XhoI. The region between HindIII and SnaI on clone 11 containing the coding sequence from transmembrane domains 3 and 4 of VMAT2 was deleted and replaced with PGK-neo. The 3' fragment of clone 11 was reserved as an external probe for Southern analysis. To facilitate PCR screening of embryonic stem cell clones, a mock construct containing the SnaI/XbaI fragment and part of the Neo cassette was generated as a positive control. pPNT and pGEM4Z were used to construct knockout and mock vectors, respectively. (Reproduced with permission from ref. 1). Fig. 2. DAT and

Infantile parkinsonism-dystonia: a dopamine “transportopathy”

OpenAIRE

Blackstone, Craig

2009-01-01

The dopamine transporter (DAT) retrieves the neurotransmitter dopamine from the synaptic cleft at dopaminergic synapses. Variations in solute carrier family 6A, member 3 (SLC6A3/DAT1), the human gene encoding DAT, have been implicated in attention deficit hyperactivity and bipolar disorders, and DAT is a prominent site of action for drugs such as amphetamines and cocaine. In this issue of the JCI, Kurian et al. report that an autosomal recessive infantile parkinsonism-dystonia is caused by lo...

[{sup 125}I]{beta}-CIT-FE and [{sup 125}I]{beta}-CIT-FP are superior to [{sup 125}I]{beta}-CIT for dopamine transporter visualization: Autoradiographic evaluation in the human brain

Energy Technology Data Exchange (ETDEWEB)

Guenther, Ilonka; Hall, Haakan; Halldin, Christer; Swahn, Carl-Gunnar; Farde, Lars; Sedvall, Goeran

1997-10-01

The binding of the three dopamine transporter radioligands ([{sup 125}I]{beta}-CIT, [{sup 125}I]{beta}-CIT-FE, and [{sup 125}I]{beta}-CIT-FP) was studied using whole-hemisphere autoradiography on postmortem human brains. The autoradiograms revealed an intense and homogeneous labeling of the nucleus caudatus and putamen but also to varying extent to serotonergic and noradrenergic transporters of neocortex and thalamus. The order of specificity estimated (striatum over neocortex ratios) was {beta}-CIT-FP > {beta}-CIT-FE >> {beta}-CIT, suggesting that {beta}-CIT-FE and {beta}-CIT-FP should be preferred for in vivo studies of the dopamine transporter in the human brain.

The dopamine transporter gene may not contribute to susceptibility and the specific personality traits of amphetamine dependence.

Science.gov (United States)

Tzeng, Nian-Sheng; Lu, Ru-Band; Yeh, Hui-Wen; Yeh, Yi-Wei; Huang, Chang-Chih; Yen, Che-Hung; Kuo, Shin-Chang; Chen, Chun-Yen; Chang, Hsin-An; Ho, Pei-Shen; Cheng, Serena; Shih, Mei-Chen; Huang, San-Yuan

2015-04-01

A substantial amount of evidence suggests that dysfunction of the dopamine transporter may be involved in the pathophysiology of amphetamine dependence (AD). The aim of this study was to examine whether the dopamine transporter gene (DAT1, SLC6A3) is associated with development of AD and whether this gene influences personality traits in patients with AD. Eighteen polymorphisms of the DAT1 gene were analyzed in a case-control study that included 909 Han Chinese men (568 patients with AD and 341 control subjects). The patients fulfilled the DSM-IV-TR criteria for AD. The Tridimensional Personality Questionnaire (TPQ) was used to assess personality traits and to examine the association between these traits and DAT1 gene variants. A weak association was found between the rs27072 polymorphism and development of AD, but these borderline associations were unconfirmed by logistic regression and haplotype analysis. Although harm avoidance and novelty seeking scores were significantly higher in patients than in controls, DAT1 polymorphisms did not influence these scores. This study suggests that high harm avoidance and novelty seeking personality traits may be a risk factor for the development of AD. However, the DAT1 gene may not contribute to AD susceptibility and specific personality traits observed in AD among Han Chinese men. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

[{sup 18}F]{beta}-CIT-FP is superior to [{sup 11}C]{beta}-CIT-FP for quantitation of the dopamine transporter

Energy Technology Data Exchange (ETDEWEB)

Lundkvist, Camilla; Halldin, Christer; Ginovart, Nathalie; Swahn, Carl-Gunnar; Farde, Lars

1997-10-01

{beta}-CIT-FP [N-(3-fluoropropyl)-2{beta}-carbomethoxy-3{beta}-(4-iodophenyl)nortropane] is a cocaine analogue with high affinity for the dopamine transporter. Positron emission tomography (PET) studies with [O-methyl-{sup 11}C]{beta}-CIT-FP ([{sup 11}C]{beta}-CIT-FP) has shown that equilibrium conditions were approached but, however, not reached at the end of measurement. Moreover, metabolite studies of [{sup 11}C]{beta}-CIT-FP in monkey plasma demonstrated a lipophilic-labelled metabolite that may enter the brain. We therefore labelled {beta}-CIT-FP with fluorine-18 in a position that may avoid the formation of labelled lipophilic metabolites. The more long-lived radionuclide ({sup 18}F) was used to allow for measurements over longer time. [N-fluoropropyl-{sup 18}F]{beta}-CIT-FP ([{sup 18}F]{beta}-CIT-FP) was prepared by N-alkylation of nor-{beta}-CIT with [{sup 18}F]fluoropropyl bromide. PET studies were performed in cynomolgus monkeys. [{sup 18}F]{beta}-CIT-FP entered the brain rapidly. There was a high concentration of radioactivity in the striatum and much lower in the thalamus, neocortex, and cerebellum. The striatum-to-cerebellum ratio was about 5 at time of transient equilibrium, which occurred after 60 to 100 min. After pretreatment with GBR 12909, radioactivity in the striatum was markedly reduced, thus indicating specific [{sup 18}F]{beta}-CIT-FP binding to the dopamine transporter. The fraction of unchanged [{sup 18}F]{beta}-CIT-FP determined by HPLC was 10-15% after 140 min. No lipophilic labelled metabolites were detected. The absence of measurable lipophilic labelled metabolites and the occurrence of transient equilibrium within the time of the PET measurement indicate that [{sup 18}F]{beta}-CIT-FP is superior to [{sup 11}C]{beta}-CIT-FP as a PET radioligand for quantification of the dopamine transporter in the human brain.

Strong Ligand-Protein Interactions Derived from Diffuse Ligand Interactions with Loose Binding Sites.

Science.gov (United States)

Marsh, Lorraine

2015-01-01

Many systems in biology rely on binding of ligands to target proteins in a single high-affinity conformation with a favorable ΔG. Alternatively, interactions of ligands with protein regions that allow diffuse binding, distributed over multiple sites and conformations, can exhibit favorable ΔG because of their higher entropy. Diffuse binding may be biologically important for multidrug transporters and carrier proteins. A fine-grained computational method for numerical integration of total binding ΔG arising from diffuse regional interaction of a ligand in multiple conformations using a Markov Chain Monte Carlo (MCMC) approach is presented. This method yields a metric that quantifies the influence on overall ligand affinity of ligand binding to multiple, distinct sites within a protein binding region. This metric is essentially a measure of dispersion in equilibrium ligand binding and depends on both the number of potential sites of interaction and the distribution of their individual predicted affinities. Analysis of test cases indicates that, for some ligand/protein pairs involving transporters and carrier proteins, diffuse binding contributes greatly to total affinity, whereas in other cases the influence is modest. This approach may be useful for studying situations where "nonspecific" interactions contribute to biological function.

Dopamine receptors in pituitary adenomas: PET visualization with 11C-N-methylspiperone

International Nuclear Information System (INIS)

Muhr, C.; Bergstroem, M.L.; Lundberg, P.O.; Bergstroem, K.H.; Hartvig, P.; Lundqvist, H.; Antoni, G.; Langstroem, B.

1986-01-01

Two patients with pituitary tumors were examined with positron emission tomography (PET) after intravenous administration of 11C-N-methylspiperone. In repeat studies the patients were given 1 mg of intravenous haloperidol prior to the administration of the radioligand to block the dopamine receptors. High uptakes of the radiolabeled ligand were seen in one of the tumors. With haloperidol pretreatment the uptake was lower, probably mainly showing the remaining unspecific binding. The most marked uptake and the largest effect of haloperidol pretreatment was seen in a patient with a hormonally active prolactinoma. Dopamine receptor binding in pituitary tumors can be demonstrated in vivo with PET, and quantification of this binding is possible using a compartmental model. This technique may be useful in improving our understanding of the variable response to medical treatment of prolactinomas with dopamine agonists as well as in the prediction of the effect of such treatment

The role of dopamine receptors in the neurotoxicity of methamphetamine.

Science.gov (United States)

Ares-Santos, S; Granado, N; Moratalla, R

2013-05-01

Methamphetamine is a synthetic drug consumed by millions of users despite its neurotoxic effects in the brain, leading to loss of dopaminergic fibres and cell bodies. Moreover, clinical reports suggest that methamphetamine abusers are predisposed to Parkinson's disease. Therefore, it is important to elucidate the mechanisms involved in methamphetamine-induced neurotoxicity. Dopamine receptors may be a plausible target to prevent this neurotoxicity. Genetic inactivation of dopamine D1 or D2 receptors protects against the loss of dopaminergic fibres in the striatum and loss of dopaminergic neurons in the substantia nigra. Protection by D1 receptor inactivation is due to blockade of hypothermia, reduced dopamine content and turnover and increased stored vesicular dopamine in D1R(-/-) mice. However, the neuroprotective impact of D2 receptor inactivation is partially dependent on an effect on body temperature, as well as on the blockade of dopamine reuptake by decreased dopamine transporter activity, which results in reduced intracytosolic dopamine levels in D2R(-/-) mice. © 2013 The Association for the Publication of the Journal of Internal Medicine.

No difference in striatal dopamine transporter availability between active smokers, ex-smokers and non-smokers using [I-123]FP-CIT (DaTSCAN) and SPECT

NARCIS (Netherlands)

Thomsen, Gerda; Knudsen, Gitte Moos; Jensen, Peter S.; Ziebell, Morten; Holst, Klaus K.; Asenbaum, Susanne; Booij, Jan; Darcourt, Jacques; Dickson, John C.; Kapucu, Ozlem L.; Nobili, Flavio; Sabri, Osama; Sera, Terez; Tatsch, Klaus; Tossici-Bolt, Livia; van Laere, Koen; Borght, Thierry Vander; Varrone, Andrea; Pagani, Marco; Pinborg, Lars Hageman

2013-01-01

Background: Mesolimbic and nigrostriatal dopaminergic pathways play important roles in both the rewarding and conditioning effects of drugs. The dopamine transporter (DAT) is of central importance in regulating dopaminergic neurotransmission and in particular in activating the striatal D-2-like

Alterations in brain extracellular dopamine and glycine levels following combined administration of the glycine transporter type-1 inhibitor Org-24461 and risperidone.

Science.gov (United States)

Nagy, Katalin; Marko, Bernadett; Zsilla, Gabriella; Matyus, Peter; Pallagi, Katalin; Szabo, Geza; Juranyi, Zsolt; Barkoczy, Jozsef; Levay, Gyorgy; Harsing, Laszlo G

2010-12-01

The most dominant hypotheses for the pathogenesis of schizophrenia have focused primarily upon hyperfunctional dopaminergic and hypofunctional glutamatergic neurotransmission in the central nervous system. The therapeutic efficacy of all atypical antipsychotics is explained in part by antagonism of the dopaminergic neurotransmission, mainly by blockade of D(2) dopamine receptors. N-methyl-D-aspartate (NMDA) receptor hypofunction in schizophrenia can be reversed by glycine transporter type-1 (GlyT-1) inhibitors, which regulate glycine concentrations at the vicinity of NMDA receptors. Combined drug administration with D(2) dopamine receptor blockade and activation of hypofunctional NMDA receptors may be needed for a more effective treatment of positive and negative symptoms and the accompanied cognitive deficit in schizophrenia. To investigate this type of combined drug administration, rats were treated with the atypical antipsychotic risperidone together with the GlyT-1 inhibitor Org-24461. Brain microdialysis was applied in the striatum of conscious rats and determinations of extracellular dopamine, DOPAC, HVA, glycine, glutamate, and serine concentrations were carried out using HPLC/electrochemistry. Risperidone increased extracellular concentrations of dopamine but failed to influence those of glycine or glutamate measured in microdialysis samples. Org-24461 injection reduced extracellular dopamine concentrations and elevated extracellular glycine levels but the concentrations of serine and glutamate were not changed. When risperidone and Org-24461 were added in combination, a decrease in extracellular dopamine concentrations was accompanied with sustained elevation of extracellular glycine levels. Interestingly, the extracellular concentrations of glutamate were also enhanced. Our data indicate that coadministration of an antipsychotic with a GlyT-1 inhibitor may normalize hypofunctional NMDA receptor-mediated glutamatergic neurotransmission with reduced

Dopamine and μ-opioid receptor dysregulation in the brains of binge-eating female rats - possible relevance in the psychopathology and treatment of binge-eating disorder.

Science.gov (United States)

Heal, David J; Hallam, Michelle; Prow, Michael; Gosden, Jane; Cheetham, Sharon; Choi, Yong K; Tarazi, Frank; Hutson, Peter

2017-06-01

Adult, female rats given irregular, limited access to chocolate develop binge-eating behaviour with normal bodyweight and compulsive/perseverative and impulsive behaviours similar to those in binge-eating disorder. We investigated whether (a) dysregulated central nervous system dopaminergic and opioidergic systems are part of the psychopathology of binge-eating and (b) these neurotransmitter systems may mediate the actions of drugs ameliorating binge-eating disorder psychopathology. Binge-eating produced a 39% reduction of striatal D 1 receptors with 22% and 23% reductions in medial and lateral caudate putamen and a 22% increase of striatal μ-opioid receptors. There was no change in D 1 receptor density in nucleus accumbens, medial prefrontal cortex or dorsolateral frontal cortex, striatal D 2 receptors and dopamine reuptake transporter sites, or μ-opioid receptors in frontal cortex. There were no changes in ligand affinities. The concentrations of monoamines, metabolites and estimates of dopamine (dopamine/dihydroxyphenylacetic acid ratio) and serotonin/5-hydroxyindolacetic acid ratio turnover rates were unchanged in striatum and frontal cortex. However, turnover of dopamine and serotonin in the hypothalamus was increased ~20% and ~15%, respectively. Striatal transmission via D 1 receptors is decreased in binge-eating rats while μ-opioid receptor signalling may be increased. These changes are consistent with the attenuation of binge-eating by lisdexamfetamine, which increases catecholaminergic neurotransmission, and nalmefene, a μ-opioid antagonist.

Dopamine D/sub 2/ and D/sub 1/ receptors: biochemical characterization

Energy Technology Data Exchange (ETDEWEB)

Niznik, H B

1986-01-01

In order to label dopamine D/sub 2/ receptors reversibly and selectively the potent substituted benzamide neuroleptic, YM-09151-2, was tritium labeled and its binding characteristics to striatal homogenates investigated. (/sup 3/H) YM-09151-2 bound to D/sub 2/ receptors with high affinity in a specific, saturable, reversible and sodium dependent fashion, displaying an appropriate pharmacological D/sub 2/ receptor profile. (/sup 3/H) YM-09151-2 appears to be the ligand of choice for labeling D/sub 2/ receptors since it displays approximately 20-fold lower affinity for serotonergic S/sub 2/ receptors than does (/sup 3/H) spiperone. As an initial step towards the molecular identification of the ligand binding subunit of the striatal D/sub 2/ receptor, photolabile analogues of the substituted benzamide clebopride were synthesized and their reversible and irreversible binding interactions to D/sub 2/ receptors characterized. D/sub 2/ receptor photoinactivation was prevented in a concentration and stereoselective manner by dopaminergic agonists and antagonists. In vivo biodistribution studies with (/sup 125/I) iodoazidoclebopride confirmed the ligand's ability to bind to D/sub 2/ receptor-rich regions and as such, may become a useful tool for the molecular characterization of D/sub 2/ receptor proteins. Digitonin solubilized striatal dopamine D/sub 2/ and D/sub 1/ receptors can be completely separated with full retention of biological activity by steric exclusion High Pressure Liquid Chromatography (HPLC) with corresponding Stokes radii of 7.1 and 5.6 nm.

The dopamine metabolite 3-methoxytyramine is a neuromodulator.

Directory of Open Access Journals (Sweden)

Tatyana D Sotnikova

2010-10-01

Full Text Available Dopamine (3-hydroxytyramine is a well-known catecholamine neurotransmitter involved in multiple physiological functions including movement control. Here we report that the major extracellular metabolite of dopamine, 3-methoxytyramine (3-MT, can induce behavioral effects in a dopamine-independent manner and these effects are partially mediated by the trace amine associated receptor 1 (TAAR1. Unbiased in vivo screening of putative trace amine receptor ligands for potential effects on the movement control revealed that 3-MT infused in the brain is able to induce a complex set of abnormal involuntary movements in mice acutely depleted of dopamine. In normal mice, the central administration of 3-MT caused a temporary mild hyperactivity with a concomitant set of abnormal movements. Furthermore, 3-MT induced significant ERK and CREB phosphorylation in the mouse striatum, signaling events generally related to PKA-mediated cAMP accumulation. In mice lacking TAAR1, both behavioral and signaling effects of 3-MT were partially attenuated, consistent with the ability of 3-MT to activate TAAR1 receptors and cause cAMP accumulation as well as ERK and CREB phosphorylation in cellular assays. Thus, 3-MT is not just an inactive metabolite of DA, but a novel neuromodulator that in certain situations may be involved in movement control. Further characterization of the physiological functions mediated by 3-MT may advance understanding of the pathophysiology and pharmacology of brain disorders involving abnormal dopaminergic transmission, such as Parkinson's disease, dyskinesia and schizophrenia.

Imaging dopamine and opiate receptors in the human brain in health and disease

International Nuclear Information System (INIS)

Wagner, H.N. Jr.; Dannals, R.F.; Frost, J.J.

1986-01-01

Chemical activity accompanies mental activity, but only recently has it been possible to begin to examine its nature. In 1983 the first imaging of a neuroreceptor in the human brain was accomplished with carbon-11 methyl spipeone, a ligand that binds preferentially to dopamine-2 receptors, 80% of which are located in the caudate nucleus and putamen. Quantitative imaging of serotonin-2, opiate, benzodiazapine and muscarinic cholinergic receptors has subsequently been accomplished. In studies of normal men and women, it has been found that dopamine and serotonin receptor activity decreases dramatically with age, such a decrease being more pronounced in men than in women and greater in the case of dopamine receptors than serotonin-2 receptors. Preliminary studies in patients with neuropsychiatric disorders suggests that dopamine-2 receptor activity is diminished in the caudate nucleus of patients with Huntington's disease. Positron tomography permits quantitative assay of picomolar quantities of neuroreceptors within the living human brain. Studies of patients with Parkinson's disease, Alzheimer's disease, depression, anxiety, schizophrenia, acute and chronic pain states and drug addiction are now in progress

Feasibility of Computed Tomography-Guided Methods for Spatial Normalization of Dopamine Transporter Positron Emission Tomography Image.

Science.gov (United States)

Kim, Jin Su; Cho, Hanna; Choi, Jae Yong; Lee, Seung Ha; Ryu, Young Hoon; Lyoo, Chul Hyoung; Lee, Myung Sik

2015-01-01

Spatial normalization is a prerequisite step for analyzing positron emission tomography (PET) images both by using volume-of-interest (VOI) template and voxel-based analysis. Magnetic resonance (MR) or ligand-specific PET templates are currently used for spatial normalization of PET images. We used computed tomography (CT) images acquired with PET/CT scanner for the spatial normalization for [18F]-N-3-fluoropropyl-2-betacarboxymethoxy-3-beta-(4-iodophenyl) nortropane (FP-CIT) PET images and compared target-to-cerebellar standardized uptake value ratio (SUVR) values with those obtained from MR- or PET-guided spatial normalization method in healthy controls and patients with Parkinson's disease (PD). We included 71 healthy controls and 56 patients with PD who underwent [18F]-FP-CIT PET scans with a PET/CT scanner and T1-weighted MR scans. Spatial normalization of MR images was done with a conventional spatial normalization tool (cvMR) and with DARTEL toolbox (dtMR) in statistical parametric mapping software. The CT images were modified in two ways, skull-stripping (ssCT) and intensity transformation (itCT). We normalized PET images with cvMR-, dtMR-, ssCT-, itCT-, and PET-guided methods by using specific templates for each modality and measured striatal SUVR with a VOI template. The SUVR values measured with FreeSurfer-generated VOIs (FSVOI) overlaid on original PET images were also used as a gold standard for comparison. The SUVR values derived from all four structure-guided spatial normalization methods were highly correlated with those measured with FSVOI (P normalization methods provided reliable striatal SUVR values comparable to those obtained with MR-guided methods. CT-guided methods can be useful for analyzing dopamine transporter PET images when MR images are unavailable.

Brain Dopamine Transporter Binding and Glucose Metabolism in Progressive Supranuclear Palsy-Like Creutzfeldt-Jakob Disease

Directory of Open Access Journals (Sweden)

Eero Rissanen

2014-01-01

Full Text Available Here, we present a patient with Creutzfeldt-Jakob disease (CJD who developed initial symptoms mimicking progressive supranuclear palsy (PSP. Before the development of typical CJD symptoms, functional imaging supported a diagnosis of PSP when [123I]-FP-CIT-SPECT showed a defect in striatal dopamine transporter binding, while [18F]-fluorodeoxyglucose PET showed cortical hypometabolism suggestive of Lewy body dementia. However, the postmortem neuropathological examination was indicative of CJD only, without tau protein or Lewy body findings. This case demonstrates that CJD should be taken into account in rapidly progressing atypical cases of parkinsonism, even when functional imaging supports a diagnosis of a movement disorder.

The signaling pathway of dopamine D2 receptor (D2R) activation using normal mode analysis (NMA) and the construction of pharmacophore models for D2R ligands.

Science.gov (United States)

Salmas, Ramin Ekhteiari; Stein, Matthias; Yurtsever, Mine; Seeman, Philip; Erol, Ismail; Mestanoglu, Mert; Durdagi, Serdar

2017-07-01

G-protein-coupled receptors (GPCRs) are targets of more than 30% of marketed drugs. Investigation on the GPCRs may shed light on upcoming drug design studies. In the present study, we performed a combination of receptor- and ligand-based analysis targeting the dopamine D2 receptor (D2R). The signaling pathway of D2R activation and the construction of universal pharmacophore models for D2R ligands were also studied. The key amino acids, which contributed to the regular activation of the D2R, were in detail investigated by means of normal mode analysis (NMA). A derived cross-correlation matrix provided us an understanding of the degree of pair residue correlations. Although negative correlations were not observed in the case of the inactive D2R state, a high degree of correlation appeared between the residues in the active state. NMA results showed that the cytoplasmic side of the TM5 plays a significant role in promoting of residue-residue correlations in the active state of D2R. Tracing motions of the amino acids Arg219, Arg220, Val223, Asn224, Lys226, and Ser228 in the position of the TM5 are found to be critical in signal transduction. Complementing the receptor-based modeling, ligand-based modeling was also performed using known D2R ligands. The top-scored pharmacophore models were found as 5-sited (AADPR.671, AADRR.1398, AAPRR.3900, and ADHRR.2864) hypotheses from PHASE modeling from a pool consisting of more than 100 initial candidates. The constructed models using 38 D2R ligands (in the training set) were validated with 15 additional test set compounds. The resulting model correctly predicted the pIC 50 values of an additional test set compounds as true unknowns.

Dopamine transporter density by [99mTc]-TRODAT-1 SPECT and neurocognitive performance - a preliminary pilot study

International Nuclear Information System (INIS)

Shih, Ming C; Amaro, Edson Jr; Souza, Sayuri de E

2006-01-01

Introduction: Cognitive deficits are associated with functional impairment as well as with poor quality of life in Parkinson's disease (PD). The main brain alteration in PD is a progressive loss of nigrostriatal dopamine neurons. Both animal and human studies have demonstrated that basal ganglia dopamine system is important for cognitive and motor functioning. Dopamine transporter (DAT) PET and SPECT radiotracers have been successfully used to estimate, in vivo, dopamine neuronal loss in humans. Objectives: The present study is aimed to examine the relationship between cognitive impairment and striatal dopamine neuronal loss, as estimated by [ 99m Tc]-TRODAT-1 SPECT in PD patients. Methods: Fifteen PD patients were scanned with [ 99m Tc]-TRODAT-1 SPECT (Dual-Head-SPECT Hwakeye, GE). SPECT images were reconstructed with FBP and Butterworth filter 0,40c/px order 10. Regions of interest (ROIs) were striatum (STR) and occipital lobe (BKG nonspecific binding) and were delineated in 3-mm transaxials slices analyzed according to this formula BP=([STR-BKG]/BKG), where BP is the striatal DAT binding potential. Neurocognitive tests, including the Rey Auditory Verbal Learning Test, Wisconsin Card Sorting Test, Ravens Progressive Matrices, Digit Span and Tavis 3, were applied to all subjects by trained neuropsychologists. Results: Striatal DAT binding potential (BP) was negatively correlated with the RAVLT tests 4 (R= 0.57, p≤0.05) and 5 (R=0.57, p≤0.05), which evaluate verbal learning. Striatal DAT BP was also negatively correlated with the WCST learning item (R=0.54, p≤0.05) and the Tavis 3 items, action error (R=0.52, p≤0.05) and number of correct responses (R=0.47, p≤0.05). Conclusions: Although preliminary, the present findings suggest that striatal DAT loss is associated with a poorer performance on verbal learning and cognitive flexibility tasks. These results are in line with a previous study that examined healthy volunteers and found a relationship between

A new synthetic drug 5-(2-aminopropyl)indole (5-IT) induces rewarding effects and increases dopamine D1 receptor and dopamine transporter mRNA levels.

Science.gov (United States)

Botanas, Chrislean Jun; Yoon, Seong Shoon; de la Peña, June Bryan; Dela Peña, Irene Joy; Kim, Mikyung; Custodio, Raly James; Woo, Taeseon; Seo, Joung-Wook; Jang, Choon-Gon; Yang, Ji Seul; Yoon, Yoon Mi; Lee, Yong Sup; Kim, Hee Jin; Cheong, Jae Hoon

2018-04-02

In recent years, there has been a marked increase in the use of recreational synthetic psychoactive substances, which is a cause of concern among healthcare providers and legal authorities. In particular, there have been reports on the misuse of 5-(2-aminopropyl)indole (5-API; 5-IT), a new synthetic drug, and of fatal and non-fatal intoxication. Despite these reports, little is known about its psychopharmacological effects and abuse potential. Here, we investigated the abuse potential of 5-IT by evaluating its rewarding and reinforcing effects through conditioned place preference (CPP) (1, 10, and 30 mg/kg, i.p.) in mice and self-administration test (0.1, 0.3, 1, and 3 mg/kg/inf., i.v.) in rats. We also examined whether 5-IT (1, 3, and 10 mg/kg, i.p.) induces locomotor sensitization in mice following a 7-day treatment and drug challenge. Then, we explored the effects of 5-IT (10 mg/kg, i.p.) on dopamine-related genes in the striatum, prefrontal cortex (PFC), and substantia nigra pars compacta (SNc)/ventral tegmental (VTA) of mice by quantitative real-time polymerase chain reaction. 5-IT produced CPP in mice but was not reliably self-administered by rats. 5-IT also induced locomotor sensitization following repeated administration and drug challenge. Moreover, 5-IT increased mRNA levels of dopamine D1 receptor in the striatum and PFC and dopamine transporter in the SNc/VTA of mice. These results indicate that 5-IT has psychostimulant and rewarding properties, which may be attributed to its ability to affect the dopaminergic system in the brain. These findings suggest that 5-IT poses a substantial risk for abuse and addiction in humans. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of dopamine D2 receptor (DRD2) and transporter (SLC6A3) polymorphisms on smoking cue-induced cigarette craving among African-American smokers.

Science.gov (United States)

Erblich, J; Lerman, C; Self, D W; Diaz, G A; Bovbjerg, D H

2005-04-01

Cue-induced craving for addictive substances has long been known to contribute to the problem of persistent addiction in humans. Research in animals over the past decade has solidly established the central role of dopamine in cue-induced craving for addictive substances, including nicotine. Analogous studies in humans, however, are lacking, especially among African-American smokers, who have lower quit rates than Caucasian smokers. Based on the animal literature, the study's objective was to test the hypothesis that smokers carrying specific variants in dopamine-related genes previously associated with risk for addictive behaviors would exhibit heightened levels of cigarette craving following laboratory exposure to cues. To this end, cigarette craving was induced in healthy African-American smokers (n=88) through laboratory exposure to smoking cues. Smokers carrying either the DRD2 (D2 dopamine receptor gene) TaqI A1 RFLP or the SLC6A3 (dopamine transporter gene) 9-repeat VNTR polymorphisms had stronger cue-induced cravings than noncarriers (Ps cue-induced craving in humans, and suggest a possible genetic risk factor for persistent smoking behavior in African-American smokers.

Fluoroethoxy-1,4-diphenethylpiperidine and piperazine derivatives: Potent and selective inhibitors of [3H]dopamine uptake at the vesicular monoamine transporter-2.

Science.gov (United States)

Hankosky, Emily R; Joolakanti, Shyam R; Nickell, Justin R; Janganati, Venumadhav; Dwoskin, Linda P; Crooks, Peter A

2017-12-15

A small library of fluoroethoxy-1,4-diphenethyl piperidine and fluoroethoxy-1,4-diphenethyl piperazine derivatives were designed, synthesized and evaluated for their ability to inhibit [ 3 H]dopamine (DA) uptake at the vesicular monoamine transporter-2 (VMAT2) and dopamine transporter (DAT), [ 3 H]serotonin (5-HT) uptake at the serotonin transporter (SERT), and [ 3 H]dofetilide binding at the human-ether-a-go-go-related gene (hERG) channel. The majority of the compounds exhibited potent inhibition of [ 3 H]DA uptake at VMAT2, Ki changes in the nanomolar range (K i  = 0.014-0.073 µM). Compound 15d exhibited the highest affinity (K i  = 0.014 µM) at VMAT2, and had 160-, 5-, and 60-fold greater selectivity for VMAT2 vs. DAT, SERT and hERG, respectively. Compound 15b exhibited the greatest selectivity (>60-fold) for VMAT2 relative to all the other targets evaluated, and 15b had high affinity for VMAT2 (K i  = 0.073 µM). Compound 15b was considered the lead compound from this analog series due to its high affinity and selectivity for VMAT2. Copyright © 2017 Elsevier Ltd. All rights reserved.

APRESS: apical regulatory super system, serotonin, and dopamine interaction

Directory of Open Access Journals (Sweden)

Hinz M

2011-08-01

Full Text Available Marty Hinz1, Alvin Stein2, Thomas Uncini31Clinical Research, NeuroResearch Clinics, Inc, Cape Coral, FL, USA; 2Stein Orthopedic Associates, Plantation, FL, USA; 3DBS Labs, Duluth, MN, USABackground: The monoamines serotonin and dopamine are known to exist in two separate states: the endogenous state and the competitive inhibition state. The presence of the competitive inhibition state has been known to science for many years, but from a functional standpoint it has been noted in the literature as being "meaningless."Methods: A large database of monoamine transporter response to amino acid precursor administration variations with clinical outcomes was accumulated. In the process, a new organic cation transporter (OCT model has been published, and OCT functional status determination along with amino acid precursor manipulation methods have been invented and refined.Results: Methodology was developed whereby manipulation of the OCT, in the competitive inhibition state, is carried out in a predictable manner. This, in turn, has disproved the long-held assertion that the monoamine competitive inhibition state is functionally meaningless.Conclusion: The most significant aspect of this paper is the documentation of newly recognized relationships between serotonin and dopamine. When transport of serotonin and dopamine are both in the competitive inhibition state, manipulation of the concentrations of one will lead to predictable changes in concentrations of the other. From a functional standpoint, processes regulated and controlled by changes to only serotonin can now be controlled by changes to dopamine, and vice versa, in a predictable manner.Keywords: catecholamine, monoamine, competitive inhibition state

A novel dopamine transporter transgenic mouse line for identification and purification of midbrain dopaminergic neurons reveals midbrain heterogeneity

DEFF Research Database (Denmark)

Christiansen, Mia Apuschkin; Stilling, Sara; Rahbek-Clemmensen, Troels

2015-01-01

Midbrain dopaminergic (DAergic) neurons are a heterogeneous cell group, composed of functionally distinct cell populations projecting to the basal ganglia, prefrontal cortex and limbic system. Despite their functional significance, the midbrain population of DAergic neurons is sparse, constituting...... of the dopamine transporter (DAT) promoter was characterized. Confocal microscopy analysis of brain sections showed strong eGFP signal reporter in midbrain regions and striatal terminals that co-localized with the DAergic markers DAT and tyrosine hydroxylase (TH). Thorough quantification of co...

Effects of Ketamine and Ketamine Metabolites on Evoked Striatal Dopamine Release, Dopamine Receptors, and Monoamine Transporters

Science.gov (United States)

Can, Adem; Zanos, Panos; Moaddel, Ruin; Kang, Hye Jin; Dossou, Katinia S. S.; Wainer, Irving W.; Cheer, Joseph F.; Frost, Douglas O.; Huang, Xi-Ping

2016-01-01

Following administration at subanesthetic doses, (R,S)-ketamine (ketamine) induces rapid and robust relief from symptoms of depression in treatment-refractory depressed patients. Previous studies suggest that ketamine’s antidepressant properties involve enhancement of dopamine (DA) neurotransmission. Ketamine is rapidly metabolized to (2S,6S)- and (2R,6R)-hydroxynorketamine (HNK), which have antidepressant actions independent of N-methyl-d-aspartate glutamate receptor inhibition. These antidepressant actions of (2S,6S;2R,6R)-HNK, or other metabolites, as well as ketamine’s side effects, including abuse potential, may be related to direct effects on components of the dopaminergic (DAergic) system. Here, brain and blood distribution/clearance and pharmacodynamic analyses at DA receptors (D1–D5) and the DA, norepinephrine, and serotonin transporters were assessed for ketamine and its major metabolites (norketamine, dehydronorketamine, and HNKs). Additionally, we measured electrically evoked mesolimbic DA release and decay using fast-scan cyclic voltammetry following acute administration of subanesthetic doses of ketamine (2, 10, and 50 mg/kg, i.p.). Following ketamine injection, ketamine, norketamine, and multiple hydroxynorketamines were detected in the plasma and brain of mice. Dehydronorketamine was detectable in plasma, but concentrations were below detectable limits in the brain. Ketamine did not alter the magnitude or kinetics of evoked DA release in the nucleus accumbens in anesthetized mice. Neither ketamine’s enantiomers nor its metabolites had affinity for DA receptors or the DA, noradrenaline, and serotonin transporters (up to 10 μM). These results suggest that neither the side effects nor antidepressant actions of ketamine or ketamine metabolites are associated with direct effects on mesolimbic DAergic neurotransmission. Previously observed in vivo changes in DAergic neurotransmission following ketamine administration are likely indirect. PMID

Enhanced striatal dopamine release during food stimulation in binge eating disorder

Energy Technology Data Exchange (ETDEWEB)

Wang, g.j.; Wang, G.-J.; Geliebter, A.; Volkow, N.D.; Telang, F.W.; Logan, Jaynbe, M.C.; Galanti, K.; Selig, P.A.; Han, H.; Zhu, W.; Wong, C.T.; Fowler, J.S.

2011-01-13

Subjects with binge eating disorder (BED) regularly consume large amounts of food in short time periods. The neurobiology of BED is poorly understood. Brain dopamine, which regulates motivation for food intake, is likely to be involved. We assessed the involvement of brain dopamine in the motivation for food consumption in binge eaters. Positron emission tomography (PET) scans with [{sup 11}C]raclopride were done in 10 obese BED and 8 obese subjects without BED. Changes in extracellular dopamine in the striatum in response to food stimulation in food-deprived subjects were evaluated after placebo and after oral methylphenidate (MPH), a drug that blocks the dopamine reuptake transporter and thus amplifies dopamine signals. Neither the neutral stimuli (with or without MPH) nor the food stimuli when given with placebo increased extracellular dopamine. The food stimuli when given with MPH significantly increased dopamine in the caudate and putamen in the binge eaters but not in the nonbinge eaters. Dopamine increases in the caudate were significantly correlated with the binge eating scores but not with BMI. These results identify dopamine neurotransmission in the caudate as being of relevance to the neurobiology of BED. The lack of correlation between BMI and dopamine changes suggests that dopamine release per se does not predict BMI within a group of obese individuals but that it predicts binge eating.

Enhanced striatal dopamine release during food stimulation in binge eating disorder

International Nuclear Information System (INIS)

Wang, G.-J.; Geliebter, A.; Volkow, N.D.; Telang, F.W.; Logan, J.; Jaynbe, M.C.; Galanti, K.; Selig, P.A.; Han, H.; Zhu, W.; Wong, C.T.; Fowler, J.S.

2011-01-01

Subjects with binge eating disorder (BED) regularly consume large amounts of food in short time periods. The neurobiology of BED is poorly understood. Brain dopamine, which regulates motivation for food intake, is likely to be involved. We assessed the involvement of brain dopamine in the motivation for food consumption in binge eaters. Positron emission tomography (PET) scans with [ 11 C]raclopride were done in 10 obese BED and 8 obese subjects without BED. Changes in extracellular dopamine in the striatum in response to food stimulation in food-deprived subjects were evaluated after placebo and after oral methylphenidate (MPH), a drug that blocks the dopamine reuptake transporter and thus amplifies dopamine signals. Neither the neutral stimuli (with or without MPH) nor the food stimuli when given with placebo increased extracellular dopamine. The food stimuli when given with MPH significantly increased dopamine in the caudate and putamen in the binge eaters but not in the nonbinge eaters. Dopamine increases in the caudate were significantly correlated with the binge eating scores but not with BMI. These results identify dopamine neurotransmission in the caudate as being of relevance to the neurobiology of BED. The lack of correlation between BMI and dopamine changes suggests that dopamine release per se does not predict BMI within a group of obese individuals but that it predicts binge eating.

Novel L-Dopa and dopamine prodrugs containing a 2-phenyl-imidazopyridine moiety.

Science.gov (United States)

Denora, Nunzio; Laquintana, Valentino; Lopedota, Angela; Serra, Mariangela; Dazzi, Laura; Biggio, Giovanni; Pal, Dhananjay; Mitra, Ashim K; Latrofa, Andrea; Trapani, Giuseppe; Liso, Gaetano

2007-07-01

The aim of this study was to gain insight into the feasibility of enhancing the delivery of L-Dopa and dopamine to the brain by linking these neurotransmitters and L-Dopa ethyl ester to 2-phenyl-3-carboxymethyl-imidazopyridine compounds giving rise to the so-called Dopimid compounds. A number of Dopimid compounds were synthesized and both stability and binding studies to dopaminergic and benzodiazepine receptors were performed. To evaluate whether Dopimid compounds are P-gp substrates, [(3)H]ritonavir uptake experiments and bi-directional transport studies on confluent MDCKII-MDR1 monolayers were carried out. The brain penetration properties of Dopimid compounds were estimated by the Clark's computational model and evaluated by investigation of their transport across BBMECs monolayers. The dopamine levels following the intraperitoneal administration of the selected Dopimid compounds were measured in vivo by using brain microdialysis in rat. Tested compounds were adequately stable in solution buffered at pH 7.4 but undergo faster cleavage in dilute rat serum at 37 degrees C. Receptor binding studies showed that Dopimid compounds are essentially devoid of affinity for dopaminergic and benzodiazepine receptors. [(3)H]ritonavir uptake experiments indicated that selected Dopimid compounds, like L-Dopa and dopamine hydrochloride, are not substrates of P-gp and it was also confirmed by bi-directional transport experiments across MDCKII-MDR1 monolayers. By Clark's model a significant brain penetration was deduced for L-Dopa ethyl ester and dopamine derivatives. Transport studies involving BBMECs monolayers indicated that some of these compounds should be able to cross the BBB. Interestingly, the rank order of apparent permeability (P (app)) values observed in these assays parallels that calculated by the computational approach. Brain microdialysis experiments in rat showed that intraperitoneal acute administration of some Dopimid compounds induced a dose-dependent increase

Effect of ligand self-assembly on nanostructure and carrier transport behaviour in CdSe quantum dots

Energy Technology Data Exchange (ETDEWEB)

Li, Kuiying, E-mail: kuiyingli@ysu.edu.cn; Xue, Zhenjie

2014-11-14

Adjustment of the nanostructure and carrier behaviour of CdSe quantum dots (QDs) by varying the ligands used during QD synthesis enables the design of specific quantum devices via a self-assembly process of the QD core–shell structure without additional technologies. Surface photovoltaic (SPV) technology supplemented by X-ray diffractometry and infrared absorption spectroscopy were used to probe the characteristics of these QDs. Our study reveals that while CdSe QDs synthesized in the presence of and capped by thioglycolic acid, 3-mercaptopropionic acid, mercaptoethanol or α-thioglycerol ligands display zinc blende nanocrystalline structures, CdSe QDs modified by L-cysteine possess wurtzite nanocrystalline structures, because different end groups in these ligands induce distinctive nucleation and growth mechanisms. Carboxyl end groups in the ligand served to increase the SPV response of the QDs, when illuminated by hν ≥ E{sub g,nano-CdSe}. Increased length of the alkyl chains and side-chain radicals in the ligands partially inhibit photo-generated free charge carrier (FCC) transfer transitions of CdSe QDs illuminated by photon energy of 4.13 to 2.14 eV. The terminal hydroxyl group might better accommodate energy released in the non-radiative de-excitation process of photo-generated FCCs in the ligand's lowest unoccupied molecular orbital in the 300–580 nm wavelength region, when compared with other ligand end groups. - Highlights: • CdSe QDs modified by L-cysteine possess wurtzite nanocrystalline structures. • Carboxyl end groups in the ligand serve to increase the SPV response of CdSe QDs. • Terminal hydroxyl group in the ligand might accommodate non-radiative de-excitation process in CdSe QDs. • Increased length of the alkyl chains and side-chain radicals in the ligands partially inhibit carriers transport of CdSe QDs.

Ligand-based transport resonances of single-molecule-magnet spin filters: Suppression of Coulomb blockade and determination of easy-axis orientation

Science.gov (United States)

Rostamzadeh Renani, Fatemeh; Kirczenow, George

2011-11-01

We investigate single-molecule-magnet transistors (SMMTs) with ligands that support transport resonances. We find the lowest unoccupied molecular orbitals of Mn12-benzoate SMMs (with and without thiol or methyl-sulfide termination) to be on ligands, the highest occupied molecular orbitals being on the Mn12 magnetic core. We predict gate-controlled switching between Coulomb blockade and coherent resonant tunneling in SMMTs based on such SMMs, strong spin filtering by the SMM in both transport regimes, and that if such switching is observed, then the magnetic easy axis of the SMM is parallel to the direction of the current through the SMM.

A molecular dynamics study on the transport of a charged biomolecule in a polymeric adsorbent medium and its adsorption onto a charged ligand.

Science.gov (United States)

Riccardi, E; Wang, J-C; Liapis, A I

2010-08-28

The transport of a charged adsorbate biomolecule in a porous polymeric adsorbent medium and its adsorption onto the covalently immobilized ligands have been modeled and investigated using molecular dynamics modeling and simulations as the third part of a novel fundamental methodology developed for studying ion-exchange chromatography based bioseparations. To overcome computational challenges, a novel simulation approach is devised where appropriate atomistic and coarse grain models are employed simultaneously and the transport of the adsorbate is characterized through a number of locations representative of the progress of the transport process. The adsorbate biomolecule for the system studied in this work changes shape, orientation, and lateral position in order to proceed toward the site where adsorption occurs and exhibits decreased mass transport coefficients as it approaches closer to the immobilized ligand. Furthermore, because the ligands are surrounded by counterions carrying the same type of charge as the adsorbate biomolecule, it takes the biomolecule repeated attempts to approach toward a ligand in order to displace the counterions in the proximity of the ligand and to finally become adsorbed. The formed adsorbate-ligand complex interacts with the counterions and polymeric molecules and is found to evolve slowly and continuously from one-site (monovalent) interaction to multisite (multivalent) interactions. Such a transition of the nature of adsorption reduces the overall adsorption capacity of the ligands in the adsorbent medium and results in a type of surface exclusion effect. Also, the adsorption of the biomolecule also presents certain volume exclusion effects by not only directly reducing the pore volume and the availability of the ligands in the adjacent regions, but also causing the polymeric molecules to change to more compact structures that could further shield certain ligands from being accessible to subsequent adsorbate molecules. These

Effects of unilateral 6-OHDA lesions on [3H]-N-propylnorapomorphine binding in striatum ex vivo and vulnerability to amphetamine-evoked dopamine release in rat

DEFF Research Database (Denmark)

Palner, Mikael; Kjaerby, Celia; Knudsen, Gitte M

2011-01-01

It has been argued that agonist ligands for dopamine D(2/3) receptors recognize a privileged subset of the receptors in living striatum, those which are functionally coupled to intracellular G-proteins. In support of this claim, the D(2/3) agonist [(3)H]-N-propylnorapomorphine ([(3)H]NPA) proved...... ligands should likewise be fitter than antagonists for detecting responses to denervation in positron emission tomography studies of idiopathic Parkinson's disease. Agonist binding increases in vivo are likely to reflect the composite of a sensitization-like phenomenon, and relatively less competition...... from endogenous dopamine, as seen in the lesioned side of 6-OHDA induced hemi-parkinsonism....

The clinical benefit of imaging striatal dopamine transporters with [123I]FP-CIT SPET in differentiating patients with presynaptic parkinsonism from those with other forms of parkinsonism

International Nuclear Information System (INIS)

Booij, J.; Speelman, J.DE.; Horstink, M. W.I.M.; Wolters, E.C.

2001-01-01

[ 123 I]FP-CIT (N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane) has been developed successfully as a radioligand for single-photon emission tomography (SPET) imaging of dopamine transporters, which are situated in the membrane of dopaminergic neurons. Imaging of these transporters has shown promise as a clinical tool to detect degeneration of the dopaminergic nigrostriatal pathway. Several ''presynaptic parkinsonian'' syndromes, such as Parkinson's disease or multiple system atrophy, are characterised by degeneration of the nigrostriatal pathway. [ 123 I]FP-CIT SPET imaging studies have shown the ability to detect loss of striatal dopamine transporters in such syndromes. However, in clinical practice it is sometimes difficult, but important, to discriminate patients with ''presynaptic parkinsonism'' from those with other forms of parkinsonism not characterised by loss of presynaptic dopaminergic cells (e.g. psychogenic parkinsonism or drug-induced postsynaptic parkinsonism). In these inconclusive cases, it may be of value to confirm or exclude the existence of degeneration of nigrostriatal dopaminergic cells by using imaging techniques such as [ 123 I]FP-CIT SPET. Using [ 123 I]FP-CIT SPET, we have imaged the striatal dopamine transporters in a group of patients with inconclusive forms of parkinsonism, and, moreover, have been able to perform clinical follow-up of these patients 2-4 years after imaging. In 33 inconclusive cases, ratios of specific to non-specific binding were calculated for the caudate nucleus and putamen following [ 123 I]FP-CIT SPET imaging and compared with ratios obtained in healthy controls. In nine of the patients, degeneration of the nigrostriatal pathway was found scintigraphically and in all these cases, presynaptic parkinsonism was confirmed by clinical follow-up. In the other 24 subjects no degeneration was found scintigraphically. Forms of parkinsonism other than the presynaptic were confirmed at follow-up in 19 cases

Firing properties of dopamine neurons in freely moving dopamine-deficient mice: Effects of dopamine receptor activation and anesthesia

OpenAIRE

Robinson, Siobhan; Smith, David M.; Mizumori, Sheri J. Y.; Palmiter, Richard D.

2004-01-01

To examine the regulation of midbrain dopamine neurons, recordings were obtained from single neurons of freely moving, genetically engineered dopamine-deficient (DD) mice. DD mice were tested without dopamine signaling (basal state) and with endogenous dopamine signaling (after L-dopa administration). In the basal state, when dopamine concentration in DD mice is

Dopamine transporter down-regulation following repeated cocaine: implications for 3,4-methylenedioxymethamphetamine-induced acute effects and long-term neurotoxicity in mice.

Science.gov (United States)

Peraile, I; Torres, E; Mayado, A; Izco, M; Lopez-Jimenez, A; Lopez-Moreno, J A; Colado, M I; O'Shea, E

2010-01-01

3,4-Methylenedioxymethamphetamine (MDMA) and cocaine are two widely abused psychostimulant drugs targeting the dopamine transporter (DAT). DAT availability regulates dopamine neurotransmission and uptake of MDMA-derived neurotoxic metabolites. We aimed to determine the effect of cocaine pre-exposure on the acute and long-term effects of MDMA in mice. Mice received a course of cocaine (20 mg*kg(-1), x2 for 3 days) followed by MDMA (20 mg*kg(-1), x2, 3 h apart). Locomotor activity, extracellular dopamine levels and dopaminergic neurotoxicity were determined. Furthermore, following the course of cocaine, DAT density in striatal plasma membrane and endosome fractions was measured. Four days after the course of cocaine, challenge with MDMA attenuated the MDMA-induced striatal dopaminergic neurotoxicity. Co-administration of the protein kinase C (PKC) inhibitor NPC 15437 prevented cocaine protection. At the same time, after the course of cocaine, DAT density was reduced in the plasma membrane and increased in the endosome fraction, and this effect was prevented by NPC 15437. The course of cocaine potentiated the MDMA-induced increase in extracellular dopamine and locomotor activity, following challenge 4 days later, compared with those pretreated with saline. Repeated cocaine treatment followed by withdrawal protected against MDMA-induced dopaminergic neurotoxicity by internalizing DAT via a mechanism which may involve PKC. Furthermore, repeated cocaine followed by withdrawal induced behavioural and neurochemical sensitization to MDMA, measures which could be indicative of increased rewarding effects of MDMA.

SPECT imaging of D2 dopamine receptors and endogenous dopamine release in mice

International Nuclear Information System (INIS)

Jongen, Cynthia; Bruin, Kora de; Booij, Jan; Beekman, Freek

2008-01-01

The dopamine D 2 receptor (D2R) is important in the mediation of addiction. [ 123 I]iodobenzamide (IBZM), a SPECT ligand for the D2R, has been used for in vivo studies of D2R availability in humans, monkeys, and rats. Although mouse models are important in the study of addiction, [ 123 I]IBZM has not been used in mice SPECT studies. This study evaluates the use of [ 123 I]IBZM for measuring D2R availability in mice. Pharmacokinetics of [ 123 I]IBZM in mice were studied with pinhole SPECT imaging after intravenous (i.v.) injection of [ 123 I]IBZM (20, 40, and 70 MBq). In addition, the ability to measure the release of endogenous dopamine after amphetamine administration with [ 123 I]IBZM SPECT was investigated. Thirdly, i.v. administration, the standard route of administration, and intraperitoneal (i.p.) administration of [ 123 I]IBZM were compared. Specific binding of [ 123 I]IBZM within the mouse striatum could be clearly visualized with SPECT. Peak specific striatal binding ratios were reached around 90 min post-injection. After amphetamine administration, the specific binding ratios of [ 123 I]IBZM decreased significantly (-27.2%; n=6; p=0.046). Intravenous administration of [ 123 I]IBZM led to significantly higher specific binding than i.p. administration of the same dose. However, we found that i.v. administration of a dose of 70 MBq [ 123 I]IBZM might result in acute ethanol intoxication because ethanol is used as a preparative aid for the routine production of [ 123 I]IBZM. Imaging of D2R availability and endogenous dopamine release in mice is feasible using [ 123 I]IBZM single pinhole SPECT. Using commercially produced [ 123 I]IBZM, a dose of 40 MBq injected i.v. can be recommended. (orig.)

Striatal Dopamine Depletion Patterns and Early Non-Motor Burden in Parkinsons Disease.

Directory of Open Access Journals (Sweden)

Su Jin Chung

Full Text Available The mechanism underlying non-motor symptoms in Parkinson's disease has not yet been elucidated. In this study, we hypothesized that Parkinson patients with more non-motor symptoms have a different pattern of striatal dopamine depletion, particularly in areas other than the sensorimotor striatum, compared to those with fewer non-motor symptoms.We conducted a prospective survey of the degree of non-motor symptoms (using the Korean version of the Non-Motor Symptoms Scale; K-NMSS in 151 patients with early-stage Parkinson's disease who had undergone a dopamine transporter PET scan as an initial diagnostic procedure. We classified the patients into two groups; high non-motor patients (HNM-PD; K-NMSS score ≥ 41 and low non-motor patients (LNM-PD.Patients in the HNM-PD group (n = 71 were older, had longer symptom duration, exhibited more severe motor deficits, and had been prescribed higher levodopa-equivalent doses at follow-up than those in the LNM-PD group. However, dopamine transporter binding to the striatal sub-regions and inter-sub-regional binding ratios were comparable between the two groups. A general linear model showed that the HNM-PD group had significantly more severe motor deficits than the LNM-PD group after controlling for age, gender, symptom duration, and dopamine transporter binding to the sensorimotor striatum.This study demonstrated that the pattern of striatal dopamine depletion does not contribute to early non-motor burden in Parkinson's disease. Our results suggest that LNM-PD patients may have a more benign course of motor symptom progression than HNM-PD patients.

Differential labeling of dopamine and sigma sites by [3H]nemonapride and [3H]raclopride in postmortem human brains.

Science.gov (United States)

Tang, S W; Helmeste, D M; Fang, H; Li, M; Vu, R; Bunney, W; Potkin, S; Jones, E G

1997-08-08

The difference between the binding of [3H]nemonapride and [3H]raclopride has been used to quantify dopamine D4 receptors in postmortem schizophrenic brain studies. Recent work, however, has suggested that at least part of the differential between [3H]nemonapride and [3H]raclopride binding may represent sigma rather than D4 receptor sites. We applied the nemonapride-raclopride subtraction method to postmortem, non-schizophrenic human striatum to examine the variation in dopaminergic receptor binding labeled by these ligands. Variation in sigma receptor binding labeled by [3H]nemonapride was studied in frontal cortex, striatum and cerebellum. Specific binding was defined by sulpiride (dopamine receptor ligand), PPAP (sigma receptor ligand) and haloperidol (mixed dopaminergic/sigma agent), respectively. Haloperidol defined a combination of sites, which were approximately the sum of the dopaminergic and sigma components defined by sulpiride and PPAP, respectively. Significant inter-individual variation in the amount of specific binding for dopaminergic and sigma receptor sites was observed. However, no significant nor consistent observation of striatal dopamine D4 receptors or D4-like binding sites was observed in the striatum even though two independent sets of tissues, with different dissections were used. The inconsistencies in some previous postmortem studies appear to be at least partially explained by the inclusion of both sigma and dopaminergic components in [3H]nemonapride binding and the inherent high inter-individual variability of the different components.

Enduring increases in anxiety-like behavior and rapid nucleus accumbens dopamine signaling in socially isolated rats.

Science.gov (United States)

Yorgason, Jordan T; España, Rodrigo A; Konstantopoulos, Joanne K; Weiner, Jeffrey L; Jones, Sara R

2013-03-01

Social isolation (SI) rearing, a model of early life stress, results in profound behavioral alterations, including increased anxiety-like behavior, impaired sensorimotor gating and increased self-administration of addictive substances. These changes are accompanied by alterations in mesolimbic dopamine function, such as increased dopamine and metabolite tissue content, increased dopamine responses to cues and psychostimulants, and increased dopamine neuron burst firing. Using voltammetric techniques, we examined the effects of SI rearing on dopamine transporter activity, vesicular release and dopamine D2-type autoreceptor activity in the nucleus accumbens core. Long-Evans rats were housed in group (GH; 4/cage) or SI (1/cage) conditions from weaning into early adulthood [postnatal day (PD) 28-77]. After this initial housing period, rats were assessed on the elevated plus-maze for an anxiety-like phenotype, and then slice voltammetry experiments were performed. To study the enduring effects of SI rearing on anxiety-like behavior and dopamine terminal function, another cohort of similarly reared rats was isolated for an additional 4 months (until PD 174) and then tested. Our findings demonstrate that SI rearing results in lasting increases in anxiety-like behavior, dopamine release and dopamine transporter activity, but not D2 activity. Interestingly, GH-reared rats that were isolated as adults did not develop the anxiety-like behavior or dopamine changes seen in SI-reared rats. Together, our data suggest that early life stress results in an anxiety-like phenotype, with lasting increases in dopamine terminal function. © 2013 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Improved delineation of human dopamine receptors using [18F]-N-methylspiroperidol and PET

International Nuclear Information System (INIS)

Arnett, C.D.; Wolf, A.P.; Shiue, C.Y.; Fowler, J.S.; MacGregor, R.R.; Christman, D.R.; Smith, M.R.

1986-01-01

The brain uptake of [18F]-N-methylspiroperidol, a butyrophenone neuroleptic with high selectivity for the dopamine receptor, has been measured in three normal human volunteers using positron emission tomography for times up to 12 hr postinjection. These studies demonstrated two unique findings concerning the in vivo distribution of this neuroleptic: (a) it is tightly bound to dopamine D-2 receptors in the caudate-putamen brain regions, and (b) these regions are the only large brain structures which exhibit appreciable long-term retention. In addition, radioactivity clears rapidly from plasma, and the percentage of unchanged [18F]-N-methylspiroperidol in plasma declines rapidly. These results suggest that this compound binds irreversibly to dopamine D-2 receptors, and that there are few if any dopamine D-2 receptors in the human frontal cortex. These studies emphasize not only the importance of characterizing neurotransmitter receptors in living human brain using a ligand labeled with a positron emitting nuclide of sufficiently long half-life to allow monitoring of brain radioactivity distribution for several hours after the injection of radioligand, but also of accurately determining the amount of unchanged tracer in plasma for tracer kinetic modeling

Incident impulse control disorder symptoms and dopamine transporter imaging in Parkinson disease.

Science.gov (United States)

Smith, Kara M; Xie, Sharon X; Weintraub, Daniel

2016-08-01

To describe the incidence of, and clinical and neurobiological risk factors for, new-onset impulse control disorder (ICD) symptoms and related behaviours in early Parkinson disease (PD). The Parkinson's Progression Markers Initiative is an international, multicenter, prospective study of de novo patients with PD untreated at baseline and assessed annually, including serial dopamine transporter imaging (DAT-SPECT) and ICD assessment (Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease short form, QUIP). Participants were included if they screened negative on the QUIP at baseline. Kaplan-Meier curves and generalised estimating equations examined frequency and predictors of incident ICD symptoms. Participants were seen at baseline (n=320), year 1 (n=284), year 2 (n=217) and year 3 (n=96). Estimated cumulative incident rates of ICD symptoms and related behaviours were 8% (year 1), 18% (year 2) and 25% (year 3) and increased each year in those on dopamine replacement therapy (DRT) and decreased in those not on DRT. In participants on DRT, risk factors for incident ICD symptoms were younger age (OR=0.97, p=0.05), a greater decrease in right caudate (OR=4.03, p=0.01) and mean striatal (OR=6.90, p=0.04) DAT availability over the first year, and lower right putamen (OR=0.06, p=0.01) and mean total striatal (OR=0.25, p=0.04) DAT availability at any post-baseline visit. The rate of incident ICD symptoms increases with time and initiation of DRT in early PD. In this preliminary study, a greater decrease or lower DAT binding over time increases risk of incident ICD symptoms, conferring additional risk to those taking DRT. NCT01141023. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

[3H]Haloperidol labels brain dopamine receptors after its injection into the internal carotid artery of the rat

International Nuclear Information System (INIS)

D'Ambrosio, A.; Zivkovic, B.; Bartholini, G.

1982-01-01

Pulse injection of [ 3 H]haloperidol (0.1 μCi; 0.003 μg) into the internal carotid artery of the rat specifically labelled dopamine receptors in striatum and olfactory tubercle, as indicated by the kinetics of, and the effects of neuroleptic drugs on, the ligand disposition. The described method may prove useful for labelling brain receptors with ligands which readily cross the blood-brain barrier but which do not selectively mark their receptors if injected systemically. (Auth.)

Diversity of natural self-derived ligands presented by different HLA class I molecules in transporter antigen processing-deficient cells.

Directory of Open Access Journals (Sweden)

Elena Lorente

Full Text Available The transporter associated with antigen processing (TAP translocates the cytosol-derived proteolytic peptides to the endoplasmic reticulum lumen where they complex with nascent human leukocyte antigen (HLA class I molecules. Non-functional TAP complexes and viral or tumoral blocking of these transporters leads to reduced HLA class I surface expression and a drastic change in the available peptide repertoire. Using mass spectrometry to analyze complex human leukocyte antigen HLA-bound peptide pools isolated from large numbers of TAP-deficient cells, we identified 334 TAP-independent ligands naturally presented by four different HLA-A, -B, and -C class I molecules with very different TAP dependency from the same cell line. The repertoire of TAP-independent peptides examined favored increased peptide lengths and a lack of strict binding motifs for all four HLA class I molecules studied. The TAP-independent peptidome arose from 182 parental proteins, the majority of which yielded one HLA ligand. In contrast, TAP-independent antigen processing of very few cellular proteins generated multiple HLA ligands. Comparison between TAP-independent peptidome and proteome of several subcellular locations suggests that the secretory vesicle-like organelles could be a relevant source of parental proteins for TAP-independent HLA ligands. Finally, a predominant endoproteolytic peptidase specificity for Arg/Lys or Leu/Phe residues in the P(1 position of the scissile bond was found for the TAP-independent ligands. These data draw a new and intricate picture of TAP-independent pathways.

4-[[sup 123]I]iodospiperone as a ligand for dopamine DA receptors: in vitro and in vivo experiments in a rat model

Energy Technology Data Exchange (ETDEWEB)

Krogt, J.A. van der; Valkenburg, C F.M. van; Pauwels, E K.J.; Buruma, O J.S. [Rijksuniversiteit Leiden (Netherlands); Reiffers, S [Hospital De Weezenlanden, Zwolle (Netherlands); Doremalen, P.A.P.M. van; Wijnhoven, G [Cygne, Eindhoven (Netherlands)

1992-10-01

Radioiodinated spiperone is of interest for dopamine (DA) receptor studies in the living human brain by single photon emission computed tomography (SPECT). Simulated by data obtained with [[sup 11]C]-N-methyl-spiperone, we synthesized 4-[[sup 123]I]iodospiperone and investigated the in vitro binding characteristics of this ligand to the striatal membrane of the rat and the in vivo distribution over various rat brain regions. The in vitro binding experiments showed that this radioligand displays about 10 times less affinity for the DA receptor than spiperone and specific binding, as shown with [[sup 3]H]spiperone, was not observed. Displacement by butaclamol was not observed. The in vivo studies demonstrated that both 4-[[sup 123]I]iodospiperone and [[sup 3]H]spiperone concentrate in striatal tissue, respectively, 1.9 and 3.5 times as high as in cerebellar tissue. Haloperidol pretreatment largely prevented this accumulation. In view of the obtained target-to-non-target ratios we believe, however, that this accumulation in brain areas rich DA-receptors does not offer prospects for clinical receptor imaging with SPECT. (Author).

The dual-gate lumen model of renal monoamine transport

Directory of Open Access Journals (Sweden)

Marty Hinz

2010-07-01

Full Text Available Marty Hinz1, Alvin Stein2, Thomas Uncini31Clinical Research, NeuroResearch Clinics, Inc. Cape Coral, Florida, USA; 2Stein Orthopedic Associates, Plantation, Florida, USA; 3DBS Labs, Duluth, Minnesota, USAAbstract: The three-phase response of urinary serotonin and dopamine in subjects ­simultaneously taking amino acid precursors of serotonin and dopamine has been defined.1,2 No model exists regarding the renal etiology of the three-phase response. This writing outlines a model explaining the origin of the three-phase response of urinary serotonin and dopamine. A “dual-gate lumen transporter model” for the basolateral monoamine transporters of the kidneys is proposed as being the etiology of the three-phase urinary serotonin and dopamine responses.Purpose: The purpose of this writing is to document the internal renal function model that has evolved in research during large-scale assay with phase interpretation of urinary serotonin and dopamine.Patients and methods: In excess of 75,000 urinary monoamine assays from more than 7,500 patients were analyzed. The serotonin and the dopamine phase were determined for specimens submitted in the competitive inhibition state. The phase determination findings were then correlated with peer-reviewed literature.Results: The correlation between the three-phase response of urinary serotonin and dopamine with internal renal processes of the bilateral monoamine transporter and the apical monoamine transporter of the proximal convoluted renal tubule cells is defined.Conclusion: The phase of urinary serotonin and dopamine is dependent on the status of the serotonin gate, dopamine gate, and lumen of the basolateral monoamine transporter while in the competitive inhibition state.Keywords: serotonin, dopamine, basolateral, apical, kidney, proximal

A Japanese Encephalitis Patient Presenting with Parkinsonism with Corresponding Laterality of Magnetic Resonance and Dopamine Transporter Imaging Findings.

Science.gov (United States)

Tadokoro, Koh; Ohta, Yasuyuki; Sato, Kota; Maeki, Takahiro; Sasaki, Ryo; Takahashi, Yoshiaki; Shang, Jingwei; Takemoto, Mami; Hishikawa, Nozomi; Yamashita, Toru; Lim, Chang Kweng; Tajima, Shigeru; Abe, Koji

2018-03-09

Japanese encephalitis (JE) survivors often present with nigrostriatal aftereffects with parkinsonian features. A 67-year-old woman with JE showed right-dominant clinical parkinsonism and left-dominant substantia nigra lesions after magnetic resonance imaging (MRI). Dopamine transporter (DAT) imaging using 123 I-labeled 2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane ( 123 I-FP-CIT) revealed a corresponding left-dominant decrease. The present case is the first to reveal a clear match of laterality between clinical parkinsonism, MRI-based substantia nigra lesions, and impaired DAT in presynaptic dopaminergic neurons in JE.

A peptide disrupting the D2R-DAT interaction protects against dopamine neurotoxicity.

Science.gov (United States)

Su, Ping; Liu, Fang

2017-09-01

Dopamine reuptake from extracellular space to cytosol leads to accumulation of dopamine, which triggers neurotoxicity in dopaminergic neurons. Previous studies have shown that both dopamine D2 receptor (D2R) and dopamine transporter (DAT) are involved in dopamine neurotoxicity. However, blockade of either D2R or DAT causes side effects due to antagonism of other physiological functions of these two proteins. We previously found that DAT can form a protein complex with D2R and its cell surface expression is facilitated via D2R-DAT interaction, which regulates dopamine reuptake and intracellular dopamine levels. Here we found that an interfering peptide (DAT-S1) disrupting the D2R-DAT interaction protects neurons against dopamine neurotoxicity, and this effect is mediated by inhibiting DAT cell surface expression and inhibiting both caspase-3 and PARP-1 cleavage. This study demonstrates the role of the D2R-DAT complex in dopamine neurotoxicity and investigated the potential mechanisms, which might help better understand the mechanisms of dopamine neurotoxicity. The peptide may provide some insights to improve treatments for dopamine neurotoxicity and related diseases, such as Parkinson's disease, as well as methamphetamine- and 3,4-methsylenedioxy methamphetamine-induced neurotoxicity. Copyright © 2017. Published by Elsevier Inc.

New copper(II) complexes with dopamine hydrochloride and vanillymandelic acid: Spectroscopic and thermal characterization

Science.gov (United States)

Mohamed, Gehad G.; Nour El-Dien, F. A.; El-Nahas, R. G.

2011-10-01

The dopamine derivatives participate in the regulation of wide variety of physiological functions in the human body and in medication life. Increase and/or decrease in the concentration of dopamine in human body reflect an indication for diseases such as Schizophrenia and/or Parkinson diseases. The Cu(II) chelates with coupled products of dopamine hydrochloride (DO.HCl) and vanillymandelic acid (VMA) with 4-aminoantipyrine (4-AAP) are prepared and characterized. Different physico-chemical techniques namely IR, magnetic and UV-vis spectra are used to investigate the structure of these chelates. Cu(II) forms 1:1 (Cu:DO) and 1:2 (Cu:VMA) chelates. DO behave as a uninegative tridentate ligand in binding to the Cu(II) ion while VMA behaves as a uninegative bidentate ligand. IR spectra show that the DO is coordinated to the Cu(II) ion in a tridentate manner with ONO donor sites of the phenolic- OH, -NH and carbonyl- O, while VMA is coordinated with OO donor sites of the phenolic- OH and -NH. Magnetic moment measurements reveal the presence of Cu(II) chelates in octahedral and square planar geometries with DO and VMA, respectively. The thermal decomposition of Cu(II) complexes is studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The activation thermodynamic parameters, such as, energy of activation, enthalpy, entropy and free energy change of the complexes are evaluated and the relative thermal stability of the complexes are discussed.

Dopamine D(3) receptors contribute to methamphetamine-induced alterations in dopaminergic neuronal function: role of hyperthermia.

Science.gov (United States)

Baladi, Michelle G; Newman, Amy H; Nielsen, Shannon M; Hanson, Glen R; Fleckenstein, Annette E

2014-06-05

Methamphetamine administration causes long-term deficits to dopaminergic systems that, in humans, are thought to be associated with motor slowing and memory impairment. Methamphetamine interacts with the dopamine transporter (DAT) and increases extracellular concentrations of dopamine that, in turn, binds to a number of dopamine receptor subtypes. Although the relative contribution of each receptor subtype to the effects of methamphetamine is not fully known, non-selective dopamine D2/D3 receptor antagonists can attenuate methamphetamine-induced changes to dopamine systems. The present study extended these findings by testing the role of the dopamine D3 receptor subtype in mediating the long-term dopaminergic, and for comparison serotonergic, deficits caused by methamphetamine. Results indicate that the dopamine D3 receptor selective antagonist, PG01037, attenuated methamphetamine-induced decreases in striatal DAT, but not hippocampal serotonin (5HT) transporter (SERT), function, as assessed 7 days after treatment. However, PG01037 also attenuated methamphetamine-induced hyperthermia. When methamphetamine-induced hyperthermia was maintained by treating rats in a warm ambient environment, PG01037 failed to attenuate the effects of methamphetamine on DAT uptake. Furthermore, PG01037 did not attenuate methamphetamine-induced decreases in dopamine and 5HT content. Taken together, the present study demonstrates that dopamine D3 receptors mediate, in part, the long-term deficits in DAT function caused by methamphetamine, and that this effect likely involves an attenuation of methamphetamine-induced hyperthermia. Copyright © 2014 Elsevier B.V. All rights reserved.

Dopamine D3 receptors contribute to methamphetamine-induced alterations in dopaminergic neuronal function: Role of hyperthermia

Science.gov (United States)

Baladi, Michelle G.; Newman, Amy H.; Nielsen, Shannon M.; Hanson, Glen R.; Fleckenstein, Annette E.

2014-01-01

Methamphetamine administration causes long-term deficits to dopaminergic systems that, in humans, are thought to be associated with motor slowing and memory impairment. Methamphetamine interacts with the dopamine transporter (DAT) and increases extracellular concentrations of dopamine that, in turn, binds to a number of dopamine receptor subtypes. Although the relative contribution of each receptor subtype to the effects of methamphetamine is not fully known, non-selective dopamine D2/D3 receptor antagonists can attenuate methamphetamine-induced changes to dopamine systems. The present study extended these findings by testing the role of the dopamine D3 receptor subtype in mediating the long-term dopaminergic, and for comparison serotonergic, deficits caused by methamphetamine. Results indicate that the dopamine D3 receptor selective antagonist, PG01037, attenuated methamphetamine-induced decreases in striatal DAT, but not hippocampal serotonin (5HT) transporter (SERT), function, as assessed 7 days after treatment. However, PG01037 also attenuated methamphetamine-induced hyperthermia. When methamphetamine-induced hyperthermia was maintained by treating rats in a warm ambient environment, PG01037 failed to attenuate the effects of methamphetamine on DAT uptake. Furthermore, PG01037 did not attenuate methamphetamine-induced decreases in dopamine and 5HT content. Taken together, the present study demonstrates that dopamine D3 receptors mediate, in part, the long-term deficits in DAT function caused by methamphetamine, and that this effect likely involves an attenuation of methamphetamine-induced hyperthermia. PMID:24685638

Self-esteem in remitted patients with mood disorders is not associated with the dopamine receptor D4 and the serotonin transporter genes.

Science.gov (United States)

Serretti, A; Macciardi, F; Di Bella, D; Catalano, M; Smeraldi, E

1998-08-17

Disturbances of the dopaminergic and serotoninergic neurotransmitter systems have been implicated in the pathogenesis of depressive symptoms. Associations have been reported between markers of the two neurotransmitter systems and the presence of illness or severity of depressive episodes, but no attention has been focused on the periods of remission. The present report focuses on a possible association of self-esteem in remitted mood disorder patients with the functional polymorphism located in the upstream regulatory region of the serotonin transporter gene (5-HTTLPR) and the dopamine receptor D4 (DRD4). Inpatients (N=162) affected by bipolar (n=103) and unipolar (n=59) disorder (DSM III-R) were assessed by the Self-Esteem Scale (SES, Rosenberg, 1965) and were typed for DRD4 and 5-HTTLPR (n=58 subjects) variants at the third exon using polymerase chain reaction (PCR) techniques. Neither DRD4 nor 5-HTTLPR variants were associated with SES scores, and consideration of possible stratification effects such as sex and psychiatric diagnosis did not reveal any association either. The serotonin transporter and dopamine receptor D4 genes do not, therefore, influence self-esteem in remitted mood disorder subjects.

Central D2-dopamine receptor occupancy in schizophrenic patients treated with antipsychotic drugs

International Nuclear Information System (INIS)

Farde, L.; Wiesel, F.A.; Halldin, C.; Sedvall, G.

1988-01-01

Using positron emission tomography and the carbon 11-labeled ligand raclopride, central D2-dopamine receptor occupancy in the putamen was determined in psychiatric patients treated with clinical doses of psychoactive drugs. Receptor occupancy in drug-treated patients was defined as the percent reduction of specific carbon 11-raclopride binding in relation to the expected binding in the absence of drug treatment. Clinical treatment of schizophrenic patients with 11 chemically distinct antipsychotic drugs (including both classic and atypical neuroleptics such as clozapine) resulted in a 65% to 85% occupancy of D2-dopamine receptors. In a depressed patient treated with the tricyclic antidepressant nortriptyline, no occupancy was found. The time course for receptor occupancy and drug levels was followed after withdrawal of sulpiride or haloperidol. D2-dopamine receptor occupancy remained above 65% for many hours despite a substantial reduction of serum drug concentrations. In a sulpiride-treated patient, the dosage was reduced in four steps over a nine-week period and a curvilinear relationship was demonstrated between central D2-dopamine receptor occupancy and serum drug concentrations. The results demonstrate that clinical doses of all the currently used classes of antipsychotic drugs cause a substantial blockade of central D2-dopamine receptors in humans. This effect appears to be selective for the antipsychotics, since it was not induced by the antidepressant nortriptyline

Reduced Striatal Dopamine Transporters in People with Internet Addiction Disorder

Directory of Open Access Journals (Sweden)

Haifeng Hou

2012-01-01

Full Text Available In recent years, internet addiction disorder (IAD has become more prevalent worldwide and the recognition of its devastating impact on the users and society has rapidly increased. However, the neurobiological mechanism of IAD has not bee fully expressed. The present study was designed to determine if the striatal dopamine transporter (DAT levels measured by T99mc-TRODAT-1 single photon emission computed tomography (SPECT brain scans were altered in individuals with IAD. SPECT brain scans were acquired on 5 male IAD subjects and 9 healthy age-matched controls. The volume (V and weight (W of bilateral corpus striatum as well as the T99mc-TRODAT-1 uptake ratio of corpus striatum/the whole brain (Ra were calculated using mathematical models. It was displayed that DAT expression level of striatum was significantly decreased and the V, W, and Ra were greatly reduced in the individuals with IAD compared to controls. Taken together, these results suggest that IAD may cause serious damages to the brain and the neuroimaging findings further illustrate IAD is associated with dysfunctions in the dopaminergic brain systems. Our findings also support the claim that IAD may share similar neurobiological abnormalities with other addictive disorders.

SPECT imaging of D{sub 2} dopamine receptors and endogenous dopamine release in mice

Energy Technology Data Exchange (ETDEWEB)

Jongen, Cynthia [University Medical Center Utrecht, Image Sciences Institute, Q0S.459, P.O. Box 85500, Utrecht (Netherlands); Bruin, Kora de; Booij, Jan [University of Amsterdam, Academic Medical Center, Department of Nuclear Medicine, Amsterdam (Netherlands); Beekman, Freek [University Medical Center Utrecht, Image Sciences Institute, Q0S.459, P.O. Box 85500, Utrecht (Netherlands); University Medical Center Utrecht, Department of Neuroscience and Pharmacology, Utrecht (Netherlands); Technical University Delft, Department R3, Section Radiation, Detection and Matter, Delft (Netherlands)

2008-09-15

The dopamine D{sub 2} receptor (D2R) is important in the mediation of addiction. [{sup 123}I]iodobenzamide (IBZM), a SPECT ligand for the D2R, has been used for in vivo studies of D2R availability in humans, monkeys, and rats. Although mouse models are important in the study of addiction, [{sup 123}I]IBZM has not been used in mice SPECT studies. This study evaluates the use of [{sup 123}I]IBZM for measuring D2R availability in mice. Pharmacokinetics of [{sup 123}I]IBZM in mice were studied with pinhole SPECT imaging after intravenous (i.v.) injection of [{sup 123}I]IBZM (20, 40, and 70 MBq). In addition, the ability to measure the release of endogenous dopamine after amphetamine administration with [{sup 123}I]IBZM SPECT was investigated. Thirdly, i.v. administration, the standard route of administration, and intraperitoneal (i.p.) administration of [{sup 123}I]IBZM were compared. Specific binding of [{sup 123}I]IBZM within the mouse striatum could be clearly visualized with SPECT. Peak specific striatal binding ratios were reached around 90 min post-injection. After amphetamine administration, the specific binding ratios of [{sup 123}I]IBZM decreased significantly (-27.2%; n=6; p=0.046). Intravenous administration of [{sup 123}I]IBZM led to significantly higher specific binding than i.p. administration of the same dose. However, we found that i.v. administration of a dose of 70 MBq [{sup 123}I]IBZM might result in acute ethanol intoxication because ethanol is used as a preparative aid for the routine production of [{sup 123}I]IBZM. Imaging of D2R availability and endogenous dopamine release in mice is feasible using [{sup 123}I]IBZM single pinhole SPECT. Using commercially produced [{sup 123}I]IBZM, a dose of 40 MBq injected i.v. can be recommended. (orig.)

Rare autism-associated variants implicate syntaxin 1 (STX1 R26Q) phosphorylation and the dopamine transporter (hDAT R51W) in dopamine neurotransmission and behaviors.

Science.gov (United States)

Cartier, Etienne; Hamilton, Peter J; Belovich, Andrea N; Shekar, Aparna; Campbell, Nicholas G; Saunders, Christine; Andreassen, Thorvald F; Gether, Ulrik; Veenstra-Vanderweele, Jeremy; Sutcliffe, James S; Ulery-Reynolds, Paula G; Erreger, Kevin; Matthies, Heinrich J G; Galli, Aurelio

2015-02-01

Syntaxin 1 (STX1) is a presynaptic plasma membrane protein that coordinates synaptic vesicle fusion. STX1 also regulates the function of neurotransmitter transporters, including the dopamine (DA) transporter (DAT). The DAT is a membrane protein that controls DA homeostasis through the high-affinity re-uptake of synaptically released DA. We adopt newly developed animal models and state-of-the-art biophysical techniques to determine the contribution of the identified gene variants to impairments in DA neurotransmission observed in autism spectrum disorder (ASD). Here, we characterize two independent autism-associated variants in the genes that encode STX1 and the DAT. We demonstrate that each variant dramatically alters DAT function. We identify molecular mechanisms that converge to inhibit reverse transport of DA and DA-associated behaviors. These mechanisms involve decreased phosphorylation of STX1 at Ser14 mediated by casein kinase 2 as well as a reduction in STX1/DAT interaction. These findings point to STX1/DAT interactions and STX1 phosphorylation as key regulators of DA homeostasis. We determine the molecular identity and the impact of these variants with the intent of defining DA dysfunction and associated behaviors as possible complications of ASD.

Reduced dopamine receptors and transporters but not synthesis capacity in normal aging adults: a meta-analysis.

Science.gov (United States)

Karrer, Teresa M; Josef, Anika K; Mata, Rui; Morris, Evan D; Samanez-Larkin, Gregory R

2017-09-01

Many theories of cognitive aging are based on evidence that dopamine (DA) declines with age. Here, we performed a systematic meta-analysis of cross-sectional positron emission tomography and single-photon emission-computed tomography studies on the average effects of age on distinct DA targets (receptors, transporters, or relevant enzymes) in healthy adults (N = 95 studies including 2611 participants). Results revealed significant moderate to large, negative effects of age on DA transporters and receptors. Age had a significantly larger effect on D1- than D2-like receptors. In contrast, there was no significant effect of age on DA synthesis capacity. The average age reductions across the DA system were 3.7%-14.0% per decade. A meta-regression found only DA target as a significant moderator of the age effect. This study precisely quantifies prior claims of reduced DA functionality with age. It also identifies presynaptic mechanisms (spared synthesis capacity and reduced DA transporters) that may partially account for previously unexplained phenomena whereby older adults appear to use dopaminergic resources effectively. Recommendations for future studies including minimum required samples sizes are provided. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Membrane mobility and microdomain association of the dopamine transporter studied with fluorescence correlation spectroscopy and fluorescence recovery after photobleaching

DEFF Research Database (Denmark)

Adkins, Erika M; Samuvel, Devadoss J; Fog, Jacob U

2007-01-01

To investigate microdomain association of the dopamine transporter (DAT), we employed FCS (fluorescence correlation spectroscopy) and FRAP (fluorescence recovery after photobleaching). In non-neuronal cells (HEK293), FCS measurements revealed for the YFP-DAT (DAT tagged with yellow fluorescent...... protein) a diffusion coefficient (D) of approximately 3.6 x 10(-9) cm2/s, consistent with a relatively freely diffusible protein. In neuronally derived cells (N2a), we were unable to perform FCS measurements on plasma membrane-associated protein due to photobleaching, suggesting partial immobilization...

(/sup 3/H)Haloperidol labels brain dopamine receptors after its injection into the internal carotid artery of the rat

Energy Technology Data Exchange (ETDEWEB)

D' Ambrosio, A; Zivkovic, B; Bartholini, G [Research Department, Synthelabo-L.E.R.S., Paris (France)

1982-04-29

Pulse injection of (/sup 3/H)haloperidol (0.1 ..mu..Ci; 0.003 ..mu..g) into the internal carotid artery of the rat specifically labelled dopamine receptors in striatum and olfactory tubercle, as indicated by the kinetics of, and the effects of neuroleptic drugs on, the ligand disposition. The described method may prove useful for labelling brain receptors with ligands which readily cross the blood-brain barrier but which do not selectively mark their receptors if injected systemically.

Cocaine Self-Administration Produces Long-Lasting Alterations in Dopamine Transporter Responses to Cocaine

OpenAIRE

Siciliano, Cody A.; Fordahl, Steve C.; Jones, Sara R.

2016-01-01

Cocaine addiction is a debilitating neuropsychiatric disorder characterized by uncontrolled cocaine intake, which is thought to be driven, at least in part, by cocaine-induced deficits in dopamine system function. A decreased ability of cocaine to elevate dopamine levels has been repeatedly observed as a consequence of cocaine use in humans, and preclinical work has highlighted tolerance to cocaine's effects as a primary determinant in the development of aberrant cocaine taking behaviors. Her...

Quantitation of dopamine transporter blockade by methylphenidate: first in vivo investigation using [123I]FP-CIT and a dedicated small animal SPECT

International Nuclear Information System (INIS)

Nikolaus, Susanne; Wirrwar, Andreas; Antke, Christina; Arkian, Shahram; Mueller, Hans-Wilhelm; Larisch, Rolf; Schramm, Nils

2005-01-01

The aim of this study was to investigate the feasibility of assessing dopamine transporter binding after treatment with methylphenidate in the rat using a recently developed high-resolution small animal single-photon emission computed tomograph (TierSPECT) and [ 123 I]FP-CIT. [ 123 I]FP-CIT was administered intravenously 1 h after intraperitoneal injection of methylphenidate (10 mg/kg) or vehicle. Animals underwent scanning 2 h after radioligand administration. The striatum was identified by superimposition of [ 123 I]FP-CIT scans with bone metabolism and perfusion scans obtained with 99m Tc-DPD and 99m Tc-tetrofosmin, respectively. As these tracers do not pass the blood-brain barrier, their distribution permits the identification of extracerebral anatomical landmarks such as the orbitae and the harderian glands. The cerebellum was identified by superimposing [ 123 I]FP-CIT scans with images of brain perfusion obtained with 99m Tc-HMPAO. Methylphenidate-treated animals and vehicle-treated animals yielded striatal equilibrium ratios (V '' 3 ) of 0.24±0.26 (mean ± SD) and 1.09±0.42, respectively (ttest, two-tailed, p '' 3 values amounted to 0.05±0.28 (methylphenidate) and 0.3±0.39 (saline, p=0.176). This first in vivo study of rat dopamine transporter binding after pre-treatment with methylphenidate showed a mean reduction of 78% in striatal [ 123 I]FP-CIT accumulation. The results can be interpreted in terms of a pharmacological blockade in the rat striatum and show that in vivo quantitation of dopamine transporter binding is feasible with [ 123 I]FP-CIT and the TierSPECT. This may be of future relevance for in vivo investigations on rat models of attention deficit/hyperactivity disorder. Furthermore, our findings suggest that investigations in other animal models, e.g. of Parkinson's and Huntington's disease, may be feasible using SPECT radioligands and small animal imaging systems. (orig.)

In vivo assessment of [11C]MRB as a prospective PET ligand for imaging the norepinephrine transporter

International Nuclear Information System (INIS)

Severance, Alin J.; Milak, Matthew S.; Dileep Kumar, J.S.; Arango, Victoria; Parsey, Ramin V.; Prabhakaran, Jaya; Majo, Vattoly J.; Simpson, Norman R.; Van Heertum, Ronald L.; Mann, J.J.

2007-01-01

Antagonism of norepinephrine reuptake is now an important pharmacological strategy in the treatment of anxiety and depressive disorders, and many antidepressants have substantial potential occupancy of the norepinephrine transporter (NET) at recommended dosages. Despite the importance of understanding this transporter's role in psychiatric disease and treatment, a suitable radioligand for studying NET has been slow to emerge. (S,S)-Methylreboxetine (MRB) is among the more promising ligands recently adapted for positron emission tomography (PET), and the present study aimed to evaluate its potential for use in higher primates. Affinities for various brain targets were determined in vitro. PET studies were conducted in baboon under both test-retest and blocking conditions using 1 mg/kg nisoxetine. MRB has sixfold higher affinity for NET than the serotonin transporter, and negligible affinity for other sites. PET studies in baboons showed little regional heterogeneity in binding and were minimally affected by pretreatment with the NET antagonist nisoxetine. Despite improvement over previous ligands for imaging NET in vivo, the low signal to noise ratio indicates [ 11 C]MRB lacks sensitivity and reliability as a PET radiotracer in humans. (orig.)

The dopamine transporter protein gene (SLC6A3): Primary linage mapping and linkage studies in Tourette syndrome

Energy Technology Data Exchange (ETDEWEB)

Gelernter, J.; Kruger, S.D.; Pakstis, A.J. [Yale Univ., New Haven, CT (United States)]|[West Haven Veterans Affairs Medical Center, CT (United States)] [and others

1995-12-10

The dopamine transporter, the molecule responsible for presynaptic reuptake of dopamine and a major site of action of psychostimulant drugs, including cocaine, is encoded by locus SLC6A3 (alias DAT1). The protein`s actions and DAT`s specific localization to dopaminergic neurons make it a candidate gene for several psychiatric illnesses. SLC6A3 has been mapped to distal chromosome 5p, using physical methods. Genetic linkage methods were used to place SLC6A3 in the genetic linkage map. Four extended pedigrees (one of which overlaps with CEPH) were typed. Linkage with Tourette syndrome (TS) was also examined. SLC6A3 showed close linkage with several markers previously mapped to distal chromosome 5p, including D5S11 (Z{sub max} = 16.0, {theta}{sub M} = {theta}{sub F} = 0.03, results from four families) and D5S678 (Z{sub max} = 7.84, {theta}{sub M} = {theta}{sub F} = 0, results from two families). Observed crossovers established that SLC6A3 is a distal marker close to D5S10 and D5S678, but these three distal markers could not be ordered. Linkage between TS and SLC6A3 could be excluded independently in two branches of a large kindred segregating TS; the lod score in a third family was also negative, but not significant. Cumulative results show a lod score of -6.2 at {theta} = 0 and of -3.9 at {theta} = 0.05 (dominant model, narrow disease definition). SLC6A3 thus maps to distal chromosome 5p by linkage analysis, in agreement with previous physical mapping data. A mutation at SLC6A3 is not causative for TS in the two large families that generated significant negative lod scores (if the parameters of our analyses were correct) and is unlikely to be causative in the family that generated a negative lod score that did not reach significance. These results do not exclude a role for the dopamine transporter in influencing risk for TS in combination with other loci. 23 refs., 1 fig., 2 tabs.

Frontal-subcortical circuits in obsessive-compulsive disorder: role of the dopamine D1 receptor

International Nuclear Information System (INIS)

Olver, J.S.; Reutens, D.C.; Maruff, P.; Burrows, G.D.; Norman, T.R.; Ellen, S.R.; Pantelis, C.; Tochon-Danguy, H.; Ackermann, U.; Stekelenberg, N.

2000-01-01

Full text: Obsessive-Compulsive Disorder (OCD) is an anxiety disorder which is increasingly being recognised as a neurobiological disorder. While serotonergic mechanisms have been proposed, the major competing theory in the pathophysiology of OCD involves the neurotransmitter dopamine. The Dopamine D1 receptor is implicated in OCD following the finding of specific spatial working memory abnormalities in a series of neuropsychological studies. Spatial working memory is known to depend on the integrity of D1 receptor function in the Dorso-lateral Prefrontal Cortex (DLPFC) of primates. This study aims to examine the role of dopamine in patients with OCD and in particular to test the hypothesis that there is an upregulation of dopamine D1 receptors in the DLPFC which correlates with spatial working memory deficits in OCD. Three OCD patients and three normal controls underwent Positron Emission Tomography (PET) following intravenous injection of the D1 antagonist PET ligand SCH23390. Reconstructed PET images were co registered with subject Magnetic Resonance Images (MRI) and regions of interest drawn manually. We will present the analysis of the Binding Potentials of SCH23390 in the regions of interest of the first three OCD patients and compare them with three normal control patients. In conclusion Dopamine-Serotonergic interactions are involved in the pathophysiology of OCD. Copyright (2000) The Australian and New Zealand Society of Nuclear Medicine Inc

Species differences in ligand specificity of auxin-controlled elongation and auxin transport: comparing Zea and Vigna

Science.gov (United States)

Zhao, Hu; Hertel, Rainer; Ishikawa, Hideo; Evans, Michael L.

2002-01-01

The plant hormone auxin affects cell elongation in both roots and shoots. In roots, the predominant action of auxin is to inhibit cell elongation while in shoots auxin, at normal physiological levels, stimulates elongation. The question of whether the primary receptor for auxin is the same in roots and shoots has not been resolved. In addition to its action on cell elongation in roots and shoots, auxin is transported in a polar fashion in both organs. Although auxin transport is well characterized in both roots and shoots, there is relatively little information on the connection, if any, between auxin transport and its action on elongation. In particular, it is not clear whether the protein mediating polar auxin movement is separate from the protein mediating auxin action on cell elongation or whether these two processes might be mediated by one and the same receptor. We examined the identity of the auxin growth receptor in roots and shoots by comparing the response of roots and shoots of the grass Zea mays L. and the legume Vigna mungo L. to indole-3-acetic acid, 2-naphthoxyacetic acid, 4,6-dichloroindoleacetic acid, and 4,7-dichloroindoleacetic acid. We also studied whether or not a single protein might mediate both auxin transport and auxin action by comparing the polar transport of indole-3-acetic acid and 2-naphthoxyacetic acid through segments from Vigna hypocotyls and maize coleoptiles. For all of the assays performed (root elongation, shoot elongation, and polar transport) the action and transport of the auxin derivatives was much greater in the dicots than in the grass species. The preservation of ligand specificity between roots and shoots and the parallels in ligand specificity between auxin transport and auxin action on growth are consistent with the hypothesis that the auxin receptor is the same in roots and shoots and that this protein may mediate auxin efflux as well as auxin action in both organ types.

Carbon-11-labelling of a novel, trishomocubane-derived, high affinity and selectivity DAT ligand

International Nuclear Information System (INIS)

Dolle, F.; Le Helleix, St.; Peyronneau, M.A.; Saba, W.; Tournier, N.; Valette, H.; Banister, S.; Kassiou, M.

2011-01-01

Complete text of publication follows: Objectives: Parkinson's disease, schizophrenia, attention deficit disorder and drug abuse are related to abnormalities within the brain's dopaminergic system. The neuronal dopamine transporter (DAT) plays a key role in regulating the synaptic concentration of dopamine and thus dopamine neurotransmission in the brain. Since the DAT can be considered as a marker of the integrity and number of the presynaptic striatal dopamine-producing neurons, considerable efforts have been spent in recent years on the design and development of DAT-selective radioligands for use in Positron Emission Tomography (PET) studies. Notably, the tropane PE2I and its fluorinated analogue LBT-999 were identified as having high affinity and selectivity for the DAT over the norepinephrine transporter (NET) and the serotonin transporter (SERT). Besides tropanes, only a few bicyclic frameworks, e.g. bicyclo[2.2.2]octanes, have delivered compounds with high affinity for the DAT. Recently, novel poly-carbocyclic DAT ligands with selectivity over the NET and the SERT were reported. The lead compound of this series (1, N-methyl-N-(3-fluoro) benzyl-pentacyclo[5.4.0.0 2, 6 .0 3, 10 .0 5, 9 ] undec-8-ylamine, Ki = 1.2 nM, ≥ 8300-fold selectivity over NET and SERT) was selected as a potential candidate for imaging the DAT with PET and isotopically labelled with carbon-11 using [ 11 C]methyl triflate. Methods: The trishomocubane derivatives 1 (reference) and 2 (precursor for labelling with carbon-11) were prepared from commercially available Cookson's diketone in 6 and 7 steps, respectively. Carbon-11 labelling of 1 was performed using a TRACERLab FX-C Pro synthesizer (GEMS) and comprises (1) trapping at -10 C of [ 11 C]MeOTf in acetone (0.4 mL) containing the nor-derivative 2 (0.6-0.9 mg, free base) and aq. 3N NaOH (8 μL); (2) heating at 110 C for 2 min; (3) concentration to dryness and taking up the residue in 1.0 mL of the HPLC mobile phase; (4) purification

Dopamine transporter gene polymorphism and psychiatric symptoms seen in schizophrenic patients at their first episode

Energy Technology Data Exchange (ETDEWEB)

Inada, Toshiya; Sugita, Tetsuyoshi; Dobashi, Izumi [National Institute of Mental Health, Chiba (Japan)] [and others

1996-07-26

To investigate the possible role of the dopamine transporter (DAT) gene in determining the phenotype in human subjects, allele frequencies for the 40-bp variable number of tandem repeats (VNTR) polymorphism at this site were compared between 117 Japanese normal controls and 118 schizophrenic patients, including six subgroups: early-onset, those with a family history, and those suffering from one of the following psychiatric symptoms at their first episode: delusion and hallucination; disorganization; bizarre behavior; and negative symptoms. No significant differences were observed between the group as a whole or any subgroup of schizophrenic patients and controls. The results indicate that VNTR polymorphism in the DAT gene is unlikely to be a major contributor to any of the psychiatric parameters examined in the present population of schizophrenic subjects. 12 refs., 1 fig., 2 tabs.

Excessive D1 Dopamine Receptor Activation in the Dorsal Striatum Promotes Autistic-Like Behaviors.

Science.gov (United States)

Lee, Yunjin; Kim, Hannah; Kim, Ji-Eun; Park, Jin-Young; Choi, Juli; Lee, Jung-Eun; Lee, Eun-Hwa; Han, Pyung-Lim

2018-07-01

The dopamine system has been characterized in motor function, goal-directed behaviors, and rewards. Recent studies recognize various dopamine system genes as being associated with autism spectrum disorder (ASD). However, how dopamine system dysfunction induces ASD pathophysiology remains unknown. In the present study, we demonstrated that mice with increased dopamine functions in the dorsal striatum via the suppression of dopamine transporter expression in substantia nigra neurons or the optogenetic stimulation of the nigro-striatal circuitry exhibited sociability deficits and repetitive behaviors relevant to ASD pathology in animal models, while these behavioral changes were blocked by a D1 receptor antagonist. Pharmacological activation of D1 dopamine receptors in normal mice or the genetic knockout (KO) of D2 dopamine receptors also produced typical autistic-like behaviors. Moreover, the siRNA-mediated inhibition of D2 dopamine receptors in the dorsal striatum was sufficient to replicate autistic-like phenotypes in D2 KO mice. Intervention of D1 dopamine receptor functions or the signaling pathways-related D1 receptors in D2 KO mice produced anti-autistic effects. Together, our results indicate that increased dopamine function in the dorsal striatum promotes autistic-like behaviors and that the dorsal striatum is the neural correlate of ASD core symptoms.

Effects of fluoxetine treatment on striatal dopamine transporter binding and cerebrospinal fluid insulin-like growth factor-1 in children with autism.

Science.gov (United States)

Makkonen, I; Kokki, H; Kuikka, J; Turpeinen, U; Riikonen, R

2011-10-01

A positive effect of fluoxetine has been shown in some children with autism. The present study was undertaken to correlate striatal dopamine transporter (DAT) binding and cerebrospinal fluid insulin-like growth factor-1 (CSF-IGF-1) with clinical response in autistic children (n=13, age 5-16 years) after a 6-month fluoxetine treatment. Good clinical responders (n=6) had a decrease (p=0.031) in DAT binding as assessed using single-photon emission computed tomography with [123I]-nor-β-CIT, whereas poor responders had a trend to an increase. An increase in CSF-IGF-1 (p=0.003) was detected after the treatment period, but no correlation between the clinical response and CSF-IGF-1 was found. In conclusion, fluoxetine decreases DAT binding indicating alleviation of the hyperdopaminergic state and increases CSF-IGF-1 concentration, which may also have a neuroprotective effect against dopamine-induced neurotoxicity in autistic children. © Georg Thieme Verlag KG Stuttgart · New York.

Quantitation of dopamine transporter blockade by methylphenidate: first in vivo investigation using [{sup 123}I]FP-CIT and a dedicated small animal SPECT

Energy Technology Data Exchange (ETDEWEB)

Nikolaus, Susanne; Wirrwar, Andreas; Antke, Christina; Arkian, Shahram; Mueller, Hans-Wilhelm; Larisch, Rolf [Heinrich-Heine University, Clinic of Nuclear Medicine, Duesseldorf (Germany); Schramm, Nils [Research Center Juelich, Central Laboratory for Electronics, Juelich (Germany)

2005-03-01

The aim of this study was to investigate the feasibility of assessing dopamine transporter binding after treatment with methylphenidate in the rat using a recently developed high-resolution small animal single-photon emission computed tomograph (TierSPECT) and [{sup 123}I]FP-CIT. [{sup 123}I]FP-CIT was administered intravenously 1 h after intraperitoneal injection of methylphenidate (10 mg/kg) or vehicle. Animals underwent scanning 2 h after radioligand administration. The striatum was identified by superimposition of [{sup 123}I]FP-CIT scans with bone metabolism and perfusion scans obtained with {sup 99m}Tc-DPD and {sup 99m}Tc-tetrofosmin, respectively. As these tracers do not pass the blood-brain barrier, their distribution permits the identification of extracerebral anatomical landmarks such as the orbitae and the harderian glands. The cerebellum was identified by superimposing [{sup 123}I]FP-CIT scans with images of brain perfusion obtained with {sup 99m}Tc-HMPAO. Methylphenidate-treated animals and vehicle-treated animals yielded striatal equilibrium ratios (V''{sub 3}) of 0.24{+-}0.26 (mean {+-} SD) and 1.09{+-}0.42, respectively (ttest, two-tailed, p<0.0001). Cortical V''{sub 3} values amounted to 0.05{+-}0.28 (methylphenidate) and 0.3{+-}0.39 (saline, p=0.176). This first in vivo study of rat dopamine transporter binding after pre-treatment with methylphenidate showed a mean reduction of 78% in striatal [{sup 123}I]FP-CIT accumulation. The results can be interpreted in terms of a pharmacological blockade in the rat striatum and show that in vivo quantitation of dopamine transporter binding is feasible with [{sup 123}I]FP-CIT and the TierSPECT. This may be of future relevance for in vivo investigations on rat models of attention deficit/hyperactivity disorder. Furthermore, our findings suggest that investigations in other animal models, e.g. of Parkinson's and Huntington's disease, may be feasible using SPECT radioligands and

Dopamine alleviates nutrient deficiency-induced stress in Malus hupehensis.

Science.gov (United States)

Liang, Bowen; Li, Cuiying; Ma, Changqing; Wei, Zhiwei; Wang, Qian; Huang, Dong; Chen, Qi; Li, Chao; Ma, Fengwang

2017-10-01

Dopamine mediates many physiological processes in plants. We investigated its role in regulating growth, root system architecture, nutrient uptake, and responses to nutrient deficiencies in Malus hupehensis Rehd. Under a nutrient deficiency, plants showed significant reductions in growth, chlorophyll concentrations, and net photosynthesis, along with disruptions in nutrient uptake, transport, and distribution. However, pretreatment with 100 μM dopamine markedly alleviated such inhibitions. Supplementation with that compound enabled plants to maintain their photosynthetic capacity and development of the root system while promoting the uptake of N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, and B, altering the way in which those nutrients were partitioned throughout the plant. The addition of dopamine up-regulated genes for antioxidant enzymes involved in the ascorbate-glutathione cycle (MdcAPX, MdcGR, MdMDHAR, MdDHAR-1, and MdDHAR-2) but down-regulated genes for senescence (SAG12, PAO, and MdHXK). These results indicate that exogenous dopamine has an important antioxidant and anti-senescence effect that might be helpful for improving nutrient uptake. Our findings demonstrate that dopamine offers new opportunities for its use in agriculture, especially when addressing the problem of nutrient deficiencies. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Ligand-based transport resonances of single-molecule magnet spin filters: Suppression of the Coulomb blockade and determination of the orientation of the magnetic easy axis

OpenAIRE

Renani, Fatemeh Rostamzadeh; Kirczenow, George

2011-01-01

We investigate single molecule magnet transistors (SMMTs) with ligands that support transport resonances. We find the lowest unoccupied molecular orbitals of Mn12-benzoate SMMs (with and without thiol or methyl-sulfide termination) to be on ligands, the highest occupied molecular orbitals being on the Mn12 magnetic core. We predict gate controlled switching between Coulomb blockade and coherent resonant tunneling in SMMTs based on such SMMs, strong spin filtering by the SMM in both transport ...

Amphetamine Elicits Opposing Actions on Readily Releasable and Reserve Pools for Dopamine

Science.gov (United States)

Covey, Dan P.; Juliano, Steven A.; Garris, Paul A.

2013-01-01

Amphetamine, a highly addictive drug with therapeutic efficacy, exerts paradoxical effects on the fundamental communication modes employed by dopamine neurons in modulating behavior. While amphetamine elevates tonic dopamine signaling by depleting vesicular stores and driving non-exocytotic release through reverse transport, this psychostimulant also activates phasic dopamine signaling by up-regulating vesicular dopamine release. We hypothesized that these seemingly incongruent effects arise from amphetamine depleting the reserve pool and enhancing the readily releasable pool. This novel hypothesis was tested using in vivo voltammetry and stimulus trains of varying duration to access different vesicular stores. We show that amphetamine actions are stimulus dependent in the dorsal striatum. Specifically, amphetamine up-regulated vesicular dopamine release elicited by a short-duration train, which interrogates the readily releasable pool, but depleted release elicited by a long-duration train, which interrogates the reserve pool. These opposing actions of vesicular dopamine release were associated with concurrent increases in tonic and phasic dopamine responses. A link between vesicular depletion and tonic signaling was supported by results obtained for amphetamine in the ventral striatum and cocaine in both striatal sub-regions, which demonstrated augmented vesicular release and phasic signals only. We submit that amphetamine differentially targeting dopamine stores reconciles the paradoxical activation of tonic and phasic dopamine signaling. Overall, these results further highlight the unique and region-distinct cellular mechanisms of amphetamine and may have important implications for its addictive and therapeutic properties. PMID:23671560

No difference in striatal dopamine transporter availability between active smokers, ex-smokers and non-smokers using (123I)FP-CIT (DaTSCAN) and SPECT

DEFF Research Database (Denmark)

Thomsen, G; Knudsen, Gitte Moos; Jensen, PS

2013-01-01

BACKGROUND: Mesolimbic and nigrostriatal dopaminergic pathways play important roles in both the rewarding and conditioning effects of drugs. The dopamine transporter (DAT) is of central importance in regulating dopaminergic neurotransmission and in particular in activating the striatal D2-like...... receptors. Molecular imaging studies of the relationship between DAT availability/dopamine synthesis capacity and active cigarette smoking have shown conflicting results. Through the collaboration between 13 SPECT centres located in 10 different European countries, a database of FP-CIT-binding in healthy...... controls was established. We used the database to test the hypothesis that striatal DAT availability is changed in active smokers compared to non-smokers and ex-smokers. METHODS: A total of 129 healthy volunteers were included. Subjects were divided into three categories according to past and present...

Functional Connectome Analysis of Dopamine Neuron Glutamatergic Connections in Forebrain Regions.

Science.gov (United States)

Mingote, Susana; Chuhma, Nao; Kusnoor, Sheila V; Field, Bianca; Deutch, Ariel Y; Rayport, Stephen

2015-12-09

In the ventral tegmental area (VTA), a subpopulation of dopamine neurons express vesicular glutamate transporter 2 and make glutamatergic connections to nucleus accumbens (NAc) and olfactory tubercle (OT) neurons. However, their glutamatergic connections across the forebrain have not been explored systematically. To visualize dopamine neuron forebrain projections and to enable photostimulation of their axons independent of transmitter status, we virally transfected VTA neurons with channelrhodopsin-2 fused to enhanced yellow fluorescent protein (ChR2-EYFP) and used DAT(IREScre) mice to restrict expression to dopamine neurons. ChR2-EYFP-expressing neurons almost invariably stained for tyrosine hydroxylase, identifying them as dopaminergic. Dopamine neuron axons visualized by ChR2-EYFP fluorescence projected most densely to the striatum, moderately to the amygdala and entorhinal cortex (ERC), sparsely to prefrontal and cingulate cortices, and rarely to the hippocampus. Guided by ChR2-EYFP fluorescence, we recorded systematically from putative principal neurons in target areas and determined the incidence and strength of glutamatergic connections by activating all dopamine neuron terminals impinging on recorded neurons with wide-field photostimulation. This revealed strong glutamatergic connections in the NAc, OT, and ERC; moderate strength connections in the central amygdala; and weak connections in the cingulate cortex. No glutamatergic connections were found in the dorsal striatum, hippocampus, basolateral amygdala, or prefrontal cortex. These results indicate that VTA dopamine neurons elicit widespread, but regionally distinct, glutamatergic signals in the forebrain and begin to define the dopamine neuron excitatory functional connectome. Dopamine neurons are important for the control of motivated behavior and are involved in the pathophysiology of several major neuropsychiatric disorders. Recent studies have shown that some ventral midbrain dopamine neurons are

Reduced dopamine transporter binding predates impulse control disorders in Parkinson's disease

NARCIS (Netherlands)

Vriend, Chris; Nordbeck, Anna H; Booij, Jan; van der Werf, Ysbrand D; Pattij, Tommy; Voorn, Pieter; Raijmakers, Pieter; Foncke, Elisabeth M J; van de Giessen, Elsmarieke; Berendse, Henk W; van den Heuvel, Odile A

Impulse control disorders (ICD) are relatively common in Parkinson's disease (PD) and generally are regarded as adverse effects of dopamine replacement therapy, although certain demographic and clinical risk factors are also involved. Previous single-photon emission computed tomography (SPECT)

Reduced Dopamine Transporter Binding Predates Impulse Control Disorders in Parkinson's Disease

NARCIS (Netherlands)

Vriend, C.; Nordbeck, A.H.; Booij, J.; van der Werf, Y.D.; Pattij, T.; Voorn, P.; Raijmakers, P.; Foncke, E.M.J.; van der Giessen, E.; Berendse, H.W.; van den Heuvel, O.A.

2014-01-01

Impulse control disorders (ICD) are relatively common in Parkinson's disease (PD) and generally are regarded as adverse effects of dopamine replacement therapy, although certain demographic and clinical risk factors are also involved. Previous single-photon emission computed tomography (SPECT)

Hypoinsulinemia regulates amphetamine-induced reverse transport of dopamine.

Directory of Open Access Journals (Sweden)

Jason M Williams

2007-10-01

Full Text Available The behavioral effects of psychomotor stimulants such as amphetamine (AMPH arise from their ability to elicit increases in extracellular dopamine (DA. These AMPH-induced increases are achieved by DA transporter (DAT-mediated transmitter efflux. Recently, we have shown that AMPH self-administration is reduced in rats that have been depleted of insulin with the diabetogenic agent streptozotocin (STZ. In vitro studies suggest that hypoinsulinemia may regulate the actions of AMPH by inhibiting the insulin downstream effectors phosphotidylinositol 3-kinase (PI3K and protein kinase B (PKB, or Akt, which we have previously shown are able to fine-tune DAT cell-surface expression. Here, we demonstrate that striatal Akt function, as well as DAT cell-surface expression, are significantly reduced by STZ. In addition, our data show that the release of DA, determined by high-speed chronoamperometry (HSCA in the striatum, in response to AMPH, is severely impaired in these insulin-deficient rats. Importantly, selective inhibition of PI3K with LY294002 within the striatum results in a profound reduction in the subsequent potential for AMPH to evoke DA efflux. Consistent with our biochemical and in vivo electrochemical data, findings from functional magnetic resonance imaging experiments reveal that the ability of AMPH to elicit positive blood oxygen level-dependent signal changes in the striatum is significantly blunted in STZ-treated rats. Finally, local infusion of insulin into the striatum of STZ-treated animals significantly recovers the ability of AMPH to stimulate DA release as measured by high-speed chronoamperometry. The present studies establish that PI3K signaling regulates the neurochemical actions of AMPH-like psychomotor stimulants. These data suggest that insulin signaling pathways may represent a novel mechanism for regulating DA transmission, one which may be targeted for the treatment of AMPH abuse and potentially other dopaminergic disorders.

Allelic association of the D2 dopamine receptor gene with receptor-binding characteristics in alcoholism

International Nuclear Information System (INIS)

Noble, E.P.; Blum, K.; Ritchie, T.; Montgomery, A.; Sheridan, P.J.

1991-01-01

The allelic association of the human D2 dopamine receptor gene with the binding characteristics of the D2 dopamine receptor was determined in 66 brains of alcoholic and non-alcoholic subjects. In a blinded experiment, DNA from the cerebral cortex was treated with the restriction endonuclease Taql and probed with a 1.5-kilobase (kb) digest of a clone (lambda hD2G1) of the human D2 dopamine receptor gene. The binding characteristics (Kd [binding affinity] and Bmax [number of binding sites]) of the D2 dopamine receptor were determined in the caudate nuclei of these brains using tritiated spiperone as the ligand. The adjusted Kd was significantly lower in alcoholic than in nonalcoholic subjects. In subjects with the A1 allele, in whom a high association with alcoholism was found, the Bmax was significantly reduced compared with the Bmax of subjects with the A2 allele. Moreover, a progressively reduced Bmax was found in subjects with A2/A2, A1/A2, and A1/A1 alleles, with subjects with A2/A2 having the highest mean values, and subjects with A1/A1, the lowest. The polymorphic pattern of the D2 dopamine receptor gene and its differential expression of receptors suggests the involvement of the dopaminergic system in conferring susceptibility to at least one subtype of severe alcoholism

Effects of Mutations and Ligands on the Thermostability of the l-Arginine/Agmatine Antiporter AdiC and Deduced Insights into Ligand-Binding of Human l-Type Amino Acid Transporters

Directory of Open Access Journals (Sweden)

Hüseyin Ilgü

2018-03-01

Full Text Available The l-arginine/agmatine transporter AdiC is a prokaryotic member of the SLC7 family, which enables pathogenic enterobacteria to survive the extremely acidic gastric environment. Wild-type AdiC from Escherichia coli, as well as its previously reported point mutants N22A and S26A, were overexpressed homologously and purified to homogeneity. A size-exclusion chromatography-based thermostability assay was used to determine the melting temperatures (Tms of the purified AdiC variants in the absence and presence of the selected ligands l-arginine (Arg, agmatine, l-arginine methyl ester, and l-arginine amide. The resulting Tms indicated stabilization of AdiC variants upon ligand binding, in which Tms and ligand binding affinities correlated positively. Considering results from this and previous studies, we revisited the role of AdiC residue S26 in Arg binding and proposed interactions of the α-carboxylate group of Arg exclusively with amide groups of the AdiC backbone. In the context of substrate binding in the human SLC7 family member l-type amino acid transporter-1 (LAT1; SLC7A5, an analogous role of S66 in LAT1 to S26 in AdiC is discussed based on homology modeling and amino acid sequence analysis. Finally, we propose a binding mechanism for l-amino acid substrates to LATs from the SLC7 family.

Dopamine dynamics and cocaine sensitivity differ between striosome and matrix compartments of the striatum

Science.gov (United States)

Salinas, Armando G.; Davis, Margaret I.; Lovinger, David M.; Mateo, Yolanda

2016-01-01

The striatum is typically classified according to its major output pathways, which consist of dopamine D1 and D2 receptor-expressing neurons. The striatum is also divided into striosome and matrix compartments, based on the differential expression of a number of proteins, including the mu opioid receptor, dopamine transporter (DAT), and Nr4a1 (nuclear receptor subfamily 4, group A, member 1). Numerous functional differences between the striosome and matrix compartments are implicated in dopamine-related neurological disorders including Parkinson’s disease and addiction. Using Nr4a1-eGFP mice, we provide evidence that electrically evoked dopamine release differs between the striosome and matrix compartments in a regionally-distinct manner. We further demonstrate that this difference is not due to differences in inhibition of dopamine release by dopamine autoreceptors or nicotinic acetylcholine receptors. Furthermore, cocaine enhanced extracellular dopamine in striosomes to a greater degree than in the matrix and concomitantly inhibited dopamine uptake in the matrix to a greater degree than in striosomes. Importantly, these compartment differences in cocaine sensitivity were limited to the dorsal striatum. These findings demonstrate a level of exquisite microanatomical regulation of dopamine by the DAT in striosomes relative to the matrix. PMID:27036891

NK3 Receptors mediate an increase in firing rate of midbrain dopamine neurons of the rat and the guinea pig

NARCIS (Netherlands)

Werkman, T.R.; McCreary, A.C.; Kruse, C.G.; Wadman, W.J.

2011-01-01

This in vitro study investigates and compares the effects of NK3 receptor ligands on the firing rate of rat and guinea pig midbrain dopamine neurons. The findings are discussed in the light of choosing suitable animal models for investigating pharmacological properties of NK3 receptor antagonists,

Photoaffinity labeling of the dopamine reuptake carrier protein with 3-azido 3H GBR-12935

International Nuclear Information System (INIS)

Berger, S.P.; Martenson, R.E.; Laing, P.; Thurkauf, A.; Decosta, B.; Rice, K.C.; Paul, S.M.

1991-01-01

A high affinity tritiated azido-diphenylpiperazine derivative, 3-azido 3 H GBR-12935, was synthesized as a potential photoaffinity probe of the dopamine transporter. Initially, the reversible binding of 3-azido 3 H GBR-12935 to crude synaptosomal membranes from the rat striatum was characterized. Specific binding was sodium dependent and inhibited by a variety of drugs that are known to potently inhibit dopamine uptake. Other neurotransmitter uptake inhibitors, as well as cis-flupenthixol, a potent inhibitor of 3 H GBR-12935 binding to piperazine binding sites, failed to inhibit specific binding at concentrations of less than or equal to 10 microM. A good correlation was observed between the relative potencies of these drugs in inhibiting dopamine uptake into synaptosomes and in inhibiting specific 3-azido 3 H GBR-12935 binding to rat striatal membranes. These data suggest that 3-azido 3 H GBR-12935, like other diphenylpiperazines such as 3 H GBR-12935 and 3 H GBR-12909, binds primarily to the dopamine transporter under defined assay conditions. After UV photolysis of crude synaptosomal membranes preincubated with 3-azido 3 H GBR-12935 (1-2 nM), a single radiolabeled polypeptide with an apparent molecular mass of 80 kDa was observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Photoincorporation of 3-azido 3 H GBR-12935 into this polypeptide was inhibited selectively by compounds that inhibit the uptake of dopamine and was completely dependent on the presence of Na+. No photolabeled proteins were observed when cerebellar membranes were substituted for striatal membranes. Essentially complete adsorption of the radiolabeled 80-kDa polypeptide to wheat germ agglutinin and elution with N-acetyl-D-glucosamine strongly suggest that the dopamine transporter polypeptide photolabeled by 3-azido 3 H GBR-12935 is glycosylated

[O-methyl-{sup 11}C]{beta}-CIT-FP, a potential radioligand for quantitation of the dopamine transporter: Preparation, autoradiography, metabolite studies, and positron emission tomography examinations

Energy Technology Data Exchange (ETDEWEB)

Lundkvist, Camilla; Halldin, Christer; Swahn, Carl-Gunnar; Hall, Haakan; Karlsson, Per; Nakashima, Yoshifumi; Wang, Shaoyin; Milius, Richard A.; Neumeyer, John L.; Farde, Lars

1995-10-01

{beta}-CIT-FP [N-(3-fluoropropyl)-2{beta}-carbomethoxy-3{beta}-(4-iodophenyl)nortropane] is a cocaine analogue with a high affinity for the dopamine transporter. [O-methyl-{sup 11}C]{beta}-CIT-FP ([{sup 11}C]{beta}-CIT-FP) was prepared byO -alkylation of the free acid with [{sup 11}C]methyl iodide. The total radiochemical yield of [{sup 11}C]{beta}-CIT-FP was 50 to 60% with an overall synthesis time of 30 min. The radiochemical purity was >99%, and the specific radioactivity at time of injection was about 37 GBq/{mu}mol (1000 Ci/mmol). Autoradiographic examination of [{sup 11}C]{beta}-CIT-FP binding in human brain postmortem demonstrated specific binding in the caudate nucleus and putamen. Positron emission tomography (PET) examination of [{sup 11}C]{beta}-CIT-FP in a Cynomolgus monkey demonstrated accumulation in the striatum with a striatum-to-cerebellum ratio of about 8 after 60 min. Equilibrium in the striatum was attained within 70 to 90 min. The radioactivity ratios of thalamus/cerebellum and neocortex/cerebellum were about 2 and 1.5, respectively. In a displacement experiment, radioactivity in the striatum but not in the cerebellum was reduced after injection of {beta}-CIT, indicating that striatal radioactivity following injection of [{sup 11}C]{beta}-CIT-FP is associated with dopamine transporter sites and that the binding is reversible. The fraction of the total radioactivity in plasma representing [{sup 11}C]{beta}-CIT-FP determined by high-performance liquid chromatography (HPLC) was 84% at 15 min and 50% at 95 min. [{sup 11}C]{beta}-CIT-FP should be a useful PET radioligand for the quantitation of dopamine transporters in the human brain in vivo.

Towards trans-diagnostic mechanisms in psychiatry: neurobehavioral profile of rats with a loss-of-function point mutation in the dopamine transporter gene

Directory of Open Access Journals (Sweden)

Valentina Vengeliene

2017-04-01

Full Text Available The research domain criteria (RDoC matrix has been developed to reorient psychiatric research towards measurable behavioral dimensions and underlying mechanisms. Here, we used a new genetic rat model with a loss-of-function point mutation in the dopamine transporter (DAT gene (Slc6a3_N157K to systematically study the RDoC matrix. First, we examined the impact of the Slc6a3_N157K mutation on monoaminergic signaling. We then performed behavioral tests representing each of the five RDoC domains: negative and positive valence systems, cognitive, social and arousal/regulatory systems. The use of RDoC may be particularly helpful for drug development. We studied the effects of a novel pharmacological approach metabotropic glutamate receptor mGluR2/3 antagonism, in DAT mutants in a comparative way with standard medications. Loss of DAT functionality in mutant rats not only elevated subcortical extracellular dopamine concentration but also altered the balance of monoaminergic transmission. DAT mutant rats showed deficits in all five RDoC domains. Thus, mutant rats failed to show conditioned fear responses, were anhedonic, were unable to learn stimulus-reward associations, showed impaired cognition and social behavior, and were hyperactive. Hyperactivity in mutant rats was reduced by amphetamine and atomoxetine, which are well-established medications to reduce hyperactivity in humans. The mGluR2/3 antagonist LY341495 also normalized hyperactivity in DAT mutant rats without affecting extracellular dopamine levels. We systematically characterized an altered dopamine system within the context of the RDoC matrix and studied mGluR2/3 antagonism as a new pharmacological strategy to treat mental disorders with underlying subcortical dopaminergic hyperactivity.

Characterisation of [11C]PR04.MZ in Papio anubis baboon: A selective high-affinity radioligand for quantitative imaging of the dopamine transporter

Energy Technology Data Exchange (ETDEWEB)

Riss P. J.; Fowler J.; Riss, P.J.; Hooker, J.M.; Shea, C.; Xu, Y.; Carter, P.; Warner, D.; Ferrari V.; Kim, S.W.; Aigbirhio, F.I.; Fowler, J.S.; Roesch, F.

2011-10-25

N-(4-fluorobut-2-yn-1-yl)-2{beta}-carbomethoxy-3{beta}-(4{prime}-tolyl)nortropane (PR04.MZ, 1) is a PET radioligand for the non-invasive exploration of the function of the cerebral dopamine transporter (DAT). A reliable automated process for routine production of the carbon-11 labelled analogue [{sup 11}C]PR04.MZ ([{sup 11}C]-1) has been developed using GMP compliant equipment. An adult female Papioanubis baboon was studied using a test-retest protocol with [{sup 11}C]-1 in order to assess test-retest reliability, metabolism and CNS distribution profile of the tracer in non-human primates. Blood sampling was performed throughout the studies for determination of the free fraction in plasma (fP), plasma input functions and metabolic degradation of the radiotracer [{sup 11}C]-1. Time-activity curves were derived for the putamen, the caudate nucleus, the ventral striatum, the midbrain and the cerebellum. Distribution volumes (VT) and non-displaceable binding potentials (BPND) for various brain regions and the blood were obtained from kinetic modelling. [{sup 11}C]-1 shows promising results as aselective marker of the presynaptic dopamine transporter. With the reliable visualisation of the extra-striatal dopaminergic neurons and no indication on labelled metabolites, the tracer provides excellent potential for translation into man.

Lack of Association between a 3'UTR VNTR Polymorphism of Dopamine Transporter Gene (SLC6A3) and ADHD in a Brazilian Sample of Adult Patients

Science.gov (United States)

Aperecida da Silva, Maria; Cordeiro, Quirino; Louza, Mario; Vallada, Homero

2011-01-01

Objective: To investigate a possible association between a 3'UTR VNTR polymorphism of the dopamine transporter gene (SLC6A3) and ADHD in a Brazilian sample of adult patients. Method: Study Case-control with 102 ADHD adult outpatients ("DSM-IV" criteria) and 479 healthy controls. The primers' sequence used were: 3'UTR-Forward: 5' TGT GGT…

Insights into the Structure, Function, and Ligand Discovery of the Large Neutral Amino Acid Transporter 1, LAT1

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Natesh Singh

2018-04-01

Full Text Available The large neutral amino acid transporter 1 (LAT1, or SLC7A5 is a sodium- and pH-independent transporter, which supplies essential amino acids (e.g., leucine, phenylalanine to cells. It plays an important role at the Blood–Brain Barrier (BBB where it facilitates the transport of thyroid hormones, pharmaceuticals (e.g., l-DOPA, gabapentin, and metabolites into the brain. Moreover, its expression is highly upregulated in various types of human cancer that are characterized by an intense demand for amino acids for growth and proliferation. Therefore, LAT1 is believed to be an important drug target for cancer treatment. With the crystallization of the arginine/agmatine antiporter (AdiC from Escherichia Coli, numerous homology models of LAT1 have been built to elucidate the substrate binding site, ligand–transporter interaction, and structure–function relationship. The use of these models in combination with molecular docking and experimental testing has identified novel chemotypes of ligands of LAT1. Here, we highlight the structure, function, transport mechanism, and homology modeling of LAT1. Additionally, results from structure–function studies performed on LAT1 are addressed, which have enhanced our knowledge of the mechanism of substrate binding and translocation. This is followed by a discussion on ligand- and structure-based approaches, with an emphasis on elucidating the molecular basis of LAT1 inhibition. Finally, we provide an exhaustive summary of different LAT1 inhibitors that have been identified so far, including the recently discovered irreversible covalent inhibitors.

(/sup 76/Br)Bromolisuride: a new tool for quantitative in vivo imaging of D-2 dopamine receptors

Energy Technology Data Exchange (ETDEWEB)

Maziere, B; Loc' h, C; Stulzaft, O; Ottaviani, M; Comar, D; Maziere, M; Hantraye, P

1986-08-15

Bromolisuride, an ergoline derivative, was labeled with the positron emitter radionuclide, bromine 76. In vitro and in vivo binding and competition studies in rats demonstrated a high affinity (K/sub D/ = 0.3 nM) and a high specificity of this new radioligand for D-2 dopamine receptors. PET kinetic studies in baboons showed an accumulation of (/sup 76/Br)bromolisuride in the striatum which reached a maximum 30 min post-injection and which could be displaced by haloperidol. All these results indicated that this new ligand is certainly suitable for the non-invasive in vivo quantitative imaging of D-2 dopamine receptor sites in human brain. 20 refs.; 6 figs.; 1 table.

Structure of the Human Dopamine D3 Receptor in Complex with a D2/D3 Selective Antagonist

Energy Technology Data Exchange (ETDEWEB)

Chien, Ellen Y.T.; Liu, Wei; Zhao, Qiang; Katritch, Vsevolod; Han, Gye Won; Hanson, Michael A.; Shi, Lei; Newman, Amy Hauck; Javitch, Jonathan A.; Cherezov, Vadim; Stevens, Raymond C. (Cornell); (Scripps); (NIDA); (Columbia); (UCSD); (Receptos)

2010-11-30

Dopamine modulates movement, cognition, and emotion through activation of dopamine G protein-coupled receptors in the brain. The crystal structure of the human dopamine D3 receptor (D3R) in complex with the small molecule D2R/D3R-specific antagonist eticlopride reveals important features of the ligand binding pocket and extracellular loops. On the intracellular side of the receptor, a locked conformation of the ionic lock and two distinctly different conformations of intracellular loop 2 are observed. Docking of R-22, a D3R-selective antagonist, reveals an extracellular extension of the eticlopride binding site that comprises a second binding pocket for the aryl amide of R-22, which differs between the highly homologous D2R and D3R. This difference provides direction to the design of D3R-selective agents for treating drug abuse and other neuropsychiatric indications.

Preparation of a dopamine transporter imaging agent 18F-FP-β-CIT and its biodistribution in rat brain

International Nuclear Information System (INIS)

Chen Zhengping; Wu Chunying; Li Xiaomin; Zhang Tongxing; Wang Songpei; Lu Chunxiong; Fu Ronggeng; Zhang Zhengwei; Guan Yihui

2003-01-01

Objective: To develop a simple and easy protocol of preparing 18 F-N-3-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane (FP-β-CIT) as a dopamine transporter imaging agent, and to study the distribution of this agent in rat brain. Methods: 18 F-FP-β-CIT was prepared by direct reaction in CH 3 CN between K 18 F and the labeling precursor, N-(3-(mesyloxy) propyl )-2β-carbomethoxy-3β-(4-iodophenyl) nortropane (MsOP-CIT), in which Kryptofix 222 was used as phase transfer catalyst. 18 F-FP-β-CIT was purified through a Sep-Pak SiO 2 cartridge and eluted with ethyl ether. The purified 18 F-FP-β-CIT was injected into the rat's tail vein. These rats were sacrificed by cervical dislocation at different time points (5, 30, 60, 120, 180 min) after injection. The brain tissue of interest was removed, weighed, and radiocounted. Results: The radiochemical purity of 18 F-FP-β-CIT was over 95%, and the radiochemical yield from starting 18 F-fluoride was about 10%. 18 F-FP-β-CIT was absorbed rapidly in rat brain and was cleaned gradually (1.49, 0.59, 0.31, 0.21, 0.17%ID at 5, 30, 60, 120, 180 min, respectively). Radiouptake of striatum was more than that of other tissues and was cleaned slower than in other tissues at 60 min. Ratios of radiouptake of striatum /cerebellum were 1.75, 3.38, 3.73, 3.71 and 3.20 at 5, 30, 60, 120, 180 min, respectively. Conclusions: 18 F-FP-β-CIT is synthesized by a one-step protocol in which the preparative high performance liquid chromatography is not necessary in purifying procedure. The dominant distribution of 18 F-FP-β-CIT in rat striatum indicates that it is a potential dopamine transporter imaging agent

Effects of Mutations and Ligands on the Thermostability of the l-Arginine/Agmatine Antiporter AdiC and Deduced Insights into Ligand-Binding of Human l-Type Amino Acid Transporters.

Science.gov (United States)

Ilgü, Hüseyin; Jeckelmann, Jean-Marc; Colas, Claire; Ucurum, Zöhre; Schlessinger, Avner; Fotiadis, Dimitrios

2018-03-20

The l-arginine/agmatine transporter AdiC is a prokaryotic member of the SLC7 family, which enables pathogenic enterobacteria to survive the extremely acidic gastric environment. Wild-type AdiC from Escherichia coli, as well as its previously reported point mutants N22A and S26A, were overexpressed homologously and purified to homogeneity. A size-exclusion chromatography-based thermostability assay was used to determine the melting temperatures ( T m s) of the purified AdiC variants in the absence and presence of the selected ligands l-arginine (Arg), agmatine, l-arginine methyl ester, and l-arginine amide. The resulting T m s indicated stabilization of AdiC variants upon ligand binding, in which T m s and ligand binding affinities correlated positively. Considering results from this and previous studies, we revisited the role of AdiC residue S26 in Arg binding and proposed interactions of the α-carboxylate group of Arg exclusively with amide groups of the AdiC backbone. In the context of substrate binding in the human SLC7 family member l-type amino acid transporter-1 (LAT1; SLC7A5), an analogous role of S66 in LAT1 to S26 in AdiC is discussed based on homology modeling and amino acid sequence analysis. Finally, we propose a binding mechanism for l-amino acid substrates to LATs from the SLC7 family.

Apo-ghrelin receptor (apo-GHSR1a Regulates Dopamine Signaling in the Brain

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Andras eKern

2014-08-01

Full Text Available The orexigenic peptide hormone ghrelin is synthesized in the stomach and its receptor growth hormone secretagogue receptor (GHSR1a is expressed mainly in the central nervous system (CNS. In this review we confine our discussion to the physiological role of GHSR1a in the brain. Paradoxically, despite broad expression of GHSR1a in the CNS, other than trace amounts in the hypothalamus, ghrelin is undetectable in the brain. In our efforts to elucidate the function of the ligand-free ghrelin receptor (apo-GHSR1a we identified subsets of neurons that co-express GHSR1a and dopamine receptors. In this review we focus on interactions between apo-GHSR1a and dopamine-2 receptor (DRD2 and formation of GHSR1a:DRD2 heteromers in hypothalamic neurons that regulate appetite, and discuss implications for the treatment of Prader-Willi syndrome. GHSR1a antagonists of distinct chemical structures, a quinazolinone and a triazole, respectively enhance and inhibit dopamine signaling through GHSR1a:DRD2 heteromers by an allosteric mechanism. This finding illustrates a potential strategy for designing the next generation of drugs for treating eating disorders as well as psychiatric disorders caused by abnormal dopamine signaling. Treatment with a GHSR1a antagonist that enhances dopamine/DRD2 activity in GHSR1a:DRD2 expressing hypothalamic neurons has the potential to inhibit the uncontrollable hyperphagia associated with Prader-Willi syndrome. DRD2 antagonists are prescribed for treating schizophrenia, but these block dopamine signaling in all DRD2 expressing neurons and are associated with adverse side effects, including enhanced appetite and excessive weight gain. A GHSR1a antagonist of structural class that allosterically blocks dopamine/DRD2 action in GHSR1a:DRD2 expressing neurons would have no effect on neurons expressing DRD2 alone; therefore, the side effects of DRD2 antagonists would potentially be reduced thereby enhancing patient compliance.

Amphetamine elevates nucleus accumbens dopamine via an action potential-dependent mechanism that is modulated by endocannabinoids

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Covey, Dan P.; Bunner, Kendra D.; Schuweiler, Douglas R.; Cheer, Joseph F.; Garris, Paul A.

2018-01-01

The reinforcing effects of abused drugs are mediated by their ability to elevate nucleus accumbens dopamine. Amphetamine (AMPH) was historically thought to increase dopamine by an action potential-independent, non-exocytotic type of release called efflux, involving reversal of dopamine transporter function and driven by vesicular dopamine depletion. Growing evidence suggests that AMPH also acts by an action potential-dependent mechanism. Indeed, fast-scan cyclic voltammetry demonstrates that AMPH activates dopamine transients, reward-related phasic signals generated by burst firing of dopamine neurons and dependent on intact vesicular dopamine. Not established for AMPH but indicating a shared mechanism, endocannabinoids facilitate this activation of dopamine transients by broad classes of abused drugs. Here, using fast-scan cyclic voltammetry coupled to pharmacological manipulations in awake rats, we investigated the action potential and endocannabinoid dependence of AMPH-induced elevations in nucleus accumbens dopamine. AMPH increased the frequency, amplitude and duration of transients, which were observed riding on top of slower dopamine increases. Surprisingly, silencing dopamine neuron firing abolished all AMPH-induced dopamine elevations, identifying an action potential-dependent origin. Blocking cannabinoid type 1 receptors prevented AMPH from increasing transient frequency, similar to reported effects on other abused drugs, but not from increasing transient duration and inhibiting dopamine uptake. Thus, AMPH elevates nucleus accumbens dopamine by eliciting transients via cannabinoid type 1 receptors and promoting the summation of temporally coincident transients, made more numerous, larger and wider by AMPH. Collectively, these findings are inconsistent with AMPH eliciting action potential-independent dopamine efflux and vesicular dopamine depletion, and support endocannabinoids facilitating phasic dopamine signalling as a common action in drug reinforcement

Amphetamine elevates nucleus accumbens dopamine via an action potential-dependent mechanism that is modulated by endocannabinoids.

Science.gov (United States)

Covey, Dan P; Bunner, Kendra D; Schuweiler, Douglas R; Cheer, Joseph F; Garris, Paul A

2016-06-01

The reinforcing effects of abused drugs are mediated by their ability to elevate nucleus accumbens dopamine. Amphetamine (AMPH) was historically thought to increase dopamine by an action potential-independent, non-exocytotic type of release called efflux, involving reversal of dopamine transporter function and driven by vesicular dopamine depletion. Growing evidence suggests that AMPH also acts by an action potential-dependent mechanism. Indeed, fast-scan cyclic voltammetry demonstrates that AMPH activates dopamine transients, reward-related phasic signals generated by burst firing of dopamine neurons and dependent on intact vesicular dopamine. Not established for AMPH but indicating a shared mechanism, endocannabinoids facilitate this activation of dopamine transients by broad classes of abused drugs. Here, using fast-scan cyclic voltammetry coupled to pharmacological manipulations in awake rats, we investigated the action potential and endocannabinoid dependence of AMPH-induced elevations in nucleus accumbens dopamine. AMPH increased the frequency, amplitude and duration of transients, which were observed riding on top of slower dopamine increases. Surprisingly, silencing dopamine neuron firing abolished all AMPH-induced dopamine elevations, identifying an action potential-dependent origin. Blocking cannabinoid type 1 receptors prevented AMPH from increasing transient frequency, similar to reported effects on other abused drugs, but not from increasing transient duration and inhibiting dopamine uptake. Thus, AMPH elevates nucleus accumbens dopamine by eliciting transients via cannabinoid type 1 receptors and promoting the summation of temporally coincident transients, made more numerous, larger and wider by AMPH. Collectively, these findings are inconsistent with AMPH eliciting action potential-independent dopamine efflux and vesicular dopamine depletion, and support endocannabinoids facilitating phasic dopamine signalling as a common action in drug reinforcement

Towards trans-diagnostic mechanisms in psychiatry: neurobehavioral profile of rats with a loss-of-function point mutation in the dopamine transporter gene.

Science.gov (United States)

Vengeliene, Valentina; Bespalov, Anton; Roßmanith, Martin; Horschitz, Sandra; Berger, Stefan; Relo, Ana L; Noori, Hamid R; Schneider, Peggy; Enkel, Thomas; Bartsch, Dusan; Schneider, Miriam; Behl, Berthold; Hansson, Anita C; Schloss, Patrick; Spanagel, Rainer

2017-04-01

The research domain criteria (RDoC) matrix has been developed to reorient psychiatric research towards measurable behavioral dimensions and underlying mechanisms. Here, we used a new genetic rat model with a loss-of-function point mutation in the dopamine transporter (DAT) gene ( Slc6a3 _N157K) to systematically study the RDoC matrix. First, we examined the impact of the Slc6a3 _N157K mutation on monoaminergic signaling. We then performed behavioral tests representing each of the five RDoC domains: negative and positive valence systems, cognitive, social and arousal/regulatory systems. The use of RDoC may be particularly helpful for drug development. We studied the effects of a novel pharmacological approach metabotropic glutamate receptor mGluR2/3 antagonism, in DAT mutants in a comparative way with standard medications. Loss of DAT functionality in mutant rats not only elevated subcortical extracellular dopamine concentration but also altered the balance of monoaminergic transmission. DAT mutant rats showed deficits in all five RDoC domains. Thus, mutant rats failed to show conditioned fear responses, were anhedonic, were unable to learn stimulus-reward associations, showed impaired cognition and social behavior, and were hyperactive. Hyperactivity in mutant rats was reduced by amphetamine and atomoxetine, which are well-established medications to reduce hyperactivity in humans. The mGluR2/3 antagonist LY341495 also normalized hyperactivity in DAT mutant rats without affecting extracellular dopamine levels. We systematically characterized an altered dopamine system within the context of the RDoC matrix and studied mGluR2/3 antagonism as a new pharmacological strategy to treat mental disorders with underlying subcortical dopaminergic hyperactivity. © 2017. Published by The Company of Biologists Ltd.

(-)PPAP: a new and selective ligand for sigma binding sites.

Science.gov (United States)

Glennon, R A; Battaglia, G; Smith, J D

1990-11-01

Most agents employed for the investigation of sigma (sigma) binding sites display relatively low affinity for these sites, bind both at sigma sites and at either phencyclidine (PCP) sites or dopamine receptors with similar affinity, and/or produce some dopaminergic activity in vivo. We describe a new agent, (-)PPAP or R(-)-N-(3-phenyl-n-propyl)-1-phenyl-2-aminopropane hydrochloride, that binds with high affinity and selectivity at sigma (IC50 = 24 nM) versus either PCP sites (IC50 greater than 75,000 nM) or D1 and D2 dopamine receptors (IC50 greater than 5,000 nM). The sigma affinity of this agent is comparable to that of the standard ligands (+)-3-PPP and DTG. Furthermore, although (-)PPAP is structurally related to amphetamine, it neither produces nor antagonizes amphetamine-like stimulus effect in rats trained to discriminate 1 mg/kg of S(+)amphetamine from saline.

Changes in Expression of Dopamine, Its Receptor, and Transporter in Nucleus Accumbens of Heroin-Addicted Rats with Brain-Derived Neurotrophic Factor (BDNF) Overexpression.

Science.gov (United States)

Li, Yixin; Xia, Baijuan; Li, Rongrong; Yin, Dan; Liang, Wenmei

2017-06-09

BACKGROUND The aim of this study was to explore how changes in the expression of BDNF in MLDS change the effect of BDNF on dopamine (DA) neurons, which may have therapeutic implications for heroin addiction. MATERIAL AND METHODS We established a rat model of heroin addiction and observed changes in the expression of BDNF, DA, dopamine receptor (DRD), dopamine transporter (DAT), and other relevant pathways in NAc. We also assessed the effect of BDNF overexpression in the NAc, behavioral changes of heroin-conditioned place preference (CPP), and naloxone withdrawal in rats with high levels of BDNF. We established 5 adult male rat groups: heroin addiction, lentivirus transfection, blank virus, sham operation, and control. The PCR gene chip was used to study gene expression changes. BDNF lentivirus transfection was used for BDNF overexpression. A heroin CPP model and a naloxone withdrawal model of rats were established. RESULTS Expression changes were found in 20 of the 84 DA-associated genes in the NAc of heroin-addicted rats. Weight loss and withdrawal symptoms in the lentivirus group for naloxone withdrawal was less than in the blank virus and the sham operation group. These 2 latter groups also showed significant behavioral changes, but such changes were not observed in the BDNF lentivirus group before or after training. DRD3 and DAT increased in the NAc of the lentivirus group. CONCLUSIONS BDNF and DA in the NAc are involved in heroin addiction. BDNF overexpression in NAc reduces withdrawal symptoms and craving behavior for medicine induced by environmental cues for heroin-addicted rats. BDNF participates in the regulation of the dopamine system by acting on DRD3 and DAT.

Dopamine transporter density in the basal ganglia assessed with 123I-IPT SPECT in children with attention deficit hyperactivity disorder

International Nuclear Information System (INIS)

Yoo, Y. H.; Cheon, K. A.; Yoon, M. J.; Kim, C. H.; Lee, J. D.; Kim, H. H.; Choi, T. H.

2002-01-01

Attention deficit hyperactivity disorder (ADHD) is known as a psychiatric disorder in childhood associated with dopamine dysregulation. We investigated dopamine transporter (DAT) density in children with ADHD in the present study using 123 I-IPT SPECT and postulated that an alteration in DAT density in the basal ganglia (BG) is responsible for dopaminergic dysfunction in children with ADHD. 9 durg-naive children with ADHD and 6 normal children were included in the study. We performed brain SPECT 2 hours after administration of 123 I-IPT and made both quantitative and qualitative analyses for assessment of specific/nonspecific DAT binding ratio in the BG. We investigated the correlation between the severity scores of ADHD symptoms in children with ADHD assessed with ADHD rating scale and specific/nonspecific DAT binding ratio in the BG. Drug-naive children with ADHD showed a significantly incresed specific/nonspecific DAT binding ratio in the BG compared with normal children. Whereas, no significant correlation was found between severity scores of symptoms in children with ADHD and specific/nonspecific DAT binding ratio n the BG. Our findings support complex dysregulation of the dopaminergic neurotransmitter system in children with ADHD

3,4-Methylenedioxypyrovalerone prevents while methylone enhances methamphetamine-induced damage to dopamine nerve endings: β-ketoamphetamine modulation of neurotoxicity by the dopamine transporter

Science.gov (United States)

Anneken, John H.; Angoa-Pérez, Mariana; Kuhn, Donald M.

2016-01-01

Methylone, 3,4-methylenedioxypyrovalerone (MDPV), and mephedrone are psychoactive ingredients of ‘bath salts’ and their abuse represents a growing public health care concern. These drugs are cathinone derivatives and are classified chemically as β-ketoamphetamines. Because of their close structural similarity to the amphetamines, methylone, MDPV, and mephedrone share most of their pharmacological, neurochemical, and behavioral properties. One point of divergence in their actions is the ability to cause damage to the CNS. Unlike methamphetamine, the β-ketoamphetamines do not damage dopamine (DA) nerve endings. However, mephedrone has been shown to significantly accentuate methamphetamine neurotoxicity. Bath salt formulations contain numerous different psychoactive ingredients, and individuals who abuse bath salts also coabuse other illicit drugs. Therefore, we have evaluated the effects of methylone, MDPV, mephedrone, and methamphetamine on DA nerve endings. The β-ketoamphetamines alone or in all possible two-drug combinations do not result in damage to DA nerve endings but do cause hyperthermia. MDPV completely protects against the neurotoxic effects of methamphetamine while methylone accentuates it. Neither MDPV nor methylone attenuates the hyperthermic effects of methamphetamine. The potent neuroprotective effects of MDPV extend to amphetamine-, 3,4-methylenedioxymethamphetamine-, and MPTP-induced neurotoxicity. These results indicate that β-ketoamphetamine drugs that are non-substrate blockers of the DA transporter (i.e., MDPV) protect against methamphetamine neurotoxicity, whereas those that are substrates for uptake by the DA transporter and which cause DA release (i.e., methylone, mephedrone) accentuate neurotoxicity. PMID:25626880

Differential Internalization Rates and Postendocytic Sorting of the Norepinephrine and Dopamine Transporters Are Controlled by Structural Elements in the N Termini

DEFF Research Database (Denmark)

Vuorenpää, Anne Elina; Jørgensen, Trine Nygaard; Newman, Amy H

2016-01-01

. Moreover, mitigating Rab11 function by overexpression of dominant negative Rab11 impaired NET function. Sorting of NET to the Rab11 recycling compartment was further supported by confocal imaging and reversible biotinylation experiments in transfected differentiated CATH.a cells. In contrast to NET......, the dopamine transporter displayed markedly less constitutive internalization and limited sorting to the Rab11 recycling compartment in the differentiated CATH.a cells. Exchange of domains between the two homologous transporters revealed that this difference was determined by non-conserved structural elements...... in the intracellular N terminus. We conclude that NET displays a distinct trafficking itinerary characterized by continuous shuffling between the plasma membrane and the Rab11 recycling compartment and that the functional integrity of the Rab11 compartment is critical for maintaining proper presynaptic NET function....

IBZM- and CIT-SPECT of the dopaminergic system in Parkinsonism

International Nuclear Information System (INIS)

Tissingh, G.; Winogradzka, A.; Wolters, E.C.; Booij, J.; Royen, E.A. van

1997-01-01

Parkinsonism is most of the time caused by idiopathic Parkinson's disease (IPD). Considering the differences in therapeutic response and prognosis. in viva discrimination between IPD and 'Parkinsonism-plus' syndromes is important. Recently, ligands have become available for imaging the pre- and postsynaptic dopaminergic system by Single Photon Emission Computed Tomography (SPECT). Visualization of postsynaptic D 2 dopamine receptors using 123 I-iodobenzamide ( 123 I-IBZM) may contribute to the differential diagnosis between IPD and 'Parkinsonism-plus' syndromes as IPD is a pure presynaptic disease. Imaging of the presynaptic dopamine transporters using [ 123 I]β-CIT (2β-carbomethoxy-3β-(4-iodophenyl)tropane) may be used as a diagnostic technique. Early disease detection in subjects suspected to be at risk for developing IPD has become possible using [ 123 I]β-CIT or other ligands for the dopamine transporter. Furthermore, with SPECT one is probably able to monitor in an objective way the efficacy of new pharmacological therapies. (author)

Motivation deficit in ADHD is associated with dysfunction of the dopamine reward pathway

International Nuclear Information System (INIS)

Volkow, N.D.; Wang, G.-J.; Newcorn, J.H.; Kollins, S.H.; Wigal, T.L.; Telang, F.; Folwer, J.S.; Goldstein, R.Z.; Klein, N.; Logan, J.; Wong, C.; Swanson, J.M.

2010-01-01

Attention-deficit hyperactivity disorder (ADHD) is typically characterized as a disorder of inattention and hyperactivity/impulsivity but there is increasing evidence of deficits in motivation. Using positron emission tomography (PET), we showed decreased function in the brain dopamine reward pathway in adults with ADHD, which, we hypothesized, could underlie the motivation deficits in this disorder. To evaluate this hypothesis, we performed secondary analyses to assess the correlation between the PET measures of dopamine D2/D3 receptor and dopamine transporter availability (obtained with ( 11 C)raclopride and ( 11 C)cocaine, respectively) in the dopamine reward pathway (midbrain and nucleus accumbens) and a surrogate measure of trait motivation (assessed using the Achievement scale on the Multidimensional Personality Questionnaire or MPQ) in 45 ADHD participants and 41 controls. The Achievement scale was lower in ADHD participants than in controls (11 ± 5 vs 14 ± 3, P < 0.001) and was significantly correlated with D2/D3 receptors (accumbens: r = 0.39, P < 0.008; midbrain: r = 0.41, P < 0.005) and transporters (accumbens: r = 0.35, P < 0.02) in ADHD participants, but not in controls. ADHD participants also had lower values in the Constraint factor and higher values in the Negative Emotionality factor of the MPQ but did not differ in the Positive Emotionality factor - and none of these were correlated with the dopamine measures. In ADHD participants, scores in the Achievement scale were also negatively correlated with symptoms of inattention (CAARS A, E and SWAN I). These findings provide evidence that disruption of the dopamine reward pathway is associated with motivation deficits in ADHD adults, which may contribute to attention deficits and supports the use of therapeutic interventions to enhance motivation in ADHD.

Motivation deficit in ADHD is associated with dysfunction of the dopamine reward pathway

Energy Technology Data Exchange (ETDEWEB)

Volkow, N.D.; Wang, G.; Volkow, N.D.; Wang, G.-J.; Newcorn, J.H.; Kollins, S.H.; Wigal, T.L.; Telang, F.; Folwer, J.S.; Goldstein, R.Z.; Klein, N.; Logan, J.; Wong, C.; Swanson, J.M.

2010-08-17

Attention-deficit hyperactivity disorder (ADHD) is typically characterized as a disorder of inattention and hyperactivity/impulsivity but there is increasing evidence of deficits in motivation. Using positron emission tomography (PET), we showed decreased function in the brain dopamine reward pathway in adults with ADHD, which, we hypothesized, could underlie the motivation deficits in this disorder. To evaluate this hypothesis, we performed secondary analyses to assess the correlation between the PET measures of dopamine D2/D3 receptor and dopamine transporter availability (obtained with [{sup 11}C]raclopride and [{sup 11}C]cocaine, respectively) in the dopamine reward pathway (midbrain and nucleus accumbens) and a surrogate measure of trait motivation (assessed using the Achievement scale on the Multidimensional Personality Questionnaire or MPQ) in 45 ADHD participants and 41 controls. The Achievement scale was lower in ADHD participants than in controls (11 {+-} 5 vs 14 {+-} 3, P < 0.001) and was significantly correlated with D2/D3 receptors (accumbens: r = 0.39, P < 0.008; midbrain: r = 0.41, P < 0.005) and transporters (accumbens: r = 0.35, P < 0.02) in ADHD participants, but not in controls. ADHD participants also had lower values in the Constraint factor and higher values in the Negative Emotionality factor of the MPQ but did not differ in the Positive Emotionality factor - and none of these were correlated with the dopamine measures. In ADHD participants, scores in the Achievement scale were also negatively correlated with symptoms of inattention (CAARS A, E and SWAN I). These findings provide evidence that disruption of the dopamine reward pathway is associated with motivation deficits in ADHD adults, which may contribute to attention deficits and supports the use of therapeutic interventions to enhance motivation in ADHD.

A new model for separation between brain dopamine and serotonin transporters in {sup 123}I-{beta}-CIT SPECT measurements: normal values and sex and age dependence

Energy Technology Data Exchange (ETDEWEB)

Ryding, Erik; Rosen, Ingmar [Department of Clinical Neurophysiology, University Hospital, Lund (Sweden); Lindstroem, Mats; Bosson, Peter; Traeskman-Bendz, Lil [Department of Psychiatry, University Hospital, Lund (Sweden); Braadvik, Bjoern; Grabowski, Martin [Department of Neurology, University Hospital, Lund (Sweden)

2004-08-01

{sup 123}I-{beta}-CIT is a radioactive ligand for single-photon emission computed tomography (SPECT) imaging of the pre-synaptic (transporter) re-uptake sites for dopamine (DAT) and serotonin (5HTT), and it is widely used to visualize monoamine turnover. Since {sup 123}I-{beta}-CIT uptake occurs at 5HTT and DAT sites in conjunction with the presence of freely soluble {sup 123}I-{beta}-CIT in brain tissue, adequate separation of these three components is necessary. However, only partial separation is possible with current methods. Two main strategies have previously been used for {sup 123}I-{beta}-CIT component separation, based on the following considerations: (1) the faster uptake rate for 5HTT compared with DAT enables temporal separation by performing 5HTT imaging at 1-2 h and DAT imaging at 20-24 h; (2) blocking the 5HTT re-uptake with citalopram renders {sup 123}I-{beta}-CIT imaging DAT (non-5HTT) specific. In a new analytical model, we combined these two approaches with methods to isolate the passively dissolved {sup 123}I-{beta}-CIT in brain tissue from the monoamine transporter uptake, and to correct the 5HTT and DAT values for concomitant uptake. The new analytical model was used to study brain 5HTT and DAT in 23 normal subjects, with the aim of clarifying the effect of age and sex. A significant correlation between 5HTT and DAT values was found only in the thalamus, indicating successful component separation. Negative correlations between age and DAT were found for basal ganglia, thalami, brain stem and temporal lobes, but not for the frontal, parietal or occipital regions. No correlation with age was found for 5HTT. We found no sex difference for 5HTT or DAT. (orig.)

The dopamine beta-hydroxylase inhibitor nepicastat increases dopamine release and potentiates psychostimulant-induced dopamine release in the prefrontal cortex.

Science.gov (United States)

Devoto, Paola; Flore, Giovanna; Saba, Pierluigi; Bini, Valentina; Gessa, Gian Luigi

2014-07-01

The dopamine-beta-hydroxylase inhibitor nepicastat has been shown to reproduce disulfiram ability to suppress the reinstatement of cocaine seeking after extinction in rats. To clarify its mechanism of action, we examined the effect of nepicastat, given alone or in association with cocaine or amphetamine, on catecholamine release in the medial prefrontal cortex and the nucleus accumbens, two key regions involved in the reinforcing and motivational effects of cocaine and in the reinstatement of cocaine seeking. Nepicastat effect on catecholamines was evaluated by microdialysis in freely moving rats. Nepicastat reduced noradrenaline release both in the medial prefrontal cortex and in the nucleus accumbens, and increased dopamine release in the medial prefrontal cortex but not in the nucleus accumbens. Moreover, nepicastat markedly potentiated cocaine- and amphetamine-induced extracellular dopamine accumulation in the medial prefrontal cortex but not in the nucleus accumbens. Extracellular dopamine accumulation produced by nepicastat alone or by its combination with cocaine or amphetamine was suppressed by the α2 -adrenoceptor agonist clonidine. It is suggested that nepicastat, by suppressing noradrenaline synthesis and release, eliminated the α2 -adrenoceptor mediated inhibitory mechanism that constrains dopamine release and cocaine- and amphetamine-induced dopamine release from noradrenaline or dopamine terminals in the medial prefrontal cortex. © 2012 The Authors, Addiction Biology © 2012 Society for the Study of Addiction.

Dopamine D(1) receptor-mediated control of striatal acetylcholine release by endogenous dopamine.

Science.gov (United States)

Acquas, E; Di Chiara, G

1999-10-27

The role of dopamine D(1) and D(2) receptors in the control of acetylcholine release in the dorsal striatum by endogenous dopamine was investigated by monitoring with microdialysis the effect of the separate or combined administration of the dopamine D(1) receptor antagonist, SCH 39166 ¿(-)-trans-6,7,7a,8,9, 13b-exahydro-3-chloro-2-hydroxy-N-methyl-5H-benzo-[d]-nap hto-[2, 1b]-azepine hydrochloride¿ (50 microg/kg subcutaneous (s.c.)), of the dopamine D(2)/D(3) receptor agonist, quinpirole (trans-(-)-4aR, 4a,5,6,7,8,8a,9-octahydro-5-propyl-1H-pyrazolo-(3,4-g)-quinoline hydrochloride) (5 and 10 microg/kg s.c.), and of the D(3) receptor selective agonist, PD 128,907 [S(+)-(4aR,10bR)-3,4,4a, 10b-tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin -9-ol hydrochloride] (50 microg/kg s.c.), on in vivo dopamine and acetylcholine release. Microdialysis was performed with a Ringer containing low concentrations (0.01 microM) of the acetylcholinesterase inhibitor, neostigmine. Quinpirole (10 microg/kg s.c.) decreased striatal dopamine and acetylcholine release. Administration of PD 128,907 (50 microg/kg) decreased dopamine but failed to affect acetylcholine release. SCH 39166 (50 microg/kg s.c.) stimulated dopamine release and reduced acetylcholine release. Pretreatment with quinpirole reduced (5 microg/kg s.c.) or completely prevented (10 microg/kg s.c.) the stimulation of dopamine release elicited by SCH 39166 (50 microg/kg s.c.); on the other hand, pretreatment with quinpirole (5 and 10 microg/kg) potentiated the reduction of striatal acetylcholine release induced by SCH 39166 (50 microg/kg s.c.). Similarly, pretreatment with PD 128,907 (50 microg/kg) which prevented the increase of dopamine release induced by SCH 39166 (50 microg/kg), potentiated the reduction of striatal acetylcholine transmission elicited by SCH 39166. Thus, pretreatment with low doses of quinpirole or PD 128,907 influences in opposite manner the effect of SCH 39166 on striatal dopamine and

Intracellular Methamphetamine Prevents the Dopamine-induced Enhancement of Neuronal Firing*

Science.gov (United States)

Saha, Kaustuv; Sambo, Danielle; Richardson, Ben D.; Lin, Landon M.; Butler, Brittany; Villarroel, Laura; Khoshbouei, Habibeh

2014-01-01

The dysregulation of the dopaminergic system is implicated in multiple neurological and neuropsychiatric disorders such as Parkinson disease and drug addiction. The primary target of psychostimulants such as amphetamine and methamphetamine is the dopamine transporter (DAT), the major regulator of extracellular dopamine levels in the brain. However, the behavioral and neurophysiological correlates of methamphetamine and amphetamine administration are unique from one another, thereby suggesting these two compounds impact dopaminergic neurotransmission differentially. We further examined the unique mechanisms by which amphetamine and methamphetamine regulate DAT function and dopamine neurotransmission; in the present study we examined the impact of extracellular and intracellular amphetamine and methamphetamine on the spontaneous firing of cultured midbrain dopaminergic neurons and isolated DAT-mediated current. In dopaminergic neurons the spontaneous firing rate was enhanced by extracellular application of amphetamine > dopamine > methamphetamine and was DAT-dependent. Amphetamine > methamphetamine similarly enhanced DAT-mediated inward current, which was sensitive to isosmotic substitution of Na+ or Cl− ion. Although isosmotic substitution of extracellular Na+ ions blocked amphetamine and methamphetamine-induced DAT-mediated inward current similarly, the removal of extracellular Cl− ions preferentially blocked amphetamine-induced inward current. The intracellular application of methamphetamine, but not amphetamine, prevented the dopamine-induced increase in the spontaneous firing of dopaminergic neurons and the corresponding DAT-mediated inward current. The results reveal a new mechanism for methamphetamine-induced dysregulation of dopaminergic neurons. PMID:24962577

Timing of caloric intake during weight loss differentially affects striatal dopamine transporter and thalamic serotonin transporter binding

NARCIS (Netherlands)

Versteeg, Ruth I.; Schrantee, Anouk; Adriaanse, Sofie M.; Unmehopa, Unga A.; Booij, Jan; Reneman, Liesbeth; Fliers, Eric; la Fleur, Susanne E.; Serlie, Mireille J.

2017-01-01

Recent studies have shown that meal timing throughout the day contributes to maintaining or regaining weight after hypocaloric diets. Although brain serotonin and dopamine are well known to be involved in regulating feeding, it is unknown whether meal timing during energy restriction affects these

Dopamine transporter imaging with [I-123]IPT SPECT in normal controls and Parkinson's patients: Feasibility study of a simplified SPECT scan protocol

International Nuclear Information System (INIS)

Kim, H. J.; Bong, J. K.; Nam, K. P.; Yang, S. O.; Moon, D. H.; Ryu, J. S.; Lee, H. K.

1997-01-01

[I-123]IPT has been used to measure changes in dopamine trasnporters with Parkinson's patients (PP). However, 2 hrs of imaging time without movement of patient's head partially limits its widespread use in routine clinical SPECT protocol. The purpose of this study was to evaluate the feasibility of a simplified IPT SPECT scan protocol using three 10 min scan data obtained at 0-10, 55-65, and 110-120 min postinjection and compared to current protocol using 23 scans obtained from O-120 min to quantify dopamine transporter binding in normal controls (NC) and PP. IPT labeled with 6.74±0.88mCi of I-123 was intravenously injected into 12 NC (age: 41±9) and 22 PP (age : 55±8) and the 5 min dynamic SPECT data were acquired for 2 hrs with Trionix triple-headed SPECT camera. SPECT images were reconstructed and attenuation corrected. [I-123] IPT quickly penetratd the blood-brain barrier and began to Ioacalize higher concentrations at the basal ganglia at 20 min after injection. The transporter parameter was measured using a variation of graphical analysis (VGA) and area ratio method (ARM) that derive the distribution volume ratios (R v =V 3 /V 2 for VGA, R A =V 3 /V 2 for ARM ) from multiple scan data without blood data, R v ' and R A ' measured from three 10 min scan data and compared with R v and R A measured from 23 scans for both NC and PP, (R v ', R v ') or NC and PP were (1.83±0.29, 2.21±0.34) and (0.63±0.34, 0.77±0.31), respectively. (R v ', R A ) for NC and PP were (1.11±0.22, 1.62±0.28) and (0.43±0.21, 0.65±0.24), respectively, Both (R v ', R v ) and (R A ', R A ) for NC were clearly separated from those for PP. R' v and R' A underestimated R v and R A by 18.4% and 33.5%, respectively, but R v ' and R A ' showed excellent correlations with R v (r=0.95) and R A (r=0.97), respectively. The results indicate that the three 10 min scan protocol may be feasible and allows us to differentiate dopamine transporter parameters in PP from those in NC

Pregnenolone rescues schizophrenia-like behavior in dopamine transporter knockout mice.

Directory of Open Access Journals (Sweden)

Peiyan Wong

Full Text Available Pregnenolone belongs to a class of endogenous neurosteroids in the central nervous system (CNS, which has been suggested to enhance cognitive functions through GABA(A receptor signaling by its metabolites. It has been shown that the level of pregnenolone is altered in certain brain areas of schizophrenic patients, and clozapine enhances pregnenolone in the CNS in rats, suggesting that pregnenolone could be used to treat certain symptoms of schizophrenia. In addition, early phase proof-of-concept clinical trials have indicated that pregnenolone is effective in reducing the negative symptoms and cognitive deficits of schizophrenia patients. Here, we evaluate the actions of pregnenolone on a mouse model for schizophrenia, the dopamine transporter knockout mouse (DAT KO. DAT KO mice mirror certain symptoms evident in patients with schizophrenia, such as the psychomotor agitation, stereotypy, deficits of prepulse inhibition and cognitive impairments. Following acute treatment, pregnenolone was found to reduce the hyperlocomotion, stereotypic bouts and pre-pulse inhibition (PPI deficits in DAT KO mice in a dose-dependent manner. At 60 mg/kg of pregnenolone, there were no significant differences in locomotor activities and stereotypy between wild-type and DAT KO mice. Similarly, acute treatment of 60 mg/kg of pregnenolone fully rescued PPI deficits of DAT KO mice. Following chronic treatment with pregnenolone at 60 mg/kg, the cognitive deficits of DAT KO mice were rescued in the paradigms of novel object recognition test and social transmission of food preference test. Pregnenolone thus holds promise as a therapeutic candidate in schizophrenia.

Dopamine plasma clearance is increased in piglets compared to neonates during continuous dopamine infusion

DEFF Research Database (Denmark)

Rasmussen, Martin B; Gramsbergen, Jan Bert; Eriksen, Vibeke Ramsgaard

2018-01-01

pharmacokinetics. METHODS: Arterial blood samples were drawn from six neonates admitted to the neonatal intensive care unit of Copenhagen University Hospital and 20 newborn piglets during continuous dopamine infusion. Furthermore, to estimate the piglet plasma dopamine half-life, blood samples were drawn at 2.......5-minute intervals after the dopamine infusion was discontinued. The plasma dopamine content was analysed by high-performance liquid chromatography with electrochemical detection. RESULTS: The dopamine displayed first-order kinetics in piglets and had a half-life of 2.5 minutes, while the median plasma...

In vivo measurement of neuronal dopamine transporter in tobacco and cannabis dependents subjects with positron tomography and [{sup 11}C]P E 2 I

Energy Technology Data Exchange (ETDEWEB)

Leroy, C; Ribeiro, M J; Trichard, C; Martinot, J L [Institut National de la Sante et de la Recherche Medicale (INSERM), U797, Research Unit, Neuroimaging and Psychiatry, IFR49, 91 - Orsay (France); CEA, Neuroimaging and Psychiatry, Unit, Hospital Dept. Frederic Joliot, I2BM, 91 - Orsay (France); Ribeiro, M J; Comtat, C; Dolle, F [Hospital Dept. Frederic Joliot, Research Medical Dept., I2BM, 91 - Orsay (France); Karila, L; Lukasiewicz, M; Reynaud, M [Paul Brousse Hospital, APHP, Psychiatry and Addictology Dept., 94 - Villejuif (France)

2008-02-15

Modifications of dopamine neurotransmission are classically involved in addictive behaviors and drug reinforcement. However, to date no data are available concerning the effects of cannabis addiction on dopaminergic neurotransmission in Human. The neuronal dopamine transporter (D.A.T.) is essential for the maintenance of normal dopamine homeostasis in the brain by ensuring the re-uptake of extracellular dopamine. Therefore, observation of D.A.T. availability abnormalities in cannabis-dependents subjects could provide further evidence for the implication of dopaminergic dysfunction in this addiction. Thus, as the cannabis dependent subjects are also most of time tobacco-dependents, this work aims studying the D.A.T. availability in age-paired control, tobacco-dependent and cannabis-dependent male subjects using Positron Emission Tomography (PET). Subjects are scanned on High Resolution Research Tomograph (H.R.R.T.) for one hour after injection of a selective D.A.T. radioligand ([{sup 11}C]P.E. 2 I.) [1]. The binding potential (B.P.) is calculated in order to obtained the specific binding of [{sup 11}C]P.E. 2 I. to the D.A.T. using the simplified reference tissue model of Lammertsma (S.R.T.M.) [2] and B.P. maps were generated according to Gunn model [3]. Comparison of mean B.P. obtained in Region Of Interest and voxel to voxel comparison of B.P. maps using S.P.M.5 were performed with M.A.N.C.O.V.A. controlled for age between control, tobacco-dependent and cannabis-dependent groups. Preliminary results are concordant between both approaches and shown significant decreases of the D.A.T. availability in the both groups of addicted subjects in comparison to controls at the level of dorsal and ventral striatum and the dorsal midbrain including substantia nigra and ventral tegmental area. However, no difference in D.A.T. binding between tobacco and cannabis dependents subjects was observed. These widespread modifications of D.A.T. availability in the dependents subjects

125I-β-CIT imaging study of striatal dopamine transporters in mice model of parkinsonism

International Nuclear Information System (INIS)

Liu Zhenguo; Sun Wenshan; Weng Zhongfang; Chen Shengdi; Shen Minghua; Zhu Chengmo

2001-01-01

Objective: To detect the activity of striatal dopamine transporters (DAT) in lesions of different order of severity of MPTP-induced mice model of parkinsonism by autoradiography with 125 I-β-CIT and to evaluate the clinical use of the β-CIT imaging for DAT detection. Methods: With regard to the different duration (days) of MPTP treatment, the C57BL mice were randomly divided into 5 groups, that is MPTP 1, 3, 5 and 7 day groups and control group treated with normal saline instead of MPTP. Two hours after intravenous administration with 125 I-β-CIT of 148 kBq, the brain tissue sections were imaged by autoradiography. The levels of dopamine (DA) and its metabolites were measured by high performance liquid chromatography and electrochemical detection (HPLC-ECD). The tyrosine hydroxylase (TH)-positive cells and fibres in the substantia nigra and striatum of the mice were observed by means of immunohistochemical technique. Results: As compared with control group, the radioactivity ratios of striatum to cortex (ST/CX) in 4 MPTP-treated groups were significantly reduced, by 20%, 42%, 45% and 52%, respectively. The concentrations of DA in the striatum of 4 MPTP-treated groups were remarkably decreased, by 47%, 75%, 95% and 95%, respectively. The gradual loss of DA neurons and fibres in the substantia nigra and striatum in 4 MPTP-treated groups was observed under microscopy. Conclusions: The functional abnormality of DAT paralleled the changes observed in neurochemistry and neuropathology studies in the lesions of different order of injury of the MPTP-treated mice. The β-CIT scanning for the activity of DAT may be useful for diagnosing PD at earlier phase and for monitoring the progression of the disease

Dopamine transporter density in the basal ganglia assessed with {sup 123}I-IPT SPECT in children with attention deficit hyperactivity disorder

Energy Technology Data Exchange (ETDEWEB)

Yoo, Y. H.; Cheon, K. A.; Yoon, M. J.; Kim, C. H.; Lee, J. D. [Yonsei University College of Medicine, Seoul (Korea, Republic of); Kim, H. H.; Choi, T. H. [Gachon Medical School, Incheon (Korea, Republic of)

2002-07-01

Attention deficit hyperactivity disorder (ADHD) is known as a psychiatric disorder in childhood associated with dopamine dysregulation. We investigated dopamine transporter (DAT) density in children with ADHD in the present study using {sup 123}I-IPT SPECT and postulated that an alteration in DAT density in the basal ganglia (BG) is responsible for dopaminergic dysfunction in children with ADHD. 9 durg-naive children with ADHD and 6 normal children were included in the study. We performed brain SPECT 2 hours after administration of {sup 123}I-IPT and made both quantitative and qualitative analyses for assessment of specific/nonspecific DAT binding ratio in the BG. We investigated the correlation between the severity scores of ADHD symptoms in children with ADHD assessed with ADHD rating scale and specific/nonspecific DAT binding ratio in the BG. Drug-naive children with ADHD showed a significantly incresed specific/nonspecific DAT binding ratio in the BG compared with normal children. Whereas, no significant correlation was found between severity scores of symptoms in children with ADHD and specific/nonspecific DAT binding ratio n the BG. Our findings support complex dysregulation of the dopaminergic neurotransmitter system in children with ADHD.

NEW DOPAMINE AGONISTS IN CARDIOVASCULAR THERAPY

NARCIS (Netherlands)

GIRBES, ARJ; VANVELDHUISEN, DJ; SMIT, AJ

1992-01-01

Dopamine, a naturally occurring catecholamine, has been extensively used in intensive care for many years. Dopamine stimulates different types of adrenergic receptors: alpha-1 and -2, beta-1 and -2, and dopamine-1 and -2. The renal effects of dopamine are the result of dopamine-1 receptor (DA1)

Expression of dopamine receptors in the subthalamic nucleus of the rat: characterization using reverse transcriptase-polymerase chain reaction and autoradiography

International Nuclear Information System (INIS)

Flores, G.; Liang, J.J.; Sierra, A.; Martinez-Fong, D.; Quirion, R.; Aceves, J.; Srivastava, L.K.

1999-01-01

We analysed the expression of dopamine receptor subtypes in the subthalamic nucleus by means of reverse transcriptase-polymerase chain reaction. We also studied, using autoradiography, all pharmacologically characterized dopamine receptors in four subregions of the subthalamic nucleus. For comparison, dopamine receptor subtypes were also evaluated in brain regions where they are more abundant and well characterized. The radioligands used were: [ 3 H]SCH-23390, [ 3 H]emonapride and [ 3 H]2-dipropylamino-7-hydroxy-1,2,3,4-tetrahydronaphthalene for dopamine D 1 , D 2 and D 3 receptors, respectively; and [ 3 H]YM-09151-2 in the presence of raclopride for dopamine D 4 receptors. Finally, we also evaluated the effect of unilateral 6-hydroxydopamine injection into the medial forebrain bundle on dopamine receptor levels expressed in the ipsilateral subthalamic nucleus. The lesion was estimated by decrease in the binding of [ 3 H]WIN-35428, a specific dopamine transporter label. D 1 , D 2 and D 3 receptor messenger RNAs and binding sites were present in the subthalamic nucleus, but no messenger RNA for D 4 receptors was found, although specific binding sites for these receptors were observed. As compared to the intact side, the 6-hydroxydopamine lesion did not change D 1 receptors, increased D 2 receptors, and decreased D 3 receptors and the dopamine transporter. The results suggest that postsynaptic D 1 , D 2 or D 3 receptors can mediate the effect of dopamine on subthalamic nucleus neuronal activity. D 4 receptors would mediate exclusively presynaptic effects.These results reinforce the idea that dopamine receptors in the subthalamic nucleus may play an important role in the physiology of the basal ganglia and in the pathophysiology of Parkinson's disease. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

Dopamine induces neutrophil apoptosis through a dopamine D-1 receptor-independent mechanism.

LENUS (Irish Health Repository)

Sookhai, S

2012-02-03

BACKGROUND: For the normal resolution of an acute inflammatory response, neutrophil (PMN) apoptosis is essential to maintain immune homeostasis and to limit inappropriate host tissue damage. A delay in PMN apoptosis has been implicated in the pathogenesis of the systemic inflammatory response syndrome (SIRS). Dopamine, a biogenic amine with known cardiovascular and neurotransmitter properties, is used in patients with SIRS to maintain hemodynamic stability. We sought to determine whether dopamine may also have immunoregulatory properties capable of influencing PMN apoptosis, function, and activation state in patients with SIRS. METHODS: PMNs were isolated from healthy volunteers and patients with SIRS and treated with varying doses of dopamine and a dopamine D-1 receptor agonist, fenoldopam. PMN apoptosis was assessed every 6 hours with use of propidium iodide DNA staining and PMN function was assessed with use of respiratory burst activity, phagocytosis ability, and CD11a, CD11b, and CD18 receptor expression as functional markers. RESULTS: There was a significant delay in PMN apotosis in patients with SIRS compared with controls. Treatment of isolated PMNs from both healthy controls and patients with SIRS with 10 and 100 mumol\\/L dopamine induced apoptosis. PMN ingestive and cytocidal capacity were both decreased in patients with SIRS compared with controls. Treatment with dopamine significantly increased phagocytic function. Fenoldopam did not induce PMN apoptosis. CONCLUSION: Our data demonstrate for the first time that dopamine induces PMN apoptosis and modulates PMN function both in healthy controls and in patients with SIRS. These results indicate that dopamine may be beneficial during SIRS through a nonhemodynamic PMN-dependent proapoptotic mechanism.

Striatal and extra-striatal dopamine transporter in cannabis and tobacco addiction: a high resolution PET study

International Nuclear Information System (INIS)

Leroy, C.; Martinot, J.L.; Duchesnay, E.; Artiges, E.; Ribeiro, M.J.; Trichard, Ch.; Karila, L.; Lukasiewicz, M.; Benyamina, A.; Reynaud, M.; Martinot, J.L.; Duchesnay, E.; Artiges, E.; Comtat, C.; Artiges, E.; Trichard, Ch.

2011-01-01

The dopamine (DA) system is known to be involved in the reward and dependence mechanisms of addiction. However, modifications in dopaminergic neurotransmission associated with long-term tobacco and cannabis use have been poorly documented in vivo. In order to assess striatal and extra-striatal dopamine transporter (DAT) availability in tobacco and cannabis addiction, three groups of male age-matched subjects were compared: 11 healthy non-smoker subjects, 14 tobacco-dependent smokers (17.6 ± 5.3 cigarettes/day for 12.1 ± 8.5 years) and 13 cannabis and tobacco smokers (CTS) (4.8 ± 5.3 cannabis joints/day for 8.7 ± 3.9 years). DAT availability was examined in positron emission tomography (HRRT) with a high resolution research tomograph after injection of [ 11 C]PE2I, a selective DAT radioligand. Region of interest and voxel-by-voxel approaches using a simplified reference tissue model were performed for the between-group comparison of DAT availability. Measurements in the dorsal striatum from both analyses were concordant and showed a mean 20% lower DAT availability in drug users compared with controls. Whole-brain analysis also revealed lower DAT availability in the ventral striatum, the midbrain, the middle cingulate and the thalamus (ranging from -15 to -30%). The DAT availability was slightly lower in all regions in CTS than in subjects who smoke tobacco only, but the difference does not reach a significant level. These results support the existence of a decrease in DAT availability associated with tobacco and cannabis addictions involving all dopaminergic brain circuits. These findings are consistent with the idea of a global decrease in cerebral DA activity in dependent subjects. (authors)

Imaging of D2 dopamine receptors of patients with Parkinson's disease using SPECT and 131I-IBZM

International Nuclear Information System (INIS)

Zhang Wei; Wang Jian; Jiang Yuping; Lu Chuanzhen

2001-01-01

Objective: To evaluate the usefulness of SPECT with 131 I-IBZM in imaging of D 2 Dopamine receptors in patients with Parkinson's disease (PD). Methods: Six patients which early unmedicated PD, six patients with moderate or advanced PD treated with long-term oral L-Dopa and Four control subjects were investigated with SPECT using 131 I-IBZM as dopamine receptor ligand. The ratio of basal ganglia to occipital cortex (BG/OC) and ratio of basal ganglia to frontal cortex (BG/FC) were calculated as semiquantitative parameter of striatal D 2 dopamine receptor's function. Results: The SPECT images revealed high uptake of IBZM in the basal ganglia. In the early unmedicated PD group, the BG/PC and BG/FC rates were significantly higher in the striatum contralateral to the parkinsonism. In the moderate or advanced PD group, no significant differences were observed bilaterally, and the BG/OC and the BG/FC rates in this group was lower than those of the control. Conclusion: 131 I-IBZM with SPECT imaging is useful in evaluating patients with Parkinson's disease

[123I]epidepride binding to cerebellar dopamine D2/D3 receptors is displaceable: implications for the use of cerebellum as a reference region

DEFF Research Database (Denmark)

Pinborg, Lars H; Videbaek, Charlotte; Ziebell, Morten

2007-01-01

The low density of cerebellar dopamine D(2)/D(3) receptors provides the basis for using the cerebellum as a representation of free- and non-specifically bound radioligand in positron emission tomography (PET) and single photon emission computed tomography (SPECT) studies. With the development...... of ultra high-affinity dopamine D(2)/D(3) ligands like [(123)I]epidepride, [(18)F]fallypride, and [(11)C]FLB-457, quantification of extrastriatal low density receptor populations including the cerebellum is possible with important implications for calculation of binding parameters. [(123)I...... [(123)I]epidepride binding to dopamine D(2)/D(3) receptors in the cerebellum. Using the cerebellum as a representation of free and non-specifically bound radioligand and neglecting the specifically bound component may lead to results that erroneously imply that antipsychotic drugs bind to extrastriatal...

Dissociable roles of dopamine and serotonin transporter function in a rat model of negative urgency.

Science.gov (United States)

Yates, Justin R; Darna, Mahesh; Gipson, Cassandra D; Dwoskin, Linda P; Bardo, Michael T

2015-09-15

Negative urgency is a facet of impulsivity that reflects mood-based rash action and is associated with various maladaptive behaviors in humans. However, the underlying neural mechanisms of negative urgency are not fully understood. Several brain regions within the mesocorticolimbic pathway, as well as the neurotransmitters dopamine (DA) and serotonin (5-HT), have been implicated in impulsivity. Extracellular DA and 5-HT concentrations are regulated by DA transporters (DAT) and 5-HT transporters (SERT); thus, these transporters may be important molecular mechanisms underlying individual differences in negative urgency. The current study employed a reward omission task to model negative urgency in rats. During reward trials, a cue light signaled the non-contingent delivery of one sucrose pellet; immediately following the non-contingent reward, rats responded on a lever to earn sucrose pellets (operant phase). Omission trials were similar to reward trials, except that non-contingent sucrose was omitted following the cue light prior to the operant phase. As expected, contingent responding was higher following omission of expected reward than following delivery of expected reward, thus reflecting negative urgency. Upon completion of behavioral training, Vmax and Km were obtained from kinetic analysis of [(3)H]DA and [(3)H]5-HT uptake using synaptosomes prepared from nucleus accumbens (NAc), dorsal striatum (Str), medial prefrontal cortex (mPFC), and orbitofrontal cortex (OFC) isolated from individual rats. Vmax for DAT in NAc and for SERT in OFC were positively correlated with negative urgency scores. The current findings suggest that mood-based impulsivity (negative urgency) is associated with enhanced DAT function in NAc and SERT function in OFC. Copyright © 2015 Elsevier B.V. All rights reserved.

Colloidal-quantum-dot photovoltaics using atomic-ligand passivation

KAUST Repository

Tang, Jiang

2011-09-18

Colloidal-quantum-dot (CQD) optoelectronics offer a compelling combination of solution processing and spectral tunability through quantum size effects. So far, CQD solar cells have relied on the use of organic ligands to passivate the surface of the semiconductor nanoparticles. Although inorganic metal chalcogenide ligands have led to record electronic transport parameters in CQD films, no photovoltaic device has been reported based on such compounds. Here we establish an atomic ligand strategy that makes use of monovalent halide anions to enhance electronic transport and successfully passivate surface defects in PbS CQD films. Both time-resolved infrared spectroscopy and transient device characterization indicate that the scheme leads to a shallower trap state distribution than the best organic ligands. Solar cells fabricated following this strategy show up to 6% solar AM1.5G power-conversion efficiency. The CQD films are deposited at room temperature and under ambient atmosphere, rendering the process amenable to low-cost, roll-by-roll fabrication. © 2011 Macmillan Publishers Limited. All rights reserved.

Mechanism of charge transport in ligand-capped crystalline CdTe nanoparticles according to surface photovoltaic and photoacoustic results

Energy Technology Data Exchange (ETDEWEB)

Li Kuiying, E-mail: kuiyingli@ysu.edu.cn [National Laboratory of Metastable Materials Manufacture Technology and Science, Yanshan University, Hebei Str. 438, Qinhuangdao, Hebei Province 066004 (China); Zhang Hao [Key Laboratory for Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 (China); Yang Weiyong; Wei Sailing [National Laboratory of Metastable Materials Manufacture Technology and Science, Yanshan University, Hebei Str. 438, Qinhuangdao, Hebei Province 066004 (China); Wang Dayang, E-mail: dayang@mpikg-golm.mpg.de [Max Planck Institute of Colloids and Interfaces, Potsdam 14424 (Germany)

2010-09-01

By combining surface photovoltaic and photoacoustic techniques, we probed the photogenerated charge transport channels of 3-mercaptopropionic acid (MPA)- and 2-mercaptoethylamine (MA)-capped crystalline CdTe nanoparticles on illumination with UV-near IR light. The results experimentally confirmed the presence of a CdS shell outside the CdTe core that formed through the self-assembly and decomposition of mercapto ligands during CdTe preparation. The data revealed that the CdS layer was partly responsible for the deexcitation behavior of the photogenerated carriers, which is related to the quantum tunnel effect. Experiments demonstrated that two quantum wells were located at wavelengths of 440 and 500 nm in buried interfacial space-charge regions, whereas the formation of a ligand layer obstructed charge transfer transitions of the core CdTe nanoparticles to a certain extent.

Infralimbic dopamine D2 receptors mediate glucocorticoid-induced facilitation of auditory fear memory extinction in rats.

Science.gov (United States)

Dadkhah, Masoumeh; Abdullahi, Payman Raise; Rashidy-Pour, Ali; Sameni, Hamid Reza; Vafaei, Abbas Ali

2018-03-01

The infralimbic (IL) cortex of the medial prefrontal cortex plays an important role in the extinction of fear memory. Also, it has been showed that both brain glucocorticoid and dopamine receptors are involved in many processes such as fear extinction that drive learning and memory; however, the interaction of these receptors in the IL cortex remains unclear. We examined a putative interaction between the effects of glucocorticoid and dopamine receptors stimulation in the IL cortex on fear memory extinction in an auditory fear conditioning paradigm in male rats. Corticosterone (the endogenous glucocorticoid receptor ligand), or RU38486 (the synthetic glucocorticoid receptor antagonist) microinfusion into the IL cortex 10 min before test 1 attenuated auditory fear expression at tests 1-3, suggesting as an enhancement of fear extinction. The effect of corticosterone, but not RU38486 was counteracted by the dopamine D2 receptor antagonist sulpiride pre-treatment administered into the IL (at a dose that failed to alter freezing behavior on its own). In contrast, intra-IL infusion of the dopamine D1 receptor antagonist SCH23390 pre-treatment failed to alter freezing behavior. These findings provide evidence for the involvement of the IL cortex D2 receptors in CORT-induced facilitation of fear memory extinction. Copyright © 2018 Elsevier B.V. All rights reserved.

Computational approaches to screen candidate ligands with anti- Parkinson's activity using R programming.

Science.gov (United States)

Jayadeepa, R M; Niveditha, M S

2012-01-01

It is estimated that by 2050 over 100 million people will be affected by the Parkinson's disease (PD). We propose various computational approaches to screen suitable candidate ligand with anti-Parkinson's activity from phytochemicals. Five different types of dopamine receptors have been identified in the brain, D1-D5. Dopamine receptor D3 was selected as the target receptor. The D3 receptor exists in areas of the brain outside the basal ganglia, such as the limbic system, and thus may play a role in the cognitive and emotional changes noted in Parkinson's disease. A ligand library of 100 molecules with anti-Parkinson's activity was collected from literature survey. Nature is the best combinatorial chemist and possibly has answers to all diseases of mankind. Failure of some synthetic drugs and its side effects have prompted many researches to go back to ancient healing methods which use herbal medicines to give relief. Hence, the candidate ligands with anti-Parkinson's were selected from herbal sources through literature survey. Lipinski rules were applied to screen the suitable molecules for the study, the resulting 88 molecules were energy minimized, and subjected to docking using Autodock Vina. The top eleven molecules were screened according to the docking score generated by Autodock Vina Commercial drug Ropinirole was computed similarly and was compared with the 11 phytochemicals score, the screened molecules were subjected to toxicity analysis and to verify toxic property of phytochemicals. R Programming was applied to remove the bias from the top eleven molecules. Using cluster analysis and Confusion Matrix two phytochemicals were computationally selected namely Rosmarinic acid and Gingkolide A for further studies on the disease Parkinson's.

Dopamine, reward learning, and active inference.

Science.gov (United States)

FitzGerald, Thomas H B; Dolan, Raymond J; Friston, Karl

2015-01-01

Temporal difference learning models propose phasic dopamine signaling encodes reward prediction errors that drive learning. This is supported by studies where optogenetic stimulation of dopamine neurons can stand in lieu of actual reward. Nevertheless, a large body of data also shows that dopamine is not necessary for learning, and that dopamine depletion primarily affects task performance. We offer a resolution to this paradox based on an hypothesis that dopamine encodes the precision of beliefs about alternative actions, and thus controls the outcome-sensitivity of behavior. We extend an active inference scheme for solving Markov decision processes to include learning, and show that simulated dopamine dynamics strongly resemble those actually observed during instrumental conditioning. Furthermore, simulated dopamine depletion impairs performance but spares learning, while simulated excitation of dopamine neurons drives reward learning, through aberrant inference about outcome states. Our formal approach provides a novel and parsimonious reconciliation of apparently divergent experimental findings.

Acute effect of intravenously applied alcohol in the human striatal and extrastriatal D2 /D3 dopamine system.

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Pfeifer, Philippe; Tüscher, Oliver; Buchholz, Hans Georg; Gründer, Gerhard; Vernaleken, Ingo; Paulzen, Michael; Zimmermann, Ulrich S; Maus, Stephan; Lieb, Klaus; Eggermann, Thomas; Fehr, Christoph; Schreckenberger, Mathias

2017-09-01

Investigations on the acute effects of alcohol in the human mesolimbic dopamine D 2 /D 3 receptor system have yielded conflicting results. With respect to the effects of alcohol on extrastriatal D 2 /D 3 dopamine receptors no investigations have been reported yet. Therefore we applied PET imaging using the postsynaptic dopamine D 2 /D 3 receptor ligand [ 18 F]fallypride addressing the question, whether intravenously applied alcohol stimulates the extrastriatal and striatal dopamine system. We measured subjective effects of alcohol and made correlation analyses with the striatal and extrastriatal D 2 /D 3 binding potential. Twenty-four healthy male μ-opioid receptor (OPRM1)118G allele carriers underwent a standardized intravenous and placebo alcohol administration. The subjective effects of alcohol were measured with a visual analogue scale. For the evaluation of the dopamine response we calculated the binding potential (BP ND ) by using the simplified reference tissue model (SRTM). In addition, we calculated distribution volumes (target and reference regions) in 10 subjects for which metabolite corrected arterial samples were available. In the alcohol condition no significant dopamine response in terms of a reduction of BP ND was observed in striatal and extrastriatal brain regions. We found a positive correlation for 'liking' alcohol and the BP ND in extrastriatal brain regions (Inferior frontal cortex (IFC) (r = 0.533, p = 0.007), orbitofrontal cortex (OFC) (r = 0.416, p = 0.043) and prefrontal cortex (PFC) (r = 0.625, p = 0.001)). The acute alcohol effects on the D 2 /D 3 dopamine receptor binding potential of the striatal and extrastriatal system in our experiment were insignificant. A positive correlation of the subjective effect of 'liking' alcohol with cortical D 2 /D 3 receptors may hint at an addiction relevant trait. © 2016 Society for the Study of Addiction.

Pharmacological characterization of the dopamine-sensitive adenylate cyclase in cockroach brain: evidence for a distinct dopamine receptor

International Nuclear Information System (INIS)

Orr, G.L.; Gole, J.W.D.; Notman, H.J.; Downer, R.G.H.

1987-01-01

Dopamine increases cyclic AMP production in crude membrane preparations of cockroach brain with plateaus in cyclic AMP production occurring between 1-10 μM and 10 mM. Maximal production of cyclic AMP is 2.25 fold greater than that of control values. Octopamine also increases cyclic AMP production with a Ka of 1.4 μM and maximal production 3.5 fold greater than that of control. 5-Hydroxytryptamine does not increase cyclic AMP production. The effects of octopamine and dopamine are fully additive. The vertebrate dopamine agonists ADTN and epinine stimulate the dopamine-sensitive adenylate cyclase (AC) with Ka values of 4.5 and 0.6 μM respectively and with maximal effectiveness 1.7 fold greater than that of control. The selective D 2 -dopamine agonist LY-171555 stimulates cyclic AMP production to a similar extent with a Ka of 50 μM. Other dopamine agonists have no stimulatory effects. With the exception of mianserin, 3 H-piflutixol is displaced from brain membranes by dopamine antagonists with an order of potency similar to that observed for the inhibition of dopamine-sensitive AC. The results indicate that the octopamine- and dopamine-sensitive AC in cockroach brain can be distinguished pharmacologically and the dopamine receptors coupled to AC have pharmacological characteristics distinct from vertebrate D 1 - and D 2 -dopamine receptors. 33 references, 3 figures, 2 tables

Synthesis, radiolabeling and baboon SPECT imaging of 2β-carbomethoxy-3β-(3'-[123I]iodophenyl)tropane ([123I]YP256) as a serotonin transporter radiotracer

International Nuclear Information System (INIS)

Bois, Frederic; Baldwin, Ronald M.; Amici, Louis; Al-Tikriti, Mohammed S.; Kula, Nora; Baldessarini, Ross; Innis, Robert B.; Staley, Julie K.; Tamagnan, Gilles D.

2008-01-01

To develop a potential SPECT probe to evaluate the integrity of the serotoninergic system (5-HTT) whose dysfunction is linked to several disease conditions such as Parkinson's disease, Alzheimer's disease and depression, we report the synthesis, radiolabeling and in vivo baboon imaging of 2β-carbomethoxy-3β-(3'-[ 123 I]iodophenyl) tropane (YP256, ). The radiolabeling was performed by iododestannylation using sodium [ 123 I]iodide and peracetic acid. Although the ligand displayed high selectivity for 5-HTT over dopamine transporter in vitro, SPECT imaging in baboons did not reveal selective 5-HTT accumulation in brain in vivo

Neurotransmission imaging by PET

International Nuclear Information System (INIS)

Takano, Akihiro; Suhara, Tetsuya

2001-01-01

PET studies on neurotransmission in psychological disorders to evaluate abnormal neurotransmission and therapeutic effects are thoroughly reviewed by type of major neurotransmitters. Studies on dopaminergic neurotransmission have focused on the function of dopamine D 2 receptors, receptor subtypes, such as the D 1 receptor, and ligands, such as transporters. PET studies of dopamine D 2 receptor, which began in the early 1980s, have predominantly been performed in schizophrenia, and most have failed to detect any statistically significant differences between schizophrenia patients and controls. The studies in the early 1980s were performed by using [ 11 C]N-methyl-spiperone (NMSP) and [ 11 C]raclopride, ligands for striatal dopamine D 2 receptors. [ 11 C]FLB457, which has much higher affinity for D 2 receptors than raclopride, began to be used in the 1990s. Dopamine D 2 occupancy after drug ingestion has also been investigated to clarify the mechanisms and effects of antipsychotic drugs, and there have also been studies on the effect of aging and personality traits on dopamine D 2 receptor levels in healthy subjects. In studies on dopamine receptor subtypes other than D 2 , dopamine D 1 receptors have been studied in connection with assessments of cognitive functions. Most studies on dopamine transporters have been related to drug dependence. Serotonin 5-HT 2A receptors have been studied with [ 11 C]NMSP in schizophrenia patients, while studies of another serotonin receptor subtype, 5-HT 1A receptors, have been mainly conducted in patients with depression. [ 11 C]NMSP PET showed no difference between schizophrenia patients who had not undergone phamacotherapy and normal subjects. Because serotonin selective reuptake inhibitors (SSRIs) affect serotonin transporters, and abnormalities in serotonin transporters detected in mood disorders, PET ligands for serotonin transporters have increasingly been developed, and serotonin transporters have recently begun to be

Dopamine, reward learning, and active inference

Directory of Open Access Journals (Sweden)

Thomas eFitzgerald

2015-11-01

Full Text Available Temporal difference learning models propose phasic dopamine signalling encodes reward prediction errors that drive learning. This is supported by studies where optogenetic stimulation of dopamine neurons can stand in lieu of actual reward. Nevertheless, a large body of data also shows that dopamine is not necessary for learning, and that dopamine depletion primarily affects task performance. We offer a resolution to this paradox based on an hypothesis that dopamine encodes the precision of beliefs about alternative actions, and thus controls the outcome-sensitivity of behaviour. We extend an active inference scheme for solving Markov decision processes to include learning, and show that simulated dopamine dynamics strongly resemble those actually observed during instrumental conditioning. Furthermore, simulated dopamine depletion impairs performance but spares learning, while simulated excitation of dopamine neurons drives reward learning, through aberrant inference about outcome states. Our formal approach provides a novel and parsimonious reconciliation of apparently divergent experimental findings.

Measurements, in vivo, of parameters of the dopamine system

International Nuclear Information System (INIS)

Friedman, A.M.; DeJesus, O.T.; Dinerstein, R.; Revenaugh, J.

1983-01-01

This paper discusses methods of measuring important parameters of the dopamine system in the living animal by use of PET techniques. One primary concern is the density and binding affinity of post-synaptic neuroreceptors. A second concern is the activity of neurons. In vivo, this is generally related to the turnover of neurotransmitter and can also be related to the uptake of precursor compounds by the neurons. If the transmitter and neuroleptic compound compete for the same binding sites (on the receptor molecule) these two effects are interwoven and are not easily isolated. It appears that the movement of neuroleptic drugs from the brain is slow enough to allow equilibrium to be maintained between ligand and receptor, especially after some time for the initial washout and translocation in the brain. To test the consequences of equilibrium binding and the possible use of the model for measurement of receptor densities by emission tomography we have modified Clark's equilibrium model of ligand binding. In this note we will describe the solutions of the equations and some comparisons of the predictions of the model with data, as well as its application to tomographic measurements

A conserved WW domain-like motif regulates invariant chain-dependent cell-surface transport of the NKG2D ligand ULBP2.

Science.gov (United States)

Uhlenbrock, Franziska; van Andel, Esther; Andresen, Lars; Skov, Søren

2015-08-01

Malignant cells expressing NKG2D ligands on their cell surface can be directly sensed and killed by NKG2D-bearing lymphocytes. To ensure this immune recognition, accumulating evidence suggests that NKG2D ligands are trafficed via alternative pathways to the cell surface. We have previously shown that the NKG2D ligand ULBP2 traffics over an invariant chain (Ii)-dependent pathway to the cell surface. This study set out to elucidate how Ii regulates ULBP2 cell-surface transport: We discovered conserved tryptophan (Trp) residues in the primary protein sequence of ULBP1-6 but not in the related MICA/B. Substitution of Trp to alanine resulted in cell-surface inhibition of ULBP2 in different cancer cell lines. Moreover, the mutated ULBP2 constructs were retained and not degraded inside the cell, indicating a crucial role of this conserved Trp-motif in trafficking. Finally, overexpression of Ii increased surface expression of wt ULBP2 while Trp-mutants could not be expressed, proposing that this Trp-motif is required for an Ii-dependent cell-surface transport of ULBP2. Aberrant soluble ULBP2 is immunosuppressive. Thus, targeting a distinct protein module on the ULBP2 sequence could counteract this abnormal expression of ULBP2. Copyright © 2015 Elsevier Ltd. All rights reserved.

Dopamine enhances duodenal epithelial permeability via the dopamine D5 receptor in rodent.

Science.gov (United States)

Feng, X-Y; Zhang, D-N; Wang, Y-A; Fan, R-F; Hong, F; Zhang, Y; Li, Y; Zhu, J-X

2017-05-01

The intestinal barrier is made up of epithelial cells and intercellular junctional complexes to regulate epithelial ion transport and permeability. Dopamine (DA) is able to promote duodenal epithelial ion transport through D1-like receptors, which includes subtypes of D 1 (D 1 R) and D 5 (D 5 R), but whether D1-like receptors influence the duodenal permeability is unclear. FITC-dextran permeability, short-circuit current (I SC ), Western blot, immunohistochemistry and ELISA were used in human D 5 R transgenic mice and hyperendogenous enteric DA (HEnD) rats in this study. Dopamine induced a downward deflection in I SC and an increase in FITC-dextran permeability of control rat duodenum, which were inhibited by the D1-like receptor antagonist, SCH-23390. However, DA decreased duodenal transepithelial resistance (TER), an effect also reversed by SCH-23390. A strong immunofluorescence signal for D 5 R, but not D 1 R, was observed in the duodenum of control rat. In human D 5 R knock-in transgenic mice, duodenal mucosa displayed an increased basal I SC with high FITC-dextran permeability and decreased TER with a lowered expression of tight junction proteins, suggesting attenuated duodenal barrier function in these transgenic mice. D 5 R knock-down transgenic mice manifested a decreased basal I SC with lowered FITC-dextran permeability. Moreover, an increased FITC-dextran permeability combined with decreased TER and tight junction protein expression in duodenal mucosa were also observed in HEnD rats. This study demonstrates, for the first time, that DA enhances duodenal permeability of control rat via D 5 R, which provides new experimental and theoretical evidence for the influence of DA on duodenal epithelial barrier function. © 2016 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Antipsychotic-like effect of the muscarinic acetylcholine receptor agonist BuTAC in non-human primates

DEFF Research Database (Denmark)

Andersen, Maibritt B; Croy, Carrie Hughes; Dencker, Ditte

2015-01-01

Cholinergic, muscarinic receptor agonists exhibit functional dopamine antagonism and muscarinic receptors have been suggested as possible future targets for the treatment of schizophrenia and drug abuse. The muscarinic ligand (5R,6R)-6-(3-butylthio-1,2,5-thiadiazol-4-yl)-1-azabicyclo[3.2.1]octane...... (BuTAC) exhibits high affinity for muscarinic receptors with no or substantially less affinity for a large number of other receptors and binding sites, including the dopamine receptors and the dopamine transporter. In the present study, we wanted to examine the possible antipsychotic-like effects...

Peripheral Dopamine in Restless Legs Syndrome

Directory of Open Access Journals (Sweden)

Ulrike H. Mitchell

2018-03-01

Full Text Available Objective/BackgroundRestless Legs Syndrome (RLS is a dopamine-dependent disorder characterized by a strong urge to move. The objective of this study was to evalulate blood levels of dopamine and other catecholamines and blood D2-subtype dopamine receptors (D2Rs in RLS.Patients/MethodsDopamine levels in blood samples from age-matched unmedicated RLS subjects, medicated RLS subjects and Controls were evaluated with high performance liquid chromatography and dopamine D2R white blood cell (WBC expression levels were determined with fluorescence-activated cell sorting and immunocytochemistry.ResultsBlood plasma dopamine levels, but not norepinepherine or epinephrine levels, were significantly increased in medicated RLS subjects vs unmedicated RLS subjects and Controls. The percentage of lymphocytes and monocytes expressing D2Rs differed between Control, RLS medicated and RLS unmedicated subjects. Total D2R expression in lymphocytes, but not monocytes, differed between Control, RLS medicated and RLS unmedicated subjects. D2Rs in lymphocytes, but not monocytes, were sensitive to dopamine in Controls only.ConclusionDownregulation of WBCs D2Rs occurs in RLS. This downregulation is not reversed by medication, although commonly used RLS medications increase plasma dopamine levels. The insensitivity of monocytes to dopamine levels, but their downregulation in RLS, may reflect their utility as a biomarker for RLS and perhaps brain dopamine homeostasis.

Copper Complexes with Tetradentate Ligands for Enhanced Charge Transport in Dye-Sensitized Solar Cells

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Hannes Michaels

2018-05-01

Full Text Available In dye-sensitized solar cells (DSCs, the redox mediator is responsible for the regeneration of the oxidized dye and for the hole transport towards the cathode. Here, we introduce new copper complexes with tetradentate 6,6′-bis(4-(S-isopropyl-2-oxazolinyl-2,2′-bipyridine ligands, Cu(oxabpy, as redox mediators. Copper coordination complexes with a square-planar geometry show low reorganization energies and thus introduce smaller losses in photovoltage. Slow recombination kinetics of excited electrons between the TiO2 and CuII(oxabpy species lead to an exceptionally long electron lifetime, a high Fermi level in the TiO2, and a high photovoltage of 920 mV with photocurrents of 10 mA∙cm−2 and 6.2% power conversion efficiency. Meanwhile, a large driving force remains for the dye regeneration of the Y123 dye with high efficiencies. The square-planar Cu(oxabpy complexes yield viscous gel-like solutions. The unique charge transport characteristics are attributed to a superposition of diffusion and electronic conduction. An enhancement in charge transport performance of 70% despite the higher viscosity is observed upon comparison of Cu(oxabpy to the previously reported Cu(tmby2 redox electrolyte.

Elevated dopamine alters consummatory pattern generation and increases behavioral variability during learning

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Mark A. Rossi

2015-05-01

Full Text Available The role of dopamine in controlling behavior remains poorly understood. In this study we examined licking behavior in an established hyperdopaminergic mouse model—dopamine transporter knockout (DAT KO mice. DAT KO mice showed higher rates of licking, which is due to increased perseveration of licking in a bout. By contrast, they showed increased individual lick durations, and reduced inter-lick-intervals. During extinction, both KO and control mice transiently increased variability in lick pattern generation while reducing licking rate, yet they showed very different behavioral patterns. Control mice gradually increased lick duration as well as variability. By contrast, DAT KO mice exhibited more immediate (within 10 licks adjustments—an immediate increase in lick duration variability, as well as more rapid extinction. These results suggest that the level of dopamine can modulate the persistence and pattern generation of a highly stereotyped consummatory behavior like licking, as well as new learning in response to changes in environmental feedback. Increased dopamine in DAT KO mice not only increased perseveration of bouts and individual lick duration, but also increased the behavioral variability in response to the extinction contingency and the rate of extinction.

Introducing Thermal Wave Transport Analysis (TWTA): A Thermal Technique for Dopamine Detection by Screen-Printed Electrodes Functionalized with Molecularly Imprinted Polymer (MIP) Particles.

Science.gov (United States)

Peeters, Marloes M; van Grinsven, Bart; Foster, Christopher W; Cleij, Thomas J; Banks, Craig E

2016-04-26

A novel procedure is developed for producing bulk modified Molecularly Imprinted Polymer (MIP) screen-printed electrodes (SPEs), which involves the direct mixing of the polymer particles within the screen-printed ink. This allowed reduction of the sample preparation time from 45 min to 1 min, and resulted in higher reproducibility of the electrodes. The samples are measured with a novel detection method, namely, thermal wave transport analysis (TWTA), relying on the analysis of thermal waves through a functional interface. As a first proof-of-principle, MIPs for dopamine are developed and successfully incorporated within a bulk modified MIP SPE. The detection limits of dopamine within buffer solutions for the MIP SPEs are determined via three independent techniques. With cyclic voltammetry this was determined to be 4.7 × 10(-6) M, whereas by using the heat-transfer method (HTM) 0.35 × 10(-6) M was obtained, and with the novel TWTA concept 0.26 × 10(-6) M is possible. This TWTA technique is measured simultaneously with HTM and has the benefits of reducing measurement time to less than 5 min and increasing effect size by nearly a factor of two. The two thermal methods are able to enhance dopamine detection by one order of magnitude compared to the electrochemical method. In previous research, it was not possible to measure neurotransmitters in complex samples with HTM, but with the improved signal-to-noise of TWTA for the first time, spiked dopamine concentrations were determined in a relevant food sample. In summary, novel concepts are presented for both the sensor functionalization side by employing screen-printing technology, and on the sensing side, the novel TWTA thermal technique is reported. The developed bio-sensing platform is cost-effective and suitable for mass-production due to the nature of screen-printing technology, which makes it very interesting for neurotransmitter detection in clinical diagnostic applications.

In vitro and in vivo evaluation of [123I]IBZM: a potential CNS D-2 dopamine receptor imaging agent

International Nuclear Information System (INIS)

Kung, H.F.; Pan, S.; Kung, M.P.; Billings, J.; Kasliwal, R.; Reilley, J.; Alavi, A.

1989-01-01

In vitro binding characteristics of a CNS dopamine D-2 receptor imaging agent, (S)-N-[(1-ethyl-2-pyrrolidinyl)] methyl-2-hydroxy-3-iodo-6-methoxybenzamide [( 125 I]IBZM), was carried out in rats. Also brain images, as well as organ biodistribution were determined in a monkey following the administration of 123 I-labeled compound. The S-(-)-I[ 125 I]IBZM showed high specific dopamine D-2 receptor binding in rat striatum (Kd = 0.426 +/- 0.082 nM, Bmax = 480 +/- 22 fmol/mg of protein). Competition of various ligands for the IBZM binding displayed the following rank order of potency: spiperone greater than S(-)IBZM much greater than R(+)IBZM greater than or equal to S(-)BZM greater than dopamine greater than ketanserin greater than SCH-23390 much greater than propranolol, norepinephrine, serotonin. In vivo planar images of a monkey injected with [ 123 I]IBZM demonstrated a high concentration in basal ganglia of brain. The ratios of activity in the basal ganglia to cerebellum and the cortex to cerebellum in monkey brain were 4.93 and 1.44, respectively, at 120 min postinjection. These preliminary results indicate that [ 123 I]IBZM is a potentially promising imaging agent for the investigation of dopamine D-2 receptors in humans

Effects of a novel, selective, sigma1-ligand, MS-377, on phencyclidine-induced behaviour.

Science.gov (United States)

Takahashi, S; Takagi, K; Horikomi, K

2001-07-01

Phencyclidine (PCP)-induced head-weaving is inhibited by a novel selective sigma1-ligand, (R)-(+)-1-(4-chlorophenyl)-3-[4-(2-methoxyethyl)piperazin-1-yl]methyl-2-pyrrolidinone L-tartrate (MS-377), but not by dopamine D2 antagonists. In the present study, we examined the effects of two potent and selective sigma1-ligands, MS-377 and N,N-dipropyl-2-(4-methoxy-3-(2-phenylethoxy)phenyl) ethylamine (NE-100), on PCP-induced rearing behaviour, hyperlocomotion and ataxia in comparison with the currently available antipsychotic agents with affinity for D2 receptors, haloperidol, sultopride and risperidone. Male Wistar rats or ddY mice were administered MS-377, NE-100, haloperidol, sultopride or risperidone, and PCP was administered 60 min later (in the case of NE-100 10 min later). Rearing behaviour, hyperlocomotion and ataxia were examined 10 min after PCP administration. MS-377, haloperidol, sultopride and risperidone dose-dependently inhibited PCP-induced rearing and hyperlocomotion, but did not antagonize PCP-induced ataxia. In contrast, the other selective sigma1-ligand, NE-100, did not affect any of the PCP-induced behaviour patterns in this study. These results suggest that there are at least two types of ligands for sigma1-receptors and that some sigma1-ligands, including MS-377, have more comprehensive effects against PCP-induced abnormal behaviour than other sigma1-ligands or D2 antagonists.

Protective actions of the vesicular monoamine transporter 2 (VMAT2) in monoaminergic neurons.

Science.gov (United States)

Guillot, Thomas S; Miller, Gary W

2009-04-01

Vesicular monoamine transporters (VMATs) are responsible for the packaging of neurotransmitters such as dopamine, serotonin, norepinephrine, and epinephrine into synaptic vesicles. These proteins evolved from precursors in the major facilitator superfamily of transporters and are among the members of the toxin extruding antiporter family. While the primary function of VMATs is to sequester neurotransmitters within vesicles, they can also translocate toxicants away from cytosolic sites of action. In the case of dopamine, this dual role of VMAT2 is combined-dopamine is more readily oxidized in the cytosol where it can cause oxidative stress so packaging into vesicles serves two purposes: neurotransmission and neuroprotection. Furthermore, the deleterious effects of exogenous toxicants on dopamine neurons, such as MPTP, can be attenuated by VMAT2 activity. The active metabolite of MPTP can be kept within vesicles and prevented from disrupting mitochondrial function thereby sparing the dopamine neuron. The highly addictive drug methamphetamine is also neurotoxic to dopamine neurons by using dopamine itself to destroy the axon terminals. Methamphetamine interferes with vesicular sequestration and increases the production of dopamine, escalating the amount in the cytosol and leading to oxidative damage of terminal components. Vesicular transport seems to resist this process by sequestering much of the excess dopamine, which is illustrated by the enhanced methamphetamine neurotoxicity in VMAT2-deficient mice. It is increasingly evident that VMAT2 provides neuroprotection from both endogenous and exogenous toxicants and that while VMAT2 has been adapted by eukaryotes for synaptic transmission, it is derived from phylogenetically ancient proteins that originally evolved for the purpose of cellular protection.

Dopamine and Caffeine Encapsulation within Boron Nitride (14,0) Nanotubes: Classical Molecular Dynamics and First Principles Calculations.

Science.gov (United States)

García-Toral, Dolores; González-Melchor, Minerva; Rivas-Silva, Juan F; Meneses-Juárez, Efraín; Cano-Ordaz, José; H Cocoletzi, Gregorio

2018-06-07

Classical molecular dynamics (MD) and density functional theory (DFT) calculations are developed to investigate the dopamine and caffeine encapsulation within boron nitride (BN) nanotubes (NT) with (14,0) chirality. Classical MD studies are done at canonical and isobaric-isothermal conditions at 298 K and 1 bar in explicit water. Results reveal that both molecules are attracted by the nanotube; however, only dopamine is able to enter the nanotube, whereas caffeine moves in its vicinity, suggesting that both species can be transported: the first by encapsulation and the second by drag. Findings are analyzed using the dielectric behavior, pair correlation functions, diffusion of the species, and energy contributions. The DFT calculations are performed according to the BLYP approach and applying the atomic base of the divided valence 6-31g(d) orbitals. The geometry optimization uses the minimum-energy criterion, accounting for the total charge neutrality and multiplicity of 1. Adsorption energies in the dopamine encapsulation indicate physisorption, which induces the highly occupied molecular orbital-lower unoccupied molecular orbital gap reduction yielding a semiconductor behavior. The charge redistribution polarizes the BNNT/dopamine and BNNT/caffeine structures. The work function decrease and the chemical potential values suggest the proper transport properties in these systems, which may allow their use in nanobiomedicine.

Central GLP-1 receptor activation modulates cocaine-evoked phasic dopamine signaling in the nucleus accumbens core.

Science.gov (United States)

Fortin, Samantha M; Roitman, Mitchell F

2017-07-01

Drugs of abuse increase the frequency and magnitude of brief (1-3s), high concentration (phasic) dopamine release events in terminal regions. These are thought to be a critical part of drug reinforcement and ultimately the development of addiction. Recently, metabolic regulatory peptides, including the satiety signal glucagon-like peptide-1 (GLP-1), have been shown to modulate cocaine reward-driven behavior and sustained dopamine levels after cocaine administration. Here, we use fast-scan cyclic voltammetry (FSCV) to explore GLP-1 receptor (GLP-1R) modulation of dynamic dopamine release in the nucleus accumbens (NAc) during cocaine administration. We analyzed dopamine release events in both the NAc shell and core, as these two subregions are differentially affected by cocaine and uniquely contribute to motivated behavior. We found that central delivery of the GLP-1R agonist Exendin-4 suppressed the induction of phasic dopamine release events by intravenous cocaine. This effect was selective for dopamine signaling in the NAc core. Suppression of phasic signaling in the core by Exendin-4 could not be attributed to interference with cocaine binding to one of its major substrates, the dopamine transporter, as cocaine-induced increases in reuptake were unaffected. The results suggest that GLP-1R activation, instead, exerts its suppressive effects by altering dopamine release - possibly by suppressing the excitability of dopamine neurons. Given the role of NAc core dopamine in the generation of conditioned responses based on associative learning, suppression of cocaine-induced dopamine signaling in this subregion by GLP-1R agonism may decrease the reinforcing properties of cocaine. Thus, GLP-1Rs remain viable targets for the treatment and prevention of cocaine seeking, taking and relapse. Copyright © 2017 Elsevier Inc. All rights reserved.

Comparison of dopamine kinetics in the larval Drosophila ventral nerve cord and protocerebrum with improved optogenetic stimulation.

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Privman, Eve; Venton, B Jill

2015-11-01

Dopamine release and uptake have been studied in the Drosophila larval ventral nerve cord (VNC) using optogenetics to stimulate endogenous release. However, other areas of the central nervous system remain uncharacterized. Here, we compare dopamine release in the VNC and protocerebrum of larval Drosophila. Stimulations were performed with CsChrimson, a new, improved, red light-activated channelrhodopsin. In both regions, dopamine release was observed after only a single, 4 ms duration light pulse. Michaelis-Menten modeling was used to understand release and uptake parameters for dopamine. The amount of dopamine released ([DA]p ) on the first stimulation pulse is higher than the average [DA]p released from subsequent pulses. The initial and average amount of dopamine released per stimulation pulse is smaller in the protocerebrum than in the VNC. The average Vmax of 0.08 μM/s in the protocerebrum was significantly higher than the Vmax of 0.05 μM/s in the VNC. The average Km of 0.11 μM in the protocerebrum was not significantly different from the Km of 0.10 μM in the VNC. When the competitive dopamine transporter (DAT) inhibitor nisoxetine was applied, the Km increased significantly in both regions while Vmax stayed the same. This work demonstrates regional differences in dopamine release and uptake kinetics, indicating important variation in the amount of dopamine available for neurotransmission and neuromodulation. We use a new optogenetic tool, red light activated CsChrimson, to stimulate the release of dopamine in the ventral nerve cord and medial protocerebrum of the larval Drosophila central nervous system. We monitored extracellular dopamine by fast scan cyclic voltammetry and used Michaelis-Menten modeling to probe the regulation of extracellular dopamine, discovering important similarities and differences in these two regions. © 2015 International Society for Neurochemistry.

Tuning the allosteric regulation of artificial muscarinic and dopaminergic ligand-gated potassium channels by protein engineering of G protein-coupled receptors

Science.gov (United States)

Moreau, Christophe J.; Revilloud, Jean; Caro, Lydia N.; Dupuis, Julien P.; Trouchet, Amandine; Estrada-Mondragón, Argel; Nieścierowicz, Katarzyna; Sapay, Nicolas; Crouzy, Serge; Vivaudou, Michel

2017-01-01

Ligand-gated ion channels enable intercellular transmission of action potential through synapses by transducing biochemical messengers into electrical signal. We designed artificial ligand-gated ion channels by coupling G protein-coupled receptors to the Kir6.2 potassium channel. These artificial channels called ion channel-coupled receptors offer complementary properties to natural channels by extending the repertoire of ligands to those recognized by the fused receptors, by generating more sustained signals and by conferring potassium selectivity. The first artificial channels based on the muscarinic M2 and the dopaminergic D2L receptors were opened and closed by acetylcholine and dopamine, respectively. We find here that this opposite regulation of the gating is linked to the length of the receptor C-termini, and that C-terminus engineering can precisely control the extent and direction of ligand gating. These findings establish the design rules to produce customized ligand-gated channels for synthetic biology applications. PMID:28145461

Correlation between the availability of dopamine transporter and olfactory function in healthy subjects

International Nuclear Information System (INIS)

Pak, Kyoungjune; Kim, Keunyoung; Kim, In Joo; Lee, Myung Jun; Lee, Jae Meen; Kim, Bum Soo; Kim, Seong-Jang

2018-01-01

Olfactory dysfunction in Parkinson's disease is usually prodromal to other symptoms. In this study, we aimed to explore the association of olfactory function with the availabilities of striatal dopamine transporter (DAT) in healthy subjects. Data used in the preparation of this article were obtained from Parkinson's Progression Markers Initiative database (www.ppmi-info.org/data). The study population consisted of healthy controls with screening 123 I-FP-CIT single photon emission tomography (SPECT). University of Pennsylvania Smell Identification Test (UPSIT) was assessed to evaluate the olfactory function. Totally, 181 healthy subjects (117 male, 64 female) with 123 I-FP-CIT SPECT data were included in this study. Specific binding ratios (SBRs) of the caudate nucleus (rho = -0.4217, p < 0.0001), putamen (rho = -0.2292, p = 0.0019), and striatum (rho=-0.3425, p < 0.0001) showed a reduction with ageing. SBRs of the caudate nucleus, putamen, and striatum were positively correlated with UPSIT (rho = 0.3716, p < 0.0001; rho = 0.3655, p < 0.0001; rho = 0.3880, p < 0.0001). After controlling for age by partial correlation, SBRs of the caudate nucleus, putamen, and striatum showed an influence on UPSIT (rho = 0.3288, p < 0.0001; rho = 0.3374, p < 0.0001; rho = 0.3511, p < 0.0001). Olfactory function is associated with the availability of striatal DAT independent of age in healthy subjects. (orig.)

Individual differences in impulsive action and dopamine transporter function in rat orbitofrontal cortex.

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Yates, J R; Darna, M; Beckmann, J S; Dwoskin, L P; Bardo, M T

2016-01-28

Impulsivity, which can be subdivided into impulsive action and impulsive choice, is implicated as a factor underlying drug abuse vulnerability. Although previous research has shown that dopamine (DA) systems in prefrontal cortex are involved in impulsivity and substance abuse, it is not known if inherent variation in DA transporter (DAT) function contributes to impulsivity. The current study determined if individual differences in either impulsive action or impulsive choice are related to DAT function in orbitofrontal (OFC) and/or medial prefrontal cortex (mPFC). Rats were first tested both for impulsive action in a cued go/no-go task and for impulsive choice in a delay-discounting task. Following behavioral evaluation, in vitro [(3)H]DA uptake assays were performed in OFC and mPFC isolated from individual rats. Vmax in OFC, but not mPFC, was correlated with performance in the cued go/no-go task, with decreased OFC DAT function being associated with high impulsive action. In contrast, Vmax in OFC and mPFC was not correlated with performance in the delay-discounting task. The current results demonstrate that impulsive behavior in cued go/no-go performance is associated with decreased DAT function in OFC, suggesting that hyperdopaminergic tone in this prefrontal subregion mediates, at least in part, increased impulsive action. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

Epistasis between dopamine regulating genes identifies a nonlinear response of the human hippocampus during memory tasks.

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Bertolino, Alessandro; Di Giorgio, Annabella; Blasi, Giuseppe; Sambataro, Fabio; Caforio, Grazia; Sinibaldi, Lorenzo; Latorre, Valeria; Rampino, Antonio; Taurisano, Paolo; Fazio, Leonardo; Romano, Raffaella; Douzgou, Sofia; Popolizio, Teresa; Kolachana, Bhaskar; Nardini, Marcello; Weinberger, Daniel R; Dallapiccola, Bruno

2008-08-01

Dopamine modulation of neuronal activity in prefrontal cortex maps to an inverted U-curve. Dopamine is also an important factor in regulation of hippocampal mediated memory processing. Here, we investigated the effect of genetic variation of dopamine inactivation via catechol-O-methyltransferase (COMT) and the dopamine transporter (DAT) on hippocampal activity in healthy humans during different memory conditions. Using blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in 82 subjects matched for a series of demographic and genetic variables, we studied the effect of the COMT valine (Val)(158)methionine (Met) and the DAT 3' variable number tandem repeat (VNTR) polymorphisms on function of the hippocampus during encoding of recognition memory and during working memory. Our results consistently demonstrated a double dissociation so that DAT 9-repeat carrier alleles modulated activity in the hippocampus in the exact opposite direction of DAT 10/10-repeat alleles based on COMT Val(158)Met genotype during different memory conditions. Similar results were evident in ventrolateral and dorsolateral prefrontal cortex. These findings suggest that genetically determined dopamine signaling during memory processing maps to a nonlinear relationship also in the hippocampus. Our data also demonstrate in human brain epistasis of two genes implicated in dopamine signaling on brain activity during different memory conditions.

Cross-hemispheric dopamine projections have functional significance

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Fox, Megan E.; Mikhailova, Maria A.; Bass, Caroline E.; Takmakov, Pavel; Gainetdinov, Raul R.; Budygin, Evgeny A.; Wightman, R. Mark

2016-01-01

Dopamine signaling occurs on a subsecond timescale, and its dysregulation is implicated in pathologies ranging from drug addiction to Parkinson’s disease. Anatomic evidence suggests that some dopamine neurons have cross-hemispheric projections, but the significance of these projections is unknown. Here we report unprecedented interhemispheric communication in the midbrain dopamine system of awake and anesthetized rats. In the anesthetized rats, optogenetic and electrical stimulation of dopamine cells elicited physiologically relevant dopamine release in the contralateral striatum. Contralateral release differed between the dorsal and ventral striatum owing to differential regulation by D2-like receptors. In the freely moving animals, simultaneous bilateral measurements revealed that dopamine release synchronizes between hemispheres and intact, contralateral projections can release dopamine in the midbrain of 6-hydroxydopamine–lesioned rats. These experiments are the first, to our knowledge, to show cross-hemispheric synchronicity in dopamine signaling and support a functional role for contralateral projections. In addition, our data reveal that psychostimulants, such as amphetamine, promote the coupling of dopamine transients between hemispheres. PMID:27298371

Zn2+ modulation of neurotransmitter transporters

DEFF Research Database (Denmark)

Nørgaard-Nielsen, K.; Gether, U.

2006-01-01

of neurotransmitter transporters have been identified based on sequence homology: (1) the neurotransmitter sodium symporter family (NSS), which includes the Na+/C1(-)-dependent transporters for dopamine, norepinephrine, and serotonin; and (2) the dicarboxylate/amino acid cation symporter family (DAACS), which...

Mutational analysis of the high-affinity zinc binding site validates a refined human dopamine transporter homology model.

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Thomas Stockner

Full Text Available The high-resolution crystal structure of the leucine transporter (LeuT is frequently used as a template for homology models of the dopamine transporter (DAT. Although similar in structure, DAT differs considerably from LeuT in a number of ways: (i when compared to LeuT, DAT has very long intracellular amino and carboxyl termini; (ii LeuT and DAT share a rather low overall sequence identity (22% and (iii the extracellular loop 2 (EL2 of DAT is substantially longer than that of LeuT. Extracellular zinc binds to DAT and restricts the transporter's movement through the conformational cycle, thereby resulting in a decrease in substrate uptake. Residue H293 in EL2 praticipates in zinc binding and must be modelled correctly to allow for a full understanding of its effects. We exploited the high-affinity zinc binding site endogenously present in DAT to create a model of the complete transmemberane domain of DAT. The zinc binding site provided a DAT-specific molecular ruler for calibration of the model. Our DAT model places EL2 at the transporter lipid interface in the vicinity of the zinc binding site. Based on the model, D206 was predicted to represent a fourth co-ordinating residue, in addition to the three previously described zinc binding residues H193, H375 and E396. This prediction was confirmed by mutagenesis: substitution of D206 by lysine and cysteine affected the inhibitory potency of zinc and the maximum inhibition exerted by zinc, respectively. Conversely, the structural changes observed in the model allowed for rationalizing the zinc-dependent regulation of DAT: upon binding, zinc stabilizes the outward-facing state, because its first coordination shell can only be completed in this conformation. Thus, the model provides a validated solution to the long extracellular loop and may be useful to address other aspects of the transport cycle.

Computational systems analysis of dopamine metabolism.

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Zhen Qi

2008-06-01

Full Text Available A prominent feature of Parkinson's disease (PD is the loss of dopamine in the striatum, and many therapeutic interventions for the disease are aimed at restoring dopamine signaling. Dopamine signaling includes the synthesis, storage, release, and recycling of dopamine in the presynaptic terminal and activation of pre- and post-synaptic receptors and various downstream signaling cascades. As an aid that might facilitate our understanding of dopamine dynamics in the pathogenesis and treatment in PD, we have begun to merge currently available information and expert knowledge regarding presynaptic dopamine homeostasis into a computational model, following the guidelines of biochemical systems theory. After subjecting our model to mathematical diagnosis and analysis, we made direct comparisons between model predictions and experimental observations and found that the model exhibited a high degree of predictive capacity with respect to genetic and pharmacological changes in gene expression or function. Our results suggest potential approaches to restoring the dopamine imbalance and the associated generation of oxidative stress. While the proposed model of dopamine metabolism is preliminary, future extensions and refinements may eventually serve as an in silico platform for prescreening potential therapeutics, identifying immediate side effects, screening for biomarkers, and assessing the impact of risk factors of the disease.

Evidence That Sleep Deprivation Downregulates Dopamine D2R in Ventral Striatum in the Human Brain

International Nuclear Information System (INIS)

Volkow, N.D.; Fowler, J.; Volkow, N.D.; Tomasi, D.; Wang, G.-J.; Fowler, J.S.; Logan, J.; Benveniste, H.; Kin, R.; Thanos, P.K.; Sergi, F.

2012-01-01

Dopamine D2 receptors are involved with wakefulness, but their role in the decreased alertness associated with sleep deprivation is unclear. We had shown that sleep deprivation reduced dopamine D2/D3 receptor availability (measured with PET and [ 11 C]raclopride in controls) in striatum, but could not determine whether this reflected dopamine increases ([ 11 C]raclopride competes with dopamine for D2/D3 receptor binding) or receptor downregulation. To clarify this, we compared the dopamine increases induced by methylphenidate (a drug that increases dopamine by blocking dopamine transporters) during sleep deprivation versus rested sleep, with the assumption that methylphenidate's effects would be greater if, indeed, dopamine release was increased during sleep deprivation. We scanned 20 controls with [ 11 C]raclopride after rested sleep and after 1 night of sleep deprivation; both after placebo and after methylphenidate. We corroborated a decrease in D2/D3 receptor availability in the ventral striatum with sleep deprivation (compared with rested sleep) that was associated with reduced alertness and increased sleepiness. However, the dopamine increases induced by methylphenidate (measured as decreases in D2/D3 receptor availability compared with placebo) did not differ between rested sleep and sleep deprivation, and were associated with the increased alertness and reduced sleepiness when methylphenidate was administered after sleep deprivation. Similar findings were obtained by microdialysis in rodents subjected to 1 night of paradoxical sleep deprivation. These findings are consistent with a downregulation of D2/D3 receptors in ventral striatum with sleep deprivation that may contribute to the associated decreased wakefulness and also corroborate an enhancement of D2 receptor signaling in the arousing effects of methylphenidate in humans.

[Scans without Evidence of Dopamine Deficit (SWEDDs)].

Science.gov (United States)

Mukai, Yohei; Murata, Miho

2016-01-01

Dopamine transporter (DaT) single-photon emission computed tomography (SPECT) and [18F]fluoro-L-DOPA ([18F]DOPA) positron emission tomography (PET) facilitate the investigation of dopaminergic hypofunction in neurodegenerative diseases. DaT SPECT and [18F]DOPA PET have been adopted as survey tools in clinical trials. In a large study on Parkinson's disease, 4-15% of subjects clinically diagnosed with early-stage Parkinson's disease had normal dopaminergic functional imaging scans. These are called Scans without Evidence of Dopamine Deficit (SWEDDs), and are considered to represent a state different from Parkinson's disease. Neurological diseases that exhibit parkinsonism and have normal dopaminergic cells in the nigrostriatal system (e.g., essential tremor, psychogenic parkinsonism, DOPA-responsive dystonia, vascular parkinsonism, drug-induced parkinsonism, manganism, brain tumor, myoclonus-dystonia (DYT11), and fragile X syndrome) might be diagnosed with SWEDDs. True bradykinesia with fatigue or decrement may be useful for distinguishing between Parkinson's disease and SWEDDs. However, because SWEDDs encompass many diseases, their properties may not be uniform. In this review, we discuss DaT SPECT, the concept of SWEDDs, and differential diagnosis.

Dopamine Release and Uptake Impairments and Behavioral Alterations Observed in Mice that Model Fragile X Mental Retardation Syndrome.

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Fulks, Jenny L; O'Bryhim, Bliss E; Wenzel, Sara K; Fowler, Stephen C; Vorontsova, Elena; Pinkston, Jonathan W; Ortiz, Andrea N; Johnson, Michael A

2010-10-20

In this study we evaluated the relationship between amphetamine-induced behavioral alterations and dopamine release and uptake characteristics in Fmr1 knockout (Fmr1 KO) mice, which model fragile X syndrome. The behavioral analyses, obtained at millisecond temporal resolution and 2 mm spatial resolution using a force-plate actometer, revealed that Fmr1 KO mice express a lower degree of focused stereotypy compared to wild type (WT) control mice after injection with 10 mg/kg (ip) amphetamine. To identify potentially related neurochemical mechanisms underlying this phenomenon, we measured electrically-evoked dopamine release and uptake using fast-scan cyclic voltammetry at carbon-fiber microelectrodes in striatal brain slices. At 10 weeks of age, dopamine release per pulse, which is dopamine release corrected for differences in uptake, was unchanged. However, at 15 (the age of behavioral testing) and 20 weeks of age, dopamine per pulse and the maximum rate of dopamine uptake was diminished in Fmr1 KO mice compared to WT mice. Dopamine uptake measurements, obtained at different amphetamine concentrations, indicated that dopamine transporters in both genotypes have equal affinities for amphetamine. Moreover, dopamine release measurements from slices treated with quinpirole, a D2-family receptor agonist, rule out enhanced D2 autoreceptor sensitivity as a mechanism of release inhibition. However, dopamine release, uncorrected for uptake and normalized against the corresponding pre-drug release peaks, increased in Fmr1 KO mice, but not in WT mice. Collectively, these data are consistent with a scenario in which a decrease in extracellular dopamine levels in the striatum result in diminished expression of focused stereotypy in Fmr1 KO mice.

Comparative MD Simulations Indicate a Dual Role for Arg1323.50 in Dopamine-Dependent D2R Activation.

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Ralf C Kling

Full Text Available Residue Arg3.50 belongs to the highly conserved DRY-motif of class A GPCRs, which is located at the bottom of TM3. On the one hand, Arg3.50 has been reported to help stabilize the inactive state of GPCRs, but on the other hand has also been shown to be crucial for stabilizing active receptor conformations and mediating receptor-G protein coupling. The combined results of these studies suggest that the exact function of Arg3.50 is likely to be receptor-dependent and must be characterized independently for every GPCR. Consequently, we now present comparative molecular-dynamics simulations that use our recently described inactive-state and Gα-bound active-state homology models of the dopamine D2 receptor (D2R, which are either bound to dopamine or ligand-free, performed to identify the function of Arg1323.50 in D2R. Our results are consistent with a dynamic model of D2R activation in which Arg1323.50 adopts a dual role, both by stabilizing the inactive-state receptor conformation and enhancing dopamine-dependent D2R-G protein coupling.

4-[18F]Fluorophenylpiperazines by Improved Hartwig-Buchwald N-Arylation of 4-[18F]fluoroiodobenzene, Formed via Hypervalent λ3-Iodane Precursors: Application to Build-Up of the Dopamine D4 Ligand [18F]FAUC 316

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Fabian Kügler

2014-12-01

Full Text Available Substituted phenylpiperazines are often neuropharmacologically active compounds and in many cases are essential pharmacophores of neuroligands for different receptors such as D2-like dopaminergic, serotoninergic and other receptors. Nucleophilic, no-carrier-added (n.c.a. 18F-labelling of these ligands in an aromatic position is desirable for studying receptors with in vivo molecular imaging. 1-(4-[18F]Fluorophenylpiperazine was synthesized in two reaction steps starting by 18F-labelling of a iodobenzene-iodonium precursor, followed by Pd-catalyzed N-arylation of the intermediate 4-[18F]fluoro-iodobenzene. Different palladium catalysts and solvents were tested with particular attention to the polar solvents dimethylformamide (DMF and dimethylsulfoxide (DMSO. Weak inorganic bases like potassium phosphate or cesium carbonate seem to be essential for the arylation step and lead to conversation rates above 70% in DMF which is comparable to those in typically used toluene. In DMSO even quantitative conversation was observed. Overall radiochemical yields of up to 40% and 60% in DMF and DMSO, respectively, were reached depending on the labelling yield of the first step. The fluorophenylpiperazine obtained was coupled in a third reaction step with 2-formyl-1H-indole-5-carbonitrile to yield the highly selective dopamine D4 ligand [18F]FAUC 316.

Allosteric mechanisms within the adenosine A2A-dopamine D2 receptor heterotetramer

Science.gov (United States)

Ferré, Sergi; Bonaventura, Jordi; Tomasi, Dardo; Navarro, Gemma; Moreno, Estefanía; Cortés, Antonio; Lluís, Carme; Casadó, Vicent; Volkow, Nora D.

2017-01-01

The structure constituted by a G protein coupled receptor (GPCR) homodimer and a G protein provides a main functional unit and oligomeric entities can be viewed as multiples of dimers. For GPCR heteromers, experimental evidence supports a tetrameric structure, comprised of two different homodimers, each able to signal with its preferred G protein. GPCR homomers and heteromers can act as the conduit of allosteric interactions between orthosteric ligands. The well-known agonist/agonist allosteric interaction in the adenosine A2A receptor (A2AR)-dopamine D2 receptor (D2R) heteromer, by which A2AR agonists decrease the affinity of D2R agonists, gave the first rationale for the use of A2AR antagonists in Parkinson’s disease. We review new pharmacological findings that can be explained in the frame of a tetrameric structure of the A2AR-D2R heteromer: first, ligand-independent allosteric modulations by the D2R that result in changes of the binding properties of A2AR ligands; second, differential modulation of the intrinsic efficacy of D2R ligands for G protein-dependent and independent signaling; third, the canonical antagonistic Gs-Gi interaction within the frame of the heteromer; and fourth, the ability of A2AR antagonists, including caffeine, to also exert the same allosteric modulations of D2R ligands than A2AR agonists, while A2AR agonists and antagonists counteract each other’s effects. These findings can have important clinical implications when evaluating the use of A2AR antagonists. They also call for the need of monitoring caffeine intake when evaluating the effect of D2R ligands, when used as therapeutic agents in neuropsychiatric disorders or as probes in imaging studies. PMID:26051403

Dynamic Factors Affecting Gaseous Ligand Binding in an Artificial Oxygen Transport Protein‡

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Zhang, Lei; Andersen, Eskil M.E.; Khajo, Abdelahad; Magliozzo, Richard S.; Koder, Ronald L.

2013-01-01

We report the functional analysis of an artificial hexacoordinate oxygen transport protein, HP7, which operates via a mechanism similar to that of human neuroglobin and cytoglobin: the destabilization of one of two heme-ligating histidine residues. In the case of HP7 this is the result of the coupling of histidine side chain ligation with the burial of three charged glutamate residues on the same helix. Here we compare gaseous ligand binding, including rates, affinities and oxyferrous state lifetimes, of both heme binding sites in HP7. We find that despite the identical sequence of helices in both binding sites, there are differences in oxygen affinity and oxyferrous state lifetime which may be the result of differences in the freedom of motion imposed by the candelabra fold on the two sites of the protein. We further examine the effect of mutational removal of the buried glutamates on function. Heme iron in the ferrous state of this mutant is rapidly oxidized when when exposed to oxygen. Compared to HP7, distal histidine affinity is increased by a 22-fold decrease in the histidine ligand off-rate. EPR comparison of these ferric hemoproteins demonstrates that the mutation increases disorder at the heme binding site. NMR-detected deuterium exchange demonstrates that the mutation greatly increases water penetration into the protein core. The inability of the mutant protein to bind oxygen may be due to increased water penetration, the large decrease in binding rate caused by the increase in distal histidine affinity, or a combination of the two factors. Together these data underline the importance of the control of protein dynamics in the design of functional artificial proteins. PMID:23249163

Single cocaine exposure does not alter striatal pre-synaptic dopamine function in mice: an [18 F]-FDOPA PET study.

Science.gov (United States)

Bonsall, David R; Kokkinou, Michelle; Veronese, Mattia; Coello, Christopher; Wells, Lisa A; Howes, Oliver D

2017-12-01

Cocaine is a recreational drug of abuse that binds to the dopamine transporter, preventing reuptake of dopamine into pre-synaptic terminals. The increased presence of synaptic dopamine results in stimulation of both pre- and post-synaptic dopamine receptors, considered an important mechanism by which cocaine elicits its reinforcing properties. However, the effects of acute cocaine administration on pre-synaptic dopamine function remain unclear. Non-invasive imaging techniques such as positron emission tomography have revealed impaired pre-synaptic dopamine function in chronic cocaine users. Similar impairments have been seen in animal studies, with microdialysis experiments indicating decreased basal dopamine release. Here we use micro positron emission tomography imaging techniques in mice to measure dopamine synthesis capacity and determine the effect of acute cocaine administration of pre-synaptic dopamine function. We show that a dose of 20 mg/kg cocaine is sufficient to elicit hyperlocomotor activity, peaking 15-20 min post treatment (p dopamine synthesis capacity in the striatum was not significantly altered by acute cocaine treatment (KiCer: 0.0097 per min vs. 0.0112 per min in vehicle controls, p > 0.05). Furthermore, expression levels of two key enzymes related to dopamine synthesis, tyrosine hydroxylase and aromatic l-amino acid decarboxylase, within the striatum of scanned mice were not significantly affected by acute cocaine pre-treatment (p > 0.05). Our findings suggest that while the regulation of dopamine synthesis and release in the striatum have been shown to change with chronic cocaine use, leading to a reduced basal tone, these adaptations to pre-synaptic dopaminergic neurons are not initiated following a single exposure to the drug. © 2017 International Society for Neurochemistry.

Dopamine transporter density in the basal ganglia assessed with [123I]IPT SPET in children with attention deficit hyperactivity disorder

International Nuclear Information System (INIS)

Cheon, Keun-Ah; Kim, Young-Kee; Namkoong, Kee; Kim, Chan-Hyung; Ryu, Young Hoon; Lee, Jong Doo

2003-01-01

Attention deficit hyperactivity disorder (ADHD) is a psychiatric disorder in childhood that is known to be associated with dopamine dysregulation. In this study, we investigated dopamine transporter (DAT) density in children with ADHD using iodine-123 labelled N-(3-iodopropen-2-yl)-2β-carbomethoxy-3β-(4-chlorophenyl) tropane ([ 123 I]IPT) single-photon emission tomography (SPET) and postulated that an alteration in DAT density in the basal ganglia is responsible for dopaminergic dysfunction in children with ADHD. Nine drug-naive children with ADHD and six normal children were included in the study. We performed brain SPET 2 h after the intravenous administration of [ 123 I]IPT and carried out both quantitative and qualitative analyses using the obtained SPET data, which were reconstructed for the assessment of the specific/non-specific DAT binding ratio in the basal ganglia. We then investigated the correlation between the severity scores of ADHD symptoms in children with ADHD assessed with ADHD rating scale-IV and the specific/non-specific DAT binding ratio in the basal ganglia. Drug-naive children with ADHD showed a significantly increased specific/non-specific DAT binding ratio in the basal ganglia compared with normal children. However, no significant correlation was found between the severity scores of ADHD symptoms in children with ADHD and the specific/non-specific DAT binding ratio in the basal ganglia. Our findings support the complex dysregulation of the dopaminergic neurotransmitter system in children with ADHD. (orig.)

Mephedrone Does not Damage Dopamine Nerve Endings of the Striatum but Enhances the Neurotoxicity of Methamphetamine, Amphetamine and MDMA

OpenAIRE

Angoa-Pérez, Mariana; Kane, Michael J.; Briggs, Denise I.; Francescutti, Dina M.; Sykes, Catherine E.; Shah, Mrudang M.; Thomas, David M.; Kuhn, Donald M.

2013-01-01

Mephedrone (4-methylmethcathinone) is a β-ketoamphetamine stimulant drug of abuse with close structural and mechanistic similarities to methamphetamine. One of the most powerful actions associated with mephedrone is the ability to stimulate dopamine (DA) release and block its reuptake through its interaction with the dopamine transporter (DAT). Although mephedrone does not cause toxicity to DA nerve endings, its ability to serve as a DAT blocker could provide protection against methamphetamin...

Neurotransmission imaging by PET

Energy Technology Data Exchange (ETDEWEB)

Takano, Akihiro; Suhara, Tetsuya [National Inst. of Radiological Sciences, Chiba (Japan)

2001-08-01

PET studies on neurotransmission in psychological disorders to evaluate abnormal neurotransmission and therapeutic effects are thoroughly reviewed by type of major neurotransmitters. Studies on dopaminergic neurotransmission have focused on the function of dopamine D{sub 2} receptors, receptor subtypes, such as the D{sub 1} receptor, and ligands, such as transporters. PET studies of dopamine D{sub 2} receptor, which began in the early 1980s, have predominantly been performed in schizophrenia, and most have failed to detect any statistically significant differences between schizophrenia patients and controls. The studies in the early 1980s were performed by using [{sup 11}C]N-methyl-spiperone (NMSP) and [{sup 11}C]raclopride, ligands for striatal dopamine D{sub 2} receptors. [{sup 11}C]FLB457, which has much higher affinity for D{sub 2} receptors than raclopride, began to be used in the 1990s. Dopamine D{sub 2} occupancy after drug ingestion has also been investigated to clarify the mechanisms and effects of antipsychotic drugs, and there have also been studies on the effect of aging and personality traits on dopamine D{sub 2} receptor levels in healthy subjects. In studies on dopamine receptor subtypes other than D{sub 2}, dopamine D{sub 1} receptors have been studied in connection with assessments of cognitive functions. Most studies on dopamine transporters have been related to drug dependence. Serotonin 5-HT{sub 2A} receptors have been studied with [{sup 11}C]NMSP in schizophrenia patients, while studies of another serotonin receptor subtype, 5-HT{sub 1A} receptors, have been mainly conducted in patients with depression. [{sup 11}C]NMSP PET showed no difference between schizophrenia patients who had not undergone phamacotherapy and normal subjects. Because serotonin selective reuptake inhibitors (SSRIs) affect serotonin transporters, and abnormalities in serotonin transporters detected in mood disorders, PET ligands for serotonin transporters have increasingly

Diagnostic imaging of dementia with Lewy bodies by susceptibility-weighted imaging of nigrosomes versus striatal dopamine transporter single-photon emission computed tomography: a retrospective observational study

Energy Technology Data Exchange (ETDEWEB)

Kamagata, Koji; Sato, Kanako; Suzuki, Michimasa; Hori, Masaaki; Kumamaru, Kanako K.; Aoki, Shigeki [Juntendo University Graduate School of Medicine, Department of Radiology, Bunkyo-ku, Tokyo (Japan); Nakatsuka, Tomoya; Inaoka, Tsutomu; Terada, Hitoshi [Toho University Sakura Medical Center, Department of Radiology, Sakura, Sakura (Japan); Sakakibara, Ryuji; Tsuyusaki, Yohei [Toho University Sakura Medical Center, Department of Neurology, Sakura, Sakura (Japan); Takamura, Tomohiro [University of Yamanashi, Department of Radiology, Chuo-shi, Yamanashi (Japan)

2017-01-15

The characteristics of dementia with Lewy bodies (DLB), Alzheimer's disease (AD) and amnestic mild cognitive impairment (a-MCI) overlap but require different treatments; therefore, it is important to differentiate these pathologies. Assessment of dopamine uptake in the striatum using dopamine transporter (DaT) single-photon emission computed tomography (SPECT) is the gold standard for diagnosing DLB; however, this modality is expensive, time consuming and involves radiation exposure. Degeneration of the substantia nigra nigrosome-1, which occurs in DLB, but not in AD/a-MCI, can be identified by 3T susceptibility-weighted imaging (SWI). Therefore, the aim of this retrospective observational study was to compare SWI with DaT-SPECT for differentiation of DLB from AD/a-MCI. SWI data were acquired for patients with clinically diagnosed DLB (n = 29), AD (n = 18), a-MCI (n = 13) and healthy controls (n = 26). Images were analysed for nigrosome-1 degeneration. Diagnostic accuracy was evaluated for DLB, AD and a-MCI compared with striatal dopamine uptake using DaT-SPECT. SWI achieved 90% diagnostic accuracy (93% sensitivity, 87% specificity) for the detection of nigrosome-1 degeneration in DLB and not in AD/a-MCI as compared with 88.3% accuracy (93% sensitivity, 84% specificity) using DaT-SPECT. SWI nigrosome-1 evaluation was useful in differentiating DLB from AD/a-MCI, with high accuracy. This less invasive and less expensive method is a potential alternative to DaT-SPECT for the diagnosis of DLB. (orig.)

Dopamine versus noradrenaline in septic shock

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Bo Xu

2011-10-01

Full Text Available BackgroundThe ‘Surviving Sepsis’ Campaign guidelines recommend theuse of dopamine or noradrenaline as the first vasopressor inseptic shock. However, information that guides clinicians inchoosing between dopamine and noradrenaline as the firstvasopressor in patients with septic shock is limited.ObjectiveThis article presents a review of the literature regarding theuse of dopamine versus noradrenaline in patients with septicshock.ResultsTwo randomised controlled trials (RCT and two largeprospective cohort studies were analysed. RCT data showeddopamine was associated with increased arrhythmic events.One cohort study found dopamine was associated with higher30-day mortality. The other cohort study found noradrenalinewas associated with higher 28-day mortality.DiscussionData on the use of dopamine versus noradrenaline in patientswith septic shock is limited. Following the recent SOAP IIstudy, there is now strong evidence that the use of dopaminein septic shock is associated with significantly morecardiovascular adverse events, compared tonoradrenaline.ConclusionNoradrenaline should be used as the initial vasopressor inseptic shock to avoid the arrhythmic events associatedwith dopamine.

Optogenetic stimulation of VTA dopamine neurons reveals that tonic but not phasic patterns of dopamine transmission reduce ethanol self-administration

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Caroline E Bass

2013-11-01

Full Text Available There is compelling evidence that acute ethanol exposure stimulates ventral tegmental area (VTA dopamine cell activity and that VTA-dependent dopamine release in terminal fields within the nucleus accumbens plays an integral role in the regulation of ethanol drinking behaviors. Unfortunately, due to technical limitations, the specific temporal dynamics linking VTA dopamine cell activation and ethanol self-administration are not known. In fact, establishing a causal link between specific patterns of dopamine transmission and ethanol drinking behaviors has proven elusive. Here, we sought to address these gaps in our knowledge using a newly developed viral-mediated gene delivery strategy to selectively express Channelrhodopsin-2 (ChR2 on dopamine cells in the VTA of wild-type rats. We then used this approach to precisely control VTA dopamine transmission during voluntary ethanol drinking sessions. The results confirmed that ChR2 was selectively expressed on VTA dopamine cells and delivery of blue light pulses to the VTA induced dopamine release in accumbal terminal fields with very high temporal and spatial precision. Brief high frequency VTA stimulation induced phasic patterns of dopamine release in the nucleus accumbens. Lower frequency stimulation, applied for longer periods mimicked tonic increases in accumbal dopamine. Notably, using this optogenetic approach in rats engaged in an intermittent ethanol drinking procedure, we found that tonic, but not phasic, stimulation of VTA dopamine cells selectively attenuated ethanol drinking behaviors. Collectively, these data demonstrate the effectiveness of a novel viral targeting strategy that can be used to restrict opsin expression to dopamine cells in standard outbred animals and provide the first causal evidence demonstrating that tonic activation of VTA dopamine neurons selectively decreases ethanol self-administration behaviors.