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Sample records for dopamine transporter investigating

  1. Genetics Home Reference: dopamine transporter deficiency syndrome

    MedlinePlus

    ... Genetics Home Health Conditions dopamine transporter deficiency syndrome dopamine transporter deficiency syndrome Enable Javascript to view the ... boxes. Download PDF Open All Close All Description Dopamine transporter deficiency syndrome is a rare movement disorder. ...

  2. Dopamine transporter mutant animals: a translational perspective

    PubMed Central

    Efimova, Evgenia V.; Gainetdinov, Raul R.; Budygin, Evgeny A.; Sotnikova, Tatiana D.

    2016-01-01

    The dopamine transporter (DAT) plays an important homeostatic role in the control of both the extracellular and intraneuronal concentrations of dopamine, thereby providing effective control over activity of dopaminergic transmission. Since brain dopamine is known to be involved in numerous neuropsychiatric disorders, investigations using mice with genetically altered DAT function and thus intensity of dopamine-mediated signaling have provided numerous insights into the pathology of these disorders and highlight novel pathological mechanisms that could be targeted to provide new therapeutic approaches for these disorders. In this brief overview we discuss recent investigations involving animals with genetically altered DAT function, particularly focusing on translational studies providing new insights into pathology and pharmacology of dopamine-related disorders. Perspective applications of these and newly developed models of DAT dysfunction are also discussed. PMID:27276191

  3. Dopamine transporter deficiency syndrome: phenotypic spectrum from infancy to adulthood

    PubMed Central

    Ng, Joanne; Zhen, Juan; Meyer, Esther; Erreger, Kevin; Li, Yan; Kakar, Naseebullah; Ahmad, Jamil; Thiele, Holger; Kubisch, Christian; Rider, Nicholas L.; Holmes Morton, D.; Strauss, Kevin A.; Puffenberger, Erik G.; D’Agnano, Daniela; Anikster, Yair; Carducci, Claudia; Hyland, Keith; Rotstein, Michael; Leuzzi, Vincenzo; Borck, Guntram; Reith, Maarten E. A.

    2014-01-01

    Dopamine transporter deficiency syndrome due to SLC6A3 mutations is the first inherited dopamine ‘transportopathy’ to be described, with a classical presentation of early infantile-onset progressive parkinsonism dystonia. In this study we have identified a new cohort of patients with dopamine transporter deficiency syndrome, including, most significantly, atypical presentation later in childhood with a milder disease course. We report the detailed clinical features, molecular genetic findings and in vitro functional investigations undertaken for adult and paediatric cases. Patients presenting with parkinsonism dystonia or a neurotransmitter profile characteristic of dopamine transporter deficiency syndrome were recruited for study. SLC6A3 mutational analysis was undertaken in all patients. The functional consequences of missense variants on the dopamine transporter were evaluated by determining the effect of mutant dopamine transporter on dopamine uptake, protein expression and amphetamine-mediated dopamine efflux using an in vitro cellular heterologous expression system. We identified eight new patients from five unrelated families with dopamine transporter deficiency syndrome. The median age at diagnosis was 13 years (range 1.5–34 years). Most significantly, the case series included three adolescent males with atypical dopamine transporter deficiency syndrome of juvenile onset (outside infancy) and progressive parkinsonism dystonia. The other five patients in the cohort presented with classical infantile-onset parkinsonism dystonia, with one surviving into adulthood (currently aged 34 years) and labelled as having ‘juvenile parkinsonism’. All eight patients harboured homozygous or compound heterozygous mutations in SLC6A3, of which the majority are previously unreported variants. In vitro studies of mutant dopamine transporter demonstrated multifaceted loss of dopamine transporter function. Impaired dopamine uptake was universally present, and more

  4. Dopamine transporter: expression in Xenopus oocytes.

    PubMed

    Uhl, G R; O'Hara, B; Shimada, S; Zaczek, R; DiGiorgianni, J; Nishimori, T

    1991-01-01

    Xenopus oocytes can express biologically relevant transport activity after injection of mRNAs encoding several carrier molecules. mRNA from PC12 cells, as well as transcripts from a rat ventral midbrain library, can be expressed in these oocytes and allow them to display pharmacologically specific dopamine uptake. mRNA-injected oocytes incubated with tritiated dopamine contain tritiated dopamine and metabolites; lower amounts of radiolabeled dopamine and more radiolabeled metabolites are found in oocytes co-incubated with cocaine or in water-injected oocytes. Tritiated dopamine uptake into mRNA-injected oocytes is time, sodium, and temperature dependent. It is blocked by cocaine and mazindol, but not by haloperidol. It is not found after injection of mRNA from other brain regions. A size-selected rat midbrain library constructed in the plasma vector pCDM8 yields mRNA transcripts whose injection into oocytes causes cocaine-blockable [3H]dopamine uptake. These findings provide an assay for purification of the dopamine transporter cDNA by sib selection techniques.

  5. Molecular model of the neural dopamine transporter

    NASA Astrophysics Data System (ADS)

    Ravna, Aina Westrheim; Sylte, Ingebrigt; Dahl, Svein G.

    2003-05-01

    The dopamine transporter (DAT) regulates the action of dopamine by reuptake of the neurotransmitter into presynaptic neurons, and is the main molecular target of amphetamines and cocaine. DAT and the Na+/H+ antiporter (NhaA) are secondary transporter proteins that carry small molecules across a cell membrane against a concentration gradient, using ion gradients as energy source. A 3-dimensional projection map of the E. coli NhaA has confirmed a topology of 12 membrane spanning domains, and was previously used to construct a 3-dimensional NhaA model with 12 trans-membrane α-helices (TMHs). The NhaA model, and site directed mutagenesis data on DAT, were used to construct a detailed 3-dimensional DAT model using interactive molecular graphics and empiric force field calculations. The model proposes a dopamine transport mechanism involving TMHs 1, 3, 4, 5, 7 and 11. Asp79, Tyr252 and Tyr274 were the primary cocaine binding residues. Binding of cocaine or its analogue, (-)-2β-carbomethoxy-3β-(4-fluorophenyl)tropane (CFT), seemed to lock the transporter in an inactive state, and thus inhibit dopamine transport. The present model may be used to design further experimental studies of the molecular structure and mechanisms of DAT and other secondary transporter proteins.

  6. Psychostimulants affect dopamine transmission through both dopamine transporter-dependent and independent mechanisms.

    PubMed

    dela Peña, Ike; Gevorkiana, Ruzanna; Shi, Wei-Xing

    2015-10-05

    The precise mechanisms by which cocaine and amphetamine-like psychostimulants exert their reinforcing effects are not yet fully defined. It is widely believed, however, that these drugs produce their effects by enhancing dopamine neurotransmission in the brain, especially in limbic areas such as the nucleus accumbens, by inducing dopamine transporter-mediated reverse transport and/or blocking dopamine reuptake though the dopamine transporter. Here, we present the evidence that aside from dopamine transporter, non-dopamine transporter-mediated mechanisms also participate in psychostimulant-induced dopamine release and contribute to the behavioral effects of these drugs, such as locomotor activation and reward. Accordingly, psychostimulants could increase norepinephrine release in the prefrontal cortex, the latter then alters the firing pattern of dopamine neurons resulting in changes in action potential-dependent dopamine release. These alterations would further affect the temporal pattern of dopamine release in the nucleus accumbens, thereby modifying information processing in that area. Hence, a synaptic input to a nucleus accumbens neuron may be enhanced or inhibited by dopamine depending on its temporal relationship to dopamine release. Specific temporal patterns of dopamine release may also be required for certain forms of synaptic plasticity in the nucleus accumbens. Together, these effects induced by psychostimulants, mediated through a non-dopamine transporter-mediated mechanism involving norepinephrine and the prefrontal cortex, may also contribute importantly to the reinforcing properties of these drugs.

  7. Phosphorylation mechanisms in dopamine transporter regulation.

    PubMed

    Foster, James D; Vaughan, Roxanne A

    2016-11-09

    The dopamine transporter (DAT) is a plasma membrane phosphoprotein that actively translocates extracellular dopamine (DA) into presynaptic neurons. The transporter is the primary mechanism for control of DA levels and subsequent neurotransmission, and is the target for abused and therapeutic drugs that exert their effects by suppressing reuptake. The transport capacity of DAT is acutely regulated by signaling systems and drug exposure, providing neurons the ability to fine-tune DA clearance in response to specific conditions. Kinase pathways play major roles in these mechanisms, and this review summarizes the current status of DAT phosphorylation characteristics and the evidence linking transporter phosphorylation to control of reuptake and other functions. Greater understanding of these processes may aid in elucidation of their possible contributions to DA disease states and suggest specific phosphorylation sites as targets for therapeutic manipulation of reuptake.

  8. Reciprocal Phosphorylation and Palmitoylation Control Dopamine Transporter Kinetics*

    PubMed Central

    Moritz, Amy E.; Rastedt, Danielle E.; Stanislowski, Daniel J.; Shetty, Madhur; Smith, Margaret A.; Vaughan, Roxanne A.; Foster, James D.

    2015-01-01

    The dopamine transporter is a neuronal protein that drives the presynaptic reuptake of dopamine (DA) and is the major determinant of transmitter availability in the brain. Dopamine transporter function is regulated by protein kinase C (PKC) and other signaling pathways through mechanisms that are complex and poorly understood. Here we investigate the role of Ser-7 phosphorylation and Cys-580 palmitoylation in mediating steady-state transport kinetics and PKC-stimulated transport down-regulation. Using both mutational and pharmacological approaches, we demonstrate that these post-translational modifications are reciprocally regulated, leading to transporter populations that display high phosphorylation-low palmitoylation or low phosphorylation-high palmitoylation. The balance between the modifications dictates transport capacity, as conditions that promote high phosphorylation or low palmitoylation reduce transport Vmax and enhance PKC-stimulated down-regulation, whereas conditions that promote low phosphorylation or high palmitoylation increase transport Vmax and suppress PKC-stimulated down-regulation. Transitions between these functional states occur when endocytosis is blocked or undetectable, indicating that the modifications kinetically regulate the velocity of surface transporters. These findings reveal a novel mechanism for control of DA reuptake that may represent a point of dysregulation in DA imbalance disorders. PMID:26424792

  9. Cloning of the cocaine-sensitive bovine dopamine transporter

    SciTech Connect

    Usdin, T.B.; Chen, C.; Brownstein, M.J.; Hoffman, B.J. ); Mezey, E. )

    1991-12-15

    A cDNA encoding the dopamine transporter from bovine brain substantia nigra was identified on the basis of its structural homology to other, recently cloned, neurotransmitter transporters. The sequence of the 693-amino acid protein is quite similar to those of the rat {gamma}-aminobutyric acid, human norepinephrine, and rat serotonin transporters. Dopamine transporter mRNA was detected by in situ hybridization in the substantia nigra but not in the locus coeruleus, raphe, caudate, or other brain areas. ({sup 3}H)Dopamine accumulation in tissue culture cells transfected with the cDNA was inhibited by amphetamine, cocaine, and specific inhibitors of dopamine transports, including GBR12909.

  10. The dopamine transporter: role in neurotoxicity and human disease

    SciTech Connect

    Bannon, Michael J. . E-mail: mbannon@med.wayne.edu

    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)

  11. The dopamine transporter and attention-deficit/hyperactivity disorder.

    PubMed

    Madras, Bertha K; Miller, Gregory M; Fischman, Alan J

    2005-06-01

    The high incidence of attention-deficit/hyperactivity disorder (ADHD) and escalating use of ADHD medications present a compelling case for clarifying the pathophysiology of, and developing laboratory or radiologic tests for, ADHD. Currently, the majority of specific genes implicated in ADHD encode components of catecholamine signaling systems. Of these, the dopamine transporter (DAT) is a principal target of the most widely used antihyperactivity medications (amphetamine and methylphenidate); the DAT gene is associated with ADHD, and some studies have detected abnormal levels of the DAT in brain striatum of ADHD subjects. Medications for ADHD interfere with dopamine transport by brain-region- and drug-specific mechanisms, indirectly activating dopamine- and possibly norepinephrine-receptor subtypes that are implicated in enhancing attention and experiential salience. The most commonly used DAT-selective ADHD medications raise extracellular dopamine levels in DAT-rich brain regions. In brain regions expressing both the DAT and the norepinephrine transporter (NET), the relative contributions of dopamine and norepinephrine to ADHD pathophysiology and therapeutic response are obfuscated by the capacity of the NET to clear dopamine as well as norepinephrine. Thus, ADHD medications targeting DAT or NET might disperse dopamine widely and consign dopamine storage and release to regulation by noradrenergic, as well as dopaminergic neurons.

  12. Direct affinity of dopamine to lipid membranes investigated by Nuclear Magnetic Resonance spectroscopy.

    PubMed

    Matam, Yashasvi; Ray, Bruce D; Petrache, Horia I

    2016-04-08

    Dopamine, a naturally occurring neurotransmitter, plays an important role in the brain's reward system and acts on sensory receptors in the brain. Neurotransmitters are contained in lipid membraned vesicles and are released by exocytosis. All neurotransmitters interact with transport and receptor proteins in glial cells, on neuronal dendrites, and at the axonal button, and also must interact with membrane lipids. However, the extent of direct interaction between lipid membranes in the absence of receptors and transport proteins has not been extensively investigated. In this report, we use UV and NMR spectroscopy to determine the affinity and the orientation of dopamine interacting with lipid vesicles made of either phosphatidylcholine (PC) or phosphatidylserine (PS) lipids which are primary lipid components of synaptic vesicles. We quantify the interaction of dopamine's aromatic ring with lipid membranes using our newly developed method that involves reference spectra in hydrophobic environments. Our measurements show that dopamine interacts with lipid membranes primarily through the aromatic side opposite to the hydroxyl groups, with this aromatic side penetrating deeper into the hydrophobic region of the membrane. Since dopamine's activity involves its release into extracellular space, we have used our method to also investigate dopamine's release from lipid vesicles. We find that dopamine trapped inside PC and PS vesicles is released into the external solution despite its affinity to membranes. This result suggests that dopamine's interaction with lipid membranes is complex and involves both binding as well as permeation through lipid bilayers, a combination that could be an effective trigger for apoptosis of dopamine-generating cells.

  13. β-phenylethylamine Requires the Dopamine Transporter to Increase Extracellular Dopamine in C. elegans Dopaminergic Neurons

    PubMed Central

    Hossain, Murad; Wickramasekara, Rochelle N.; Carvelli, Lucia

    2013-01-01

    β-phenylethylamine (βPEA) is an endogenous amine that has been shown to increase the synaptic levels of dopamine (DA). A number of in vitro and behavioral studies suggest the dopamine transporter (DAT) plays a role in the effects generated by βPEA, however the mechanism through which βPEA affects DAT has not yet been elucidated. Here, we used Caenorhabditis (C.) elegans DAT (DAT-1) expressing LLC-pk1 cells and neuronal cultures to investigate whether the βPEA-induced increase of extracellular DA required DAT-1. Our data show that βPEA increases extracellular dopamine both in DAT-1 transfected cells and cultures of differentiated neurons. RTI-55, a cocaine homologue and DAT inhibitor, completely blocked the βPEA-induced effect in transfected cells. However in neuronal cultures, RTI-55 only partly inhibited the increase of extracellular DA generated by βPEA. These results suggest that βPEA requires DAT-1 and other, not yet identified proteins, to increase extracellular DA when tested in a native system. Furthermore, our results suggest that βPEA-induced increase of extracellular DA does not require functional monoamine vesicles as genetic ablation of the C. elegans homologue vesicular monoamine transporter, cat-1, did not compromise the ability of βPEA to increase extracellular DA. Finally, our electrophysiology data show that βPEA caused fast-rising and self-inactivating amperometric currents in a subset of wild-type DA neurons but not in neurons isolated from dat-1 knockout animals. Taken together, these data demonstrate that in both DA neurons and heterogeneous cultures of differentiated C. elegans neurons, βPEA releases cytoplasmic DA through DAT-1 to ultimately increase the extracellular concentration of DA. PMID:24161617

  14. Dopamine transporter availability in clinically normal aging is associated with individual differences in white matter integrity.

    PubMed

    Rieckmann, Anna; Hedden, Trey; Younger, Alayna P; Sperling, Reisa A; Johnson, Keith A; Buckner, Randy L

    2016-02-01

    Aging-related differences in white matter integrity, the presence of amyloid plaques, and density of biomarkers indicative of dopamine functions can be detected and quantified with in vivo human imaging. The primary aim of the present study was to investigate whether these imaging-based measures constitute independent imaging biomarkers in older adults, which would speak to the hypothesis that the aging brain is characterized by multiple independent neurobiological cascades. We assessed MRI-based markers of white matter integrity and PET-based marker of dopamine transporter density and amyloid deposition in the same set of 53 clinically normal individuals (age 65-87). A multiple regression analysis demonstrated that dopamine transporter availability is predicted by white matter integrity, which was detectable even after controlling for chronological age. Further post-hoc exploration revealed that dopamine transporter availability was further associated with systolic blood pressure, mirroring the established association between cardiovascular health and white matter integrity. Dopamine transporter availability was not associated with the presence of amyloid burden. Neurobiological correlates of dopamine transporter measures in aging are therefore likely unrelated to Alzheimer's disease but are aligned with white matter integrity and cardiovascular risk. More generally, these results suggest that two common imaging markers of the aging brain that are typically investigated separately do not reflect independent neurobiological processes. Hum Brain Mapp 37:621-631, 2016. © 2015 Wiley Periodicals, Inc.

  15. Extracellular dopamine and alterations on dopamine transporter are related to reserpine toxicity in Caenorhabditis elegans.

    PubMed

    Reckziegel, Patrícia; Chen, Pan; Caito, Sam; Gubert, Priscila; Soares, Félix Alexandre Antunes; Fachinetto, Roselei; Aschner, Michael

    2016-03-01

    Reserpine is used as an animal model of parkinsonism. We hypothesized that the involuntary movements induced by reserpine in rodents are induced by dopaminergic toxicity caused by extracellular dopamine accumulation. The present study tested the effects of reserpine on the dopaminergic system in Caenorhabditis elegans. Reserpine was toxic to worms (decreased the survival, food intake, development and changed egg laying and defecation cycles). In addition, reserpine increased the worms' locomotor rate on food and decreased dopamine levels. Morphological evaluations of dopaminergic CEP neurons confirmed neurodegeneration characterized by decreased fluorescence intensity and the number of worms with intact CEP neurons, and increased number of shrunken somas per worm. These effects were unrelated to reserpine's effect on decreased expression of the dopamine transporter, dat-1. Interestingly, the locomotor rate on food and the neurodegenerative parameters fully recovered to basal conditions upon reserpine withdrawal. Furthermore, reserpine decreased survival in vesicular monoamine transporter and dat-1 loss-of-function mutant worms. In addition, worms pre-exposed to dopamine followed by exposure to reserpine had decreased survival. Reserpine activated gst-4, which controls a phase II detoxification enzymes downstream of nuclear factor (erythroid-derived-2)-like 2. Our findings establish that the dopamine transporter, dat-1, plays an important role in reserpine toxicity, likely by increasing extracellular dopamine concentrations.

  16. SKF-83566, a D1-dopamine receptor antagonist, inhibits the dopamine transporter.

    PubMed

    Stouffer, Melissa A; Ali, Solav; Reith, Maarten E A; Patel, Jyoti C; Sarti, Federica; Carr, Kenneth D; Rice, Margaret E

    2011-09-01

    Dopamine (DA) is an important transmitter in both motor and limbic pathways. We sought to investigate the role of D(1)-receptor activation in axonal DA release regulation in dorsal striatum using a D(1)-receptor antagonist, SKF-83566. Evoked DA release was monitored in rat striatal slices using fast-scan cyclic voltammetry. SKF-83566 caused a concentration-dependent increase in peak single-pulse evoked extracellular DA concentration, with a maximum increase of ∼ 65% in 5 μM SKF-83566. This was accompanied by a concentration-dependent increase in extracellular DA concentration clearance time. Both effects were occluded by nomifensine (1 μM), a dopamine transporter (DAT) inhibitor, suggesting that SKF-83566 acted via the DAT. We tested this by examining [(3)H]DA uptake into LLc-PK cells expressing rat DAT, and confirmed that SKF-83566 is a competitive DAT inhibitor with an IC(50) of 5.7 μM. Binding studies with [(3)H]CFT, a cocaine analog, showed even more potent action of SKF-83566 at the DAT cocaine binding site (IC(50) = 0.51 μM). Thus, data obtained using SKF-83566 as a D(1) DA-receptor antagonist may be confounded by concurrent DAT inhibition. More positively, however, SKF-83566 might be a candidate to attenuate cocaine effects in vivo because of the greater potency of this drug at the cocaine versus DA binding site of the DAT.

  17. Recovery of dopamine transporters with methamphetamine detoxification is not linked to changes in dopamine release.

    PubMed

    Volkow, Nora D; Wang, Gene-Jack; Smith, Lisa; Fowler, Joanna S; Telang, Frank; Logan, Jean; Tomasi, Dardo

    2015-11-01

    Methamphetamine's widepread abuse and concerns that it might increase Parkinson's disease led us to assess if the reported loss of dopamine transporters (DAT) in methamphetamine abusers (MA) reflected damage to dopamine neurons. Using PET with [(11)C]cocaine to measure DAT, and with [(11)C]raclopride to measure dopamine release (assessed as changes in specific binding of [(11)C]raclopride between placebo and methylphenidate), which was used as a marker of dopamine neuronal function, we show that MA (n=16), tested during early detoxification, had lower DAT (20-30%) but overall normal DA release in striatum (except for a small decrease in left putamen), when compared to controls (n=15). In controls, DAT were positively correlated with DA release (higher DAT associated with larger DA increases), consistent with DAT serving as markers of DA terminals. In contrast, MA showed a trend for a negative correlation (p=0.07) (higher DAT associated with lower DA increases), consistent with reduced DA re-uptake following DAT downregulation. MA who remained abstinent nine-months later (n=9) showed significant increases in DAT (20%) but methylphenidate-induced dopamine increases did not change. In contrast, in controls, DAT did not change when retested 9 months later but methylphenidate-induced dopamine increases in ventral striatum were reduced (p=0.05). Baseline D2/D3 receptors in caudate were lower in MA than in controls and did not change with detoxification, nor did they change in the controls upon retest. The loss of DAT in the MA, which was not associated with a concomitant reduction in dopamine release as would have been expected if DAT loss reflected DA terminal degneration; as well as the recovery of DAT after protracted detoxification, which was not associated with increased dopamine release as would have been expected if DAT increases reflected terminal regeneration, indicate that the loss of DAT in these MA does not reflect degeneration of dopamine terminals.

  18. Expression of dopamine receptors and transporter in neuroendocrine gastrointestinal tumor cells.

    PubMed

    Lemmer, K; Ahnert-Hilger, G; Höpfner, M; Hoegerle, S; Faiss, S; Grabowski, P; Jockers-Scherübl, M; Riecken, E O; Zeitz, M; Scherübl, H

    2002-06-28

    C-11- or F-18-DOPA positron emission tomography (DOPA PET) is a new sensitive imaging technique for small neuroendocrine gastrointestinal tumors which evaluates the decarboxylase activity. To further characterize the dopaminergic system in neuroendocrine gastrointestinal tumor cells, we investigated the expression of both dopamine receptors and the transmembrane dopamine transporter (DAT) in the human neuroendocrine pancreatic cell line BON and in the neuroendocrine gut cell line STC-1. Both BON and STC-1 cells expressed mRNA of the dopamine receptors D2-D5 and DAT. mRNA of the dopamine receptor D1 was detected in BON cells only. Both in BON and STC-1 cells, expression of D2 and D5 receptors and DAT was also demonstrated immunocytochemically. For functional receptor characterization intracellular cAMP levels ([cAMP]i) were determined. Whereas in STC-1 cells dopamine and the D1-like (D1/D5) receptor agonist SKF 38393 increased [cAMP]i, [cAMP]i was decreased by dopamine or the D2-like (D2-D4) receptor agonist quinpirole in BON cells. Functional DAT activity was, however, not detected in either cell line. The presence of both dopamine receptors and of the DAT suggests an autocrine and/or paracrine function of dopamine in neuroendocrine gastrointestinal tumor cells. Yet neither the transmembrane dopamine transporter nor dopamine receptors are likely to contribute to positive DOPA PET imaging of neuroendocrine gastrointestinal tumors. However, these molecules may be of diagnostic importance when applying other dopaminergic system tracers.

  19. Conformational changes in dopamine transporter intracellular regions upon cocaine binding and dopamine translocation.

    PubMed

    Dehnes, Yvette; Shan, Jufang; Beuming, Thijs; Shi, Lei; Weinstein, Harel; Javitch, Jonathan A

    2014-07-01

    The dopamine transporter (DAT), a member of the neurotransmitter:sodium symporter family, mediates the reuptake of dopamine at the synaptic cleft. DAT is the primary target for psychostimulants such as cocaine and amphetamine. We previously demonstrated that cocaine binding and dopamine transport alter the accessibility of Cys342 in the third intracellular loop (IL3). To study the conformational changes associated with the functional mechanism of the transporter, we made cysteine substitution mutants, one at a time, from Phe332 to Ser351 in IL3 of the background DAT construct, X7C, in which 7 endogenous cysteines were mutated. The accessibility of the 20 engineered cysteines to polar charged sulfhydryl reagents was studied in the absence and presence of cocaine or dopamine. Of the 11 positions that reacted with methanethiosulfonate ethyl ammonium, as evidenced by inhibition of ligand binding, 5 were protected against this inhibition by cocaine and dopamine (S333C, S334C, N336C, M342C and T349C), indicating that reagent accessibility is affected by conformational changes associated with inhibitor and substrate binding. In some of the cysteine mutants, transport activity is disrupted, but can be rescued by the presence of zinc, most likely because the distribution between inward- and outward-facing conformations is restored by zinc binding. The experimental data were interpreted in the context of molecular models of DAT in both the inward- and outward-facing conformations. Differences in the solvent accessible surface area for individual IL3 residues calculated for these states correlate well with the experimental accessibility data, and suggest that protection by ligand binding results from the stabilization of the outward-facing configuration. Changes in the residue interaction networks observed from the molecular dynamics simulations also revealed the critical roles of several positions during the conformational transitions. We conclude that the IL3 region of DAT

  20. Atypical Dopamine Uptake Inhibitors that Provide Clues About Cocaine's Mechanism at the Dopamine Transporter

    NASA Astrophysics Data System (ADS)

    Hauck Newman, Amy; Katz, Jonathan L.

    The dopamine transporter (DAT) has been a primary target for cocaine abuse/addiction medication discovery. However predicted addiction liability and limited clinical evaluation has provided a formidable challenge for development of these agents for human use. The unique and atypical pharmacological profile of the benztropine (BZT) class of dopamine uptake inhibitors, in preclinical models of cocaine effects and abuse, has encouraged further development of these agents. Moreover, in vivo studies have challenged the original DAT hypothesis and demonstrated that DAT occupancy and subsequent increases in dopamine produced by BZT analogues are significantly delayed and long lasting, as compared to cocaine. These important and distinctive elements are critical to the lack of abuse liability among BZT analogues, and improve their potential for development as treatments for cocaine abuse and possibly other neuropsychiatric disorders.

  1. A Physical Interaction between the Dopamine Transporter and DJ-1 Facilitates Increased Dopamine Reuptake.

    PubMed

    Luk, Beryl; Mohammed, Mohinuddin; Liu, Fang; Lee, Frank J S

    2015-01-01

    The regulation of the dopamine transporter (DAT) impacts extracellular dopamine levels after release from dopaminergic neurons. Furthermore, a variety of protein partners have been identified that can interact with and modulate DAT function. In this study we show that DJ-1 can potentially modulate DAT function. Co-expression of DAT and DJ-1 in HEK-293T cells leads to an increase in [3H] dopamine uptake that does not appear to be mediated by increased total DAT expression but rather through an increase in DAT cell surface localization. In addition, through a series of GST affinity purifications and co-immunoprecipitations, we provide evidence that the DAT can be found in a complex with DJ-1, which involve distinct regions within both DAT and DJ-1. Using in vitro binding experiments we also show that this complex can be formed in part by a direct interaction between DAT and DJ-1. Co-expression of a mini-gene that can disrupt the DAT/DJ-1 complex appears to block the increase in [3H] dopamine uptake by DJ-1. Mutations in DJ-1 have been linked to familial forms of Parkinson's disease, yet the normal physiological function of DJ-1 remains unclear. Our study suggests that DJ-1 may also play a role in regulating dopamine levels by modifying DAT activity.

  2. A Physical Interaction between the Dopamine Transporter and DJ-1 Facilitates Increased Dopamine Reuptake

    PubMed Central

    Luk, Beryl; Mohammed, Mohinuddin; Liu, Fang; Lee, Frank J. S.

    2015-01-01

    The regulation of the dopamine transporter (DAT) impacts extracellular dopamine levels after release from dopaminergic neurons. Furthermore, a variety of protein partners have been identified that can interact with and modulate DAT function. In this study we show that DJ-1 can potentially modulate DAT function. Co-expression of DAT and DJ-1 in HEK-293T cells leads to an increase in [3H] dopamine uptake that does not appear to be mediated by increased total DAT expression but rather through an increase in DAT cell surface localization. In addition, through a series of GST affinity purifications and co-immunoprecipitations, we provide evidence that the DAT can be found in a complex with DJ-1, which involve distinct regions within both DAT and DJ-1. Using in vitro binding experiments we also show that this complex can be formed in part by a direct interaction between DAT and DJ-1. Co-expression of a mini-gene that can disrupt the DAT/DJ-1 complex appears to block the increase in [3H] dopamine uptake by DJ-1. Mutations in DJ-1 have been linked to familial forms of Parkinson’s disease, yet the normal physiological function of DJ-1 remains unclear. Our study suggests that DJ-1 may also play a role in regulating dopamine levels by modifying DAT activity. PMID:26305376

  3. Dopamine Transporter Genotype Predicts Attentional Asymmetry in Healthy Adults

    ERIC Educational Resources Information Center

    Newman, Daniel P.; O'Connell, Redmond G.; Nathan, Pradeep J.; Bellgrove, Mark A.

    2012-01-01

    A number of recent studies suggest that DNA variation in the dopamine transporter gene (DAT1) influences spatial attention asymmetry in clinical populations such as ADHD, but confirmation in non-clinical samples is required. Since non-spatial factors such as attentional load have been shown to influence spatial biases in clinical conditions, here…

  4. Recovery of dopamine transporters with methamphetamine detoxification is not linked to changes in dopamine release

    DOE PAGES

    Volkow, Nora D.; Wang, Gene-Jack; Smith, Lisa; ...

    2015-07-21

    Metamphetamine’s widepread abuse and concerns that it may increase Parkinson’s disease led us to assess if the reported loss of dopamine transporters (DAT) in methamphetamine abusers (MA) reflected damage to dopamine neurons. Using PET with [11C]cocaine to measure DAT, and with [11C]raclopride to measure dopamine release (assessed as changes in specific binding of [11C]raclopride between placebo and methylphenidate), which was used as marker of dopamine neuronal function, we show that MA (n=16), tested during early detoxification, had lower DAT (20-30%) but overall normal DA release in striatum (except for a small decrease in left putamen), when compared to controls (n=15).more » In controls, DAT were positively correlated with DA release (higher DAT associated with larger DA increases), consistent with DAT serving as markers of DA terminals. In contrast, MA showed a trend for a negative correlation (p=0.07) (higher DAT associated with lower DA increases), consistent with reduced DA re-uptake following DAT downregulation. MA who remained abstinent nine-months later (n=9) showed significant increases in DAT (20%) but methylphenidate-induced dopamine increases did not change. In contrast, in controls, DAT did not change when retested 9 months later but methylphenidate-induced dopamine increases in ventral striatum were reduced (p=0.05). Baseline D2/D3 receptors in caudate were lower in MA than in controls and did not change with detoxification, nor did they change in the controls upon retest. The loss of DAT in the MA, which was not associated with a concomitant reduction in dopamine release as would have been expected if DAT loss reflected DA terminal degneration; as well as the recovery of DAT after protracted detoxification, which was not associated with increased dopamine release as would have been expected if DAT increases reflected terminal regeneration, indicate that the loss of DAT in these MA does not reflect degeneration of dopamine terminals.« less

  5. Recovery of dopamine transporters with methamphetamine detoxification is not linked to changes in dopamine release

    SciTech Connect

    Volkow, Nora D.; Wang, Gene-Jack; Smith, Lisa; Fowler, Joanna S.; Telang, Frank; Logan, Jean; Tomasi, Dardo

    2015-07-21

    Metamphetamine’s widepread abuse and concerns that it may increase Parkinson’s disease led us to assess if the reported loss of dopamine transporters (DAT) in methamphetamine abusers (MA) reflected damage to dopamine neurons. Using PET with [11C]cocaine to measure DAT, and with [11C]raclopride to measure dopamine release (assessed as changes in specific binding of [11C]raclopride between placebo and methylphenidate), which was used as marker of dopamine neuronal function, we show that MA (n=16), tested during early detoxification, had lower DAT (20-30%) but overall normal DA release in striatum (except for a small decrease in left putamen), when compared to controls (n=15). In controls, DAT were positively correlated with DA release (higher DAT associated with larger DA increases), consistent with DAT serving as markers of DA terminals. In contrast, MA showed a trend for a negative correlation (p=0.07) (higher DAT associated with lower DA increases), consistent with reduced DA re-uptake following DAT downregulation. MA who remained abstinent nine-months later (n=9) showed significant increases in DAT (20%) but methylphenidate-induced dopamine increases did not change. In contrast, in controls, DAT did not change when retested 9 months later but methylphenidate-induced dopamine increases in ventral striatum were reduced (p=0.05). Baseline D2/D3 receptors in caudate were lower in MA than in controls and did not change with detoxification, nor did they change in the controls upon retest. The loss of DAT in the MA, which was not associated with a concomitant reduction in dopamine release as would have been expected if DAT loss reflected DA terminal degneration; as well as the recovery of DAT after protracted detoxification, which was not associated with increased dopamine release as would have been expected if DAT increases reflected terminal regeneration, indicate that the loss of DAT in these MA does not reflect degeneration of

  6. Presence and Function of Dopamine Transporter (DAT) in Stallion Sperm: Dopamine Modulates Sperm Motility and Acrosomal Integrity

    PubMed Central

    Covarrubias, Alejandra A.; Rodríguez-Gil, Joan Enric; Ramírez-Reveco, Alfredo; Concha, Ilona I.

    2014-01-01

    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-(Dimethylamino)styryl]-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. PMID:25402186

  7. Dopamine mediates striatal malonate toxicity via dopamine transporter-dependent generation of reactive oxygen species and D2 but not D1 receptor activation.

    PubMed

    Xia, X G; Schmidt, N; Teismann, P; Ferger, B; Schulz, J B

    2001-10-01

    Intrastriatal injection of the reversible succinate dehydrogenase inhibitor malonate results in both chemically induced hypoxia and striatal lesions that are similar to those seen in Huntington's disease and cerebral ischaemia. The mechanisms leading to neuronal death involve secondary excitotoxicity, the release of dopamine from nigrostriatal fibres and the generation of reactive oxygen species (ROS) including nitric oxide (NO) and hydroxyl radicals. Here, we further investigated the contribution and mechanism of dopamine on malonate-induced striatal lesions. Prior lesions of the nigrostriatal pathway with 6-OHDA or the depletion of striatal dopamine stores by pretreatment with reserpine, an inhibitor or the vesicular monoamine transporter type-2 (VMAT2), in combination with alpha-methyl-p-tyrosine resulted in a significant reduction of malonate-induced striatal lesion volumes. This was paralleled by block or reduction of the malonate-induced generation of ROS, as measured by the conversions of salicylate to 2,3-dihydroxybenzoic acid (2,3-DHBA) using microdialysis. Systemic or intrastriatal application of L-DOPA or dopamine, respectively, reconstituted malonate toxicity and the generation of ROS in 6-OHDA-lesioned rats. Block of the dopamine transporter by GBR12909 did not result in a reduction of malonate-induced dopamine release, but significantly reduced the generation of hydroxyl radicals. The D2 receptor agonist lisuride and the mixed D1 and D2 receptor agonist apomorphine, but not the D1 receptor agonist SKF38393, partially restored malonate toxicity in 6-OHDA-lesioned rats without increasing the generation of ROS. In line with these results sulpiride, an inhibitor of D2 receptors, reduced the malonate-induced lesion volume, whereas SCH23390, an inhbitor of D1 receptors, was ineffective. Our data suggest that malonate-induced dopamine toxicity to energetically impaired neurons is mediated by two independent pathways: (i) dopamine transporter uptake

  8. Dopamine denervation of the prefrontal cortex increases expression of the astrocytic glutamate transporter GLT-1

    PubMed Central

    Vollbrecht, Peter J.; Simmler, Linda D.; Blakely, Randy D.; Deutch, Ariel Y.

    2014-01-01

    Both dopamine and glutamate are critically involved in cognitive processes such as working memory. Astrocytes, which express dopamine receptors, are essential elements in the termination of glutamatergic signaling: the astrocytic glutamate transporter GLT-1 is responsible for >90% of cortical glutamate uptake. The effect of dopamine depletion on glutamate transporters in the prefrontal cortex (PFC) is unknown. In an effort to determine if astrocytes are a locus of cortical dopamine-glutamate interactions, we examined the effects of chronic dopamine denervation on PFC protein and mRNA levels of glutamate transporters. PFC dopamine denervation elicited a marked increase in GLT-1 protein levels, but had no effect on levels of other glutamate transporters; high affinity glutamate transport was positively correlated with the extent of dopamine depletion. GLT-1 gene expression was not altered. Our data suggests that dopamine depletion may lead to post-translational modifications that result in increased expression and activity of GLT-1 in PFC astrocytes. PMID:24611756

  9. Pyrethroid pesticide-induced alterations in dopamine transporter function

    SciTech Connect

    Elwan, Mohamed A.; Richardson, Jason R.; Guillot, Thomas S.; Caudle, W. Michael; Miller, Gary W. . E-mail: gary.miller@emory.edu

    2006-03-15

    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 {mu}M) had no effect on DAT-mediated dopamine uptake. Extending exposures to both pesticides for 30 min (10 {mu}M) or 24 h (1, 5, and 10 {mu}M) 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.

  10. A Role for Accumbal Glycine Receptors in Modulation of Dopamine Release by the Glycine Transporter-1 Inhibitor Org25935

    PubMed Central

    Lidö, Helga Höifödt; Ericson, Mia; Marston, Hugh; Söderpalm, Bo

    2010-01-01

    Accumbal 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. PMID:21556278

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

    PubMed Central

    Narayanaswami, V; Thompson, AC; Cassis, LA; Bardo, MT; Dwoskin, LP

    2013-01-01

    OBJECTIVE 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. DESIGN 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. METHODS Striatal D2-receptor density was determined by in vitro kinetic analysis of [3H]raclopride binding. DAT function was determined using in vitro kinetic analysis of [3H]dopamine uptake, methamphetamine-evoked [3H]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. RESULTS 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 [3H]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. CONCLUSION Human studies are limited by their ability to determine if impulsivity, motivation and DAT function are causes or consequences of DIO. The

  12. Missense dopamine transporter mutations associate with adult parkinsonism and ADHD

    PubMed Central

    Hansen, Freja H.; Skjørringe, Tina; Yasmeen, Saiqa; Arends, Natascha V.; Sahai, Michelle A.; Erreger, Kevin; Andreassen, Thorvald F.; Holy, Marion; Hamilton, Peter J.; Neergheen, Viruna; Karlsborg, Merete; Newman, Amy H.; Pope, Simon; Heales, Simon J.R.; Friberg, Lars; Law, Ian; Pinborg, Lars H.; Sitte, Harald H.; Loland, Claus; Shi, Lei; Weinstein, Harel; Galli, Aurelio; Hjermind, Lena E.; Møller, Lisbeth B.; Gether, Ulrik

    2014-01-01

    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 analyzed a cohort of patients with atypical movement disorder and identified 2 DAT coding variants, DAT-Ile312Phe and a presumed de novo mutant DAT-Asp421Asn, in an adult male with early-onset parkinsonism and ADHD. According to DAT single-photon emission computed tomography (DAT-SPECT) scans and a fluoro-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 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, and electrophysiological analyses identified a large cation leak that might further perturb dopaminergic neurotransmission. Our results link specific DAT missense mutations to neurodegenerative early-onset parkinsonism. Moreover, the neuropsychiatric comorbidity provides additional support for the idea that DAT missense mutations are an ADHD risk factor and suggests that complex DAT genotype and phenotype correlations contribute to different dopaminergic pathologies. PMID:24911152

  13. Increased expression of the dopamine transporter leads to loss of dopamine neurons, oxidative stress and l-DOPA reversible motor deficits.

    PubMed

    Masoud, S T; Vecchio, L M; Bergeron, Y; Hossain, M M; Nguyen, L T; Bermejo, M K; Kile, B; Sotnikova, T D; Siesser, W B; Gainetdinov, R R; Wightman, R M; Caron, M G; Richardson, J R; Miller, G W; Ramsey, A J; Cyr, M; Salahpour, A

    2015-02-01

    The dopamine transporter is a key protein responsible for regulating dopamine homeostasis. Its function is to transport dopamine from the extracellular space into the presynaptic neuron. Studies have suggested that accumulation of dopamine in the cytosol can trigger oxidative stress and neurotoxicity. Previously, ectopic expression of the dopamine transporter was shown to cause damage in non-dopaminergic neurons due to their inability to handle cytosolic dopamine. However, it is unknown whether increasing dopamine transporter activity will be detrimental to dopamine neurons that are inherently capable of storing and degrading dopamine. To address this issue, we characterized transgenic mice that over-express the dopamine transporter selectively in dopamine neurons. We report that dopamine transporter over-expressing (DAT-tg) mice display spontaneous loss of midbrain dopamine neurons that is accompanied by increases in oxidative stress markers, 5-S-cysteinyl-dopamine and 5-S-cysteinyl-DOPAC. In addition, metabolite-to-dopamine ratios are increased and VMAT2 protein expression is decreased in the striatum of these animals. Furthermore, DAT-tg mice also show fine motor deficits on challenging beam traversal that are reversed with l-DOPA treatment. Collectively, our findings demonstrate that even in neurons that routinely handle dopamine, increased uptake of this neurotransmitter through the dopamine transporter results in oxidative damage, neuronal loss and l-DOPA reversible motor deficits. In addition, DAT over-expressing animals are highly sensitive to MPTP-induced neurotoxicity. The effects of increased dopamine uptake in these transgenic mice could shed light on the unique vulnerability of dopamine neurons in Parkinson's disease.

  14. Increased expression of the dopamine transporter leads to loss of dopamine neurons, oxidative stress and L-DOPA reversible motor deficits

    PubMed Central

    Masoud, ST; Vecchio, LM; Bergeron, Y; Hossain, MM; Nguyen, LT; Bermejo, MK; Kile, B; Sotnikova, TD; Siesser, WB; Gainetdinov, RR; Wightman, RM; Caron, MG; Richardson, JR; Miller, GW; Ramsey, AJ; Cyr, M; Salahpour, A

    2015-01-01

    The dopamine transporter is a key protein responsible for regulating dopamine homeostasis. Its function is to transport dopamine from the extracellular space into the presynaptic neuron. Studies have suggested that accumulation of dopamine in the cytosol can trigger oxidative stress and neurotoxicity. Previously, ectopic expression of the dopamine transporter was shown to cause damage in non-dopaminergic neurons due to their inability to handle cytosolic dopamine. However, it is unknown whether increasing dopamine transporter activity will be detrimental to dopamine neurons that are inherently capable of storing and degrading dopamine. To address this issue, we characterized transgenic mice that over-express the dopamine transporter selectively in dopamine neurons. We report that dopamine transporter over-expressing (DAT-tg) mice display spontaneous loss of midbrain dopamine neurons that is accompanied by increases in oxidative stress markers, 5-S-cysteinyl-dopamine and 5-S-cysteinyl-DOPAC. In addition, metabolite-to-dopamine ratios are increased and VMAT2 protein expression is decreased in the striatum of these animals. Furthermore, DAT-tg mice also show fine motor deficits on challenging beam traversal that are reversed with L-DOPA treatment. Collectively, our findings demonstrate that even in neurons that routinely handle dopamine, increased uptake of this neurotransmitter through the dopamine transporter results in oxidative damage, neuronal loss and LDOPA reversible motor deficits. In addition, DAT over-expressing animals are highly sensitive to MPTP-induced neurotoxicity. The effects of increased dopamine uptake in these transgenic mice could shed light on the unique vulnerability of dopamine neurons in Parkinson’s disease. PMID:25447236

  15. Rats overexpressing the dopamine transporter display behavioral and neurobiological abnormalities with relevance to repetitive disorders

    PubMed Central

    Hadar, Ravit; Edemann-Callesen, Henriette; Reinel, Claudia; Wieske, Franziska; Voget, Mareike; Popova, Elena; Sohr, Reinhard; Avchalumov, Yosef; Priller, Josef; van Riesen, Christoph; Puls, Imke; Bader, Michael; Winter, Christine

    2016-01-01

    The dopamine transporter (DAT) plays a pivotal role in maintaining optimal dopamine signaling. DAT-overactivity has been linked to various neuropsychiatric disorders yet so far the direct pathological consequences of it has not been fully assessed. We here generated a transgenic rat model that via pronuclear microinjection overexpresses the DAT gene. Our results demonstrate that DAT-overexpression induces multiple neurobiological effects that exceeded the expected alterations in the corticostriatal dopamine system. Furthermore, transgenic rats specifically exhibited behavioral and pharmaco-therapeutic profiles phenotypic of repetitive disorders. Together our findings suggest that the DAT rat model will constitute a valuable tool for further investigations into the pathological influence of DAT overexpression on neural systems relevant to neuropsychiatric disorders. PMID:27974817

  16. Dopamine Transporter Activity Is Modulated by α-Synuclein.

    PubMed

    Butler, Brittany; Saha, Kaustuv; Rana, Tanu; Becker, Jonas P; Sambo, Danielle; Davari, Paran; Goodwin, J Shawn; Khoshbouei, Habibeh

    2015-12-04

    The duration and strength of the dopaminergic signal are regulated by the dopamine transporter (DAT). Drug addiction and neurodegenerative and neuropsychiatric diseases have all been associated with altered DAT activity. The membrane localization and the activity of DAT are regulated by a number of intracellular proteins. α-Synuclein, a protein partner of DAT, is implicated in neurodegenerative disease and drug addiction. Little is known about the regulatory mechanisms of the interaction between DAT and α-synuclein, the cellular location of this interaction, and the functional consequences of this interaction on the basal, amphetamine-induced DAT-mediated dopamine efflux, and membrane microdomain distribution of the transporter. Here, we found that the majority of DAT·α-synuclein protein complexes are found at the plasma membrane of dopaminergic neurons or mammalian cells and that the amphetamine-mediated increase in DAT activity enhances the association of these proteins at the plasma membrane. Further examination of the interaction of DAT and α-synuclein revealed a transient interaction between these two proteins at the plasma membrane. Additionally, we found DAT-induced membrane depolarization enhances plasma membrane localization of α-synuclein, which in turn increases dopamine efflux and enhances DAT localization in cholesterol-rich membrane microdomains.

  17. Mechanisms of dopamine transporter regulation in normal and disease states.

    PubMed

    Vaughan, Roxanne A; Foster, James D

    2013-09-01

    The dopamine (DA) transporter (DAT) controls the spatial and temporal dynamics of DA neurotransmission by driving reuptake of extracellular transmitter into presynaptic neurons. Many diseases such as depression, bipolar disorder, Parkinson's disease (PD), and attention deficit hyperactivity disorder (ADHD) are associated with abnormal DA levels, implicating DAT as a factor in their etiology. Medications used to treat these disorders and many addictive drugs target DAT and enhance dopaminergic signaling by suppressing transmitter reuptake. We now understand that the transport and binding properties of DAT are regulated by complex and overlapping mechanisms that provide neurons with the ability to modulate DA clearance in response to physiological demands. These processes are controlled by endogenous signaling pathways and affected by exogenous transporter ligands, demonstrating their importance for normal neurotransmission, drug abuse, and disease treatments. Increasing evidence supports the disruption of these mechanisms in DA disorders, implicating dysregulation of transport in disease etiologies and suggesting these processes as potential points for therapeutic manipulation of DA availability.

  18. Dopamine denervation of the prefrontal cortex increases expression of the astrocytic glutamate transporter GLT-1.

    PubMed

    Vollbrecht, Peter J; Simmler, Linda D; Blakely, Randy D; Deutch, Ariel Y

    2014-07-01

    Both dopamine and glutamate are critically involved in cognitive processes such as working memory. Astrocytes, which express dopamine receptors, are essential elements in the termination of glutamatergic signaling: the astrocytic glutamate transporter GLT-1 is responsible for > 90% of cortical glutamate uptake. The effect of dopamine depletion on glutamate transporters in the prefrontal cortex (PFC) remains unknown. In an effort to determine if astrocytes are a locus of cortical dopamine-glutamate interactions, we examined the effects of chronic dopamine denervation on PFC protein and mRNA levels of glutamate transporters. PFC dopamine denervation elicited a marked increase in GLT-1 protein levels, but had no effect on levels of other glutamate transporters; high-affinity glutamate transport was positively correlated with the extent of dopamine depletion. GLT-1 gene expression was not altered. Our data suggest that dopamine depletion may lead to post-translational modifications that result in increased expression and activity of GLT-1 in PFC astrocytes. The glutamate transporter GLT-1 is expressed by astrocytes, which also express dopamine receptors. Regulation of prefrontal cortical (PFC) GLT-1 potentially offers a novel treatment approach to the cognitive deficits of schizophrenia. Partial PFC dopamine deafferentation increased membrane expression of GLT-1 protein and glutamate uptake, but did not alter levels of the other two neocortical glutamate transporters, GLAST and EAAC1.

  19. Relationship between cocaine-induced subjective effects and dopamine transporter occupancy

    SciTech Connect

    Volkow, N.D.; Fischman, M.; Wang, G.J.

    1997-05-01

    The ability of cocaine to occupy the dopamine transporter has been linked to its reinforcing properties. However, such a relationship has not been demonstrated in humans. Methods: Positron Emission Tomography and [C-11]cocaine were used to estimate dopamine transporter occupancies after different doses of cocaine in 18 active cocaine abusers. The ratio of the distribution volume of [C-11]cocaine in striatum to that in cerebellum, which corresponds to Bmax/Kd +1 and is insensitive to changes in cerebral blood flow, was our measure of dopamine transporter availability. In parallel subjective effects were measured to assess the relationship between dopamine transporter occupancy and cocaines behavioral effects. Intravenous cocaine produced a significant dose,-dependent blockade of dopamine transporters: 73 % for 0.6 mg/kg; 601/6 for 0.3 mg/kg; 48 % for 0.1 mg/kg iv and 40 % for 0.05 mg/kg. In addition, dopamine transporter occupancies were significantly correlated with cocaine plasma concentration (r = 0.55 p < 0.001). Cocaine also produced dose-dependent increases in self-reported ratings of {open_quotes}high{close_quotes} which were significantly correlated with the levels of dopamine transporter blockade. Discussion: These results provide the first documentation in humans that dopamine transporter occupancy is associated with cocaine induced subjective effects. They also suggest that dopamine transporter occupancies equal to or greater than 60% are required to produce significant effects on ratings of {open_quotes}high{close_quotes}.

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

    ERIC Educational Resources Information Center

    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…

  1. Impact of subcortical white matter lesions on dopamine transporter SPECT.

    PubMed

    Funke, Elisabeth; Kupsch, Andreas; Buchert, Ralph; Brenner, Winfried; Plotkin, Michail

    2013-07-01

    Subcortical arteriosclerotic encephalopathy (SAE) can affect the nigrostriatal system and presumably cause vascular parkinsonism (VP). However, in patients with SAE, the differentiation of VP from idiopathic Parkinson's disease (IPS) is challenging. The aim of the present study was to examine the striatal dopamine transporter (DAT) density in patients with parkinsonism and SAE. Fifteen consecutive patients with parkinsonian symptoms displayed SAE, as detected by magnetic resonance imaging (MRI). Fifteen retrospectively chosen, matched patients with diagnosis of IPS without any abnormalities in MRI served as a reference group. DAT SPECT was performed using the tracer ¹²³I-FP-CIT. Scans were acquired on a triple-head SPECT system (Multispect 3, Siemens) and analysed using the investigator-independent BRASS™ software (HERMES). In the SAE group, a DAT deficit was observed in 9/15 patients. In contrast, all patients from the IPS group showed a reduced DAT binding (p = 0.008). The specific binding ratios (BR) of putamen contralateral to the side of the more affected limb versus occipital lobe were in trend higher in patients with SAE versus patients in the IPS-group (p = 0.053). Indices for putaminal asymmetry (p = 0.036) and asymmetry caudate-to-putamen (p = 0.026) as well as the ratio caudate-to-putamen (p = 0.048) were significantly higher in IPS patients having no SAE. DAT deficit was less pronounced in patients with SAE and parkinsonism than in patients with IPS without any abnormalities in the MRI. A potential role of DAT SPECT in the differential diagnosis of VP and IPS requires more assessments within prospective studies.

  2. Altered Neurocircuitry in the Dopamine Transporter Knockout Mouse Brain

    PubMed Central

    Zhang, Xiaowei; Bearer, Elaine L.; Boulat, Benoit; Hall, F. Scott; Uhl, George R.; Jacobs, Russell E.

    2010-01-01

    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 Mn2+ into the prefrontal cortex indicated that DAT KO mice have a truncated Mn2+ distribution within this circuitry with little accumulation beyond the thalamus or contralateral to the injection site. By contrast, WT littermates exhibit Mn2+ transport into more posterior midbrain nuclei and contralateral mesolimbic structures at

  3. Simultaneous measurement of extracellular dopamine and dopamine transporter occupancy by cocaine analogs in squirrel monkeys.

    PubMed

    Kimmel, Heather L; Nye, Jonathon A; Voll, Ronald; Mun, Jiyoung; Stehouwer, Jeffrey; Goodman, Mark M; Votaw, John R; Carroll, F I; Howell, Leonard L

    2012-06-01

    Several classes of drugs bind to the dopamine transporter (DAT) with high affinity, but some are weaker positive reinforcers than cocaine, suggesting that affinity for and occupancy of the DAT is not the only determinant of a drug's reinforcing effectiveness. Other factors such as the rate of onset have been positively and strongly correlated with the reinforcing effects of DAT inhibitors in nonhuman primates. In the current studies, we examined the effects of acute systemic administration of cocaine and three cocaine analogs (RTI-150, RTI-177, and RTI-366) on binding to DAT in squirrel monkey brain using positron emission tomography (PET) neuroimaging. During the PET scan, we also measured drug effects on dopamine (DA) levels in the caudate using in vivo microdialysis. In general, our results suggest a lack of concordance between drug occupancy at DAT and changes in DA levels. These studies also indicate that acute cocaine administration decreases the availability of plasma membrane DAT for binding, even after cocaine is no longer blocking DA uptake as evidence by a return to basal DA levels.

  4. Restoration of the Dopamine Transporter through Cell Therapy Improves Dyskinesia in a Rat Model of Parkinson's Disease.

    PubMed

    Tomas, D; Stanic, D; Chua, H K; White, K; Boon, W C; Horne, M

    2016-01-01

    The dyskinesia of Parkinson's Disease is most likely due to excess levels of dopamine in the striatum. The mechanism may be due to aberrant synthesis but also, a deficiency or absence of the Dopamine Transporter. In this study we have examined the proposition that reinstating Dopamine Transporter expression in the striatum would reduce dyskinesia. We transplanted c17.2 cells that stably expressed the Dopamine Transporter into dyskinetic rats. There was a reduction in dyskinesia in rats that received grafts expressing the Dopamine Transporter. Strategies designed to increase Dopamine Transporter in the striatum may be useful in treating the dyskinesia associated with human Parkinson's Disease.

  5. Mechanism for cocaine blocking the transport of dopamine: insights from molecular modeling and dynamics simulations.

    PubMed

    Huang, Xiaoqin; Gu, Howard H; Zhan, Chang-Guo

    2009-11-12

    Molecular modeling and dynamics simulations have been performed to study how cocaine inhibits dopamine transporter (DAT) for the transport of dopamine. The computationally determined DAT-ligand binding mode is totally different from the previously proposed overlap binding mode in which cocaine- and dopamine-binding sites are the same (Beuming, T.; et al. Nat. Neurosci. 2008, 11, 780-789). The new cocaine-binding site does not overlap with, but is close to, the dopamine-binding site. Analysis of all results reveals that when cocaine binds to DAT, the initial binding site is likely the one modeled in this study because this binding site can naturally accommodate cocaine. Then cocaine may move to the dopamine-binding site after DAT makes some necessary conformational change and expands the binding site cavity. It has been demonstrated that cocaine may inhibit the transport of dopamine through both blocking the initial DAT-dopamine binding and reducing the kinetic turnover of the transporter following the DAT-dopamine binding. The relative contributions to the phenomenological inhibition of the transport of dopamine from blocking the initial binding and reducing the kinetic turnover can be different in different types of assays. The obtained general structural and mechanistic insights are consistent with available experimental data and could be valuable for guiding future studies toward understanding cocaine's inhibiting of other transporters.

  6. Lack of Association between Polymorphisms of the Dopamine Receptor D4 and Dopamine Transporter Genes and Personality Traits in a Korean Population

    PubMed Central

    Kim, Se Joo; Kim, Young Shin; Lee, Hong Shick

    2006-01-01

    Human personality traits have a considerable genetic component. Cloninger et al. were the first to postulate that certain personality traits, such as novelty seeking, are related to the dopamine neurotransmitter system. In this study, we investigated the associations between dopamine receptor D4 (DRD4) exon III and dopamine transporter (DAT1) polymorphisms and personality traits. The DRD4 and DAT1 gene polymorphisms were genotyped in 214 healthy Korean subjects, whose personality traits were assessed with the Temperament and Character Inventory (TCI). There were no significant differences between scores of TCI temperament dimensions (novelty seeking, harm avoidance, reward dependence, and persistence) and DRD4 gene polymorphism. The DAT1 gene polymorphisms also showed no significant association with any of the temperament subscales of the TCI. These data suggest that DRD4 and DAT1 gene polymorphism may not associated with personality traits in a Korean population. PMID:17191306

  7. Role of Histidine 547 of Human Dopamine Transporter in Molecular Interaction with HIV-1 Tat and Dopamine Uptake

    PubMed Central

    Yuan, Yaxia; Quizon, Pamela M.; Sun, Wei-Lun; Yao, Jianzhuang; Zhu, Jun; Zhan, Chang-Guo

    2016-01-01

    HIV-1 Tat plays an important role in HIV-associated neurocognitive disorders (HAND) by disrupting neurotransmission including dopamine uptake by human dopamine transporter (hDAT). Previous studies have demonstrated that HIV-1 Tat directly binds to hDAT and some amino-acid mutations that attenuate the hDAT-Tat binding also significantly decreased dopamine uptake activity of hDAT. This combined computational-experimental study demonstrates that histidine-547 (H547) of hDAT plays a crucial role in the hDAT-Tat binding and dopamine uptake by hDAT, and that the H547A mutation can not only considerably attenuate Tat-induced inhibition of dopamine uptake, but also significantly increase the Vmax of hDAT for dopamine uptake. The finding of such an unusual hDAT mutant capable of both increasing the Vmax of hDAT for dopamine uptake and disrupting the hDAT-Tat binding may provide an exciting knowledge basis for development of novel concepts for therapeutic treatment of the HAND. PMID:27250920

  8. Single and Binge Methamphetamine Administrations Have Different Effects on the Levels of Dopamine D2 Autoreceptor and Dopamine Transporter in Rat Striatum

    PubMed Central

    Chauhan, Heli; Killinger, Bryan A.; Miller, Cheryl V.; Moszczynska, Anna

    2014-01-01

    Methamphetamine (METH) is a central nervous system psychostimulant with a high potential for abuse. At high doses, METH causes a selective degeneration of dopaminergic terminals in the striatum. Dopamine D2 receptor antagonists and dopamine transporter (DAT) inhibitors protect against neurotoxicity of the drug by decreasing intracellular dopamine content and, consequently, dopamine autoxidation and production of reactive oxygen species. In vitro, amphetamines regulate D2 receptor and DAT functions via regulation of their intracellular trafficking. No data exists on axonal transport of both proteins and there is limited data on their interactions in vivo. The aim of the present investigation was to examine synaptosomal levels of presynaptic D2 autoreceptor and DAT after two different regimens of METH and to determine whether METH affects the D2 autoreceptor-DAT interaction in the rat striatum. We found that, as compared to saline controls, administration of single high-dose METH decreased D2 autoreceptor immunoreactivity and increased DAT immunoreactivity in rat striatal synaptosomes whereas binge high-dose METH increased immunoreactivity of D2 autoreceptor and had no effect on DAT immunoreactivity. Single METH had no effect on D2 autoreceptor-DAT interaction whereas binge METH increased the interaction between the two proteins in the striatum. Our results suggest that METH can affect axonal transport of both the D2 autoreceptor and DAT in an interaction-dependent and -independent manner. PMID:24717411

  9. Raman Spectroscopic Signature Markers of Dopamine-Human Dopamine Transporter Interaction in Living Cells.

    PubMed

    Silwal, Achut Prasad; Yadav, Rajeev; Sprague, Jon E; Lu, H Peter

    2017-04-04

    Dopamine (DA) controls many psychological and behavioral activities in the central nervous system (CNS) through interactions with the human dopamine transporter (hDAT) and dopamine receptors. The roles of DA in the function of the CNS are affected by the targeted binding of drugs to hDAT; thus, hDAT plays a critical role in neurophysiology and neuropathophysiology. An effective experimental method is necessary to study the DA-hDAT interaction and effects of variety of drugs like psychostimulants and anti-depressants that are dependent on this interaction. In searching for obtaining and identifying the Raman spectral signatures, we have used surface enhanced Raman scattering (SERS) spectroscopy to record SERS spectrum from DA, Human Embryonic Kidney 293 cells (HEK293), hDAT-HEK293, DA-HEK293, and DA-hDAT-HEK293. We have demonstrated a specific 2D-distribution SERS spectral analytical approach to analyze DA-hDAT interaction. Our study shows that the Raman modes at 807, 839, 1076, 1090, 1538, and 1665 cm-1 are related to DA-hDAT interaction, where Raman shift at 807 and 1076 cm-1 are the signature marker for bound state of DA to probe DA-hDAT interaction. On the basis of density function theory (DFT) calculation, Raman shift of bound state of DA at 807 cm-1 is related to combination of bending modes α(C3-O10-H21), α(C2-O11-H22), α(C7-C8-H18), α(C6-C4-H13), α(C7-C8-H19), α(C7-C8-N9), and Raman shift at 1076 cm-1 is related to combination of bending modes α(H19-N9-C8), γ(N9-H19), γ(C8-H19), γ(N9-H20), γ(C8-H18), and α(C7-C8-H18). These findings demonstrate that protein-ligand interactions can be confirmed by probing change in Raman shift of ligand molecules, which could be crucial to understanding molecular interactions between neurotransmitters and their receptors or transporters.

  10. Brain Region-Specific Trafficking of the Dopamine Transporter

    PubMed Central

    Block, Ethan R.; Nuttle, Jacob; Balcita-Pedicino, Judith Joyce; Caltagarone, John; Watkins, Simon C.

    2015-01-01

    The dopamine (DA) transporter (DAT) controls dopaminergic neurotransmission by removing extracellular DA. Although DA reuptake is proposed to be regulated by DAT traffic to and from the cell surface, the membrane trafficking system involved in the endocytic cycling of DAT in the intact mammalian brain has not been characterized. Hence, we performed immunolabeling and quantitative analysis of the subcellular and regional distribution of DAT using the transgenic knock-in mouse expressing hemagglutinin (HA) epitope-tagged DAT (HA-DAT) and by using a combination of electron microscopy and a novel method for immunofluorescence labeling of HA-DAT in acute sagittal brain slices. Both approaches demonstrated that, in midbrain somatodendritic regions, HA-DAT was present in the plasma membrane, endoplasmic reticulum, and Golgi complex, with a small fraction in early and recycling endosomes and an even smaller fraction in late endosomes and lysosomes. In the striatum and in axonal tracts between the midbrain and striatum, HA-DAT was detected predominantly in the plasma membrane, and quantitative analysis revealed increased DAT density in striatal compared with midbrain plasma membranes. Endosomes were strikingly rare and lysosomes were absent in striatal axons, in which there was little intracellular HA-DAT. Acute administration of amphetamine in vivo (60 min) or to slices ex vivo (10–60 min) did not result in detectable changes in DAT distribution. Altogether, these data provide evidence for regional differences in DAT plasma membrane targeting and retention and suggest a surprisingly low level of endocytic trafficking of DAT in the striatum along with limited DAT endocytic activity in somatodendritic areas. SIGNIFICANCE STATEMENT The dopamine transporter (DAT) is the key regulator of the dopamine neurotransmission in the CNS. In the present study, we developed a new approach for studying DAT localization and dynamics in intact neurons in acute sagittal brain slices from

  11. Amphetamine modulates excitatory neurotransmission through endocytosis of the glutamate transporter EAAT3 in dopamine neurons.

    PubMed

    Underhill, Suzanne M; Wheeler, David S; Li, Minghua; Watts, Spencer D; Ingram, Susan L; Amara, Susan G

    2014-07-16

    Amphetamines modify the brain and alter behavior through mechanisms generally attributed to their ability to regulate extracellular dopamine concentrations. However, the actions of amphetamine are also linked to adaptations in glutamatergic signaling. We report here that when amphetamine enters dopamine neurons through the dopamine transporter, it stimulates endocytosis of an excitatory amino acid transporter, EAAT3, in dopamine neurons. Consistent with this decrease in surface EAAT3, amphetamine potentiates excitatory synaptic responses in dopamine neurons. We also show that the process of internalization is dynamin- and Rho-mediated and requires a unique sequence in the cytosolic C terminus of EAAT3. Introduction of a peptide based on this motif into dopamine neurons blocks the effects of amphetamine on EAAT3 internalization and its action on excitatory responses. These data indicate that the internalization of EAAT3 triggered by amphetamine increases glutamatergic signaling and thus contributes to the effects of amphetamine on neurotransmission.

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

    PubMed

    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.

  13. Dopamine transporter occupancy by RTI-55, inhibition of dopamine transport and stimulation of locomotor activity

    SciTech Connect

    Gatley, S.J.; Gifford, A.N.; Volkow, N.D.

    1997-05-01

    Cocaine analogs such as RTI-55 (or {beta}CIT) with a higher affinity for the DAT are potentially useful as therapeutic drugs in cocaine abuse as well as for radiopharmaceutical use. Previously we showed that in mice RTI-55 (2 mg/Kg, i/p) reduced H-3 cocaine striatum-to-cerebellum ratios (St/Cb, {lg_bullet}) from 1.6 to 1.2 at 3 h after administration, with recovery by 12 h. In the present study we demonstrate a very similar time-course for transport {triangle} measured in striatal homo within 2 min of sacrifice. The maximum inhibition of uptake at about 1 h corresponded to about 80% of the control uptake rate, similar to the percent reduction in St/Cb. The time-course of the effect of this dose of RTI-55 on locomotor activity ({sq_bullet}) was complex, with a drop in the activity measure at 7 h, after a further injection of RTI-55, but activity remained higher than in saline controls. In spite of this complexity, which may be associated with stereotypies and/or exhaustion, the duration of increased activity is consistent with the duration of transporter blockade. These experiments support the notion that PET/SPECT measures of transporter occupancy accurately reflect transporter inhibition.

  14. An acute, epitope-specific modification in the dopamine transporter associated with methamphetamine-induced neurotoxicity.

    PubMed

    Fricks-Gleason, Ashley N; German, Christopher L; Hoonakker, Amanda J; Friend, Danielle M; Ganesh, Kamala K; Carver, Aaron S; Hanson, Glen R; Fleckenstein, Annette E; Keefe, Kristen A

    2016-04-01

    Preclinical studies demonstrate that repeated, high-dose methamphetamine administrations rapidly decrease plasmalemmal dopamine uptake, which may contribute to aberrant dopamine accumulation, reactive species generation, and long-term dopaminergic deficits. The present study extends these findings by demonstrating a heretofore unreported, epitope-specific modification in the dopamine transporter caused by a methamphetamine regimen that induces these deficits. Specifically, repeated, high-dose methamphetamine injections (4 × 10 mg/kg/injection, 2-h intervals) rapidly decreased immunohistochemical detection of striatal dopamine transporter as assessed 1 h after the final methamphetamine exposure. In contrast, neither a single high dose (1 × 10 mg/kg) nor repeated injections of a lower dose (4 × 2 mg/kg/injection) induced this change. The high-dose regimen-induced alteration was only detected using antibodies directed against the N-terminus. Immunohistochemical staining using antibodies directed against the C-terminus did not reveal any changes. The high-dose regimen also did not alter dopamine transporter expression as assessed using [(125) I]RTI-55 autoradiography. These data suggest that the repeated, high-dose methamphetamine regimen alters the N-terminus of the dopamine transporter. Further, these data may be predictive of persistent dopamine deficits caused by the stimulant. Future studies of the signaling cascades involved should provide novel insight into potential mechanisms underlying the physiological and pathophysiological regulation of the dopamine transporter.

  15. Molecular mechanism: the human dopamine transporter histidine 547 regulates basal and HIV-1 Tat protein-inhibited dopamine transport

    PubMed Central

    Quizon, Pamela M.; Sun, Wei-Lun; Yuan, Yaxia; Midde, Narasimha M.; Zhan, Chang-Guo; Zhu, Jun

    2016-01-01

    Abnormal dopaminergic transmission has been implicated as a risk determinant of HIV-1-associated neurocognitive disorders. HIV-1 Tat protein increases synaptic dopamine (DA) levels by directly inhibiting DA transporter (DAT) activity, ultimately leading to dopaminergic neuron damage. Through integrated computational modeling prediction and experimental validation, we identified that histidine547 on human DAT (hDAT) is critical for regulation of basal DA uptake and Tat-induced inhibition of DA transport. Compared to wild type hDAT (WT hDAT), mutation of histidine547 (H547A) displayed a 196% increase in DA uptake. Other substitutions of histidine547 showed that DA uptake was not altered in H547R but decreased by 99% in H547P and 60% in H547D, respectively. These mutants did not alter DAT surface expression or surface DAT binding sites. H547 mutants attenuated Tat-induced inhibition of DA transport observed in WT hDAT. H547A displays a differential sensitivity to PMA- or BIM-induced activation or inhibition of DAT function relative to WT hDAT, indicating a change in basal PKC activity in H547A. These findings demonstrate that histidine547 on hDAT plays a crucial role in stabilizing basal DA transport and Tat-DAT interaction. This study provides mechanistic insights into identifying targets on DAT for Tat binding and improving DAT-mediated dysfunction of DA transmission. PMID:27966610

  16. GABA, glutamate, dopamine and serotonin transporters expression on forgetting.

    PubMed

    Tellez, Ruth; Gómez-Viquez, Leticia; Liy-Salmeron, Gustavo; Meneses, Alfredo

    2012-07-01

    Notwithstanding several neurotransmission systems are frequently related to memory formation; forgetting process and neurotransmission systems or their transporters; the role of γ-aminobutyric acid (GAT1), glutamate (EACC1), dopamine (DAT) and serotonin (SERT) is poorly understood. Hence, in this paper western-blot analysis was used to evaluate expression of GAT1, EAAC1, DAT and SERT during forgetting in trained and untrained rats treated with the selective serotonin transporter inhibitor fluoxetine, the amnesic drug d-methamphetamine (METH) and fluoxetine plus METH. Transporters expression was determined in the hippocampus (HIP), prefrontal cortex (PFC) and striatum (STR). Results indicated that forgetting of Pavlovian/instrumental autoshaping was associated to up-regulation of GAT1 (PFC and HIP) and DAT (PFC) while SERT (HIP) was down-regulated; no-changes were observed in striatum. Methamphetamine administration did not affect forgetting at 216 h post-training but up-regulated hippocampal DAT and EACC, prefrontal cortex DAT and striatal GAT1 or EACC1. Fluoxetine alone prevented forgetting, which was associated to striatal GAT1 and hippocampal DAT up-regulation, but prefrontal cortex GAT1 down-regulation. Fluoxetine plus METH administration was also able to prevent forgetting, which was associated to hippocampal DAT, prefrontal cortex SERT and striatal GAT1, DAT or SERT up-regulation, but prefrontal cortex GAT1 down-regulation. Together these data show that forgetting provokes primarily hippocampal and prefrontal cortex transporters changes; forgetting represent a behavioral process hardly modifiable and its prevention could causes different transporters expression patterns.

  17. A heterocyclic compound CE-103 inhibits dopamine reuptake and modulates dopamine transporter and dopamine D1-D3 containing receptor complexes.

    PubMed

    Sase, Ajinkya; Aher, Yogesh D; Saroja, Sivaprakasam R; Ganesan, Minu Karthika; Sase, Sunetra; Holy, Marion; Höger, Harald; Bakulev, Vasiliy; Ecker, Gerhard F; Langer, Thierry; Sitte, Harald H; Leban, Johann; Lubec, Gert

    2016-03-01

    A series of compounds have been reported to enhance memory via the DA system and herein a heterocyclic compound was tested for working memory (WM) enhancement. 2-((benzhydrylsulfinyl)methyl)thiazole (CE-103) was synthesized in a six-step synthesis. Binding of CE-103 to the dopamine (DAT), serotonin (SERT) and norepinephrine (NET) transporters and dopamine reuptake inhibition was tested as well as blood brain permeation and a screen for GPCR targets. 60 male Sprague Dawley rats were divided into six groups: CE-103 treated 1-10 mg/kg body weight, trained (TDI) and yoked (YDI) and vehicle treated, trained (TVI) and yoked (YVI) rats. Daily single intraperitoneal injections for a period of 10 days were administered and rats were tested in a radial arm maze (RAM). Hippocampi were taken 6 h following the last day of training and complexes containing the unphosphorylated or phosphorylated dopamine transporter (DAT) and complexes containing the D1-3 dopamine receptor subunits were determined. CE-103 was binding to the DAT but insignificantly to SERT or NET and dopamine reuptake was blocked specifically (IC50 = 14.73 μM). From day eight the compound was decreasing WM errors in the RAM significantly at both doses tested as compared to the vehicle controls. In the trained CE-103-treated group levels of the complex containing the phosphorylated dopamine transporter (pDAT) as well as D1R were decreased while levels of complexes containing D2R and D3R were significantly increased. CE-103 was shown to enhance spatial WM and DA reuptake inhibition with subsequent modulation of D1-3 receptors is proposed as a possible mechanism of action.

  18. Prolonged treatment with pramipexole promotes physical interaction of striatal dopamine D3 autoreceptors with dopamine transporters to reduce dopamine uptake.

    PubMed

    Castro-Hernández, Javier; Afonso-Oramas, Domingo; Cruz-Muros, Ignacio; Salas-Hernández, Josmar; Barroso-Chinea, Pedro; Moratalla, Rosario; Millan, Mark J; González-Hernández, Tomás

    2015-02-01

    The dopamine (DA) transporter (DAT), a membrane glycoprotein expressed in dopaminergic neurons, clears DA from extracellular space and is regulated by diverse presynaptic proteins like protein kinases, α-synuclein, D2 and D3 autoreceptors. DAT dysfunction is implicated in Parkinson's disease and depression, which are therapeutically treated by dopaminergic D2/D3 receptor (D2/D3R) agonists. It is, then, important to improve our understanding of interactions between D3R and DAT. We show that prolonged administration of pramipexole (0.1mg/kg/day, 6 to 21 days), a preferential D3R agonist, leads to a decrease in DA uptake in mouse striatum that reflects a reduction in DAT affinity for DA in the absence of any change in DAT density or subcellular distribution. The effect of pramipexole was absent in mice with genetically-deleted D3R (D3R(-/-)), yet unaffected in mice genetically deprived of D2R (D2R(-/-)). Pramipexole treatment induced a physical interaction between D3R and DAT, as assessed by co-immunoprecipitation and in situ proximity ligation assay. Furthermore, it promoted the formation of DAT dimers and DAT association with both D2R and α-synuclein, effects that were abolished in D3R(-/-) mice, yet unaffected in D2R(-/-) mice, indicating dependence upon D3R. Collectively, these data suggest that prolonged treatment with dopaminergic D3 agonists provokes a reduction in DA reuptake by dopaminergic neurons related to a hitherto-unsuspected modification of the DAT interactome. These observations provide novel insights into the long-term antiparkinson, antidepressant and additional clinical actions of pramipexole and other D3R agonists.

  19. Amphetamine activates calcium channels through dopamine transporter-mediated depolarization.

    PubMed

    Cameron, Krasnodara N; Solis, Ernesto; Ruchala, Iwona; De Felice, Louis J; Eltit, Jose M

    2015-11-01

    Amphetamine (AMPH) and its more potent enantiomer S(+)AMPH are psychostimulants used therapeutically to treat attention deficit hyperactivity disorder and have significant abuse liability. AMPH is a dopamine transporter (DAT) substrate that inhibits dopamine (DA) uptake and is implicated in DA release. Furthermore, AMPH activates ionic currents through DAT that modify cell excitability presumably by modulating voltage-gated channel activity. Indeed, several studies suggest that monoamine transporter-induced depolarization opens voltage-gated Ca(2+) channels (CaV), which would constitute an additional AMPH mechanism of action. In this study we co-express human DAT (hDAT) with Ca(2+) channels that have decreasing sensitivity to membrane depolarization (CaV1.3, CaV1.2 or CaV2.2). Although S(+)AMPH is more potent than DA in transport-competition assays and inward-current generation, at saturating concentrations both substrates indirectly activate voltage-gated L-type Ca(2+) channels (CaV1.3 and CaV1.2) but not the N-type Ca(2+) channel (CaV2.2). Furthermore, the potency to achieve hDAT-CaV electrical coupling is dominated by the substrate affinity on hDAT, with negligible influence of L-type channel voltage sensitivity. In contrast, the maximal coupling-strength (defined as Ca(2+) signal change per unit hDAT current) is influenced by CaV voltage sensitivity, which is greater in CaV1.3- than in CaV1.2-expressing cells. Moreover, relative to DA, S(+)AMPH showed greater coupling-strength at concentrations that induced relatively small hDAT-mediated currents. Therefore S(+)AMPH is not only more potent than DA at inducing hDAT-mediated L-type Ca(2+) channel currents but is a better depolarizing agent since it produces tighter electrical coupling between hDAT-mediated depolarization and L-type Ca(2+) channel activation.

  20. Relationship between psychostimulant-induced "high" and dopamine transporter occupancy.

    PubMed Central

    Volkow, N D; Wang, G J; Fowler, J S; Gatley, S J; Ding, Y S; Logan, J; Dewey, S L; Hitzemann, R; Lieberman, J

    1996-01-01

    The ability of cocaine to inhibit the dopamine transporter (DAT) appears to be crucial for its reinforcing properties. The potential use of drugs that produce long-lasting inhibition of the DAT as a mean of preventing the "high" and reducing drug-seeking behavior has become a major strategy in medication development. However, neither the relation between the high and DAT inhibition nor the ability to block the high by prior DAT blockade have ever been demonstrated. To evaluate if DAT could prevent the high induced by methylphenidate (MP), a drug which like cocaine inhibits the DAT, we compared the responses in eight non-drug-abusing subjects between the first and the second of two MP doses (0.375 mg/kg, i.v.) given 60 min apart. At 60 min the high from MP has returned to baseline, but 75-80% of the drug remains in brain. Positron-emission tomography and [11C]d-threo-MP were used to estimate DAT occupancies at different times after MP. DAT inhibition by MP did not block or attenuate the high from a second dose of MP given 60 min later, despite a 80% residual transporter occupancy from the first dose. Furthermore some subjects did not perceive a high after single or repeated administration despite significant DAT blockade. These results indicate that DAT occupancy is not sufficient to account for the high, and that for DAT inhibitors to be therapeutically effective, occupancies > 80% may be required. Images Fig. 1 PMID:8816810

  1. Dopamine Transporter Blockade Increases LTP in the CA1 Region of the Rat Hippocampus via Activation of the D3 Dopamine Receptor

    ERIC Educational Resources Information Center

    Swant, Jarod; Wagner, John J.

    2006-01-01

    Dopamine has been demonstrated to be involved in the modulation of long-term potentiation (LTP) in the CA1 region of the hippocampus. As monoamine transporter blockade will increase the actions of endogenous monoamine neurotransmitters, the effect of a dopamine transporter (DAT) antagonist on LTP was assessed using field excitatory postsynaptic…

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

    PubMed Central

    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

  3. Mitochondrial stress-induced dopamine efflux and neuronal damage by malonate involves the dopamine transporter.

    PubMed

    Moy, Lily Y; Wang, Sheng-Ping; Sonsalla, Patricia K

    2007-02-01

    Endogenous striatal dopamine (DA) overflow has been associated with neuropathological conditions resulting from ischemia, psychostimulants, and metabolic inhibition. Malonate, a reversible inhibitor of succinate dehydrogenase, models the effects of energy impairment in neurodegenerative disorders. We have previously reported that the striatal DA efflux and damage to DA nerve terminals resulting from intrastriatal malonate infusions is prevented by prior DA depletion, suggesting that DA plays a role in the neuronal damage. We presently report that the malonate-induced DA efflux is partially mediated by reverse transport of DA from the cytosol to the extracellular space via the DA transporter (DAT). Pharmacological blockade of the DAT with a series of structurally different inhibitors [cocaine, mazindol, 1-(2-(bis(4-fluophenyl methoxy) ethyl)-4-(3-(4-fluorophenyl)-propyl)piperazine) dimethane sulfonate (GBR 13098) and methyl(-)-3beta-(p-fluorophenyl)-1alphaH,5alphaH-tropane-2beta-carboxylate1,5-naphthalene (Win 35,428)] attenuated malonate-induced DA overflow in vivo and protected mice against subsequent damage to DA nerve terminals. Consistent with these findings, the DAT inhibitors prevented malonate-induced damage to DA neurons in mesencephalic cultures and also protected against the loss of GABA neurons in this system. The DAT inhibitors did not modify malonate-induced formation of reactive oxygen species or lactate production, indicating that the DAT inhibitors neither exert antioxidant effects nor interfere with the actions of malonate. Taken together, these findings provide direct evidence that mitochondrial impairment and metabolic stress cause striatal DA efflux via the DAT and suggest that disruptions in DA homeostasis resulting from energy impairment may contribute to the pathogenesis of neurodegenerative diseases.

  4. Dopamine Transporter Genotype Conveys Familial Risk of Attention-Deficit/Hyperactivity Disorder through Striatal Activation

    ERIC Educational Resources Information Center

    Durston, Sarah; Fossella, John A.; Mulder, Martijn J.; Casey B. J.; Ziermans, Tim B.; Vessaz, M. Nathalie; Van Engeland, Herman

    2008-01-01

    The study examines the effect of the dopamine transporter (DAT1) genotype in attention-deficit/hyperactivity disorder (ADHD). The results confirm that DAT1 translates the genetic risk of ADHD through striatal activation.

  5. Mephedrone and Methylenedioxypyrovalerone (MDPV), Major Constituents of Bath Salts, Produce Opposite Effects at the Human Dopamine Transporter*

    PubMed Central

    Cameron, Krasnodara; Kolanos, Renata; Verkariya, Rakesh; De Felice, Louis; Glennon, Richard A.

    2013-01-01

    Rationale Psychoactive ‘bath salts’ represents a relatively new drug of abuse combination that was placed in Schedule I in October 2011. Two common ingredients of ‘bath salts’ include the cathinone analogs: mephedrone and methylenedioxy-pyrovalerone (MDPV). The mechanism of action of these synthetic cathinone analogs has not been well investigated. Materials and methods Because cathinone and methcathinone are known to act as releasing agents at the human dopamine transporter (hDAT), mephedrone and MDPV were investigated at hDAT expressed in Xenopus oocytes. Results Whereas mephedrone was found to have the signature of a dopamine releasing agent similar to methamphetamine or methcathinone, MDPV behaved as a cocaine-like reuptake inhibitor of dopamine. Conclusions Mephedrone and MDPV produce opposite electrophysiological signatures through hDAT expressed in oocytes. Implications are that the combination (as found in ‘bath salts’) might produce effects similar to a combination of methamphetamine and cocaine. PMID:23371489

  6. Electrophysiological and amperometric evidence that modafinil blocks the dopamine uptake transporter to induce behavioral activation.

    PubMed

    Federici, M; Latagliata, E C; Rizzo, F R; Ledonne, A; Gu, H H; Romigi, A; Nisticò, R; Puglisi-Allegra, S; Mercuri, N B

    2013-11-12

    Although the wake-promoting drug modafinil has been shown to bind quite exclusively to the dopamine transporter (DAT), its action in the brain has been thought to be partially independent from the facilitation of the dopaminergic signals. Here we used electrophysiological and amperometric techniques to investigate the effects of modafinil on the dopaminergic neurons of the substantia nigra pars compacta (SNpc) and on the synaptic overflow of dopamine in the dorsal striatum from the sliced tissue of wild-type and cocaine-insensitive genetically modified mice (DAT-CI). Moreover, we examined the consequences of modafinil administration on the locomotor behavior of wild-type and DAT-CI mice. In in vitro experiments, modafinil inhibited the spontaneous firing discharge of the dopaminergic neurons. More consistently, it potentiated firing inhibition and the membrane responses caused by exogenously applied dopamine on these cells. Furthermore, it augmented the stimulus-evoked outflow of DA in the striatum. Noteworthy, modafinil caused locomotor activation in wild-type mice. On the other hand, neither the electrophysiological nor the behavioral effects of modafinil were detected in DAT-CI animals. These results demonstrate that modafinil potentiates brain dopaminergic signals via DAT inhibition by acting at the same binding site of cocaine. Therefore, this mechanism of action explains most of the pharmacological properties of this compound in the clinical setting.

  7. Cloning, pharmacological characterization, and chromosome assignment of the human dopamine transporter.

    PubMed

    Giros, B; el Mestikawy, S; Godinot, N; Zheng, K; Han, H; Yang-Feng, T; Caron, M G

    1992-09-01

    We have screened a human substantia nigra cDNA library with probes derived from the rat dopamine transporter. A 3.5-kilobase cDNA clone was isolated and its corresponding gene was located on the distal end of chromosome 5 (5p15.3). This human clone codes for a 620-amino acid protein with a calculated molecular weight of 68,517. Hydropathicity analysis suggests the presence of 12 putative transmembrane domains, a characteristic feature of sodium-dependent neurotransmitter carriers. The rat and the human dopamine transporters are 92% homologous. When permanently expressed in mouse fibroblast Ltk- cells, the human clone is able to induce a saturable, time- and sodium-dependent, dopamine uptake. This transport is blocked by psychostimulant drugs (cocaine, l- and d-amphetamine, and phenyclidine), neurotoxins (6-hydroxydopamine and N-methyl-4-phenylpyridine (MPP))+), neurotransmitters (epinephrine, norepinephrine, gamma-aminobutyric acid, and serotonin), antidepressants (amitriptyline, bupropion, desipramine, mazindol, nomifensine, and nortriptyline), and various uptake inhibitors (mazindol, GBR 12783, GBR 12909, and amfonelic acid). The rank orders of the Ki values of these substances at the human and the rat dopamine transporters are highly correlated (r = 0.998). The cloning of DNA human dopamine transporter gene has allowed establishment of a cell line stably expressing the human dopamine transporter and, for the first time, an extensive characterization of its pharmacology. Furthermore, these newly developed tools will help in the study of the regulation of dopamine transport in humans and in the clarification of the potential role of the dopamine transporter in a variety of disease states.

  8. Dual Action of Zn2+ on the Transport Cycle of the Dopamine Transporter*

    PubMed Central

    Li, Yang; Hasenhuetl, Peter S.; Schicker, Klaus; Sitte, Harald H.; Freissmuth, Michael; Sandtner, Walter

    2015-01-01

    The dopamine transporter shapes dopaminergic neurotransmission by clearing extracellular dopamine and by replenishing vesicular stores. The dopamine transporter carries an endogenous binding site for Zn2+, but the nature of the Zn2+-dependent modulation has remained elusive: both, inhibition and stimulation of DAT have been reported. Here, we exploited the high time resolution of patch-clamp recordings to examine the effects of Zn2+ on the transport cycle of DAT: we recorded peak currents associated with substrate translocation and steady-state currents reflecting the forward transport mode of DAT. Zn2+ depressed the peak current but enhanced the steady-state current through DAT. The parsimonious explanation is preferential binding of Zn2+ to the outward facing conformation of DAT, which allows for an allosteric activation of DAT, in both, the forward transport mode and substrate exchange mode. We directly confirmed that Zn2+ dissociated more rapidly from the inward- than from the outward-facing state of DAT. Finally, we formulated a kinetic model for the action of Zn2+ on DAT that emulated all current experimental observations and accounted for all previous (in part contradictory) findings. Importantly, the model predicts that the intracellular Na+ concentration determines whether substrate uptake by DAT is stimulated or inhibited by Zn2+. This prediction was directly verified. The mechanistic framework provided by the current model is of relevance for the rational design of allosteric activators of DAT. These are of interest for treating de novo loss-of-function mutations of DAT associated with neuropsychiatric disorders such as attention deficit hyperactivity disorder (ADHD). PMID:26504078

  9. Association between amygdala reactivity and a dopamine transporter gene polymorphism

    PubMed Central

    Bergman, O; Åhs, F; Furmark, T; Appel, L; Linnman, C; Faria, V; Bani, M; Pich, E M; Bettica, P; Henningsson, S; Manuck, S B; Ferrell, R E; Nikolova, Y S; Hariri, A R; Fredrikson, M; Westberg, L; Eriksson, E

    2014-01-01

    Essential for detection of relevant external stimuli and for fear processing, the amygdala is under modulatory influence of dopamine (DA). The DA transporter (DAT) is of fundamental importance for the regulation of DA transmission by mediating reuptake inactivation of extracellular DA. This study examined if a common functional variable number tandem repeat polymorphism in the 3′ untranslated region of the DAT gene (SLC6A3) influences amygdala function during the processing of aversive emotional stimuli. Amygdala reactivity was examined by comparing regional cerebral blood flow, measured with positron emission tomography and [15O]water, during exposure to angry and neutral faces, respectively, in a Swedish sample comprising 32 patients with social anxiety disorder and 17 healthy volunteers. In a separate US sample, comprising 85 healthy volunteers studied with blood oxygen level-dependent functional magnetic resonance imaging, amygdala reactivity was assessed by comparing the activity during exposure to threatening faces and neutral geometric shapes, respectively. In both the Swedish and the US sample, 9-repeat carriers displayed higher amygdala reactivity than 10-repeat homozygotes. The results suggest that this polymorphism contributes to individual variability in amygdala reactivity. PMID:25093598

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

    PubMed

    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.

  11. Increased vesicular monoamine transporter enhances dopamine release and opposes Parkinson disease-related neurodegeneration in vivo.

    PubMed

    Lohr, Kelly M; Bernstein, Alison I; Stout, Kristen A; Dunn, Amy R; Lazo, Carlos R; Alter, Shawn P; Wang, Minzheng; Li, Yingjie; Fan, Xueliang; Hess, Ellen J; Yi, Hong; Vecchio, Laura M; Goldstein, David S; Guillot, Thomas S; Salahpour, Ali; Miller, Gary W

    2014-07-08

    Disruption of neurotransmitter vesicle dynamics (transport, capacity, release) has been implicated in a variety of neurodegenerative and neuropsychiatric conditions. Here, we report a novel mouse model of enhanced vesicular function via bacterial artificial chromosome (BAC)-mediated overexpression of the vesicular monoamine transporter 2 (VMAT2; Slc18a2). A twofold increase in vesicular transport enhances the vesicular capacity for dopamine (56%), dopamine vesicle volume (33%), and basal tissue dopamine levels (21%) in the mouse striatum. The elevated vesicular capacity leads to an increase in stimulated dopamine release (84%) and extracellular dopamine levels (44%). VMAT2-overexpressing mice show improved outcomes on anxiety and depressive-like behaviors and increased basal locomotor activity (41%). Finally, these mice exhibit significant protection from neurotoxic insult by the dopaminergic toxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), as measured by reduced dopamine terminal damage and substantia nigra pars compacta cell loss. The increased release of dopamine and neuroprotection from MPTP toxicity in the VMAT2-overexpressing mice suggest that interventions aimed at enhancing vesicular capacity may be of therapeutic benefit in Parkinson disease.

  12. Increased vesicular monoamine transporter enhances dopamine release and opposes Parkinson disease-related neurodegeneration in vivo

    PubMed Central

    Lohr, Kelly M.; Bernstein, Alison I.; Stout, Kristen A.; Dunn, Amy R.; Lazo, Carlos R.; Alter, Shawn P.; Wang, Minzheng; Li, Yingjie; Fan, Xueliang; Hess, Ellen J.; Yi, Hong; Vecchio, Laura M.; Goldstein, David S.; Guillot, Thomas S.; Salahpour, Ali; Miller, Gary W.

    2014-01-01

    Disruption of neurotransmitter vesicle dynamics (transport, capacity, release) has been implicated in a variety of neurodegenerative and neuropsychiatric conditions. Here, we report a novel mouse model of enhanced vesicular function via bacterial artificial chromosome (BAC)-mediated overexpression of the vesicular monoamine transporter 2 (VMAT2; Slc18a2). A twofold increase in vesicular transport enhances the vesicular capacity for dopamine (56%), dopamine vesicle volume (33%), and basal tissue dopamine levels (21%) in the mouse striatum. The elevated vesicular capacity leads to an increase in stimulated dopamine release (84%) and extracellular dopamine levels (44%). VMAT2-overexpressing mice show improved outcomes on anxiety and depressive-like behaviors and increased basal locomotor activity (41%). Finally, these mice exhibit significant protection from neurotoxic insult by the dopaminergic toxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), as measured by reduced dopamine terminal damage and substantia nigra pars compacta cell loss. The increased release of dopamine and neuroprotection from MPTP toxicity in the VMAT2-overexpressing mice suggest that interventions aimed at enhancing vesicular capacity may be of therapeutic benefit in Parkinson disease. PMID:24979780

  13. Improvement of Learning and Increase in Dopamine Level in the Frontal Cortex by Methylphenidate in Mice Lacking Dopamine Transporter

    PubMed Central

    Takamatsu, Y.; Hagino, Y.; Sato, A.; Takahashi, T.; Nagasawa, S.Y.; Kubo, Y.; Mizuguchi, M.; Uhl, G.R.; Sora, I.; Ikeda, K.

    2015-01-01

    The symptoms of attention-deficit/hyperactivity disorder (ADHD) are characterized by inattention and hyperactivity-impulsivity. It is a common childhood neurodevelopmental disorder that often persists into adulthood. Improvements in ADHD symptoms using psychostimulants have been recognized as a paradoxical calming effect. The psychostimulant methylphenidate (MPH) is currently used as the first-line medication for the management of ADHD. Recent studies have drawn attention to altered dopamine-mediated neurotransmission in ADHD, particularly reuptake by the dopamine transporter (DAT). This hypothesis is supported by the observation that DAT knockout mice exhibit marked hyperactivity that is responsive to acute MPH treatment. However, other behaviors relevant to ADHD have not been fully clarified. In the present study, we observed learning impairment in shuttle-box avoidance behavior together with hyperactivity in a novel environment in DAT knockout mice. Methylphenidate normalized these behaviors and enhanced escape activity in the tail suspension test. Interestingly, the effective dose of MPH increased extracellular dopamine in the prefrontal cortex but not striatum, suggesting an important role for changes in prefrontal dopamine in ADHD. Research that uses rodent models such as DAT knockout mice may be useful for elucidating the pathophysiology of ADHD. PMID:25817856

  14. Cocaine and amphetamine elicit differential effects in rats with a unilateral injection of dopamine transporter antisense oligodeoxynucleotides.

    PubMed

    Silvia, C P; Jaber, M; King, G R; Ellinwood, E H; Caron, M G

    1997-02-01

    We have developed an antisense oligodeoxynucleotide to the dopamine transporter and used it to discriminate the behavioral properties of amphetamine and cocaine. In SK-N-MC cells permanently transfected with the dopamine transporter complementary DNA, treatment with 5 mM antisense oligodeoxynucleotide reduced dopamine uptake by 25% when compared to sense control. Unilateral intranigral administration of dopamine transporter antisense (50 microM) twice daily in freely moving rats for 2.5 days was sufficient to reduce dopamine transporter messenger RNA by 70% as measured by in situ hybridization, but not protein levels as measured by [3H]mazindol binding. However, intranigral treatment via implanted osmotic minipump over a period of seven days produced reductions in both dopamine transporter messenger RNA and protein levels (32%) at a dose of 500 pmol/day. These results indicate a longer half-life for the dopamine transporter than expected. Potassium chloride depolarization of ipsilateral striatal slices showed a greater than 200% increase in dopamine overflow on the antisense-treated side compared to the control side. Since imbalance of dopamine tone is known to induce rotational activity, we tested this behavioral paradigm in rats treated with various oligodeoxynucleotides at different doses and time-points. We have found that antisense-treated animals did not rotate spontaneously under any experimental conditions. Using various psychostimulants that target the dopamine transporter and increase dopamine levels, we found that the antisense-treated animals consistently rotated contralaterally in response to amphetamine (2 mg/kg), but not to cocaine (10 mg/kg) or nomifensine (10 mg/kg). These results bring in vivo evidence for a different mode of action of amphetamine and cocaine on the dopamine transporter and lend direct support to the view that amphetamine acts as a dopamine releaser, whereas cocaine acts by blocking dopamine transport.

  15. Dopamine transporters participate in the physiological regulation of prolactin.

    PubMed

    Demaria, J E; Nagy, G M; Lerant, A A; Fekete, M I; Levenson, C W; Freeman, M E

    2000-01-01

    Three populations of hypothalamic neuroendocrine dopaminergic (NEDA) neurons, arising from the arcuate and periventricular nuclei of the hypothalamus release dopamine (DA) that acts at the pituitary gland to regulate the secretion of PRL. It is generally accepted that NEDA neurons lack functional DA transporters (DATs), which are responsible for uptake of DA from the synaptic cleft into the presynaptic axon terminal. This study localized DATs to the hypothalamo-pituitary axis and evaluated the effect of DAT blockade on the hypothalamo-pituitary regulation of PRL. After 7 days of treatment with cocaine (a nonspecific amine transporter blocker) or mazindol (a specific DAT blocker), the relative abundance of PRL messenger RNA (mRNA) in the anterior lobe (AL) of OVX rats was significantly decreased, whereas the relative abundance of tyrosine hydroxylase mRNA in the hypothalamus was significantly increased. The effect of cocaine or mazindol administration on DA turnover and serum PRL concentration was examined in estradiol (E2)-treated OVX rats. E2 administration (i.v.) resulted in a significant increase in serum PRL within 4 h; however, cocaine or mazindol administration abolished the E2-induced increase of PRL. Cocaine or mazindol significantly increased the concentration of DA at the site of the axon terminals within the median eminence (ME), intermediate lobe (IL) and neural lobe (NL), indicating blockade of uptake. Because formation of DOPAC requires uptake of DA, concentrations of DOPAC in the ME, IL and NL decreased following treatment with either cocaine or mazindol. These data, together with the presence of immunopositive DAT in the ME, pituitary stalk, IL, and NL, suggest that a functional DAT system is present within all three populations of NEDA neurons. Moreover, similarity between the effects of cocaine and mazindol treatment indicate that blockade of the DAT, but not other amine transporters, is responsible for suppression of PRL gene expression and

  16. Animal models of depression in dopamine, serotonin, and norepinephrine transporter knockout mice: prominent effects of dopamine transporter deletions.

    PubMed

    Perona, Maria T G; Waters, Shonna; Hall, Frank Scott; Sora, Ichiro; Lesch, Klaus-Peter; Murphy, Dennis L; Caron, Marc; Uhl, George R

    2008-09-01

    Antidepressant drugs produce therapeutic actions and many of their side effects via blockade of the plasma membrane transporters for serotonin (SERT/SLC6A2), norepinephrine (NET/SLC6A1), and dopamine (DAT/SLC6A3). Many antidepressants block several of these transporters; some are more selective. Mouse gene knockouts of these transporters provide interesting models for possible effects of chronic antidepressant treatments. To examine the role of monoamine transporters in models of depression DAT, NET, and SERT knockout (KO) mice and wild-type littermates were studied in the forced swim test (FST), the tail suspension test, and for sucrose consumption. To dissociate general activity from potential antidepressant effects three types of behavior were assessed in the FST: immobility, climbing, and swimming. In confirmation of earlier reports, both DAT KO and NET KO mice exhibited less immobility than wild-type littermates whereas SERT KO mice did not. Effects of DAT deletion were not simply because of hyperactivity, as decreased immobility was observed in DAT+/- mice that were not hyperactive as well as in DAT-/- mice that displayed profound hyperactivity. Climbing was increased, whereas swimming was almost eliminated in DAT-/- mice, and a modest but similar effect was seen in NET KO mice, which showed a modest decrease in locomotor activity. Combined increases in climbing and decreases in immobility are characteristic of FST results in antidepressant animal models, whereas selective effects on swimming are associated with the effects of stimulant drugs. Therefore, an effect on climbing is thought to more specifically reflect antidepressant effects, as has been observed in several other proposed animal models of reduced depressive phenotypes. A similar profile was observed in the tail suspension test, where DAT, NET, and SERT knockouts were all found to reduce immobility, but much greater effects were observed in DAT KO mice. However, to further determine whether

  17. Classic Studies on the Interaction of Cocaine and the Dopamine Transporter

    PubMed Central

    Verma, Vivek

    2015-01-01

    The dopamine transporter is responsible for recycling dopamine after release. Inhibitors of the dopamine transporter, such as cocaine, will stop the reuptake of dopamine and allow it to stay extracellularly, causing prominent changes at the molecular, cellular, and behavioral levels. There is much left to be known about the mechanism and site(s) of binding, as well as the effect that cocaine administration does to dopamine transporter-cocaine binding sites and gene expression which also plays a strong role in cocaine abusers and their behavioral characteristics. Thus, if more light is shed on the dopamine transporter-cocaine interaction, treatments for addiction and even other diseases of the dopaminergic system may not be too far ahead. As today’s ongoing research expands on the shoulders of classic research done in the 1990s and 2000s, the foundation of core research done in that time period will be reviewed, which forms the basis of today’s work and tomorrow’s therapies. PMID:26598579

  18. Association of polymorphisms of dopamine D2 receptor (DRD2), and dopamine transporter (DAT1) genes with schizoid/avoidant behaviors (SAB).

    PubMed

    Blum, K; Braverman, E R; Wu, S; Cull, J G; Chen, T J; Gill, J; Wood, R; Eisenberg, A; Sherman, M; Davis, K R; Matthews, D; Fischer, L; Schnautz, N; Walsh, W; Pontius, A A; Zedar, M; Kaats, G; Comings, D E

    1997-05-01

    The dopaminergic system, and in particular the dopamine D2 receptor, has been implicated in reward mechanisms in the brain. Dysfunction of the D2 dopamine receptors leads to aberrant substance-seeking behaviors (ethanol, drugs, tobacco, and food) and other related behaviors (pathological gambling, Tourette's disorder, attention-deficit/hyperactivity disorder). This is the first study supporting a strong association between the dopamine D2 receptor Taq A1 allele with schizoid/avoidant behavior (SAB). Additionally, an albeit weaker association between the 480-bp VNTR 10/10 allele of the dopamine transporter (DAT1) gene with SAB was similarly found.

  19. Sensitized nucleus accumbens dopamine terminal responses to methylphenidate and dopamine transporter releasers after intermittent-access self-administration.

    PubMed

    Calipari, Erin S; Jones, Sara R

    2014-07-01

    Long-access methylphenidate (MPH) self-administration has been shown to produce enhanced amphetamine potency at the dopamine transporter and concomitant changes in reinforcing efficacy, suggesting that MPH abuse may change the dopamine system in a way that promotes future drug abuse. While long-access self-administration paradigms have translational validity for cocaine, it may not be as relevant a model of MPH abuse, as it has been suggested that people often take MPH intermittently. Although previous work outlined the neurochemical and behavioral consequences of long-access MPH self-administration, it was not clear whether intermittent access (6 h session; 5 min access/30 min) would result in similar changes. For cocaine, long-access self-administration resulted in tolerance to cocaine's effects on dopamine and behavior while intermittent-access resulted in sensitization. Here we assessed the neurochemical consequences of intermittent-access MPH self-administration on dopamine terminal function. We found increased maximal rates of uptake, increased stimulated release, and subsensitive D2-like autoreceptors. Consistent with previous work using extended-access MPH paradigms, the potencies of amphetamine and MPH, but not cocaine, were increased, demonstrating that unlike cocaine, MPH effects were not altered by the pattern of intake. Although the potency results suggest that MPH may share properties with releasers, dopamine release was increased following acute application of MPH, similar to cocaine, and in contrast to the release decreasing effects of amphetamine. Taken together, these data demonstrate that MPH exhibits properties of both blockers and releasers, and that the compensatory changes produced by MPH self-administration may increase the abuse liability of amphetamines, independent of the pattern of administration.

  20. Polymorphism of the dopamine transporter type 1 gene modifies the treatment response in Parkinson's disease.

    PubMed

    Moreau, Caroline; Meguig, Sayah; Corvol, Jean-Christophe; Labreuche, Julien; Vasseur, Francis; Duhamel, Alain; Delval, Arnaud; Bardyn, Thomas; Devedjian, Jean-Christophe; Rouaix, Nathalie; Petyt, Gregory; Brefel-Courbon, Christine; Ory-Magne, Fabienne; Guehl, Dominique; Eusebio, Alexandre; Fraix, Valérie; Saulnier, Pierre-Jean; Lagha-Boukbiza, Ouhaid; Durif, Frank; Faighel, Mirela; Giordana, Caroline; Drapier, Sophie; Maltête, David; Tranchant, Christine; Houeto, Jean-Luc; Debû, Bettina; Azulay, Jean-Philippe; Tison, François; Destée, Alain; Vidailhet, Marie; Rascol, Olivier; Dujardin, Kathy; Defebvre, Luc; Bordet, Régis; Sablonnière, Bernard; Devos, David

    2015-05-01

    After more than 50 years of treating Parkinson's disease with l-DOPA, there are still no guidelines on setting the optimal dose for a given patient. The dopamine transporter type 1, now known as solute carrier family 6 (neurotransmitter transporter), member 3 (SLC6A3) is the most powerful determinant of dopamine neurotransmission and might therefore influence the treatment response. We recently demonstrated that methylphenidate (a dopamine transporter inhibitor) is effective in patients with Parkinson's disease with motor and gait disorders. The objective of the present study was to determine whether genetic variants of the dopamine transporter type 1-encoding gene (SLC6A3) are associated with differences in the response to treatment of motor symptoms and gait disorders with l-DOPA and methylphenidate (with respect to the demographic, the disease and the treatment parameters and the other genes involved in the dopaminergic neurotransmission). This analysis was part of a multicentre, parallel-group, double-blind, placebo-controlled, randomized clinical trial of methylphenidate in Parkinson's disease (Protocol ID:2008-005801-20; ClinicalTrials.gov:NCT00914095). We scored the motor Unified Parkinson's Disease Rating Scale and the Stand-Walk-Sit Test before and after a standardized acute l-DOPA challenge before randomization and then after 3 months of methylphenidate treatment. Patients were screened for variants of genes involved in dopamine metabolism: rs28363170 and rs3836790 polymorphisms in the SLC6A3 gene, rs921451 and rs3837091 in the DDC gene (encoding the aromatic L-amino acid decarboxylase involved in the synthesis of dopamine from l-DOPA), rs1799836 in the MAOB gene (coding for monoamine oxidase B) and rs4680 in the COMT gene (coding for catechol-O-methyltransferase). Investigators and patients were blinded to the genotyping data throughout the study. Eighty-one subjects were genotyped and 61 were analysed for their acute motor response to l-DOPA. The SLC6A3

  1. Vesicular Glutamate Transport Promotes Dopamine Storage and Glutamate Corelease In Vivo

    PubMed Central

    Hnasko, Thomas S.; Chuhma, Nao; Zhang, Hui; Goh, Germaine Y.; Sulzer, David; Palmiter, Richard D.; Rayport, Stephen; Edwards, Robert H.

    2010-01-01

    SUMMARY Dopamine neurons in the ventral tegmental area (VTA) play an important role in the motivational systems underlying drug addiction, and recent work has suggested that they also release the excitatory neurotransmitter glutamate. To assess a physiological role for glutamate corelease, we disrupted the expression of vesicular glutamate transporter 2 selectively in dopamine neurons. The conditional knockout abolishes glutamate release from midbrain dopamine neurons in culture and severely reduces their excitatory synaptic output in mesoaccumbens slices. Baseline motor behavior is not affected, but stimulation of locomotor activity by cocaine is impaired, apparently through a selective reduction of dopamine stores in the projection of VTA neurons to ventral striatum. Glutamate co-entry promotes monoamine storage by increasing the pH gradient that drives vesicular monoamine transport. Remarkably, low concentrations of glutamate acidify synaptic vesicles more slowly but to a greater extent than equimolar Cl−, indicating a distinct, presynaptic mechanism to regulate quantal size. PMID:20223200

  2. Distribution of dopamine transporter immunoreactive fibers in the human amygdaloid complex.

    PubMed

    García-Amado, María; Prensa, Lucía

    2013-12-01

    The nuclei of the human amygdaloid complex can be distinguished from each other on the basis of their cytoarchitecture, chemistry and connections, all of which process the information needed for the different functions (ranging from attention to memory and emotion) of the amygdala. This complex receives dopaminergic input that exerts modulatory effects over its intrinsic network and is critical for reward-related learning and fear conditioning. To determine the specific distribution of the dopaminergic input through the different nuclei and nuclear subdivisions of this structure we used stereological tools to quantify the fibers containing the dopamine transporter (used to signal the dopaminergic phenotype) in post-mortem samples from control individuals. Dopaminergic axons targeted every nucleus of the amygdaloid complex, and the density of dopamine transporter-containing axons varied considerably among its nuclear groups. The central group showed the greatest density of dopamine transporter-positive fibers, more than double the density of the basolateral group, the second most densely innervated structure. The dopamine transporter-positive innervation is very scant in the corticomedial group. The density of dopamine transporter-positive fibers did not vary among the nuclei of the basolateral group - i.e. basal, lateral and accessory basal nuclei - although there were significant density gradients among the subdivisions of these nuclei. These detailed quantitative data on dopamine transporter-positive innervation in the human amygdaloid complex can offer a useful reference in future studies aimed at analysing putative dysfunctions of this system in diseases involving brain dopamine, such as certain anxiety disorders, Parkinson's disease and schizophrenia.

  3. 2'-Substitution of cocaine selectively enhances dopamine and norepinephrine transporter binding.

    PubMed

    Seale, T W; Avor, K; Singh, S; Hall, N; Chan, H M; Basmadjian, G P

    1997-11-10

    Few studies have characterized the effect of substituents at the 2'-position of cocaine on transporter binding potency and selectivity. We synthesized 2'-OH-, 2'-F- and 2'-acetoxy-cocaines and compared their binding potencies for rat dopamine, norepinephrine and 5-hydroxytryptamine transporters to cocaine, 3'-OH-, 4'-OH-, 2'-OH,4'-I-cocaine derivatives, and to the transporter selective ligands WIN 35,428, nisoxetine and paroxetine. Unlike most substitutions, 2'-OH- and 2'-acetoxy-groups increased cocaine's binding potency for the dopamine transporter (10- and 4-fold, respectively). These substituents also enhanced binding to the norepinephrine transporter (52- and 35-fold, respectively) but had less effect on 5-hydroxytryptamine transporter binding. 2'-Hydroxylation also enhanced binding of 4'-I cocaine, an analog with low DA binding potency. The ability of 2'-substituents to substantially increase cocaine binding potency and to alter selectivity for brain transporters indicates the potential importance of the 2'-position in transporter binding.

  4. Dopamine D1, D2, D3 Receptors, Vesicular Monoamine Transporter Type-2 (VMAT2) and Dopamine Transporter (DAT) Densities in Aged Human Brain

    PubMed Central

    Sun, Jianjun; Xu, Jinbin; Cairns, Nigel J.; Perlmutter, Joel S.; Mach, Robert H.

    2012-01-01

    The dopamine D1, D2, D3 receptors, vesicular monoamine transporter type-2 (VMAT2), and dopamine transporter (DAT) densities were measured in 11 aged human brains (aged 77–107.8, mean: 91 years) by quantitative autoradiography. The density of D1 receptors, VMAT2, and DAT was measured using [3H]SCH23390, [3H]dihydrotetrabenazine, and [3H]WIN35428, respectively. The density of D2 and D3 receptors was calculated using the D3-preferring radioligand, [3H]WC-10 and the D2-preferring radioligand [3H]raclopride using a mathematical model developed previously by our group. Dopamine D1, D2, and D3 receptors are extensively distributed throughout striatum; the highest density of D3 receptors occurred in the nucleus accumbens (NAc). The density of the DAT is 10–20-fold lower than that of VMAT2 in striatal regions. Dopamine D3 receptor density exceeded D2 receptor densities in extrastriatal regions, and thalamus contained a high level of D3 receptors with negligible D2 receptors. The density of dopamine D1 linearly correlated with D3 receptor density in the thalamus. The density of the DAT was negligible in the extrastriatal regions whereas the VMAT2 was expressed in moderate density. D3 receptor and VMAT2 densities were in similar level between the aged human and aged rhesus brain samples, whereas aged human brain samples had lower range of densities of D1 and D2 receptors and DAT compared with the aged rhesus monkey brain. The differential density of D3 and D2 receptors in human brain will be useful in the interpretation of PET imaging studies in human subjects with existing radiotracers, and assist in the validation of newer PET radiotracers having a higher selectivity for dopamine D2 or D3 receptors. PMID:23185343

  5. Dopamine Transporters in Striatum Correlated with Deactivation in the Default Mode Network during Visuospatial Attention

    SciTech Connect

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

    2009-06-01

    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 [{sup 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.

  6. Dopamine transport sites selectively labeled by a novel photoaffinity probe: 125I-DEEP

    SciTech Connect

    Grigoriadis, D.E.; Wilson, A.A.; Lew, R.; Sharkey, J.S.; Kuhar, M.J. )

    1989-08-01

    The dopamine transporter was labeled using a photosensitive compound related to GBR-12909, {sup 125}I-1-(2-(diphenylmethoxy)ethyl)-4-(2- (4-azido-3-iodophenyl)ethyl)piperazine ({sup 125}I-DEEP). {sup 125}I-DEEP bound reversibly and with high affinity to the dopamine transport protein in the absence of light and could be covalently attached to the protein following exposure to UV light. In rat striatal homogenates, {sup 125}I-DEEP was found to incorporate covalently into a protein with apparent molecular weight of 58,000 Da. The properties of this binding protein were characteristic of the dopamine transporter since covalent attachment could be inhibited by dopamine-uptake blockers with the proper pharmacological rank order of potencies. Covalent binding was also inhibited in a stereospecific manner by (+) and (-) cocaine, as well as other cocaine analogs. The protein was not found in the cerebellum. The dopamine transporter appears to exist in a glycosylated form since photoaffinity-labeled transport sites could adsorb to wheat germ-agglutinin and could be specifically eluted from the column by beta-N-acetylglucosamine.

  7. Glycine Transporter-1 Inhibition Promotes Striatal Axon Sprouting via NMDA Receptors in Dopamine Neurons

    PubMed Central

    Castagna, Candace; Mrejeru, Ana; Lizardi-Ortiz, José E.; Klein, Zoe; Lindsley, Craig W.

    2013-01-01

    NMDA receptor activity is involved in shaping synaptic connections throughout development and adulthood. We recently reported that brief activation of NMDA receptors on cultured ventral midbrain dopamine neurons enhanced their axon growth rate and induced axonal branching. To test whether this mechanism was relevant to axon regrowth in adult animals, we examined the reinnervation of dorsal striatum following nigral dopamine neuron loss induced by unilateral intrastriatal injections of the toxin 6-hydroxydopamine. We used a pharmacological approach to enhance NMDA receptor-dependent signaling by treatment with an inhibitor of glycine transporter-1 that elevates levels of extracellular glycine, a coagonist required for NMDA receptor activation. All mice displayed sprouting of dopaminergic axons from spared fibers in the ventral striatum to the denervated dorsal striatum at 7 weeks post-lesion, but the reinnervation in mice treated for 4 weeks with glycine uptake inhibitor was approximately twice as dense as in untreated mice. The treated mice also displayed higher levels of striatal dopamine and a complete recovery from lateralization in a test of sensorimotor behavior. We confirmed that the actions of glycine uptake inhibition on reinnervation and behavioral recovery required NMDA receptors in dopamine neurons using targeted deletion of the NR1 NMDA receptor subunit in dopamine neurons. Glycine transport inhibitors promote functionally relevant sprouting of surviving dopamine axons and could provide clinical treatment for disorders such as Parkinson's disease. PMID:24133278

  8. Enhanced Dopamine Transporter Activity in Middle-Aged Gdnf Heterozygous Mice

    PubMed Central

    Littrell, Ofelia M.; Pomerleau, Francois; Huettl, Peter; Surgener, Stewart; McGinty, Jacqueline F.; Middaugh, Lawrence D.; Granholm, Ann-Charlotte; Gerhardt, Greg A.; Boger, Heather A.

    2010-01-01

    Glial cell line-derived neurotrophic factor (GDNF) supports the viability of midbrain dopamine (DA) neurons that degenerate in Parkinson’s disease. Middle aged, 12-month-old, Gdnf heterozygous (Gdnf+/−) mice have diminished spontaneous locomotor activity and enhanced synaptosomal DA uptake compared to wildtype mice. In this study, dopamine transporter (DAT) function in middle-aged, 12-month-old Gdnf+/− mice was more thoroughly investigated using in vivo electrochemistry. Gdnf+/− mice injected with the DAT inhibitor, nomifensine, exhibited significantly more locomotor activity than wildtype mice. In vivo electrochemistry with carbon fiber microelectrodes demonstrated enhanced clearance of DA in the striatum of Gdnf+/− mice, suggesting greater surface expression of DAT than in wildtype littermates. Additionally, 12 month old Gdnf+/− mice expressed greater D2 receptor mRNA and protein in the striatum than wildtype mice. Neurochemical analyses of striatal tissue samples indicated significant reductions in DA and a faster DA metabolic rate in Gdnf+/− mice than in wildtype mice. Altogether, these data support an important role for GDNF in the regulation of uptake, synthesis, and metabolism of DA during aging. PMID:21144620

  9. Characterization of the dopamine transporter gene expression and binding sites in cultured human amniotic epithelial cells.

    PubMed

    Elwan, Mohamed A; Ishii, Takashi; Sakuragawa, Norio

    2003-05-15

    In this study we sought to investigate whether the dopamine transporter, DAT, and its binding sites are expressed in the human amniotic epithelial cells (HAEC) using reverse transcription-polymerase chain reaction (RT-PCR) and radioligand binding studies, respectively. The RT-PCR findings showed that HAEC expressed DAT mRNA with 100% homology to the human brain DAT. Saturation binding studies using [3H]mazindol showed a high affinity DAT binding site with K(D) and B(max) values of 12.32+/-1.67 nM and 82.7+/-9.74 fmol/mg protein, respectively. Competition experiments showed that selective DAT blockers are potent displacers of [3H]mazindol binding. The rank order of potency of the competing drugs is consistent with the pharmacology of the DAT. The present results provide compelling evidence that HAEC natively express the DAT mRNA and binding sites. More importantly, these results may suggest that HAEC is an appropriate human cell model for studying dopamine release and uptake processes and potential ligands at these sites.

  10. Age-related decline in motor behavior and striatal dopamine transporter in cynomolgus monkeys.

    PubMed

    Yue, Feng; Zeng, Sien; Wu, Di; Yi, Deqiao; Alex Zhang, Y; Chan, Piu

    2012-08-01

    Advanced human aging is associated with progressive declines of motor function and a risk factor for Parkinson's disease, which mainly involves central nigrostriatal dopaminergic system. The present study investigated age-related changes in motor behaviors and alterations of the number of nigrostriatal dopaminergic terminals in non-human primates. A total of 30 cynomolgus monkeys (Macaca fascicularis) of age 3.5-15.5 years were studied. Motor behaviors including upper limb movement time and the amount of overall home cage activity were quantitatively assessed using a modified movement assessment panel and a newly developed webcam-based monitoring system. The function of the dopaminergic system was semi-quantitatively measured by (99m)Tc-TRODAT-1 uptake rates, a dopamine transporter (DAT) specific radiopharmaceutical with SPECT imaging. The results showed a significant decline in motor behaviors associated with aging which were significantly correlated with age-related decreases of (99m)Tc-TRODAT-1 uptake. A further partial correlation analysis independent of age indicated that age contributed to the relationship between striatal DAT levels and motor behaviors. Our results indicate that normal aging-related dopamine physiology influences certain aspects of motor behaviors and suggest that aging-associated dysfunction in the nigrostriatal dopaminergic system may be an important factor contributing to the decline of motor behaviors in aging cynomolgus monkeys.

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

    PubMed Central

    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

  12. Influence of striatal dopamine transporter availability on the response to methylphenidate in adult patients with ADHD.

    PubMed

    Krause, Johanna; la Fougere, Christian; Krause, Klaus-Henning; Ackenheil, Manfred; Dresel, Stefan H

    2005-12-01

    In this study, we investigated whether availability of striatal dopamine transporter (DAT) may have an influence on the response of adult patients with attention deficit hyperactivity disorder (ADHD) on methylphenidate (MPH). In 18 non-smoking and non-medicated adult patients with ADHD, availability of DAT was measured with [(99m)Tc] TRODAT-1 SPECT. Then, the patients received methylphenidate (MPH), individually titrated up to 60 mg per day. Ten weeks later, clinical improvement was rated by Clinical Global Impressions scale. In all, 6 patients were classified as non-responders, and 12 responded to MPH. From the non-responders, 5 presented with a DAT availability below that of normal controls of the same age, whereas in the group of responders all patients had elevated DAT availability. There was a significant negative correlation between values for global clinical improvement and striatal DAT availability. In conclusion, ADHD patients with low DAT availability seem not to respond to therapy with MPH.

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

    SciTech Connect

    Inada, Toshiya; Sugita, Tetsuyoshi; Dobashi, Izumi

    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.

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

    ERIC Educational Resources Information Center

    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…

  15. Association of attention-deficit disorder and the dopamine transporter gene

    SciTech Connect

    Cook, E.H. Jr.; Stein, M.A.; Krasowski, M.D.; Cox, N.J.; Olkon, D.M.; Kieffer, J.E.; Leventhal, B.L.

    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.

  16. Phase I Report: Technetium Radiotracers for the Dopamine Transporter. [September 1998 - March 1999

    SciTech Connect

    Baldwin, R.N.

    1999-03-17

    This project (a) demonstrated specific dopamine transporter (DAT) uptake in vivo and metabolic stability of a radiolabelled cycloplentadieny rhenium compound in rats and baboons, (b) showed that cyclopentadieny tricarbonyl rhenium and technetium compounds conjugated tropanel could be made by metal transfer with ferrocenes; and (c) explored new methods of synthesizing these compounds under mild conditions.

  17. Insights from molecular dynamics: the binding site of cocaine in the dopamine transporter and permeation pathways of substrates in the leucine and dopamine transporters

    PubMed Central

    Merchant, Bonnie A.; Madura, Jeffry D.

    2012-01-01

    The dopamine transporter (DAT) facilitates the regulation of synaptic neurotransmitter levels. As a target for therapeutic and illicit psycho-stimulant drugs like antidepressants and cocaine, DAT has been studied intensively. Despite a wealth of mutational and physiological data regarding DAT, the structure remains unsolved and details of the transport mechanism, binding sites and conformational changes remain debated. A bacterial homologue of DAT, the leucine transporter (LeuTAa) has been used as a template and framework for modeling and understanding DAT. Free energy profiles obtained from Multi-Configuration Thermodynamic Integration allowed us to correctly identify the primary and secondary binding pockets of LeuTAa. A comparison of free energy profiles for dopamine and cocaine in DAT suggests that the binding site of cocaine is located in a secondary pocket, not the primary substrate site. Two recurring primary pathways for intracellular substrate release from the primary pocket are identified in both transporters using the Random Acceleration Molecular Dynamics method. One pathway appears to follow transmembranes (TMs) 1a and 6b while the other pathway follows along TMs 6b and 8. Interestingly, we observe that a single sodium ion is co-transported with leucine during both simulations types. PMID:23079638

  18. Lack of Association between a 3'UTR VNTR Polymorphism of Dopamine Transporter Gene (SLC6A3) and ADHD in a Brazilian Sample of Adult Patients

    ERIC Educational Resources Information Center

    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…

  19. Structural Modification of the Designer Stimulant α-Pyrrolidinovalerophenone (α-PVP) Influences Potency at Dopamine Transporters.

    PubMed

    Kolanos, R; Sakloth, F; Jain, A D; Partilla, J S; Baumann, M H; Glennon, R A

    2015-10-21

    α-Pyrrolidinovalerophenone (α-PVP, 7) is an illegal synthetic stimulant that is being sold on the clandestine market as "flakka" and "gravel". The potent pharmacological effects of α-PVP are presumably mediated by inhibition of dopamine uptake at the dopamine transporter (DAT). However, little is known about how structural modification of α-PVP influences activity at DAT. Eleven analogs of α-PVP were synthesized and examined for their ability to inhibit uptake of [(3)H]dopamine and [(3)H]serotonin in rat brain synaptosomes. None of the analogs significantly inhibited [(3)H]serotonin uptake when tested at 10 μM at the serotonin transporter (SERT). All of the analogs behaved as DAT reuptake inhibitors, but potencies varied over a >1500-fold range. Potency was primarily associated with the nature of the α-substituent, with the more bulky substituents imparting the highest potency. Expansion of the pyrrolidine ring to a piperidine reduced potency up to 10-fold, whereas conformational constraint in the form of an aminotetralone resulted in the least potent compound. Our study provides the first systematic and comparative structure-activity investigation on the ability of α-PVP analogs to act as inhibitors of DAT.

  20. Impact of disruption of secondary binding site S2 on dopamine transporter function.

    PubMed

    Zhen, Juan; Reith, Maarten E A

    2016-09-01

    The structures of the leucine transporter, drosophila dopamine transporter, and human serotonin transporter show a secondary binding site (designated S2 ) for drugs and substrate in the extracellular vestibule toward the membrane exterior in relation to the primary substrate recognition site (S1 ). The present experiments are aimed at disrupting S2 by mutating Asp476 and Ile159 to Ala. Both mutants displayed a profound decrease in [(3) H]DA uptake compared with wild-type associated with a reduced turnover rate kcat . This was not caused by a conformational bias as the mutants responded to Zn(2+) (10 μM) similarly as WT. The dopamine transporters with either the D476A or I159A mutation both displayed a higher Ki for dopamine for the inhibition of [3H](-)-2-β-carbomethoxy-3-β-(4-fluorophenyl)tropane binding than did the WT transporter, in accordance with an allosteric interaction between the S1 and S2 sites. The results provide evidence in favor of a general applicability of the two-site allosteric model of the Javitch/Weinstein group from LeuT to dopamine transporter and possibly other monoamine transporters. X-ray structures of transporters closely related to the dopamine (DA) transporter show a secondary binding site S2 in the extracellular vestibule proximal to the primary binding site S1 which is closely linked to one of the Na(+) binding sites. This work examines the relationship between S2 and S1 sites. We found that S2 site impairment severely reduced DA transport and allosterically reduced S1 site affinity for the cocaine analog [(3) H]CFT. Our results are the first to lend direct support for the application of the two-site allosteric model, advanced for bacterial LeuT, to the human DA transporter. The model states that, after binding of the first DA molecule (DA1 ) to the primary S1 site (along with Na(+) ), binding of a second DA (DA2 ) to the S2 site triggers, through an allosteric interaction, the release of DA1 and Na(+) into the cytoplasm.

  1. Assessment of the in vitro binding of JHW 007, a dopamine transport inhibitor that blocks the effects of cocaine

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Benztropine (BZT) and its analogues, like cocaine, bind to the dopamine transporter and block dopamine uptake. However, while BZT analogues bind the DAT with high affinity, they generally do not have cocaine-like behavioral effects. JHW 007 is a BZT analogue that displaces [3H]WIN 35,428 from the D...

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

    PubMed Central

    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

    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 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 2 h 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 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. Conclusions: The results: (a

  3. Regulation of dopamine transporter function by protein-protein interactions: new discoveries and methodological challenges.

    PubMed

    Eriksen, Jacob; Jørgensen, Trine Nygaard; Gether, Ulrik

    2010-04-01

    The dopamine transporter (DAT) plays a key role in regulating dopaminergic signalling in the brain by mediating rapid clearance of dopamine from the synaptic clefts. The psychostimulatory actions of cocaine and amphetamine are primarily the result of a direct interaction of these compounds with DAT leading to attenuated dopamine clearance and for amphetamine even increased dopamine release. In the last decade, intensive efforts have been directed towards understanding the molecular and cellular mechanisms governing the activity and availability of DAT in the plasma membrane of the pre-synaptic neurons. This has led to the identification of a plethora of different kinases, receptors and scaffolding proteins that interact with DAT and hereby either modulate the catalytic activity of the transporter or regulate its trafficking and degradation. Several new tools for studying DAT regulation in live cells have also recently become available such as fluorescently tagged cocaine analogues and fluorescent substrates. Here we review the current knowledge about the role of protein-protein interactions in DAT regulation as well as we describe the most recent methodological developments that have been established to overcome the challenges associated with the study of DAT in endogenous systems.

  4. Dopamine transporter; solubilization and characterization of ( sup 3 H) GBR-12935 binding in canine caudate

    SciTech Connect

    Sallee, F.R.

    1988-01-01

    The dopamine (DA) transporter protein, as indexed by ({sup 3}H)GBR-12935 binding, was solubilized from canine striatal membranes with the detergent digitonin. This solubilized protein retained the same pharmacological characteristics as membrane attached uptake sites. The binding of ({sup 3}H)GBR-12935 to solubilized preparations was specific, saturable and reversible with an equilibrium dissociation constant of approximately 3 nM and a maximum ligand binding (B{sub max}) of 3.4 pmol/mg protein. ({sup 3}H)GBR-12935 also bound to solubilized sites in a sodium-independent manner with a K{sub D} of approximately 6 nM and a B{sub max} of 1.2 {plus minus} 0.2 pmol/mg protein. Dopamine uptake inhibitors and substrates of DA uptake inhibited ({sup 3}H)GBR-12935 binding in a stereoselective and concentration dependent manner. For these compounds rank order of potency for inhibition of ({sup 3}H)GBR-12935 binding correlated with their potency for inhibition of dopamine uptake. K{sub D} values for DA uptake inhibitors in solubilized preparations correlated with those obtained on ({sup 3}H)GBR-12935 binding in the native state. The dopamine transporter appears to be a transmembrane glycoprotein by virtue of its absorption and specific elution from wheat germ agglutinin (WGA)-lectin column. Solubilization of the putative dopamine transporter with full retention of binding activity now allows for the purification and biochemical characterization of this important membrane protein.

  5. Nonclassical pharmacology of the dopamine transporter: atypical inhibitors, allosteric modulators, and partial substrates.

    PubMed

    Schmitt, Kyle C; Rothman, Richard B; Reith, Maarten E A

    2013-07-01

    The dopamine transporter (DAT) is a sodium-coupled symporter protein responsible for modulating the concentration of extraneuronal dopamine in the brain. The DAT is a principle target of various psychostimulant, nootropic, and antidepressant drugs, as well as certain drugs used recreationally, including the notoriously addictive stimulant cocaine. DAT ligands have traditionally been divided into two categories: cocaine-like inhibitors and amphetamine-like substrates. Whereas inhibitors block monoamine uptake by the DAT but are not translocated across the membrane, substrates are actively translocated and trigger DAT-mediated release of dopamine by reversal of the translocation cycle. Because both inhibitors and substrates increase extraneuronal dopamine levels, it is often assumed that all DAT ligands possess an addictive liability equivalent to that of cocaine. However, certain recently developed ligands, such as atypical benztropine-like DAT inhibitors with reduced or even a complete lack of cocaine-like rewarding effects, suggest that addictiveness is not a constant property of DAT-affecting compounds. These atypical ligands do not conform to the classic preconception that all DAT inhibitors (or substrates) are functionally and mechanistically alike. Instead, they suggest the possibility that the DAT exhibits some of the ligand-specific pleiotropic functional qualities inherent to G-protein-coupled receptors. That is, ligands with different chemical structures induce specific conformational changes in the transporter protein that can be differentially transduced by the cell, ultimately eliciting unique behavioral and psychological effects. The present overview discusses compounds with conformation-specific activity, useful not only as tools for studying the mechanics of dopamine transport, but also as leads for medication development in addictive disorders.

  6. Structure-activity studies of 3'-4'-dichloro-meperidine analogues at dopamine and serotonin transporters.

    PubMed

    Rhoden, Jill B; Bouvet, Maud; Izenwasser, Sari; Wade, Dean; Lomenzo, Stacey A; Trudell, Mark L

    2005-10-01

    The structure-activity relationships of 3',4'-dichloro-meperidine were investigated at dopamine (DAT) and serotonin transporters (SERT). Large ester substituents and lipophilic groups at the 4-position favored molecular recognition at the SERT. The benzyl ester of 3',4'-dichloro-meperidine exhibited high potency and high selectivity for the SERT (DAT/SERT=760). Chemical modification of the ester group and N-substitution generally led to compounds with decreased DAT affinity. Only small esters and alkyl groups were tolerated at the 4-position of the meperidine ring system by the DAT. Overall, the meperidine analogues were generally more selective for the SERT than for the DAT.

  7. Dopamine transporter is essential for the maintenance of spontaneous activity of auditory nerve neurones and their responsiveness to sound stimulation.

    PubMed

    Ruel, Jérôme; Wang, Jing; Demêmes, Danielle; Gobaille, Serge; Puel, Jean-Luc; Rebillard, Guy

    2006-04-01

    Dopamine, a neurotransmitter released by the lateral olivocochlear efferents, has been shown tonically to inhibit the spontaneous and sound-evoked activity of auditory nerve fibres. This permanent inhibition probably requires the presence of an efficient transporter to remove dopamine from the synaptic cleft. Here, we report that the dopamine transporter is located in the lateral efferent fibres both below the inner hair cells and in the inner spiral bundle. Perilymphatic perfusion of the dopamine transporter inhibitors nomifensine and N-[1-(2-benzo[b]thiophenyl)cyclohexyl]piperidine into the cochlea reduced the spontaneous neural noise and the sound-evoked compound action potential of the auditory nerve in a dose-dependent manner, leading to both neural responses being completely abolished. We observed no significant change in cochlear responses generated by sensory hair cells (cochlear microphonic, summating potential, distortion products otoacoustic emissions) or in the endocochlear potential reflecting the functional state of the stria vascularis. This is consistent with a selective action of dopamine transporter inhibitors on auditory nerve activity. Capillary electrophoresis with laser-induced fluorescence (EC-LIF) measurements showed that nomifensine-induced inhibition of auditory nerve responses was due to increased extracellular dopamine levels in the cochlea. Altogether, these results show that the dopamine transporter is essential for maintaining the spontaneous activity of auditory nerve neurones and their responsiveness to sound stimulation.

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

    PubMed Central

    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

  9. Graft-induced dyskinesias in Parkinson's disease: High striatal serotonin/dopamine transporter ratio.

    PubMed

    Politis, Marios; Oertel, Wolfgang H; Wu, Kit; Quinn, Niall P; Pogarell, Oliver; Brooks, David J; Bjorklund, Anders; Lindvall, Olle; Piccini, Paola

    2011-09-01

    Graft-induced dyskinesias are a serious complication after neural transplantation in Parkinson's disease. One patient with Parkinson's disease, treated with fetal grafts 14 years ago and deep brain stimulation 6 years ago, showed marked improvement of motor symptoms but continued to suffer from OFF-medication graft-induced dyskinesias. The patient received a series of clinical and imaging assessments. Positron emission tomography and single-photon emission computed tomography 14 years posttransplantation revealed an elevated serotonin/dopamine transporter ratio in the grafted striatum compatible with serotonergic hyperinnervation. Inhibition of serotonin neuron activity by systemic administration of a 5-HT(1A) agonist suppressed graft-induced dyskinesias. Our data provide further evidence that serotonergic neurons mediate graft-induced dyskinesias in Parkinson's disease. Achieving a normal striatal serotonin/dopamine transporter ratio following transplantation of fetal tissue or stem cells should be necessary to avoid the development of graft-induced dyskinesias.

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

    PubMed Central

    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

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

    PubMed

    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.

  12. Rab 11 regulates constitutive dopamine transporter trafficking and function in N2A neuroblastoma cells.

    PubMed

    Furman, Cheryse A; Lo, Charles B; Stokes, Stephanie; Esteban, Jose A; Gnegy, Margaret E

    2009-09-29

    The dopamine transporter (DAT) is a crucial regulator of dopaminergic neurotransmission which undergoes constitutive and substrate-mediated trafficking to and from the membrane. Although, considerable research has been done to elucidate the regulation of substrate-stimulated DAT trafficking, less is known about which trafficking proteins are involved in constitutive DAT trafficking. Rab proteins are GTPases known to regulate the trafficking of proteins to and from specific endocytic compartments. Rabs 8 and 11, in particular, are involved in trafficking proteins from intracellular compartments to the plasma membrane. In this study, we sought to determine whether Rabs 8 and 11 would modulate DAT activity and trafficking in N2A neuroblastoma cells. We used Rab mutations known to confer constitutively active or dominant negative activity of these proteins to investigate the role of Rab activity in constitutive DAT trafficking and function. We found that constitutively active Rab 11 upregulates DAT function and surface expression while neither the constitutively active nor the dominant negative mutant of Rab 8 had any effect on DA uptake. Furthermore, immunofluorescence experiments revealed that dominant negative Rab 11 overexpression results in decreased surface DAT indicating a necessary function of Rab 11 in DAT trafficking to the plasma membrane. These data show for the first time a functional role of Rab proteins in the constitutive recycling of DAT to the plasma membrane.

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

    PubMed Central

    Sunwoo, Mun Kyung; Oh, Jungsu S.; Kim, Jae Seung; Sohn, Young H.; Lee, Phil Hyu

    2016-01-01

    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. PMID:27294367

  14. Dopamine transporter availability in motor subtypes of de novo drug-naïve Parkinson's disease.

    PubMed

    Moccia, Marcello; Pappatà, Sabina; Picillo, Marina; Erro, Roberto; Coda, Anna Rita Daniela; Longo, Katia; Vitale, Carmine; Amboni, Marianna; Brunetti, Arturo; Capo, Giuseppe; Salvatore, Marco; Barone, Paolo; Pellecchia, Maria Teresa

    2014-11-01

    Tremor dominant (TD) and akinetic-rigid type (ART) are two motor subtypes of Parkinson's disease associated with different disease progression and neurochemical/neuropathological features. The role of presynaptic nigrostriatal dopaminergic damage is still controversial, poorly explored, and only assessed in medicated patients. In this study, we investigated with FP-CIT SPECT the striatal dopamine transporter (DAT) availability in drug-naïve PD patients with ART and TD phenotypes. Fifty-one de novo, drug-naïve patients with PD underwent FP-CIT SPECT studies. Patients were evaluated with Unified Parkinson's Disease Rating Scale (UPDRS) part III and Hoehn and Yahr scale (H&Y) and divided into ART (24/51) and TD (27/51) according to UPDRS part III. ART and TD patients were not different with regard to age, gender, and disease duration. However, compared to TD, ART patients presented higher UPDRS part III (p = 0.01) and H&Y (p = 0.02) and lower DAT availability in affected and unaffected putamen (p = 0.008 and p = 0.007, respectively), whereas no differences were found in caudate. Moreover, in the whole group of patients, rigidity and bradykinesia, but not tremor scores of UPDRS part III were significantly related to FP-CIT binding in the putamen. These results suggest that in newly diagnosed drug-naïve PD patients DAT availability might be different between ART and TD in relation to different disease severity.

  15. Short-term manganese inhalation decreases brain dopamine transporter levels without disrupting motor skills in rats.

    PubMed

    Saputra, Devina; Chang, JuOae; Lee, Byeong-Jae; Yoon, Jin-Ha; Kim, Jonghan; Lee, Kyuhong

    2016-01-01

    Manganese (Mn) is used in industrial metal alloys and can be released into the atmosphere during methylcyclopentadienyl manganese tricarbonyl combustion. Increased Mn deposition in the brain after long-term exposure to the metal by inhalation is associated with altered dopamine metabolism and neurobehavioral problems, including impaired motor skills. However, neurotoxic effects of short-term exposure to inhaled Mn are not completely characterized. The purpose of this study is to define the neurobehavioral and neurochemical effects of short-term inhalation exposure to Mn at a high concentration using rats. Male Sprague-Dawley rats were exposed to MnCl2 aerosol in a nose-only inhalation chamber for 3 weeks (1.2 µm, 39 mg/m(3)). Motor coordination was tested on the day after the last exposure using a rotarod device at a fixed speed of 10 rpm for 2 min. Also, dopamine transporter and dopamine receptor protein expression levels in the striatum region of the brain were determined by Western blot analysis. At a rotarod speed of 10 rpm, there were no significant differences in the time on the bar before the first fall or the number of falls during the two-minute test observed in the exposed rats, as compared with controls. The Mn-exposed group had significantly higher Mn levels in the lung, blood, olfactory bulb, prefrontal cortex, striatum, and cerebellum compared with the control group. A Mn concentration gradient was observed from the olfactory bulb to the striatum, supporting the idea that Mn is transported via the olfactory pathway. Our results demonstrated that inhalation exposure to 39 mg/m(3) Mn for 3 weeks induced mild lung injury and modulation of dopamine transporter expression in the brain, without altering motor activity.

  16. Serotonin and Dopamine Gene Variation and Theory of Mind Decoding Accuracy in Major Depression: A Preliminary Investigation

    PubMed Central

    Zahavi, Arielle Y.; Sabbagh, Mark A.; Washburn, Dustin; Mazurka, Raegan; Bagby, R. Michael; Strauss, John; Kennedy, James L.; Ravindran, Arun; Harkness, Kate L.

    2016-01-01

    Theory of mind–the ability to decode and reason about others’ mental states–is a universal human skill and forms the basis of social cognition. Theory of mind accuracy is impaired in clinical conditions evidencing social impairment, including major depressive disorder. The current study is a preliminary investigation of the association of polymorphisms of the serotonin transporter (SLC6A4), dopamine transporter (DAT1), dopamine receptor D4 (DRD4), and catechol-O-methyl transferase (COMT) genes with theory of mind decoding in a sample of adults with major depression. Ninety-six young adults (38 depressed, 58 non-depressed) completed the ‘Reading the Mind in the Eyes task’ and a non-mentalistic control task. Genetic associations were only found for the depressed group. Specifically, superior accuracy in decoding mental states of a positive valence was seen in those homozygous for the long allele of the serotonin transporter gene, 9-allele carriers of DAT1, and long-allele carriers of DRD4. In contrast, superior accuracy in decoding mental states of a negative valence was seen in short-allele carriers of the serotonin transporter gene and 10/10 homozygotes of DAT1. Results are discussed in terms of their implications for integrating social cognitive and neurobiological models of etiology in major depression. PMID:26974654

  17. Enhanced Dopamine Release by Dopamine Transport Inhibitors Described by a Restricted Diffusion Model and Fast-Scan Cyclic Voltammetry.

    PubMed

    Hoffman, Alexander F; Spivak, Charles E; Lupica, Carl R

    2016-06-15

    Fast-scan cyclic voltammetry (FSCV) using carbon fiber electrodes is widely used to rapidly monitor changes in dopamine (DA) levels in vitro and in vivo. Current analytical approaches utilize parameters such as peak oxidation current amplitude and decay times to estimate release and uptake processes, respectively. However, peak amplitude changes are often observed with uptake inhibitors, thereby confounding the interpretation of these parameters. To overcome this limitation, we demonstrate that a simple five-parameter, two-compartment model mathematically describes DA signals as a balance of release (r/ke) and uptake (ku), summed with adsorption (kads and kdes) of DA to the carbon electrode surface. Using nonlinear regression, we demonstrate that our model precisely describes measured DA signals obtained in brain slice recordings. The parameters extracted from these curves were then validated using pharmacological manipulations that selectively alter vesicular release or DA transporter (DAT)-mediated uptake. Manipulation of DA release through altering the Ca(2+)/Mg(2+) ratio or adding tetrodotoxin reduced the release parameter with no effect on the uptake parameter. DAT inhibitors methylenedioxypyrovalerone, cocaine, and nomifensine significantly reduced uptake and increased vesicular DA release. In contrast, a low concentration of amphetamine reduced uptake but had no effect on DA release. Finally, the kappa opioid receptor agonist U50,488 significantly reduced vesicular DA release but had no effect on uptake. Together, these data demonstrate a novel analytical approach to distinguish the effects of manipulations on DA release or uptake that can be used to interpret FSCV data.

  18. Dopamine transporter, gender, and number of sexual partners among young adults.

    PubMed

    Guo, Guang; Tong, Yuying; Xie, Cui-Wei; Lange, Leslie A

    2007-03-01

    The dopamine transporter gene (DAT1) codes for a dopamine transporter protein, which limits the level and duration of dopamine receptor activation. The DAT1 gene is a strong candidate gene for reward-seeking behavior. This article reports compelling evidence for the association between the 40 bp variable number of tandem repeats in the DAT1 gene and the self-reported number of sexual partners among young adults in the United States using the sibling subsample of more than 2500 individuals who participated in the National Longitudinal Study of Adolescent Health. We performed tests of genotype-gender interaction as well as analyses stratified by gender. Among the males, possessing one or two alleles of the 10 repeat is associated with an 80-100% increase (P<0.0001, 2df) in the number of sexual partners as compared with the homozygotes for the 9 repeat. The association holds in race/ethnicity-stratified analyses, in Allison's procedure that tests population stratification, and in within-family fixed-effects models. Covariate adjustment for a standard set of socioeconomic factors including religiosity, family structure, parental education, marital and cohabitation history, and neighborhood poverty did not attenuate these associations. Discussion is provided why this finding is absent among females.

  19. Identification of an intronic cis-acting element in the human dopamine transporter gene

    PubMed Central

    Zhao, Ying; Zhou, Yanhong; Lin, Zhicheng

    2017-01-01

    The human dopamine transporter gene (hDAT) encodes the dopamine transporter in dopamine (DA) neurons to regulate DA transmission. hDAT expression varies significantly from neuron to neuron, and from individual to individual so that dysregulation of hDAT is related to many neuropsychiatric disorders. It is critical to identify hDAT-specific cis-acting elements that regulate the hDAT expression. Previous studies showed that hDAT Intron 1 displayed inhibitory activity for reporter gene expression. Here we report that the hDAT Intron 1 contains a 121-bp fragment that down-regulated both SV40 and hDAT promoter activities by 80% in vitro. Subfragments of 121-bp still down-regulated the SV40 promoter but not the hDAT promoter, as supported by nuclear protein-binding activities. Collectively, 121-bp is a silencer in vitro that might coordinate with transcriptional activities both inside and outside 121-bp in regulation of hDAT. PMID:22160470

  20. Dissociable effects of the prodrug phendimetrazine and its metabolite phenmetrazine at dopamine transporters

    PubMed Central

    Solis, Ernesto; Suyama, Julie A.; Lazenka, Matthew F.; DeFelice, Louis J.; Negus, S. Stevens; Blough, Bruce E.; Banks, Matthew L.

    2016-01-01

    Phendimetrazine (PDM) is a clinically available anorectic and a candidate pharmacotherapy for cocaine addiction. PDM has been hypothesized to function as a prodrug that requires metabolism to the amphetamine-like monoamine transporter substrate phenmetrazine (PM) to produce its pharmacological effects; however, whether PDM functions as an inactive prodrug or has pharmacological activity on its own remains unclear. The study aim was to determine PDM pharmacological mechanisms using electrophysiological, neurochemical, and behavioral procedures. PDM blocked the endogenous basal hDAT (human dopamine transporter) current in voltage-clamped (−60 mV) oocytes consistent with a DAT inhibitor profile, whereas its metabolite PM induced an inward hDAT current consistent with a DAT substrate profile. PDM also attenuated the PM-induced inward current during co-application, providing further evidence that PDM functions as a DAT inhibitor. PDM increased nucleus accumbens dopamine levels and facilitated electrical brain stimulation reinforcement within 10 min in rats, providing in vivo evidence supporting PDM pharmacological activity. These results demonstrate that PDM functions as a DAT inhibitor that may also interact with the pharmacological effects of its metabolite PM. Overall, these results suggest a novel mechanism for PDM therapeutic effects via initial PDM DAT inhibition followed by PM DAT substrate-induced dopamine release. PMID:27514281

  1. Dopamine transporter comparative molecular modeling and binding site prediction using the LeuT(Aa) leucine transporter as a template.

    PubMed

    Indarte, Martín; Madura, Jeffry D; Surratt, Christopher K

    2008-02-15

    Pharmacological and behavioral studies indicate that binding of cocaine and the amphetamines by the dopamine transporter (DAT) protein is principally responsible for initiating the euphoria and addiction associated with these drugs. The lack of an X-ray crystal structure for the DAT or any other member of the neurotransmitter:sodium symporter (NSS) family has hindered understanding of psychostimulant recognition at the atomic level; structural information has been obtained largely from mutagenesis and biophysical studies. The recent publication of a crystal structure for the bacterial leucine transporter LeuT(Aa), a distantly related NSS family homolog, provides for the first time a template for three-dimensional comparative modeling of NSS proteins. A novel computational modeling approach using the capabilities of the Molecular Operating Environment program MOE 2005.06 in conjunction with other comparative modeling servers generated the LeuT(Aa)-directed DAT model. Probable dopamine and amphetamine binding sites were identified within the DAT model using multiple docking approaches. Binding sites for the substrate ligands (dopamine and amphetamine) overlapped substantially with the analogous region of the LeuT(Aa) crystal structure for the substrate leucine. The docking predictions implicated DAT side chains known to be critical for high affinity ligand binding and suggest novel mutagenesis targets in elucidating discrete substrate and inhibitor binding sites. The DAT model may guide DAT ligand QSAR studies, and rational design of novel DAT-binding therapeutics.

  2. Uptake inhibitors but not substrates induce protease resistance in extracellular loop two of the dopamine transporter.

    PubMed

    Gaffaney, Jon D; Vaughan, Roxanne A

    2004-03-01

    Changes in protease sensitivity of extracellular loop two (EL2) of the dopamine transporter (DAT) during inhibitor and substrate binding were examined using trypsin proteolysis and epitope-specific immunoblotting. In control rat striatal membranes, proteolysis of DAT in a restricted region of EL2 was produced by 0.001 to 10 microg/ml trypsin. However, in the presence of the dopamine uptake blockers [2-(diphenylmethoxyl) ethyl]-4-(3phenylpropyl) piperazine (GBR 12909), mazindol, 2beta-carbomethoxy-3beta-(4-flourophenyl)tropane (beta-CFT), nomifensine, benztropine, or (-)-cocaine, 100- to 1000-fold higher concentrations of trypsin were required to produce comparable levels of proteolysis. Protease resistance induced by ligands was correlated with their affinity for DAT binding, was not observed with Zn2+, (+)-cocaine, or inhibitors of norepinephrine or serotonin transporters, and was not caused by altered catalytic activity of trypsin. Together, these results support the hypothesis that the interaction of uptake inhibitors with DAT induces a protease-resistant conformation in EL2. In contrast, binding of substrates did not induce protease resistance in EL2, suggesting that substrates and inhibitors interact with DAT differently during binding. To assess the effects of EL2 proteolysis on DAT function, the binding and transport properties of trypsin-digested DAT were assayed with [3H]CFT and [3H]dopamine. Digestion decreased the Bmax for binding and the Vmax for uptake in amounts that were proportional to the extent of proteolysis, indicating that the structural integrity of EL2 is required for maintenance of both DAT binding and transport functions. Together this data provides novel information about inhibitor and substrate interactions at EL2, possibly relating the protease resistant DAT conformation to a mechanism of transport inhibition.

  3. Methylphenidate amplifies the potency and reinforcing effects of amphetamines by increasing dopamine transporter expression.

    PubMed

    Calipari, Erin S; Ferris, Mark J; Salahpour, Ali; Caron, Marc G; Jones, Sara R

    2013-01-01

    Methylphenidate (MPH) is commonly diverted for recreational use, but the neurobiological consequences of exposure to MPH at high, abused doses are not well defined. Here we show that MPH self-administration in rats increases dopamine transporter (DAT) levels and enhances the potency of MPH and amphetamine on dopamine responses and drug-seeking behaviours, without altering cocaine effects. Genetic overexpression of the DAT in mice mimics these effects, confirming that MPH self-administration-induced increases in DAT levels are sufficient to induce the changes. Further, this work outlines a basic mechanism by which increases in DAT levels, regardless of how they occur, are capable of increasing the rewarding and reinforcing effects of select psychostimulant drugs, and suggests that individuals with elevated DAT levels, such as ADHD sufferers, may be more susceptible to the addictive effects of amphetamine-like drugs.

  4. Urinary Dopamine as a Potential Index of the Transport Activity of Multidrug and Toxin Extrusion in the Kidney.

    PubMed

    Kajiwara, Moto; Ban, Tsuyoshi; Matsubara, Kazuo; Nakanishi, Yoichi; Masuda, Satohiro

    2016-07-30

    Dopamine is a cationic natriuretic catecholamine synthesized in proximal tubular cells (PTCs) of the kidney before secretion into the lumen, a key site of its action. However, the molecular mechanisms underlying dopamine secretion into the lumen remain unclear. Multidrug and toxin extrusion (MATE) is a H⁺/organic cation antiporter that is highly expressed in the brush border membrane of PTCs and mediates the efflux of organic cations, including metformin and cisplatin, from the epithelial cells into the urine. Therefore, we hypothesized that MATE mediates dopamine secretion, a cationic catecholamine, into the tubule lumen, thereby regulating natriuresis. Here, we show that [³H]dopamine uptake in human (h) MATE1-, hMATE-2K- and mouse (m) MATE-expressing cells exhibited saturable kinetics. Fluid retention and decreased urinary excretion of dopamine and Na⁺ were observed in Mate1-knockout mice compared to that in wild-type mice. Imatinib, a MATE inhibitor, inhibited [³H]dopamine uptake by hMATE1-, hMATE2-K- and mMATE1-expressing cells in a concentration-dependent manner. At clinically-relevant concentrations, imatinib inhibited [³H]dopamine uptake by hMATE1- and hMATE2-K-expressing cells. The urinary excretion of dopamine and Na⁺ decreased and fluid retention occurred in imatinib-treated mice. In conclusion, MATE transporters secrete renally-synthesized dopamine, and therefore, urinary dopamine has the potential to be an index of the MATE transporter activity.

  5. Dopamine transporters are markedly reduced in Lesch-Nyhan disease in vivo.

    PubMed Central

    Wong, D F; Harris, J C; Naidu, S; Yokoi, F; Marenco, S; Dannals, R F; Ravert, H T; Yaster, M; Evans, A; Rousset, O; Bryan, R N; Gjedde, A; Kuhar, M J; Breese, G R

    1996-01-01

    Dopamine (DA) deficiency has been implicated in Lesch-Nyhan disease (LND), a genetic disorder that is characterized by hyperuricemia, choreoathetosis, dystonia, and compulsive self-injury. To establish that DA deficiency is present in LND, the ligand WIN-35,428, which binds to DA transporters, was used to estimate the density of DA-containing neurons in the caudate and putamen of six patients with classic LND. Comparisons were made with 10 control subjects and 3 patients with Rett syndrome. Three methods were used to quantify the binding of the DA transporter so that its density could be estimated by a single dynamic positron emission tomography study. These approaches included the caudate- or putamen-to-cerebellum ratio of ligand at 80-90 min postinjection, kinetic analysis of the binding potential [Bmax/(Kd x Vd)] using the assumption of equal partition coefficients in the striatum and the cerebellum, and graphical analysis of the binding potential. Depending on the method of analysis, a 50-63% reduction of the binding to DA transporters in the caudate, and a 64-75% reduction in the putamen of the LND patients was observed compared to the normal control group. When LND patients were compared to Rett syndrome patients, similar reductions were found in the caudate (53-61%) and putamen (67-72%) in LND patients. Transporter binding in Rett syndrome patients was not significantly different from the normal controls. Finally, volumetric magnetic resonance imaging studies detected a 30% reduction in the caudate volume of LND patients. To ensure that a reduction in the caudate volume would not confound the results, a rigorous partial volume correction of the caudate time activity curve was performed. This correction resulted in an even greater decrease in the caudate-cerebellar ratio in LND patients when contrasted to controls. To our knowledge, these findings provide the first in vivo documentation of a dopaminergic reduction in LND and illustrate the role of positron

  6. Effects of a short-course MDMA binge on dopamine transporter binding and on levels of dopamine and its metabolites in adult male rats.

    PubMed

    Biezonski, Dominik K; Piper, Brian J; Shinday, Nina M; Kim, Peter J; Ali, Syed F; Meyer, Jerrold S

    2013-02-15

    Although the recreational drug 3,4-methylenedioxymethamphetamine (MDMA) is often described as a selective serotonergic neurotoxin, some research has challenged this view. The objective of this study was to determine the influence of MDMA on subsequent levels of two different markers of dopaminergic function, the dopamine transporter (DAT) as well as dopamine and its major metabolites. In experiment I, adult male Sprague-Dawley rats were administered either a low or moderate dose MDMA binge (2.5 or 5.0mg/kg×4 with an inter-dose interval of 1h) or saline, and were killed 1 week later. The moderate dose dramatically reduced [(3)H]WIN 35,428 binding to striatal DAT by 73.7% (P≤0.001). In experiment II, animals were binged with a higher dose of MDMA (10mg/kg×4) to determine the drug's effects on concentrations of serotonin (5-HT), dopamine, and their respective major metabolites 5-hydroxyindoleacetic acid (5-HIAA), dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in the striatum and frontal cortex 1 week later. As expected, MDMA significantly reduced 5-HT and 5-HIAA (≥50%) in these structures, while only a marginal decrease in dopamine was noted in the striatum. In contrast, levels of DOPAC (34.3%, P<0.01) and HVA (33.5%, P<0.001) were reduced by MDMA treatment, suggesting a decrease in dopamine turnover. Overall, these findings indicate that while serotonergic markers are particularly vulnerable to MDMA-induced depletion, significant dopaminergic deficits may also occur under some conditions. Importantly, DAT expression may be more vulnerable to perturbation by MDMA than dopamine itself.

  7. Effects of a short-course MDMA binge on dopamine transporter binding and on levels of dopamine and its metabolites in adult male rats

    PubMed Central

    Biezonski, Dominik K.; Piper, Brian J.; Shinday, Nina M.; Kim, Peter J.; Ali, Syed F.; Meyer, Jerrold S.

    2013-01-01

    Although the recreational drug 3,4-methylenedioxymethamphetamine (MDMA) is often described as a selective serotonergic neurotoxin, some research has challenged this view. The objective of this study was to determine the influence of MDMA on subsequent levels of two different markers of dopaminergic function, the dopamine transporter (DAT) as well as dopamine and its major metabolites. In experiment I, adult male Sprague–Dawley rats were administered either a low or moderate dose MDMA binge (2.5 or 5.0 mg/kg × 4 with an inter-dose interval of 1 h) or saline, and were killed 1 week later. The moderate dose dramatically reduced [3H]WIN 35,428 binding to striatal DAT by 73.7% (P ≤ 0.001). In experiment II, animals were binged with a higher dose of MDMA (10 mg/kg × 4) to determine the drug’s effects on concentrations of serotonin (5-HT), dopamine, and their respective major metabolites 5-hydroxyindoleacetic acid (5-HIAA), dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) in the striatum and frontal cortex 1 week later. As expected, MDMA significantly reduced 5-HT and 5-HIAA (≥ 50%) in these structures, while only a marginal decrease in dopamine was noted in the striatum. In contrast, levels of DOPAC (34.3%, P < 0.01) and HVA (33.5%, P < 0.001) were reduced by MDMA treatment, suggesting a decrease in dopamine turnover. Overall, these findings indicate that while serotonergic markers are particularly vulnerable to MDMA-induced depletion, significant dopaminergic deficits may also occur under some conditions. Importantly, DAT expression may be more vulnerable to perturbation by MDMA than dopamine itself. PMID:23276666

  8. Living without DAT: Loss and compensation of the dopamine transporter gene in sauropsids (birds and reptiles)

    PubMed Central

    Lovell, P. V.; Kasimi, B.; Carleton, J.; Velho, T. A.; Mello, C. V.

    2015-01-01

    The dopamine transporter (DAT) is a major regulator of synaptic dopamine (DA) availability. It plays key roles in motor control and motor learning, memory formation, and reward-seeking behavior, is a major target of cocaine and methamphetamines, and has been assumed to be conserved among vertebrates. We have found, however, that birds, crocodiles, and lizards lack the DAT gene. We also found that the unprecedented loss of this important gene is compensated for by the expression of the noradrenaline transporter (NAT) gene, and not the serotonin transporter genes, in dopaminergic cells, which explains the peculiar pharmacology of the DA reuptake activity previously noted in bird striatum. This unexpected pattern contrasts with that of ancestral vertebrates (e.g. fish) and mammals, where the NAT gene is selectively expressed in noradrenergic cells. DA circuits in birds/reptiles and mammals thus operate with an analogous reuptake mechanism exerted by different genes, bringing new insights into gene expression regulation in dopaminergic cells and the evolution of a key molecular player in reward and addiction pathways. PMID:26364979

  9. Individual Variation in Incentive Salience Attribution and Accumbens Dopamine Transporter Expression and Function

    PubMed Central

    Singer, Bryan F.; Guptaroy, Bipasha; Austin, Curtis J.; Wohl, Isabella; Lovic, Vedran; Seiler, Jillian L; Vaughan, Roxanne A.; Gnegy, Margaret E.; Robinson, Terry E.; Aragona, Brandon J.

    2015-01-01

    Cues (conditioned stimuli; CSs) associated with rewards can come to motivate behavior, but there is considerable individual variation in their ability to do so. For example, a lever-CS that predicts food reward becomes attractive, wanted, and elicits reward-seeking behavior to a greater extent in some rats (“sign-trackers”; STs), than others (“goal-trackers”; GTs). Variation in dopamine (DA) neurotransmission in the nucleus accumbens (NAc) core is thought to contribute to such individual variation. Given that the DA transporter (DAT) exerts powerful regulation over DA signaling, we characterized the expression and function of the DAT in the accumbens of STs and GTs. STs showed greater DAT surface expression in ventral striatal synaptosomes than GTs, and ex vivo fast-scan cyclic voltammetry recordings of electrically-evoked DA release confirmed enhanced DAT function in STs, as indicated by faster DA uptake, specifically in the NAc core. Consistent with this, systemic amphetamine (AMPH) produced greater inhibition of DA uptake in STs than in GTs. Furthermore, injection of AMPH directly into the NAc core enhanced lever-directed approach in STs, presumably by amplifying the incentive value of the CS, but had no effect on goal tracking behavior. On the other hand, there were no differences between STs and GTs in electrically-evoked DA release in slices, or in total ventral striatal DA content. We conclude that greater DAT surface expression may facilitate the attribution of incentive salience to discrete reward cues. Investigating this variability in animal sub-populations may help explain why some people abuse drugs, while others do not. PMID:26613374

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

    PubMed

    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.

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

    PubMed Central

    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

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

    PubMed Central

    German, Christopher L.; Baladi, Michelle G.; McFadden, Lisa M.; Hanson, Glen R.

    2015-01-01

    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. PMID:26408528

  13. Molecular dynamics of leucine and dopamine transporter proteins in a model cell membrane lipid bilayer.

    PubMed

    Gedeon, Patrick C; Indarte, Martín; Surratt, Christopher K; Madura, Jeffry D

    2010-03-01

    The dopamine transporter (DAT) operates via facilitated diffusion, harnessing an inward Na(+) gradient to drive dopamine from the extracellular synaptic cleft to the neuron interior. The DAT is relevant to central nervous system disorders such as Parkinson disease and attention-deficit hyperactivity disorder and is the primary site of action for the abused psychostimulants cocaine and amphetamines. Crystallization of a DAT homolog, the bacterial leucine transporter LeuT, provided the first reliable 3-D DAT template. Here, the LeuT crystal structure and the DAT molecular model have been combined with their respective substrates, leucine and dopamine, in lipid bilayer molecular dynamics simulations toward tracking substrate movement along the protein's substrate/ion permeation pathway. Specifically, movement of residue pairs that comprise the "external gate" was followed as a function of substrate presence. The transmembrane (TM) 1 arginine-TM 10 aspartate strut formed less readily in DAT compared with LeuT, with or without substrate present. For LeuT but not DAT, the addition of substrate enhanced the chances of forming the TM 1-10 bridge. Also, movement of the fourth extracellular loop EL-4 in the presence of substrate was more pronounced for DAT, the EL-4 unwinding to a degree. The overall similarity between the LeuT and DAT molecular dynamics simulations indicated that LeuT was a legitimate model to guide DAT structure-function predictions. There were, nevertheless, differences significant enough to allow for DAT-unique insights, which may include how cocaine, methylphenidate (Ritalin, NIDA Drug Supply, Rockville, MD), and other DAT blockers are not recognized as substrates even though they can access the primary substrate binding pocket. Proteins 2010. (c) 2009 Wiley-Liss, Inc.

  14. Salvinorin A Regulates Dopamine Transporter Function Via A Kappa Opioid Receptor and ERK1/2-Dependent Mechanism

    PubMed Central

    Kivell, Bronwyn; Uzelac, Zeljko; Sundaramurthy, Santhanalakshmi; Rajamanickam, Jeyaganesh; Ewald, Amy; Chefer, Vladimir; Jaligam, Vanaja; Bolan, Elizabeth; Simonson, Bridget; Annamalai, Balasubramaniam; Mannangatti, Padmanabhan; Prisinzano, Thomas; Gomes, Ivone; Devi, Lakshmi A.; Jayanthi, Lankupalle D.; Sitte, Harald H.; Ramamoorthy, Sammanda; Shippenberg, Toni S.

    2014-01-01

    Salvinorin A (SalA), a selective κ-opioid receptor (KOR) agonist, produces dysphoria and pro-depressant like effects. These actions have been attributed to inhibition of striatal dopamine release. The dopamine transporter (DAT) regulates dopamine transmission via uptake of released neurotransmitter. KORs are apposed to DAT in dopamine nerve terminals suggesting an additional target by which SalA modulates dopamine transmission. SalA produced a concentration-dependent, nor-binaltorphimine (BNI)- and pertussis toxin-sensitive increase of ASP+ accumulation in EM4 cells coexpressing myc-KOR and YFP-DAT, using live cell imaging and the fluorescent monoamine transporter substrate, trans 4-(4-(dimethylamino)-styryl)-N-methylpyridinium) (ASP+). Other KOR agonists also increased DAT activity that was abolished by BNI pretreatment. While SalA increased DAT activity, SalA treatment decreased serotonin transporter (SERT) activity and had no effect on norepinephrine transporter (NET) activity. In striatum, SalA increased the Vmax for DAT mediated DA transport and DAT surface expression. SalA up-regulation of DAT function is mediated by KOR activation and the KOR-linked extracellular signal regulated kinase-½ (ERK1/2) pathway. Co-immunoprecipitation and BRET studies revealed that DAT and KOR exist in a complex. In live cells, DAT and KOR exhibited robust FRET signals under basal conditions. SalA exposure caused a rapid and significant increase of the FRET signal. This suggests that the formation of KOR and DAT complexes is promoted in response to KOR activation. Together, these data suggest that enhanced DA transport and decreased DA release resulting in decreased dopamine signaling may contribute to the dysphoric and pro-depressant like effects of SalA and other KOR agonists. PMID:25107591

  15. Salvinorin A regulates dopamine transporter function via a kappa opioid receptor and ERK1/2-dependent mechanism.

    PubMed

    Kivell, Bronwyn; Uzelac, Zeljko; Sundaramurthy, Santhanalakshmi; Rajamanickam, Jeyaganesh; Ewald, Amy; Chefer, Vladimir; Jaligam, Vanaja; Bolan, Elizabeth; Simonson, Bridget; Annamalai, Balasubramaniam; Mannangatti, Padmanabhan; Prisinzano, Thomas E; Gomes, Ivone; Devi, Lakshmi A; Jayanthi, Lankupalle D; Sitte, Harald H; Ramamoorthy, Sammanda; Shippenberg, Toni S

    2014-11-01

    Salvinorin A (SalA), a selective κ-opioid receptor (KOR) agonist, produces dysphoria and pro-depressant like effects. These actions have been attributed to inhibition of striatal dopamine release. The dopamine transporter (DAT) regulates dopamine transmission via uptake of released neurotransmitter. KORs are apposed to DAT in dopamine nerve terminals suggesting an additional target by which SalA modulates dopamine transmission. SalA produced a concentration-dependent, nor-binaltorphimine (BNI)- and pertussis toxin-sensitive increase of ASP(+) accumulation in EM4 cells coexpressing myc-KOR and YFP-DAT, using live cell imaging and the fluorescent monoamine transporter substrate, trans 4-(4-(dimethylamino)-styryl)-N-methylpyridinium) (ASP(+)). Other KOR agonists also increased DAT activity that was abolished by BNI pretreatment. While SalA increased DAT activity, SalA treatment decreased serotonin transporter (SERT) activity and had no effect on norepinephrine transporter (NET) activity. In striatum, SalA increased the Vmax for DAT mediated DA transport and DAT surface expression. SalA up-regulation of DAT function is mediated by KOR activation and the KOR-linked extracellular signal regulated kinase-½ (ERK1/2) pathway. Co-immunoprecipitation and BRET studies revealed that DAT and KOR exist in a complex. In live cells, DAT and KOR exhibited robust FRET signals under basal conditions. SalA exposure caused a rapid and significant increase of the FRET signal. This suggests that the formation of KOR and DAT complexes is promoted in response to KOR activation. Together, these data suggest that enhanced DA transport and decreased DA release resulting in decreased dopamine signalling may contribute to the dysphoric and pro-depressant like effects of SalA and other KOR agonists.

  16. Ca2+/Calmodulin-dependent Protein Kinase IIα (αCaMKII) Controls the Activity of the Dopamine Transporter

    PubMed Central

    Steinkellner, Thomas; Yang, Jae-Won; Montgomery, Therese R.; Chen, Wei-Qiang; Winkler, Marie-Therese; Sucic, Sonja; Lubec, Gert; Freissmuth, Michael; Elgersma, Ype; Sitte, Harald H.; Kudlacek, Oliver

    2012-01-01

    The dopamine transporter (DAT) is a crucial regulator of dopaminergic neurotransmission, controlling the length and brevity of dopaminergic signaling. DAT is also the primary target of psychostimulant drugs such as cocaine and amphetamines. Conversely, methylphenidate and amphetamine are both used clinically in the treatment of attention-deficit hyperactivity disorder and narcolepsy. The action of amphetamines, which induce transport reversal, relies primarily on the ionic composition of the intra- and extracellular milieus. Recent findings suggest that DAT interacting proteins may also play a significant role in the modulation of reverse dopamine transport. The pharmacological inhibition of the serine/threonine kinase αCaMKII attenuates amphetamine-triggered DAT-mediated 1-methyl-4-phenylpyridinium (MPP+) efflux. More importantly, αCaMKII has also been shown to bind DAT in vitro and is therefore believed to be an important player within the DAT interactome. Herein, we show that αCaMKII co-immunoprecipitates with DAT in mouse striatal synaptosomes. Mice, which lack αCaMKII or which express a permanently self-inhibited αCaMKII (αCaMKIIT305D), exhibit significantly reduced amphetamine-triggered DAT-mediated MPP+ efflux. Additionally, we investigated mice that mimic a neurogenetic disease known as Angelman syndrome. These mice possess reduced αCaMKII activity. Angelman syndrome mice demonstrated an impaired DAT efflux function, which was comparable with that of the αCaMKII mutant mice, indicating that DAT-mediated dopaminergic signaling is affected in Angelman syndrome. PMID:22778257

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

    PubMed

    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

  18. Reversal by [D-Ala2,D-Leu5]enkephalin of the dopamine transporter loss caused by methamphetamine.

    PubMed

    Tsao, L I; Cadet, J L; Su, T P

    1999-05-21

    A single administration of 40 mg/kg (i.p.) of methamphetamine caused a loss of dopamine transporter in the striatum of albino Swiss (CD-1) mouse for at least 3 weeks. The administration of a single dose of [D-Ala2,D-Leu5]enkephalin (DADLE) (18 mg/kg, i.p.), given at day 14 after the administration of methamphetamine, caused a significant, transient restoration of dopamine transporter level in the striatum. These results suggest that delta-opioid peptide DADLE is able to reverse the neuronal damage caused by methamphetamine.

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

    PubMed Central

    Karabacak, Yasemin; Sase, Sunetra; Aher, Yogesh D.; Sase, Ajinkya; Saroja, Sivaprakasam R.; Cicvaric, Ana; Höger, Harald; Berger, Michael; Bakulev, Vasiliy; Sitte, Harald H.; Leban, Johann; Monje, Francisco J.; Lubec, Gert

    2015-01-01

    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. Sixty 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 6 h 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 μM; SERT 1547 μM; NET 182 μM). From day 8 (day 9 for 1 mg/kg body weight) modafinil was decreasing WM errors (WMEs) 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. PMID:26347626

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

    PubMed

    Karabacak, Yasemin; Sase, Sunetra; Aher, Yogesh D; Sase, Ajinkya; Saroja, Sivaprakasam R; Cicvaric, Ana; Höger, Harald; Berger, Michael; Bakulev, Vasiliy; Sitte, Harald H; Leban, Johann; Monje, Francisco J; Lubec, Gert

    2015-01-01

    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. Sixty 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 6 h 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 μM; SERT 1547 μM; NET 182 μM). From day 8 (day 9 for 1 mg/kg body weight) modafinil was decreasing WM errors (WMEs) 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.

  1. Decreased vesicular monoamine transporter 2 (VMAT2) and dopamine transporter (DAT) function in knockout mice affects aging of dopaminergic systems

    PubMed Central

    Hall, F. S.; Itokawa, K.; Schmitt, A.; Moessner, R.; Sora, I.; Lesch, K. P.; Uhl, G. R.

    2013-01-01

    Dopamine (DA) is accumulated and compartmentalized by the dopamine transporter (DAT; SLC3A6) and the vesicular monoamine transporter 2 (VMAT2; SLC18A2). These transporters work at the plasma and vesicular membranes of dopaminergic neurons, respectively, and thus regulate levels of DA in neuronal compartments that include the extravesicular cytoplasmic compartment. DA in this compartment has been hypothesized to contribute to oxidative damage that can reduce the function of dopaminergic neurons in aging brains and may contribute to reductions in dopaminergic neurochemical markers, locomotor behavior and responses to dopaminergic drugs that are found in aged animals. The studies reported here examined aged mice with heterozygous deletions of VMAT2 or of DAT, which each reduce transporter expression to about 50% of levels found in wild-type (WT) mice. Aged mice displayed reduced locomotor responses under a variety of circumstances, including in response to locomotor stimulants, as well as changes in monoamine levels and metabolites in a regionally dependent manner. Several effects of aging were more pronounced in heterozygous VMAT2 knockout (KO) mice, including aging induced reductions in locomotion and reduced locomotor responses to cocaine. By contrast, some effects of aging were reduced or not observed in heterozygous DAT KO mice. These findings support the idea that altered DAT and VMAT2 expression affect age-related changes in dopaminergic function. These effects are most likely mediated by alterations in DA compartmentalization, and might be hypothesized to be more exacerbated by other factors that affect the metabolism of cytosolic DA. PMID:23978383

  2. Differences in Behavior and Activity Associated with a Poly(A) Expansion in the Dopamine Transporter in Belgian Malinois

    PubMed Central

    Lit, Lisa; Belanger, Janelle M.; Boehm, Debby; Lybarger, Nathan; Oberbauer, Anita M.

    2013-01-01

    In Belgian Malinois dogs, a 38-base pair variable number tandem repeat in the dopamine transporter gene (SLC6A3) is associated with behavior changes in Malinois. By additional sequencing in SLC6A3, we identified an intronic 12-nucleotide poly(A) insertion (“PolyA(22)”) before the terminal exon that was associated with seizure, “glazing over” behaviors, and episodic biting behaviors in a sample of 138 Malinois. We next investigated whether PolyA(22) was associated with 1) increased locomotor activity and 2) response to novelty. Using a sample of 22 Malinois and 25 dogs of other breeds, dogs’ activity was monitored in a novel and non-novel environment while wearing activity monitoring collars. All dogs were more active in novel compared with non-novel environments, and Malinois were more active overall than other breeds. There was an effect of PolyA(22) genotype on activity levels, and this effect appeared to underlie the difference detected between Malinois and other breeds. There was no effect of PolyA(22) genotype on the relative decrease in activity between novel and non-novel environments for either group or all dogs considered together. In addition to an association between PolyA(22) and owner reports of seizure, “glazing over” behaviors, and episodic biting behaviors, these findings support an effect of PolyA(22) on dopamine transporter function related to activity. Further investigation is required to confirm mechanistic effects of PolyA(22) on SLC6A3. The complex polygenic nature of behavior and the range of behaviors associated with this insertion predict that effects are likely also modified by additional genetic and environmental factors. PMID:24376613

  3. Loss of dopamine transporters in methamphetamine abusers recovers with protracted abstinence.

    PubMed

    Volkow, N D; Chang, L; Wang, G J; Fowler, J S; Franceschi, D; Sedler, M; Gatley, S J; Miller, E; Hitzemann, R; Ding, Y S; Logan, J

    2001-12-01

    Methamphetamine is a popular drug of abuse that is neurotoxic to dopamine (DA) terminals when administered to laboratory animals. Studies in methamphetamine abusers have also documented significant loss of DA transporters (used as markers of the DA terminal) that are associated with slower motor function and decreased memory. The extent to which the loss of DA transporters predisposes methamphetamine abusers to neurodegenerative disorders such as Parkinsonism is unclear and may depend in part on the degree of recovery. Here we assessed the effects of protracted abstinence on the loss of DA transporters in striatum, in methamphetamine abusers using positron emission tomography and [(11)C]d-threo-methylphenidate (DA transporter radioligand). Brain DA transporters in five methamphetamine abusers evaluated during short abstinence (<6 months) and then retested during protracted abstinence (12-17 months) showed significant increases with protracted abstinence (caudate, +19%; putamen, +16%). Although performance in some of the tests for which we observed an association with DA transporters showed some improvement, this effect was not significant. The DA transporter increases with abstinence could indicate that methamphetamine-induced DA transporter loss reflects temporary adaptive changes (i.e., downregulation), that the loss reflects DA terminal damage but that terminals can recover, or that remaining viable terminals increase synaptic arborization. Because neuropsychological tests did not improve to the same extent, this suggests that the increase of the DA transporters was not sufficient for complete function recovery. These findings have treatment implications because they suggest that protracted abstinence may reverse some of methamphetamine-induced alterations in brain DA terminals.

  4. Differential Influence of Dopamine Transport Rate on the Potencies of Cocaine, Amphetamine, and Methylphenidate

    PubMed Central

    2015-01-01

    Dopamine transporter (DAT) levels vary across brain regions and individuals, and are altered by drug history and disease states; however, the impact of altered DAT expression on psychostimulant effects in brain has not been systematically explored. Using fast scan cyclic voltammetry, we measured the effects of elevated DAT levels on presynaptic dopamine parameters as well as the uptake inhibition potency of the blockers cocaine and methylphenidate (MPH) and the releaser amphetamine (AMPH) in the nucleus accumbens core. Here we found that increases in DAT levels, resulting from either genetic overexpression or MPH self-administration, caused markedly increased maximal rates of uptake (Vmax) that were positively correlated with the uptake inhibition potency of AMPH and MPH, but not cocaine. AMPH and MPH were particularly sensitive to DAT changes, with a 100% increase in Vmax resulting in a 200% increase in potency. The relationship between Vmax and MPH potency was the same as that for AMPH, but was different from that for cocaine, indicating that MPH more closely resembles a releaser with regard to uptake inhibition. Conversely, the effects of MPH on stimulated dopamine release were similar to those of cocaine, with inverted U-shaped increases in release over a concentration–response curve. This was strikingly different from the release profile of AMPH, which showed only reductions at high concentrations, indicating that MPH is not a pure releaser. These data indicate that although MPH is a DAT blocker, its uptake-inhibitory actions are affected by DAT changes in a similar manner to releasers. Together, these data show that fluctuations in DAT levels alter the potency of releasers and MPH but not blockers and suggest an integral role of the DAT in the addictive potential of AMPH and related compounds. PMID:25474655

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

    PubMed Central

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

    2014-01-01

    Objective 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 [11C]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 [123I]FP-CIT (2β-carbomethoxy-3β-(4-iodophenyl)tropane) single photon emission computed tomography (SPECT), to assess striatal dopamine transporter (DAT) density. Methods The [123I]FP-CIT binding data in the striatum were compared between 15 PD patients with and 15 without impulse control disorders using independent t tests. Results 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. Conclusions 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. PMID:23899625

  6. Behavioral, biological, and chemical perspectives on atypical agents targeting the dopamine transporterɸ

    PubMed Central

    Reith, Maarten E.A.; Blough, Bruce E.; Hong, Weimin C.; Jones, Kymry T.; Schmitt, Kyle C.; Baumann, Michael H.; Partilla, John S.; Rothman, Richard B.; Katz, Jonathan L.

    2014-01-01

    Background Treatment of Stimulant-Use Disorders remains a formidable challenge, and the dopamine transporter (DAT) remains a potential target for antagonist or agonist-like substitution therapies. Methods This review focuses on DAT ligands, such as benztropine, GBR 12909, modafinil, and DAT substrates derived from phenethylamine or cathinone that have atypical DAT-inhibitor effects, either in vitro or in vivo. The compounds are described from a molecular mechanistic, behavioral, and medicinal-chemical perspective. Results Possible mechanisms for atypicality at the molecular level can be deduced from the conformational cycle for substrate translocation. For each conformation, a crystal structure of a bacterial homolog is available, with a possible role of cholesterol, which is also present in the crystal of drosophila DAT. Although there is a direct relationship between behavioral potencies of most DAT inhibitors and their DAT affinities, a number of compounds bind to the DAT and inhibit dopamine uptake but do not share cocaine-like effects. Such atypical behavior, depending on the compound, may be related to slow DAT association, combined sigma-receptor actions, or bias for cytosol-facing DAT. Some structures are sterically small enough to serve as DAT substrates but large enough to also inhibit transport. Such compounds may display partial DA releasing effects, and may be combined with release or uptake inhibition at other monoamine transporters. Conclusions Mechanisms of atypical DAT inhibitors may serve as targets for the development of treatments for stimulant abuse. These mechanisms are novel and their further exploration may produce compounds with unique therapeutic potential as treatments for stimulant abuse. PMID:25548026

  7. Lobelane inhibits methamphetamine-evoked dopamine release via inhibition of the vesicular monoamine transporter-2.

    PubMed

    Nickell, Justin R; Krishnamurthy, Sairam; Norrholm, Seth; Deaciuc, Gabriela; Siripurapu, Kiran B; Zheng, Guangrong; Crooks, Peter A; Dwoskin, Linda P

    2010-02-01

    Lobeline is currently being evaluated in clinical trials as a methamphetamine abuse treatment. Lobeline interacts with nicotinic receptor subtypes, dopamine transporters (DATs), and vesicular monoamine transporters (VMAT2s). Methamphetamine inhibits VMAT2 and promotes dopamine (DA) release from synaptic vesicles, resulting ultimately in increased extracellular DA. The present study generated structure-activity relationships by defunctionalizing the lobeline molecule and determining effects on [(3)H]dihydrotetrabenazine binding, inhibition of [(3)H]DA uptake into striatal synaptic vesicles and synaptosomes, the mechanism of VMAT2 inhibition, and inhibition of methamphetamine-evoked DA release. Compared with lobeline, the analogs exhibited greater potency inhibiting DA transporter (DAT) function. Saturated analogs, lobelane and nor-lobelane, exhibited high potency (K(i) = 45 nM) inhibiting vesicular [(3)H]DA uptake, and lobelane competitively inhibited VMAT2 function. Lobeline and lobelane exhibited 67- and 35-fold greater potency, respectively, in inhibiting VMAT2 function compared to DAT function. Lobelane potently decreased (IC(50) = 0.65 microM; I(max) = 73%) methamphetamine-evoked DA overflow, and with a greater maximal effect compared with lobeline (IC(50) = 0.42 microM, I(max) = 56.1%). These results provide support for VMAT2 as a target for inhibition of methamphetamine effects. Both trans-isomers and demethylated analogs of lobelane had reduced or unaltered potency inhibiting VMAT2 function and lower maximal inhibition of methamphetamine-evoked DA release compared with lobelane. Thus, defunctionalization, cis-stereochemistry of the side chains, and presence of the piperidino N-methyl are structural features that afford greatest inhibition of methamphetamine-evoked DA release and enhancement of selectivity for VMAT2. The current results reveal that lobelane, a selective VMAT2 inhibitor, inhibits methamphetamine-evoked DA release and is a promising lead for

  8. Dopamine transporter regulates the enhancement of novelty processing by a negative emotional context.

    PubMed

    Garcia-Garcia, Manuel; Clemente, Immaculada; Domínguez-Borràs, Judith; Escera, Carles

    2010-04-01

    The dopaminergic (DA) system has been recently related the emotional modulation of cognitive processes. Moreover, patients with midbrain DA depletion, such as Parkinson's Disease (PD), have shown diminished reactivity during unpleasant events. Here, we examined the role of DA in the enhancement of novelty processing during negative emotion. Forty healthy volunteers were genotyped for the dopamine transporter (DAT) gene SLC6A3 or DAT1 and performed an auditory-visual distraction paradigm in negative and neutral emotional context conditions. 9R- individuals, associated to a lesser striatal DA display, failed to show increased distraction during negative emotion, but experienced an enhancement of the early phase of the novelty-P3 brain response, associated to the evaluation of novel events, in the negative relative to the neutral context. However, 9R+ individuals (associated to larger striatal DA display) showed larger distraction during negative emotion and larger amplitudes of the novelty-P3, irrespective of the condition. These results suggest a blunted reactivity to novelty during negative emotion in 9R- individuals due to a lesser DA display and stronger activation of the representation of novel events in the 9R+ group, due to a larger DA availability, thus reaching a ceiling effect in the neutral context condition with no further enhancement during negative emotion. The present results might help to understand the functional implications of dopamine in some neuropsychiatric disorders.

  9. Predicting childhood effortful control from interactions between early parenting quality and children's dopamine transporter gene haplotypes.

    PubMed

    Li, Yi; Sulik, Michael J; Eisenberg, Nancy; Spinrad, Tracy L; Lemery-Chalfant, Kathryn; Stover, Daryn A; Verrelli, Brian C

    2016-02-01

    Children's observed effortful control (EC) at 30, 42, and 54 months (n = 145) was predicted from the interaction between mothers' observed parenting with their 30-month-olds and three variants of the solute carrier family C6, member 3 (SLC6A3) dopamine transporter gene (single nucleotide polymorphisms in intron8 and intron13, and a 40 base pair variable number tandem repeat [VNTR] in the 3'-untranslated region [UTR]), as well as haplotypes of these variants. Significant moderating effects were found. Children without the intron8-A/intron13-G, intron8-A/3'-UTR VNTR-10, or intron13-G/3'-UTR VNTR-10 haplotypes (i.e., haplotypes associated with the reduced SLC6A3 gene expression and thus lower dopamine functioning) appeared to demonstrate altered levels of EC as a function of maternal parenting quality, whereas children with these haplotypes demonstrated a similar EC level regardless of the parenting quality. Children with these haplotypes demonstrated a trade-off, such that they showed higher EC, relative to their counterparts without these haplotypes, when exposed to less supportive maternal parenting. The findings revealed a diathesis-stress pattern and suggested that different SLC6A3 haplotypes, but not single variants, might represent different levels of young children's sensitivity/responsivity to early parenting.

  10. Nurr1 enhances transcription of the human dopamine transporter gene through a novel mechanism.

    PubMed

    Sacchetti, P; Mitchell, T R; Granneman, J G; Bannon, M J

    2001-03-01

    The importance of the nuclear receptor nurr1 for the appropriate development of mesencephalic dopamine-synthesizing neurons has been clearly demonstrated through the targeted disruption of the nurr1 gene. The persistence of nurr1 expression in adult tissue suggests a possible role for this transcription factor in the maintenance, as well as development, of the dopaminergic phenotype. To address this issue, we analyzed the effects of nurr1 on the transcriptional expression of the human dopamine transporter gene (hDAT), one of the most specific phenotypic markers for dopaminergic neurons. Nurr1 enhanced the transcriptional activity of hDAT gene constructs transiently transfected into a newly described cell line (SN4741) that expresses a dopaminergic phenotype, whereas other members of the NGFI-B subfamily of nuclear receptors had lesser or no effects. Nurr1 activation of hDAT was not dependent upon heterodimerization with the retinoid X receptor. Unexpectedly, functional analysis of a series of gene constructs revealed that a region of the hDAT 5'-flanking sequence devoid of NGFI-B response element (NBRE)-like sites mediated nurr1 activation. Additional experiments using a nurr1 mutant construct suggest that nurr1 activates hDAT transcription via a novel NBRE-independent mechanism.

  11. Dopamine transporter gene susceptibility to methylation is associated with impulsivity in nonhuman primates

    PubMed Central

    Rajala, Abigail Z.; Zaitoun, Ismail; Henriques, Jeffrey B.; Converse, Alexander K.; Murali, Dhanabalan; Epstein, Miles L.

    2014-01-01

    Impulsivity, the predisposition to act without regard for negative consequences, is a characteristic of several psychiatric disorders and is thought to result in part from genetic variation in the untranslated region of the dopamine transporter (DAT) gene. As the exact link between genetic mutations and impulsivity has not been established, we used oculomotor behavior to characterize rhesus monkeys as impulsive or calm and genetic/epigenetic analysis and positron emission tomography (PET) to correlate phenotype to DAT genotype, DAT gene methylation, and DAT availability. We found three single nucleotide polymorphisms (SNPs) in the 3′-UTR of the DAT gene, one of which provided a potential site for methylation in the impulsive group. Bisulfite analysis showed that the DNA of the impulsive but not the calm subjects was methylated at one SNP. Because genetic/epigenetic modifications could lead to differences in protein expression, we measured DAT availability using [18F]2β-carbomethoxy-3β-(4-chlorophenyl)-8-(2-fluoroethyl)-nortropane ([18F]FECNT) PET and found higher DAT availability in the internal globus pallidus, an output nucleus of the basal ganglia, of the impulsive group. Higher DAT availability lowers dopamine levels, potentially altering neuronal circuits involved in the initiation of action, thus contributing to the impulsive phenotype. The association between increased methylation in the DAT gene and greater DAT availability suggests that mutations to the regulatory portion of the DAT gene lead to a susceptibility to epigenetic modification resulting in a discrete behavioral phenotype. PMID:25122707

  12. Interaction of Dopamine Transporter Gene and Observed Parenting Behaviors on Attention-Deficit/Hyperactivity Disorder: A Structural Equation Modeling Approach

    ERIC Educational Resources Information Center

    Li, James J.; Lee, Steve S.

    2013-01-01

    Emerging evidence suggests that some individuals may be simultaneously more responsive to the effects from environmental adversity "and" enrichment (i.e., differential susceptibility). Given that parenting behavior and a variable number tandem repeat polymorphism in the 3'untranslated region of the dopamine transporter (DAT1) gene are…

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

    PubMed Central

    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. PMID:28059145

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Evolution of a Compact Photoprobe for the Dopamine Transporter Based on (±)-threo-Methylphenidate

    PubMed Central

    2012-01-01

    The development of photoaffinity ligands for determining covalent points of attachment to the dopamine transporter (DAT) has predominantly focused on tropane-based compounds bearing variable-length linkers between the photoreactive group and the inhibitor pharmacophore. To expand the array of photoprobes useful for mapping inhibitor-binding pockets within the DAT, a compact nontropane ligand was synthesized featuring a photoreactive azide and iodine tag directly attached to the aromatic ring of (±)-threo-methylphenidate. (±)-threo-4-Azido-3-iodomethylphenidate [(±)-6; Ki = 4.0 ± 0.8 nM] displayed high affinity for hDAT. Moreover, a radioiodinated analogue of (±)-6 demonstrated covalent ligation to the DAT in cultured cells and rat striatal membranes, thus suggesting the potential utility of this photoprobe in DAT structure–function studies. PMID:23066448

  16. Membrane potential shapes regulation of dopamine transporter trafficking at the plasma membrane

    PubMed Central

    Richardson, Ben D.; Saha, Kaustuv; Krout, Danielle; Cabrera, Elizabeth; Felts, Bruce; Henry, L. Keith; Swant, Jarod; Zou, Mu-Fa; Newman, Amy Hauck; Khoshbouei, Habibeh

    2016-01-01

    The dopaminergic system is essential for cognitive processes, including reward, attention and motor control. In addition to DA release and availability of synaptic DA receptors, timing and magnitude of DA neurotransmission depend on extracellular DA-level regulation by the dopamine transporter (DAT), the membrane expression and trafficking of which are highly dynamic. Data presented here from real-time TIRF (TIRFM) and confocal microscopy coupled with surface biotinylation and electrophysiology suggest that changes in the membrane potential alone, a universal yet dynamic cellular property, rapidly alter trafficking of DAT to and from the surface membrane. Broadly, these findings suggest that cell-surface DAT levels are sensitive to membrane potential changes, which can rapidly drive DAT internalization from and insertion into the cell membrane, thus having an impact on the capacity for DAT to regulate extracellular DA levels. PMID:26804245

  17. Metabolism of dopamine by the nasal mucosa.

    PubMed

    Chemuturi, Nagendra V; Donovan, Maureen D

    2006-11-01

    The nasal route of administration offers several advantages over oral and intravenous administration, including the ability to avoid hepatic first pass metabolism. Dopamine deficiency has been associated with several neurological disorders; it has been shown to have good systemic bioavailability and significant uptake into the CNS following intranasal administration. The purpose of these studies was to investigate the limiting role of mucosal metabolism of dopamine during nasal absorption. In vitro transport and initial rate studies were carried out using nasal mucosal explants to study dopamine permeability and metabolism. Dihydroxyphenylacetic acid (DOPAC) was the only metabolite detected. Monoamine oxidase (MAO), the enzyme responsible for DOPAC formation, was localized to the submucosal region of the nasal explants. The amount of DOPAC formed during the transport studies was less than 0.5% of the initial amount of dopamine placed into the system. Iproniazid, an MAO inhibitor, blocked DOPAC formation but had no effect on dopamine transport. The limited extent of dopamine metabolism compared to its mucosal transport demonstrates that nasal dopamine transport is not significantly reduced by mucosal metabolism and suggests that the nasal route may be promising for the efficient delivery of dopamine to the CNS.

  18. A variable number of tandem repeats in the 3'-untranslated region of the dopamine transporter modulates striatal function during working memory updating across the adult age span.

    PubMed

    Sambataro, Fabio; Podell, Jamie E; Murty, Vishnu P; Das, Saumitra; Kolachana, Bhaskar; Goldberg, Terry E; Weinberger, Daniel R; Mattay, Venkata S

    2015-08-01

    Dopamine modulation of striatal function is critical for executive functions such as working memory (WM) updating. The dopamine transporter (DAT) regulates striatal dopamine signaling via synaptic reuptake. A variable number of tandem repeats in the 3'-untranslated region of SLC6A3 (DAT1-3'-UTR-VNTR) is associated with DAT expression, such that 9-repeat allele carriers tend to express lower levels (associated with higher extracellular dopamine concentrations) than 10-repeat homozygotes. Aging is also associated with decline of the dopamine system. The goal of the present study was to investigate the effects of aging and DAT1-3'-UTR-VNTR on the neural activity and functional connectivity of the striatum during WM updating. Our results showed both an age-related decrease in striatal activity and an effect of DAT1-3'-UTR-VNTR. Ten-repeat homozygotes showed reduced striatal activity and increased striatal-hippocampal connectivity during WM updating relative to the 9-repeat carriers. There was no age by DAT1-3'-UTR-VNTR interaction. These results suggest that, whereas striatal function during WM updating is modulated by both age and genetically determined DAT levels, the rate of the age-related decline in striatal function is similar across both DAT1-3'-UTR-VNTR genotype groups. They further suggest that, because of the baseline difference in striatal function based on DAT1-3'-UTR-VNTR polymorphism, 10-repeat homozygotes, who have lower levels of striatal function throughout the adult life span, may reach a threshold of decreased striatal function and manifest impairments in cognitive processes mediated by the striatum earlier in life than the 9-repeat carriers. Our data suggest that age and DAT1-3'-UTR-VNTR polymorphism independently modulate striatal function.

  19. The effects of the calcium ionophore, A23187, on the axoplasmic transport of dopamine beta-hydroxylase.

    PubMed Central

    Esquerro, E.; Garcia, A. G.; Sanchez-Garcia, P.

    1980-01-01

    1 The effects of the ionophore, A23187, on the intra-axonal transport of dopamine beta-hydroxylase (DBH) were investigated in the cat hypogastric nerve-inferior mesenteric ganglion preparation by monitoring, in vitro, the enzyme accumulation above a ligature, 2 to 2.5 cm distal to the ganglion. 2 DBH accumulation in the proximal segment immediately above the ligature (P1) increased linearly up to 6 h, during incubation in normal Krebs solution at 37 degrees C. The ionophore, A23187, interfered with the enzyme accumulation, but did not modify the previously accumulated DBH activity present in P1. 3 The blocking effects of A23187 on DBH transport were greatly impaired in the absence of extracellular calcium ions; an excess of calcium in the bathing solution (7.5 mM) itself blocked the enzyme transport by 50%. 4 A23187 did not significantly modify the levels of adenosine triphosphate (ATP) in the segments P1 and P2 of the nerve proximal to the ligature. 5 Nerves incubated in an A23187-containing medium showed many mitochondria of normal shape and fine structure; however, typical microtubules or filaments were not seen in these preparations. 6 The results suggest that the ionophore A23187, by considerably raising the axoplasmic ionized calcium levels, interferes with the assembling of microtubules. In this manner, the ionophore would inhibit the transport of adrenergic vesicles and therefore of DBH along the axon. The results also provide additional evidence in favour of the view that for the transport system to work adequately, it is necessary to maintain the intra-axoplasmic ionized calcium concentration between certain critical levels. Images Figure 5 PMID:6159942

  20. Direct evidence that two cysteines in the dopamine transporter form a disulfide bond.

    PubMed

    Chen, Rong; Wei, Hua; Hill, Erik R; Chen, Lucy; Jiang, Liying; Han, Dawn D; Gu, Howard H

    2007-04-01

    We have generated a fully functional dopamine transporter (DAT) mutant (dmDATx7) with all cysteines removed except the two cysteines in extracellular loop 2 (EL2). Random mutagenesis at either or both EL2 cysteines did not produce any functional transporter mutants, suggesting that the two cysteines cannot be replaced by any other amino acids. The cysteine-specific reagent MTSEA-biotin labeled dmDATx7 only after a DTT treatment which reduces disulfide bond. Since there are no other cysteines in dmDATx7, the MTSEA-biotin labeling must be on the EL2 cysteines made available by the DTT treatment. This result provides the first direct evidence that the EL2 cysteines form a disulfide bond. Interestingly, the DTT treatment had little effect on transport activity suggesting that the disulfide bond is not necessary for the uptake function of DAT. Our results and previous results are consistent with the notion that the disulfide bond between EL2 cysteines is required for DAT biosynthesis and/or its delivery to the cell surface.

  1. Investigation of the enzymology and pharmacology of novel substrates and inhibitors of dopamine beta-monooxygenase

    SciTech Connect

    Roberts, S.F.

    1987-01-01

    Dopamine beta-monooxygenase (DBM) was shown to catalyze the selenoxidation of 2-(phenylseleno)ethylamines, selenium-containing analogues of dopamine, by the normal monooxygenase pathway. The compounds 2-(phenylseleno)-ethylamine (PAESe), 2-(4'-hydroxyphenylseleno)ethylamine (pOH PAESe), and 1-(phenylseleno)-2-propylamine (Me PAESe) were synthesized and fully characterized as DBM substrates. Two other classes of compounds were investigated as potential alternate substrates for DBM. The possibility of stereoselective sulfonylation of 2-(phenylsulfenyl)- ethylamine (PAESO) was considered. A unique class of compounds, 2-(phenylthio)ethanols were designed and synthesized as DBM substrates but were found to be a novel class of potent competitive inhibitors of DBM with respect to tyramine. Preliminary experiments were also performed in an effort to demonstrate that the potent antihypertensive and indirect-acting sympathomimetic activity of 2-(phenylthio)ethylamine (PAES) was a result of DBM-oxygenation of this compound in vivo. The specific reserpine-sensitive uptake of (/sup 3/H)-norepinephrine into rat brain synaptosomes was demonstrated as was the synaptosomal conversion of (/sup 3/H)-dopamine to (/sup 3/H)-norepinephrine.

  2. Putamen-midbrain functional connectivity is related to striatal dopamine transporter availability in patients with Lewy body diseases.

    PubMed

    Rieckmann, A; Gomperts, S N; Johnson, K A; Growdon, J H; Van Dijk, K R A

    2015-01-01

    Prior work has shown that functional connectivity between the midbrain and putamen is altered in patients with impairments in the dopamine system. This study examines whether individual differences in midbrain-striatal connectivity are proportional to the integrity of the dopamine system in patients with nigrostriatal dopamine loss (Parkinson's disease and dementia with Lewy bodies). We assessed functional connectivity of the putamen during resting state fMRI and dopamine transporter (DAT) availability in the striatum using 11C-Altropane PET in twenty patients. In line with the hypothesis that functional connectivity between the midbrain and the putamen reflects the integrity of the dopaminergic neurotransmitter system, putamen-midbrain functional connectivity was significantly correlated with striatal DAT availability even after stringent control for effects of head motion. DAT availability did not relate to functional connectivity between the caudate and thalamus/prefrontal areas. As such, resting state functional connectivity in the midbrain-striatal pathway may provide a useful indicator of underlying pathology in patients with nigrostriatal dopamine loss.

  3. THE MODERATING ROLE OF THE DOPAMINE TRANSPORTER 1 GENE ON P50 SENSORY GATING AND ITS MODULATION BY NICOTINE

    PubMed Central

    MILLAR, A.; SMITH, D.; CHOUEIRY, J.; FISHER, D.; ALBERT, P.; KNOTT, V.

    2015-01-01

    Although schizophrenia has been considered primarily a disease of dopaminergic neurotransmission, the role of dopamine in auditory sensory gating deficits in this disorder and their amelioration by smoking/nicotine is unclear. Hypothesizing that individual differences in striatal dopamine levels may moderate auditory gating and its modulation by nicotine, this preliminary study used the mid-latency (P50) auditory event-related potential (ERP) to examine the single dose (6 mg) effects of nicotine (vs. placebo) gum on sensory gating in 24 healthy nonsmokers varying in the genetic expression of the dopamine transporter (DAT). Consistent with an inverted-U relationship between dopamine level and the drug effects, individuals carrying the 9R (lower gene expression) allele, which is related to greater striatal dopamine levels, tended to evidence increased baseline gating compared to 10R (higher gene expression) allele carriers and showed a reduction in gating with acute nicotine. The present results may help to understand the link between excessive smoking and sensory gating deficits in schizophrenia and to explain the potential functional implications of genetic disposition on nicotinic treatment in schizophrenia. PMID:21315807

  4. The association between heroin expenditure and dopamine transporter availability--a single-photon emission computed tomography study.

    PubMed

    Lin, Shih-Hsien; Chen, Kao Chin; Lee, Sheng-Yu; Chiu, Nan Tsing; Lee, I Hui; Chen, Po See; Yeh, Tzung Lieh; Lu, Ru-Band; Chen, Chia-Chieh; Liao, Mei-Hsiu; Yang, Yen Kuang

    2015-03-30

    One of the consequences of heroin dependency is a huge expenditure on drugs. This underlying economic expense may be a grave burden for heroin users and may lead to criminal behavior, which is a huge cost to society. The neuropsychological mechanism related to heroin purchase remains unclear. Based on recent findings and the established dopamine hypothesis of addiction, we speculated that expenditure on heroin and central dopamine activity may be associated. A total of 21 heroin users were enrolled in this study. The annual expenditure on heroin was assessed, and the availability of the dopamine transporter (DAT) was assessed by single-photon emission computed tomography (SPECT) using [(99m)TC]TRODAT-1. Parametric and nonparametric correlation analyses indicated that annual expenditure on heroin was significantly and negatively correlated with the availability of striatal DAT. After adjustment for potential confounders, the predictive power of DAT availability was significant. Striatal dopamine function may be associated with opioid purchasing behavior among heroin users, and the cycle of spiraling dysfunction in the dopamine reward system could play a role in this association.

  5. GABA, glutamate, dopamine and serotonin transporters expression on memory formation and amnesia.

    PubMed

    Tellez, Ruth; Gómez-Víquez, Leticia; Meneses, Alfredo

    2012-02-01

    Notwithstanding several neurotransmission systems are frequently related to memory formation, amnesia and/or therapeutic targets for memory alterations, the role of transporters γ-aminobutyric acid (GABA, GAT1), glutamate (neuronal glutamate transporter excitatory amino acid carrier; EACC1), dopamine (DAT) and serotonin (SERT) is poorly understood. Hence, in this paper Western-blot analysis was used to evaluate expression changes on them during memory formation in trained and untrained rats treated with the selective serotonin transporter inhibitor fluoxetine, the amnesic drug d-methamphetamine (METH) and fluoxetine plus METH. Transporters expression was evaluated in the hippocampus, prefrontal cortex and striatum. Data indicated that in addition of memory performance other behavioral parameters (e.g., explorative behavior, food-intake, etc.) that memory formation was recorded. Thus, memory formation in a Pavlovian/instrumental autoshaping was associated to up-regulation of prefrontal cortex GAT1 and EAAC1, striatal SERT, DAT and EACC1; while, hippocampal EACC1, GAT1 and SERT were down-regulated. METH impaired short (STM) and long-term memory (LTM), at 24 or 48h. The METH-induced amnesia down-regulated SERT, DAT, EACC1 and GAT1 in hippocampus and the GAT1 in striatum; no-changes were observed in prefrontal cortex. Post-training administration of fluoxetine improved LTM (48h), which was associated to DAT, GAT1 (prefrontal cortex) up-regulation, but GAT1 (striatum) and SERT (hippocampus) down-regulation. Fluoxetine plus METH administration was able to prevent amnesia, which was associated to DAT, EACC1 and GAT1 (prefrontal cortex), SERT and DAT (hippocampus) and EACC1 or DAT (striatal) up-regulation. Together these data show that memory formation, amnesia and anti-amnesic effects are associated to specific patters of transporters expression.

  6. meso-Transdiene analogs inhibit vesicular monoamine transporter-2 function and methamphetamine-evoked dopamine release.

    PubMed

    Horton, David B; Siripurapu, Kiran B; Norrholm, Seth D; Culver, John P; Hojahmat, Marhaba; Beckmann, Joshua S; Harrod, Steven B; Deaciuc, Agripina G; Bardo, Michael T; Crooks, Peter A; Dwoskin, Linda P

    2011-03-01

    Lobeline, a nicotinic receptor antagonist and neurotransmitter transporter inhibitor, is a candidate pharmacotherapy for methamphetamine abuse. meso-Transdiene (MTD), a lobeline analog, lacks nicotinic receptor affinity, retains affinity for vesicular monoamine transporter 2 (VMAT2), and, surprisingly, has enhanced affinity for dopamine (DA) and serotonin transporters [DA transporter (DAT) and serotonin transporter (SERT), respectively]. In the current study, MTD was evaluated for its ability to decrease methamphetamine self-administration in rats relative to food-maintained responding. MTD specifically decreased methamphetamine self-administration, extending our previous work. Classical structure-activity relationships revealed that more conformationally restricted MTD analogs enhanced VMAT2 selectivity and drug likeness, whereas affinity at the dihydrotetrabenazine binding and DA uptake sites on VMAT2 was not altered. Generally, MTD analogs exhibited 50- to 1000-fold lower affinity for DAT and were equipotent or had 10-fold higher affinity for SERT, compared with MTD. Representative analogs from the series potently and competitively inhibited [(3)H]DA uptake at VMAT2. (3Z,5Z)-3,5-bis(2,4-dichlorobenzylidene)-1-methylpiperidine (UKMH-106), the 3Z,5Z-2,4-dichlorophenyl MTD analog, had improved selectivity for VMAT2 over DAT and importantly inhibited methamphetamine-evoked DA release from striatal slices. In contrast, (3Z,5E)-3,5-bis(2,4-dichlorobenzylidene)-1-methylpiperidine (UKMH-105), the 3Z,5E-geometrical isomer, inhibited DA uptake at VMAT2, but did not inhibit methamphetamine-evoked DA release. Taken together, these results suggest that these geometrical isomers interact at alternate sites on VMAT2, which are associated with distinct pharmacophores. Thus, structural modification of the MTD molecule resulted in analogs exhibiting improved drug likeness and improved selectivity for VMAT2, as well as the ability to decrease methamphetamine-evoked DA release

  7. Regulation of ethanol intake under chronic mild stress: roles of dopamine receptors and transporters

    PubMed Central

    Delis, Foteini; Rombola, Christina; Bellezza, Robert; Rosko, Lauren; Grandy, David K.; Volkow, Nora D.; Thanos, Panayotis K.

    2015-01-01

    Studies have shown that exposure to chronic mild stress decreases ethanol intake and preference in dopamine D2 receptor wild-type mice (Drd2+/+), while it increases intake in heterozygous (Drd2+/−) and knockout (Drd2−/−) mice. Dopaminergic neurotransmission in the basal forebrain plays a major role in the reinforcing actions of ethanol as well as in brain responses to stress. In order to identify neurochemical changes associated with the regulation of ethanol intake, we used in vitro receptor autoradiography to measure the levels and distribution of dopamine D1 and D2 receptors and dopamine transporters (DAT). Receptor levels were measured in the basal forebrain of Drd2+/+, Drd2+/−, and Drd2−/− mice belonging to one of four groups: control (C), ethanol intake (E), chronic mild stress exposure (S), and ethanol intake under chronic mild stress (ES). D2 receptor levels were higher in the lateral and medial striatum of Drd2+/+ ES mice, compared with Drd2+/+ E mice. Ethanol intake in Drd2+/+ mice was negatively correlated with striatal D2 receptor levels. D2 receptor levels in Drd2+/− mice were the same among the four treatment groups. DAT levels were lower in Drd2+/− C and Drd2−/− C mice, compared with Drd2+/+ C mice. Among Drd2+/− mice, S and ES groups had higher DAT levels compared with C and E groups in most regions examined. In Drd2−/− mice, ethanol intake was positively correlated with DAT levels in all regions studied. D1 receptor levels were lower in Drd2+/− and Drd2−/− mice, compared with Drd2+/+, in all regions examined and remained unaffected by all treatments. The results suggest that in normal mice, ethanol intake is associated with D2 receptor-mediated neurotransmission, which exerts a protective effect against ethanol overconsumption under stress. In mice with low Drd2 expression, where DRD2 levels are not further modulated, ethanol intake is associated with DAT function which is upregulated under stress leading to ethanol

  8. Manganese accumulation in striatum of mice exposed to toxic doses is dependent upon a functional dopamine transporter.

    PubMed

    Erikson, Keith M; John, Carrie E; Jones, Sara R; Aschner, Michael

    2005-11-01

    The objective of this study was to determine the importance of the dopamine transporter (DAT) in manganese transport. Excessive manganese exposure is associated with a neurotoxicological disease known as manganism characterized by a specific accumulation of manganese in dopamine-rich brain regions. It has been hypothesized that the DAT mediates this specific transport, but its role in manganese neurotoxicity has not been directly examined. We examined brain tissues from manganese-exposed dopamine transporter knockout (DAT-KO) and wild-type (WT) mice. There was significantly less (p<0.05) manganese in the striatum of exposed DAT-KO mice compared to WT. However, the absence of a functioning DAT did not affect manganese accumulation in other brain regions examined. Furthermore, both iron and divalent metal transporter levels (two known modulators of brain manganese) were similar between DAT-KO and WT mice in all brain regions. These studies demonstrate that the DAT is involved in the facilitation of striatal manganese accumulation and that it may play a critical role in mediating manganese neurotoxicity.

  9. Neurotransplantation of stem cells genetically modified to express human dopamine transporter reduces alcohol consumption

    PubMed Central

    2010-01-01

    Introduction Regulated neurotransmitter actions in the mammalian central nervous system determine brain function and control peripheral organs and behavior. Although drug-seeking behaviors, including alcohol consumption, depend on central neurotransmission, modification of neurotransmitter actions in specific brain nuclei remains challenging. Herein, we report a novel approach for neurotransmission modification in vivo by transplantation of stem cells engineered to take up the neurotransmitter dopamine (DA) efficiently through the action of the human dopamine transporter (hDAT). As a functional test in mice, we used voluntary alcohol consumption, which is known to release DA in nucleus accumbens (NAC), an event hypothesized to help maintain drug-seeking behavior. We reasoned that reducing extracellular DA levels, by engrafting into NAC DA-sequestering stem cells expressing hDAT, would alter alcohol intake. Methods We have generated a neural stem cell line stably expressing the hDAT. Uptake kinetics of DA were determined to select a clone for transplantation. These genetically modified stem cells (or cells transfected with a construct lacking the hDAT sequence) were transplanted bilaterally into the NAC of wild-type mice trained to consume 10% alcohol in a two-bottle free-choice test for alcohol consumption. Alcohol intake was then ascertained for 1 week after transplantation, and brain sections through the NAC were examined for surviving grafted cells. Results Modified stem cells expressed hDAT and uptaken DA selectively via hDAT. Mice accustomed to drinking 10% ethanol by free choice reduced their alcohol consumption after being transplanted with hDAT-expressing stem cells. By contrast, control stem cells lacked that effect. Histologic examination revealed surviving stem cells in the NAC of all engrafted brains. Conclusions Our findings represent proof of principle suggesting that genetically engineered stem cells can be useful for exploring the role of

  10. Serotonergic involvement in the amelioration of behavioral abnormalities in dopamine transporter knockout mice by nicotine.

    PubMed

    Uchiumi, Osamu; Kasahara, Yoshiyuki; Fukui, Asami; Hall, F Scott; Uhl, George R; Sora, Ichiro

    2013-01-01

    Dopamine transporter knockout (DAT KO) mice exhibit elevated extracellular dopamine levels in brain regions that include the striatum and the nucleus accumbens, but not the prefrontal cortex. DAT KO mice model some aspects of psychiatric disorders, including schizophrenia. Smoking is more common in patients with schizophrenia, suggesting that nicotine might ameliorate aspects of the behavioral abnormalities and/or treatment side effects seen in these individuals. We report nicotine-induced normalization of effects on locomotion and prepulse inhibition of acoustic startle (PPI) in DAT KO mice that require intact serotonin 5-HT1A systems. First, we observed that the marked hyperactivity displayed by DAT KO mice was reduced by administration of nicotine. This nicotine effect was blocked by pretreatment with the non-specific nicotinic acetylcholine (nACh) receptor antagonist mecamylamine, or the 5-HT1A antagonist WAY100635. Secondly, we examined the effects of nicotine on PPI in DAT KO mice. Treatment with nicotine significantly ameliorated the PPI deficits observed in DAT KO mice. The ameliorating action of nicotine on PPI deficits in DAT KO mice was blocked by mecamylamine, the α₇ nACh receptor antagonist methyllycaconitine or WAY100635, while the α₄β₂ nACh receptor antagonist dihydro-β-erythroidinehydrobromide (DHβE) produced only a non-significant trend toward attenuation of nicotine effects. Finally, we observed that administration of the 5-HT1A receptor agonist 8-OH-DPAT also ameliorated the deficit in PPI observed in DAT KO mice. This amelioration was antagonized by pretreatment with WAY100635. These data support the idea that nicotine might ameliorate some of the cognitive dysfunctions found in schizophrenia in a 5-HT1A-dependent fashion. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

  11. Protection of malonate-induced GABA but not dopamine loss by GABA transporter blockade in rat striatum.

    PubMed

    Zeevalk, Gail D; Manzino, Lawrence; Sonsalla, Patricia K

    2002-07-01

    Previous work has shown that overstimulation of GABA(A) receptors can potentiate neuronal cell damage during excitotoxic or metabolic stress in vitro and that GABA(A) antagonists or GABA transport blockers are neuroprotective under these situations. Malonate, a reversible succinate dehydrogenase/mitochondrial complex II inhibitor, is frequently used in animals to model cell loss in neurodegenerative diseases such as Parkinson's and Huntington's diseases. To determine if GABA transporter blockade during mitochondrial impairment can protect neurons in vivo as compared with in vitro studies, rats received a stereotaxic infusion of malonate (2 micromol) into the left striatum to induce a metabolic stress. The nonsubstrate GABA transport blocker, NO711 (20 nmol) was infused in some rats 30 min before and 3 h following malonate infusion. After 1 week, dopamine and GABA levels in the striata were measured. Malonate caused a significant loss of striatal dopamine and GABA. Blockade of the GABA transporter significantly attenuated GABA, but not dopamine loss. In contrast with several in vitro reports, GABA(A) receptors were not a downstream mediator of protection by NO711. Intrastriatal infusion of malonate (2 micromol) plus or minus the GABA(A) receptor agonist muscimol (1 micromol), the GABA(A) Cl- binding site antagonist picrotoxin (50 nmol) or the GABA(B) receptor antagonist saclofen (33 nmol) did not modify loss of striatal dopamine or GABA when examined 1 week following infusion. These data show that GABA transporter blockade during mitochondrial impairment in the striatum provides protection to GABAergic neurons. GABA transporter blockade, which is currently a pharmacological strategy for the treatment of epilepsy, may thus also be beneficial in the treatment of acute and chronic conditions involving energy inhibition such as stroke/ischemia or Huntington's disease. These findings also point to fundamental differences between immature and adult neurons in the

  12. 2beta-Substituted analogues of 4'-iodococaine: synthesis and dopamine transporter binding potencies.

    PubMed

    Avor, K S; Singh, S; Seale, T W; Pouw, B; Basmadjian, G P

    1998-06-18

    A series of 2beta-substituted analogues of 4'-iodococaine (3) was synthesized and evaluated in an in vitro dopamine transporter (DAT) binding assay. Selective hydrolysis at the 2beta-position of 3 gave the carboxylic acid 15 that served as the intermediate for the synthesis of compounds 4, 5, and 6-11. The 2beta-alkyl derivatives were obtained from ecgonine methyl ester (17) through a series of reactions leading to the aldehyde 20. Wittig reaction of 20 with methyltriphenylphosphorane followed by hydrogenation and benzoylation gave the products 12 and 13. The binding affinity of 4'-iodococaine (3) was 10-fold less than that of cocaine. The hydroxymethane, acetate, amide, benzyl ester, oxidazole, and ethane derivatives of 3 exhibited decreased binding while the vinyl, phenyl, and ethyl esters showed a moderate increase in binding affinity. Only the isopropyl derivative 8 exhibited a 2-fold increase in binding affinity compared with 4'-iodococaine (3). Hydroxylation of 8 at the 2'-position gave 14 which enhanced not only the binding potency at the DAT by another 2-fold but also the selectivity at the DAT over the norepinephrine and serotonin transporters. Compound 14 failed to stimulate locomotor activity in C57BL/6J mice over a wide dose range and blocked cocaine-induced locomotor stimulant action.

  13. Dopamine and angiotensin type 2 receptors cooperatively inhibit sodium transport in human renal proximal tubule cells.

    PubMed

    Gildea, John J; Wang, Xiaoli; Shah, Neema; Tran, Hanh; Spinosa, Michael; Van Sciver, Robert; Sasaki, Midori; Yatabe, Junichi; Carey, Robert M; Jose, Pedro A; Felder, Robin A

    2012-08-01

    Little is known regarding how the kidney shifts from a sodium and water reclaiming state (antinatriuresis) to a state where sodium and water are eliminated (natriuresis). In human renal proximal tubule cells, sodium reabsorption is decreased by the dopamine D(1)-like receptors (D(1)R/D(5)R) and the angiotensin type 2 receptor (AT(2)R), whereas the angiotensin type 1 receptor increases sodium reabsorption. Aberrant control of these opposing systems is thought to lead to sodium retention and, subsequently, hypertension. We show that D(1)R/D(5)R stimulation increased plasma membrane AT(2)R 4-fold via a D(1)R-mediated, cAMP-coupled, and protein phosphatase 2A-dependent specific signaling pathway. D(1)R/D(5)R stimulation also reduced the ability of angiotensin II to stimulate phospho-extracellular signal-regulated kinase, an effect that was partially reversed by an AT(2)R antagonist. Fenoldopam did not increase AT(2)R recruitment in renal proximal tubule cells with D(1)Rs uncoupled from adenylyl cyclase, suggesting a role of cAMP in mediating these events. D(1)Rs and AT(2)Rs heterodimerized and cooperatively increased cAMP and cGMP production, protein phosphatase 2A activation, sodium-potassium-ATPase internalization, and sodium transport inhibition. These studies shed new light on the regulation of renal sodium transport by the dopaminergic and angiotensin systems and potential new therapeutic targets for selectively treating hypertension.

  14. Brominated and radioiodinated derivatives of methylphenidate (MP): Potential imaging agents for the dopamine (DA) transporter

    SciTech Connect

    Pan, D.; Gatley, S.J.; Dewey, S.L.

    1994-05-01

    MP (Ritalin) is a psychomotor stimulant used in the treatment of attention-deficit hyperactivity disorder. The therapeutic properties of MP are thought to be mediated by its binding to a site on the DA transporter, resulting in inhibition of DA reuptake and enhanced levels of synaptic dopamine. MP also inhibits reuptake of norepinephrine (NE) in vitro. MP has two chiral centers, but its pharmacological activity is believed due solely to the d-threo isomer. We have found that d,l-threo-C-11 MP has favorable properties for PET studies, and therefore examined the effects of incorporating halogen atoms into the phenyl ring of MP, with a view to preparing C-11 and I-123 MP analogs as potential PET/SPECT tracers. We synthesized the 2-, 3- and 4-bromo MP analogs from the corresponding bromophenylacetonitriles by modification of the original synthesis of MP. In in vitro binding assays all three d,l-threo bromo compounds had higher affinities than MP for DA transporter sites labeled with tritiated WIN 35,428 (3->4-, 2->MP). They also showed high activity with NE reuptake sites labeled with tritiated nisoxetine. They were active in vivo as demonstrated by inhibition of heart uptake of tritiated NE in the mouse, and elevation of striatal extracellular DA (microdialysis) and stimulation of locomotor activity in the rat.

  15. Binding site residues control inhibitor selectivity in the human norepinephrine transporter but not in the human dopamine transporter.

    PubMed

    Andersen, Jacob; Ringsted, Kristoffer B; Bang-Andersen, Benny; Strømgaard, Kristian; Kristensen, Anders S

    2015-10-27

    The transporters for norepinephrine and dopamine (NET and DAT, respectively) constitute the molecular targets for recreational drugs and therapeutics used in the treatment of psychiatric disorders. Despite a strikingly similar amino acid sequence and predicted topology between these transporters, some inhibitors display a high degree of selectivity between NET and DAT. Here, a systematic mutational analysis of non-conserved residues within the extracellular entry pathway and the high affinity binding site in NET and DAT was performed to examine their role for selective inhibitor recognition. Changing the six diverging residues in the central binding site of NET to the complementary residues in DAT transferred a DAT-like pharmacology to NET, showing that non-conserved binding site residues in NET are critical determinants for inhibitor selectivity. In contrast, changing the equivalent residues in the central site of DAT to the corresponding residues in NET had modest effects on the same inhibitors, suggesting that non-conserved binding site residues in DAT play a minor role for selective inhibitor recognition. Our data points towards distinct structural determinants governing inhibitor selectivity in NET and DAT, and provide important new insight into the molecular basis for NET/DAT selectivity of therapeutic and recreational drugs.

  16. Binding site residues control inhibitor selectivity in the human norepinephrine transporter but not in the human dopamine transporter

    PubMed Central

    Andersen, Jacob; Ringsted, Kristoffer B.; Bang-Andersen, Benny; Strømgaard, Kristian; Kristensen, Anders S.

    2015-01-01

    The transporters for norepinephrine and dopamine (NET and DAT, respectively) constitute the molecular targets for recreational drugs and therapeutics used in the treatment of psychiatric disorders. Despite a strikingly similar amino acid sequence and predicted topology between these transporters, some inhibitors display a high degree of selectivity between NET and DAT. Here, a systematic mutational analysis of non-conserved residues within the extracellular entry pathway and the high affinity binding site in NET and DAT was performed to examine their role for selective inhibitor recognition. Changing the six diverging residues in the central binding site of NET to the complementary residues in DAT transferred a DAT-like pharmacology to NET, showing that non-conserved binding site residues in NET are critical determinants for inhibitor selectivity. In contrast, changing the equivalent residues in the central site of DAT to the corresponding residues in NET had modest effects on the same inhibitors, suggesting that non-conserved binding site residues in DAT play a minor role for selective inhibitor recognition. Our data points towards distinct structural determinants governing inhibitor selectivity in NET and DAT, and provide important new insight into the molecular basis for NET/DAT selectivity of therapeutic and recreational drugs. PMID:26503701

  17. Dopamine reuptake transporter (DAT) "inverse agonism"--a novel hypothesis to explain the enigmatic pharmacology of cocaine.

    PubMed

    Heal, David J; Gosden, Jane; Smith, Sharon L

    2014-12-01

    The long held view is cocaine's pharmacological effects are mediated by monoamine reuptake inhibition. However, drugs with rapid brain penetration like sibutramine, bupropion, mazindol and tesofensine, which are equal to or more potent than cocaine as dopamine reuptake inhibitors, produce no discernable subjective effects such as drug "highs" or euphoria in drug-experienced human volunteers. Moreover they are dysphoric and aversive when given at high doses. In vivo experiments in animals demonstrate that cocaine's monoaminergic pharmacology is profoundly different from that of other prescribed monoamine reuptake inhibitors, with the exception of methylphenidate. These findings led us to conclude that the highly unusual stimulant profile of cocaine and related compounds, eg methylphenidate, is not mediated by monoamine reuptake inhibition alone. We describe the experimental findings which suggest cocaine serves as a negative allosteric modulator to alter the function of the dopamine reuptake transporter (DAT) and reverse its direction of transport. This results in a firing-dependent, retro-transport of dopamine into the synaptic cleft. The proposed mechanism of cocaine is, therefore, different from other small molecule negative allostereric modulators of the monoamine reuptake transporters, eg SoRI-6238, which merely reduce the rate of inward transport. Because the physiological role of DAT is to remove dopamine from the synapse and the action of cocaine is the opposite of this, we have postulated that cocaine's effect is analogous to an inverse agonist. If this hypothesis is validated then cocaine is the prototypical compound that exemplifies a new class of monoaminergic drugs; DAT "inverse agonists". This article is part of the Special Issue entitled 'CNS Stimulants'.

  18. Dosimetry of an iodine-123-labeled tropane to image dopamine transporters

    SciTech Connect

    Mozley, P.D.; Stubbs, J.B.; Kim, H.J.

    1996-01-01

    N-(3-iodopropen-2-yl)-2{beta}-carbomethoxy-3{beta}(4-chlorophenyl)tropane (IPT) is an analog of cocaine that selectively binds the presynaptic dopamine transporter. The present study sought to measure the radiation dosimetry of IPT in seven healthy human volunteers. Dynamic renal scans were acquired immediately after the intravenous administration of 165 {+-} 16 MBq (4.45 {+-} 0.42 mCi) of [{sup 123}I]IPT. Between 7 and 12 sets of whole-body scans were acquired over the next 24 hr. The 24-hr renal excretion fractions were measured from conjugate emission scans of 7-11 discreet voided urine specimens. The fraction of the administered dose in 11 organs and each urine specimen was quantified from the attenuation-corrected geometric mean counts in opposing views. Subject-specific residence times were evaluated for each subject independently by fitting the time-activity curves to a multicompartmental model. The radiation doses were estimated with the MIRD technique from the residence times for each subject individually before any results were averaged. The findings showed that IPT was excreted rapidly by the renal system. There were no reservoirs of retained activity outside the basal ganglia, where SPECT images in these subjects showed that the mean ratio of caudate to calcarine cortex averaged 25:1 at 3 hr after injection (range 19.6-32 hr). The basal ganglia received a radiation dose of 0.028 mGy/MBq (0.10 rad/mCi). The dose-limiting organ in men was the stomach, which received an estimated 0.11 mGy/MBq (0.37 rad/mCi). In women, the critical organ was the urinary bladder at 0.14 mGy/MBq (0.51 rad/mCi). Relatively high-contrast images of the presynaptic dopamine transporters in the basal ganglia can be acquired with 185 MBq (5 mCi) of [{sup 123}I]IPT. The radiation exposure that results is significantly less than the maximum allowed by current safety guidelines for research volunteers. 33 refs., 4 figs., 3 tabs.

  19. Studies of the Biogenic Amine Transporters 15. Identification of Novel Allosteric Dopamine Transporter Ligands with Nanomolar Potency

    PubMed Central

    Ananthan, Subramaniam; Partilla, John S.; Saini, Surendra K.; Moukha-Chafiq, Omar; Pathak, Vibha; Baumann, Michael H.

    2015-01-01

    Novel allosteric modulators of the dopamine transporter (DAT) have been identified. We have shown previously that SRI-9804 [N-(diphenylmethyl)-2-phenyl-4-quinazolinamine], SRI-20040 [N-(2,2-diphenylethyl)-2-phenyl-4-quinazolinamine], and SRI-20041 [N-(3,3-diphenylpropyl)-2-phenyl-4-quinazolinamine] partially inhibit [125I]RTI-55 ([125I]3β-(4′-iodophenyl)tropan-2β-carboxylic acid methyl ester) binding and [3H]dopamine ([3H]DA) uptake, slow the dissociation rate of [125I]RTI-55 from the DAT, and allosterically modulate d-amphetamine–induced, DAT-mediated DA release. We synthesized and evaluated the activity of >500 analogs of these ligands and report here on 36 selected compounds. Using synaptosomes prepared from rat caudate, we conducted [3H]DA uptake inhibition assays, DAT binding assays with [3H]WIN35428 ([3H]2β-carbomethoxy-3β-(4-fluorophenyl)tropane), and DAT-mediated release assays with either [3H]MPP+ ([3H]1-methyl-4-phenylpyridinium) or [3H]DA. We observed three groups of [3H]DA uptake inhibitors: 1) full-efficacy agents with a one-site fit, 2) full-efficacy agents with a two-site fit, and 3) partial-efficacy agents with a one-site fit—the focus of further studies. These agents partially inhibited DA, serotonin, and norepinephrine uptake, yet were much less potent at inhibiting [3H]WIN35428 binding to the DAT. For example, SRI-29574 [N-(2,2-diphenylethyl)-2-(imidazo[1,2-a]pyridin-6-yl)quinazolin-4-amine] partially inhibited DAT uptake, with an IC50 = 2.3 ± 0.4 nM, without affecting binding to the DAT. These agents did not alter DAT-mediated release of [3H]MPP+ in the absence or presence of 100 nM d-amphetamine. SRI-29574 had no significant effect on the d-amphetamine EC50 or Emax value for DAT-mediated release of [3H]MPP+. These studies demonstrate the existence of potent DAT ligands that partially block [3H]DA uptake, without affecting DAT binding or d-amphetamine–induced [3H]MPP+ release. These compounds may prove to be useful probes of

  20. Function of dopamine transporter is compromised in DYT1 transgenic animal model in vivo

    PubMed Central

    Hewett, Jeff; Johansen, Peter; Sharma, Nutan; Standaert, David; Balcioglu, Aygul

    2011-01-01

    Early onset torsion dystonia (DYT1), the most common form of hereditary primary dystonia, is caused by a mutation in the TOR1A gene, which codes for the protein, torsinA. We previously examined the effect of the human mutant torsinA on striatal dopaminergic function in a conventional transgenic mouse model of DYT1 dystonia (hMT1), in which human mutant torsinA is expressed under the cytomegalovirus promotor. Systemic administration of amphetamine did not increase dopamine (DA) release as efficiently in these mice as compared with wild-type transgenic and non-transgenic mice. We, now, studied the contribution of the DA transporter (DAT) to amphetamine-induced DA release in hMT1 transgenic mice using in vivo no-net flux microdialysis. This method applies different concentrations of DA through the microdialysis probe and measures DA concentration at the output of the probe following an equilibrium period. The slope (extraction fraction) is the measure of the DAT activity in vivo. The slope for hMT1 transgenic mice was 0.58 ± 0.07 and for non-transgenic animals, 0.87 ± 0.06 (p < 0.05). We further investigated the efficacy of nomifensine (a specific DAT inhibitor) in inhibiting amphetamine-induced DA release. Local application of nomifensine 80 min before the systemic application of amphetamine inhibited DA release in both transgenic mice and their non-transgenic littermates. The efficiency of the inhibition appeared to be different, with mean values of 48% for hMT1 transgenic mice versus 84% for non-transgenic littermates. Moreover, we have evaluated basal and amphetamine-induced locomotion in hMT1 transgenic mice compared with their non-transgenic littermates, using an O-maze behavioral chamber. Basal levels of locomotion in the hMT1 transgenic mice showed that they moved much less than their non-transgenic littermates (0.9 ± 0.3 m for transgenic mice vs. 2.4 ± 0.7 m for non-transgenic littermates, p < 0.05). This relative reduction in locomotion was also observed

  1. Association between reward-related activation in the ventral striatum and trait reward sensitivity is moderated by dopamine transporter genotype.

    PubMed

    Hahn, Tim; Heinzel, Sebastian; Dresler, Thomas; Plichta, Michael M; Renner, Tobias J; Markulin, Falko; Jakob, Peter M; Lesch, Klaus-Peter; Fallgatter, Andreas J

    2011-10-01

    The impact of individual differences on human reward processing has been a focus of research in recent years, particularly, as they are associated with a variety of neuropsychiatric diseases including addiction and attention-deficit/hyperactivity disorder. Studies exploring the neural basis of individual differences in reward sensitivity have consistently implicated the ventral striatum (VS) as a core component of the human reward system. However, the mechanisms of dopaminergic neurotransmission underlying ventral striatal activation as well as trait reward sensitivity remain speculative. We addressed this issue by investigating the triadic interplay between VS reactivity during reward anticipation using functional magnetic resonance imaging, trait reward sensitivity, and dopamine (DA) transporter genotype (40-bp 3'VNTR of DAT, SLC6A3) affecting synaptic DA neurotransmission. Our results show that DAT variation moderates the association between VS-reactivity and trait reward sensitivity. Specifically, homozygote carriers of the DAT 10-repeat allele exhibit a strong positive correlation between reward sensitivity and reward-related VS activity whereas this relationship is absent in the DAT 9-repeat allele carriers. We discuss the possibility that this moderation of VS-trait relation might arise from DAT-dependent differences in DA availability affecting synaptic plasticity within the VS. Generally, studying the impact of dopaminergic gene variations on the relation between reward-related brain activity and trait reward sensitivity might facilitate the investigation of complex mechanisms underlying disorders linked to dysregulation of DA neurotransmission.

  2. Dissociable roles of dopamine and serotonin transporter function in a rat model of negative urgency.

    PubMed

    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.

  3. The metal transporter SMF-3/DMT-1 mediates aluminum-induced dopamine neuron degeneration.

    PubMed

    VanDuyn, Natalia; Settivari, Raja; LeVora, Jennifer; Zhou, Shaoyu; Unrine, Jason; Nass, Richard

    2013-01-01

    Aluminum (Al(3+)) is the most prevalent metal in the earth's crust and is a known human neurotoxicant. Al(3+) has been shown to accumulate in the substantia nigra of patients with Parkinson's disease (PD), and epidemiological studies suggest correlations between Al(3+) exposure and the propensity to develop both PD and the amyloid plaque-associated disorder Alzheimer's disease (AD). Although Al(3+) exposures have been associated with the development of the most common neurodegenerative disorders, the molecular mechanism involved in Al(3+) transport in neurons and subsequent cellular death has remained elusive. In this study, we show that a brief exposure to Al(3+) decreases mitochondrial membrane potential and cellular ATP levels, and confers dopamine (DA) neuron degeneration in the genetically tractable nematode Caenorhabditis elegans (C. elegans). Al(3+) exposure also exacerbates DA neuronal death conferred by the human PD-associated protein α-synuclein. DA neurodegeneration is dependent on SMF-3, a homologue to the human divalent metal transporter (DMT-1), as a functional null mutation partially inhibits the cell death. We also show that SMF-3 is expressed in DA neurons, Al(3+) exposure results in a significant decrease in protein levels, and the neurodegeneration is partially dependent on the PD-associated transcription factor Nrf2/SKN-1 and caspase Apaf1/CED-4. Furthermore, we provide evidence that the deletion of SMF-3 confers Al(3+) resistance due to sequestration of Al(3+) into an intracellular compartment. This study describes a novel model for Al(3+)-induced DA neurodegeneration and provides the first molecular evidence of an animal Al(3+) transporter.

  4. Dissociable Roles of Dopamine and Serotonin Transporter Function in a Rat Model of Negative Urgency

    PubMed Central

    Yates, Justin R.; Darna, Mahesh; Gipson, Cassandra D.; Dwoskin, Linda P.; Bardo, Michael T.

    2015-01-01

    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 [3H]DA and [3H]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. PMID:26005123

  5. Slow-onset, long-duration, alkyl analogues of methylphenidate with enhanced selectivity for the dopamine transporter.

    PubMed

    Froimowitz, Mark; Gu, Yonghong; Dakin, Les A; Nagafuji, Pamela M; Kelley, Charles J; Parrish, Damon; Deschamps, Jeffrey R; Janowsky, Aaron

    2007-01-25

    Methylphenidate analogues, in which the carbomethoxy has been replaced by an alkyl group and with different phenyl substituents, have been synthesized and tested in monoamine transporter assays. As predicted from a pharmacophore model, most of the RR/SS diastereomers showed high potency as dopamine reuptake inhibitors. Analogues with a 4-chlorophenyl group and an unbranched initial alkyl atom had consistently enhanced selectivity for the dopamine transporter. The most potent compounds were those with a three- or four-carbon chain. The "inactive" RS/SR diastereomers showed substantial activity when the phenyl substituent was 3,4-dichloro. On a locomotor assay, one compound was found to have a slow onset and a long duration of action. The activity of these compounds provides additional evidence for a conformational/superposition model of methylphenidate with cocaine-like structures. A ketone analogue, obtained by hydrogenating a previously described vinylogous amide, had activity similar to that of methylphenidate.

  6. PET evaluation of the dopamine system of the human brain

    SciTech Connect

    Volkow, N.D.; Fowler, J.S.; Gatley, S. |

    1996-07-01

    Dopamine plays a pivotal role in the regulation and control of movement, motivation and cognition. It also is closely linked to reward, reinforcement and addiction. Abnormalities in brain dopamine are associated with many neurological and psychiatric disorders including Parkinson`s disease, schizophrenia and substance abuse. This close association between dopamine and neurological and psychiatric diseases and with substance abuse make it an important topic in research in the neurosciences and an important molecular target in drug development. PET enables the direct measurement of components of the dopamine system in the living human brain. It relies on radiotracers which label dopamine receptors, dopamine transporters, precursors of dopamine or compounds which have specificity for the enzymes which degrade dopamine. Additionally, by using tracers that provide information on regional brain metabolism or blood flow as well as neurochemically specific pharmacological interventions, PET can be used to assess the functional consequences of change in brain dopamine activity. PET dopamine measurements have been used to investigate the normal human brain and its involvement in psychiatric and neurological diseases. It has also been used in psychopharmacological research to investigate dopamine drugs used in the treatment of Parkinson`s disease and of schizophrenia as well as to investigate the effects of drugs of abuse on the dopamine system. Since various functional and neurochemical parameters can be studied in the same subject, PET enables investigation of the functional integrity of the dopamine system in the human brain and investigation of the interactions of dopamine with other neurotransmitters. This paper summarizes the different tracers and experimental strategies developed to evaluate the various elements of the dopamine system in the human brain with PET and their applications to clinical research. 254 refs., 7 figs., 3 tabs.

  7. Synthesis and ligand binding studies of 4'-iodobenzoyl esters of tropanes and piperidines at the dopamine transporter.

    PubMed

    Singh, S; Basmadjian, G P; Avor, K S; Pouw, B; Seale, T W

    1997-08-01

    Four analogs and two homologs of cocaine, designed as potent cocaine antagonists, were synthesized. The SN2 reaction between ecgonine methyl ester (13) or appropriately substituted piperidinol (19, 21) and appropriately substituted 4-iodobenzoyl chloride gave 4-iodobenzoyl esters of tropanes and piperidines (5-8). 2'-Hydroxycocaine (9) was obtained from 2'-acetoxycocaine (12) by selective transesterification with MeOH saturated with dry HCl gas. 2'-Acetoxycocaine (12) was synthesized from acetylsalicyloyl chloride (23) and ecgonine methyl ester (13). The binding affinities of these compounds were determined at the dopamine transporter for the displacement of [3H]WIN-35428. An iodo group substitution at the 4'-position of cocaine decreased dopamine transporter binding potency, while a hydroxy or acetoxy group at the 2'-position exhibited increased binding potency for the dopamine transporter compared to cocaine (10- and 3.58-fold, respectively). 2'-Hydroxylation also enhanced the bidning potency of 4'-iodococaine (5) by 10-fold. Replacement of the tropane ring with piperidine led to poor binding affinities.

  8. Extended access to methamphetamine self-administration up-regulates dopamine transporter levels 72 hours after withdrawal in rats.

    PubMed

    D'Arcy, Christina; Luevano, Joe E; Miranda-Arango, Manuel; Pipkin, Joseph A; Jackson, Jonathan A; Castañeda, Eddie; Gosselink, Kristin L; O'Dell, Laura E

    2016-01-01

    Previous studies have demonstrated that there are persistent changes in dopamine systems following withdrawal from methamphetamine (METH). This study examined changes in striatal dopamine transporter (DAT), tyrosine hydroxylase (TH) and dopamine receptor 2 (D2) 72 h after withdrawal from METH intravenous self- administration (IVSA). Rats were given limited (1h) or extended (6h) access to METH IVSA (0.05 mg/kg/0.1 ml infusion) for 22 days. Controls did not receive METH IVSA. The rats given extended access to IVSA displayed higher METH intake during the first hour of drug access compared to rats given limited access. Extended access to METH also produced a concomitant increase in striatal DAT levels relative to drug-naïve controls. There were no changes in TH or D2 levels across groups. Previous studies have reported a decrease in striatal DAT levels during protracted periods (>7 days) of withdrawal from METH IVSA. This study extends previous work by showing an increase in striatal DAT protein expression during an earlier time point of withdrawal from this drug. These results are an important step toward understanding the dynamic changes in dopamine systems that occur during different time points of withdrawal from METH IVSA.

  9. Role of the dopamine transporter in the action of psychostimulants, nicotine, and other drugs of abuse.

    PubMed

    Zhu, J; Reith, M E A

    2008-11-01

    A number of studies over the last two decades have demonstrated the critical importance of dopamine (DA) in the behavioral pharmacology and addictive properties of abused drugs. The DA transporter (DAT) is a major target for drugs of abuse in the category of psychostimulants, and for methylphenidate (MPH), a drug used for treating attention deficit hyperactivity disorder (ADHD), which can also be a psychostimulant drug of abuse. Other drugs of abuse such as nicotine, ethanol, heroin and morphine interact with the DAT in more indirect ways. Despite the different ways in which drugs of abuse can affect DAT function, one evolving theme in all cases is regulation of the DAT at the level of surface expression. DAT function is dynamically regulated by multiple intracellular and extracellular signaling pathways and several protein-protein interactions. In addition, DAT expression is regulated through the removal (internalization) and recycling of the protein from the cell surface. Furthermore, recent studies have demonstrated that individual differences in response to novel environments and psychostimulants can be predicted based on individual basal functional DAT expression. Although current knowledge of multiple factors regulating DAT activity has greatly expanded, many aspects of this regulation remain to be elucidated; these data will enable efforts to identify drugs that might be used therapeutically for drug dependence therapeutics.

  10. Tissue Specific Expression of Cre in Rat Tyrosine Hydroxylase and Dopamine Active Transporter-Positive Neurons

    PubMed Central

    Liu, Zhenyi; Brown, Andrew; Fisher, Dan; Wu, Yumei; Warren, Joe; Cui, Xiaoxia

    2016-01-01

    The rat is a preferred model system over the mouse for neurological studies, and cell type-specific Cre expression in the rat enables precise ablation of gene function in neurons of interest, which is especially valuable for neurodegenerative disease modeling and optogenetics. Yet, few such Cre rats are available. Here we report the characterization of two Cre rats, tyrosine hydroxylase (TH)-Cre and dopamine active transporter (DAT or Slc6a3)-Cre, by using a combination of immunohistochemistry (IHC) and mRNA fluorescence in situ hybridization (FISH) as well as a fluorescent reporter for Cre activity. We detected Cre expression in expected neurons in both Cre lines. Interestingly, we also found that in Th-Cre rats, but not DAT-Cre rats, Cre is expressed in female germ cells, allowing germline excision of the floxed allele and hence the generation of whole-body knockout rats. In summary, our data demonstrate that targeted integration of Cre cassette lead to faithful recapitulation of expression pattern of the endogenous promoter, and mRNA FISH, in addition to IHC, is an effective method for the analysis of the spatiotemporal gene expression patterns in the rat brain, alleviating the dependence on high quality antibodies that are often not available against rat proteins. The Th-Cre and the DAT-Cre rat lines express Cre in selective subsets of dopaminergic neurons and should be particularly useful for researches on Parkinson’s disease. PMID:26886559

  11. Dopamine Transporter Gene Variant Affecting Expression in Human Brain is Associated with Bipolar Disorder

    PubMed Central

    Pinsonneault, Julia K; Han, Dawn D; Burdick, Katherine E; Kataki, Maria; Bertolino, Alessandro; Malhotra, Anil K; Gu, Howard H; Sadee, Wolfgang

    2011-01-01

    The gene encoding the dopamine transporter (DAT) has been implicated in CNS disorders, but the responsible polymorphisms remain uncertain. To search for regulatory polymorphisms, we measured allelic DAT mRNA expression in substantia nigra of human autopsy brain tissues, using two marker SNPs (rs6347 in exon 9 and rs27072 in the 3′-UTR). Allelic mRNA expression imbalance (AEI), an indicator of cis-acting regulatory polymorphisms, was observed in all tissues heterozygous for either of the two marker SNPs. SNP scanning of the DAT locus with AEI ratios as the phenotype, followed by in vitro molecular genetics studies, demonstrated that rs27072 C>T affects mRNA expression and translation. Expression of the minor T allele was dynamically regulated in transfected cell cultures, possibly involving microRNA interactions. Both rs6347 and rs3836790 (intron8 5/6 VNTR) also seemed to affect DAT expression, but not the commonly tested 9/10 VNTR in the 3′UTR (rs28363170). All four polymorphisms (rs6347, intron8 5/6 VNTR, rs27072 and 3′UTR 9/10 VNTR) were genotyped in clinical cohorts, representing schizophrenia, bipolar disorder, depression, and controls. Only rs27072 was significantly associated with bipolar disorder (OR=2.1, p=0.03). This result was replicated in a second bipolar/control population (OR=1.65, p=0.01), supporting a critical role for DAT regulation in bipolar disorder. PMID:21525861

  12. 2'-substituted analogs of cocaine: synthesis and dopamine transporter binding potencies.

    PubMed

    el-Moselhy, T F; Avor, K S; Basmadjian, G P

    2001-09-01

    A series of 2'-substituted cocaine analogs (4-8) was prepared and evaluated in an in vitro dopamine transporter (DAT) binding assay. Compounds 4-7 were prepared by esterifying the 3 beta-hydroxyl group of ecgonine methyl ester (3) using the appropriate acid chloride in the presence of Et3N and benzene. Compound 3 was obtained from cocaine (1) by hydrolysis using 1N HCl to afford ecgonine.HCl which was subjected to acid catalyzed esterification using methanol saturated with HCl gas. Compound 8 was obtained by hydrogenation of 7 using H2/Pd-C. The IC50 values were calculated from displacement experiment of the radioligand [3H]WIN-35,428 (2). 2'-Aminococaine (8) showed high binding affinity to the DAT (14- and 1.3-fold more active than cocaine and the radioligand 2, respectively). These results, along with previous results, emphasize the importance of a hydrogen-bond donor group at the 2'-position of cocaine to enhance binding affinity to the DAT.

  13. Individual differences in impulsive action and dopamine transporter function in rat orbitofrontal cortex.

    PubMed

    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.

  14. Epigenetic Regulation of Dopamine Transporter mRNA Expression in Human Neuroblastoma Cells

    PubMed Central

    Green, Ashley L.; Hossain, Muhammad M.; Tee, Siew C.; Zarbl, Helmut; Guo, Grace L.; Richardson, Jason R.

    2016-01-01

    The dopamine transporter (DAT) is a key regulator of dopaminergic neurotransmission. As such, proper regulation of DAT expression is important to maintain homeostasis, and disruption of DAT expression can lead to neurobehavioral dysfunction. Based on genomic features within the promoter of the DAT gene, there is potential for DAT expression to be regulated through epigenetic mechanisms, including DNA methylation and histone acetylation. However, the relative contribution of these mechanisms to DAT expression has not been empirically determined. Using pharmacologic and genetic approaches, we demonstrate that inhibition of DNA methyltransferase (DNMT) activity increased DAT mRNA approximately 1.5–2 fold. This effect was confirmed by siRNA knockdown of DNMT1. Likewise, the histone deacetylase (HDAC) inhibitors valproate and butyrate also increased DAT mRNA expression, but the response was much more robust with expression increasing over tenfold. Genetic knockdown of HDAC1 by siRNA also increased DAT expression, but not to the extent seen with pharmacological inhibition, suggesting additional isoforms of HDAC or other targets may contribute to the observed effect. Together, these data identify the relative contribution of DNMTs and HDACs in regulating expression. These finding may aid in understanding the mechanistic basis for changes in DAT expression in normal and pathophysiological states. PMID:25963949

  15. Comparison of striatal dopamine transporter levels in chronic heroin-dependent and methamphetamine-dependent subjects.

    PubMed

    Yuan, Jie; Liu, Xing Dang; Han, Mei; Lv, Rong Bin; Wang, Yuan Kai; Zhang, Guang Ming; Li, Yu

    2017-01-01

    To compare the effects of heroin and methamphetamine (METH) addiction on dopamine transporters (DATs) in the same dose and duration, we assessed DAT levels in the striatum by (99m) Tc-TRODAT-1 single-photon emission computed tomography (SPECT) brain images in people with heroin and METH dependence. We recruited 21 healthy human controls, 23 heroin-dependent subjects and 25 METH abusers. The heroin- and METH-dependent subjects exhibited negative urine toxicology after undergoing physiological detoxification. All subjects underwent SPECT brain imaging, and specific tracer uptake ratios (SURs) were assessed bilaterally in the regions of interest. A significant SUR reduction in heroin-dependent subjects and METH-dependent subjects compared with healthy controls was found in the left striatum, right striatum, left caudate nucleus, right caudate nucleus, left putamen and right putamen. There were no significant differences in the heroin group and METH group for the left striatum, right striatum, left caudate nucleus, right caudate nucleus, left putamen and right putamen. The scores of craving, HAMA (Hamilton Anxiety Rating Scale), in heroin abusers were lower than in the METH abusers. Our results show that people with heroin and METH dependence who are currently abstinent had lower DAT levels in the striatum than healthy controls. There were no differences in striatal DAT in heroin and METH users. These results suggest that chronic heroin and METH abuse appears to produce similar effects in striatal DAT in humans. METH users may have more serious craving and anxiety symptoms than heroin users with prolonged abstinence.

  16. Molecular mechanisms of cocaine reward: Combined dopamine and serotonin transporter knockouts eliminate cocaine place preference

    PubMed Central

    Sora, Ichiro; Hall, F. Scott; Andrews, Anne M.; Itokawa, Masanari; Li, Xiao-Fei; Wei, Hong-Bing; Wichems, Christine; Lesch, Klaus-Peter; Murphy, Dennis L.; Uhl, George R.

    2001-01-01

    Cocaine blocks uptake by neuronal plasma membrane transporters for dopamine (DAT), serotonin (SERT), and norepinephrine (NET). Cocaine reward/reinforcement has been linked to actions at DAT or to blockade of SERT. However, knockouts of neither DAT, SERT, or NET reduce cocaine reward/reinforcement, leaving substantial uncertainty about cocaine's molecular mechanisms for reward. Conceivably, the molecular bases of cocaine reward might display sufficient redundancy that either DAT or SERT might be able to mediate cocaine reward in the other's absence. To test this hypothesis, we examined double knockout mice with deletions of one or both copies of both the DAT and SERT genes. These mice display viability, weight gain, histologic features, neurochemical parameters, and baseline behavioral features that allow tests of cocaine influences. Mice with even a single wild-type DAT gene copy and no SERT copies retain cocaine reward/reinforcement, as measured by conditioned place-preference testing. However, mice with no DAT and either no or one SERT gene copy display no preference for places where they have previously received cocaine. The serotonin dependence of cocaine reward in DAT knockout mice is thus confirmed by the elimination of cocaine place preference in DAT/SERT double knockout mice. These results provide insights into the brain molecular targets necessary for cocaine reward in knockout mice that develop in their absence and suggest novel strategies for anticocaine medication development. PMID:11320258

  17. Effects of chronic cocaine administration on dopamine transporter mRNA and protein in the rat.

    PubMed

    Letchworth, S R; Daunais, J B; Hedgecock, A A; Porrino, L J

    1997-03-07

    Male Sprague-Dawley rats were administered cocaine (10, 15 or 25 mg/kg) or vehicle, i.p., once daily for 8 consecutive days and killed 1 h after the last injection. Acute cocaine administration produced dose-dependent increases in spontaneous locomotor activity. These levels of activity were further enhanced by 8 days of chronic treatment, indicating the emergence of behavioral sensitization. Chronic cocaine administration resulted in dose-dependent decreases in the density of dopamine transporter (DAT) mRNA in both the substantia nigra pars compacta and ventral tegmental area as shown by in situ hybridization histochemistry. Changes in DAT binding sites were assessed using [3H]mazindol quantitative autoradiography. In contrast to the levels of mRNA, there were few changes in the number of [3H]mazindol binding sites. Although the density of binding sites was unaltered in most regions, [3H]mazindol binding was increased in the anterior nucleus accumbens. This study extends previous findings by demonstrating the dose-dependent nature of the changes in DAT mRNA that accompanies chronic cocaine administration. The levels of DAT binding sites within the dorsal and ventral striatum, however, were largely unchanged. This mismatch suggests that cocaine may differentially influence the gene expression of DAT in the ventral midbrain as compared to the density of DAT binding sites in the basal forebrain.

  18. [Role of dopamine transporter gene (DAT1) polymorphisms in personality traits variation].

    PubMed

    Kazantseva, A V; Gaĭsina, D A; Malykh, S B; Khusnutdinova, E K

    2009-08-01

    According to psychobiological model of personality proposed by Cloninger, personality traits characterizing enhanced tendency to novel stimuli, impulsivity and sociability are influenced by dopaminergic system functioning. The present study considered both the main effect of two polymorphic loci (VNTR and 2319G>A) in dopamine transporter gene (DAT1) and the role of distinct DAT1 gene haplotypes in personality traits variation in 592 healthy individuals belonging to different ethnicities (men and women). The results of the study revealed the involvement of VNTR and 2319G>A polymorphisms in Novelty Seeking variation and the main effect of 2319G>A polymorphism on Reward Dependence (TCI) observed in Russian females. Moreover, DAT1 gene haplotype effect on Novelty Seeking in Russian females and on Persistence (TCI) in Tatar females was demonstrated. Reported in the current study results pointed to the involvement of dopaminergic system (DAT1 gene in particular) in variation of personality traits characterizing the tendency to novel stimuli, purposefulness, and sociability specifically in women.

  19. Child dopamine active transporter 1 genotype and parenting: evidence for evocative gene-environment correlations.

    PubMed

    Hayden, Elizabeth P; Hanna, Brigitte; Sheikh, Haroon I; Laptook, Rebecca S; Kim, Jiyon; Singh, Shiva M; Klein, Daniel N

    2013-02-01

    The dopamine active transporter 1 (DAT1) gene is implicated in psychopathology risk. Although the processes by which this gene exerts its effects on risk are poorly understood, a small body of research suggests that the DAT1 gene influences early emerging negative emotionality, a marker of children's psychopathology risk. As child negative emotionality evokes negative parenting practices, the DAT1 gene may also play a role in gene-environment correlations. To test this model, children (N = 365) were genotyped for the DAT1 gene and participated in standardized parent-child interaction tasks with their primary caregiver. The DAT1 gene 9-repeat variant was associated with child negative affect expressed toward the parent during parent-child interactions, and parents of children with a 9-repeat allele exhibited more hostility and lower guidance/engagement than parents of children without a 9-repeat allele. These gene-environment associations were partially mediated by child negative affect toward the parent. The findings implicate a specific polymorphism in eliciting negative parenting, suggesting that evocative associations play a role in elevating children's risk for emotional trajectories toward psychopathology risk.

  20. Ca(2+)/calmodulin-dependent protein kinase IIα (αCaMKII) controls the activity of the dopamine transporter: implications for Angelman syndrome.

    PubMed

    Steinkellner, Thomas; Yang, Jae-Won; Montgomery, Therese R; Chen, Wei-Qiang; Winkler, Marie-Therese; Sucic, Sonja; Lubec, Gert; Freissmuth, Michael; Elgersma, Ype; Sitte, Harald H; Kudlacek, Oliver

    2012-08-24

    The dopamine transporter (DAT) is a crucial regulator of dopaminergic neurotransmission, controlling the length and brevity of dopaminergic signaling. DAT is also the primary target of psychostimulant drugs such as cocaine and amphetamines. Conversely, methylphenidate and amphetamine are both used clinically in the treatment of attention-deficit hyperactivity disorder and narcolepsy. The action of amphetamines, which induce transport reversal, relies primarily on the ionic composition of the intra- and extracellular milieus. Recent findings suggest that DAT interacting proteins may also play a significant role in the modulation of reverse dopamine transport. The pharmacological inhibition of the serine/threonine kinase αCaMKII attenuates amphetamine-triggered DAT-mediated 1-methyl-4-phenylpyridinium (MPP(+)) efflux. More importantly, αCaMKII has also been shown to bind DAT in vitro and is therefore believed to be an important player within the DAT interactome. Herein, we show that αCaMKII co-immunoprecipitates with DAT in mouse striatal synaptosomes. Mice, which lack αCaMKII or which express a permanently self-inhibited αCaMKII (αCaMKII(T305D)), exhibit significantly reduced amphetamine-triggered DAT-mediated MPP(+) efflux. Additionally, we investigated mice that mimic a neurogenetic disease known as Angelman syndrome. These mice possess reduced αCaMKII activity. Angelman syndrome mice demonstrated an impaired DAT efflux function, which was comparable with that of the αCaMKII mutant mice, indicating that DAT-mediated dopaminergic signaling is affected in Angelman syndrome.

  1. Visualization of the dopamine transporter in the human brain postmortem with the new selective ligand [125I]PE2I.

    PubMed

    Hall, H; Halldin, C; Guilloteau, D; Chalon, S; Emond, P; Besnard, J; Farde, L; Sedvall, G

    1999-01-01

    Using a new, 125I-labeled, selective high affinity dopamine transporter ligand, N-(3-iodoprop-2E-enyl)-2beta-carbomethoxy-3beta-(4'-methy lph enyl)nort ropane (PE2I), the distribution of the dopamine transporter was characterized in the normal postmortem human brain using whole hemisphere autoradiography. PE2I was radioiodinated to high specific radioactivity (2200 Ci/mmol, 81 GBq/micromol). PE2I binds to the dopamine transporter with high potency and, in contrast to beta-CIT, it has very low affinities for the serotonin and noradrenaline transporters. The autoradiograms showed very intense binding in basal ganglia (putamen, nucleus caudatus, nucleus accumbens) and lower binding in substantia nigra. Very low or no binding was found in other brain structures, including the neocortex or cerebellum. The labeling of human dopamine transporters with [125I]PE2I was inhibited by the dopamine transporter inhibitors GBR 12909 and beta-CIT, but not by citalopram (serotonin transporter inhibitor) or maprotiline (noradrenaline transporter inhibitor). Possibly due to the relatively high lipophilicity of the compound (theoretical log p = 4.68), it accumulated slightly in white matter. Thus, in vitro autoradiography using [125I]PE2I provided detailed qualitative and quantitative evidence that the dopamine transporter is almost exclusively localized in the basal ganglia of the human brain. Moreover, the autoradiograms indicate that [11C]PE2I and [123I]PE2I should be suitable for the in vivo visualization of the human dopamine transporter with PET or SPECT, respectively.

  2. Pharmacological characterization of a dopamine transporter ligand that functions as a cocaine antagonist.

    PubMed

    Desai, Rajeev I; Grandy, David K; Lupica, Carl R; Katz, Jonathan L

    2014-01-01

    An N-butyl analog of benztropine, JHW007 [N-(n-butyl)-3α-[bis(4'-fluorophenyl)methoxy]-tropane], binds to dopamine transporters (DAT) but has reduced cocaine-like behavioral effects and antagonizes various effects of cocaine. The present study further examined mechanisms underlying these effects. Cocaine dose-dependently increased locomotion, whereas JHW007 was minimally effective but increased activity 24 hours after injection. JHW007 (3-10 mg/kg) dose-dependently and fully antagonized the locomotor-stimulant effects of cocaine (5-60 mg/kg), whereas N-methyl and N-allyl analogs and the dopamine (DA) uptake inhibitor GBR12909 [1-(2-[bis(4-fluorophenyl)methoxy]ethyl)-4-(3-phenylpropyl)piperazine dihydrochloride] stimulated activity and failed to antagonize effects of cocaine. JHW007 also blocked the locomotor-stimulant effects of the DAT inhibitor GBR12909 but not stimulation produced by the δ-opioid agonist SNC 80 [4-[(R)-[(2S,5R)-4-allyl-2,5-dimethylpiperazin-1-yl](3-methoxyphenyl)methyl]-N,N-diethylbenzamide], which increases activity through nondopaminergic mechanisms. JHW007 blocked locomotor-stimulant effects of cocaine in both DA D2- and CB1-receptor knockout and wild-type mice, indicating a lack of involvement of these targets. Furthermore, JHW007 blocked effects of cocaine on stereotyped rearing but enhanced stereotyped sniffing, suggesting that interference with locomotion by enhanced stereotypies is not responsible for the cocaine-antagonist effects of JHW007. Time-course data indicate that administration of JHW007 antagonized the locomotor-stimulant effects of cocaine within 10 minutes of injection, whereas occupancy at the DAT, as determined in vivo, did not reach a maximum until 4.5 hours after injection. The σ1-receptor antagonist BD 1008 [N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(1-pyrrolidinyl)ethylamine dihydrobromide] blocked the locomotor-stimulant effects of cocaine. Overall, these findings suggest that JHW007 has cocaine-antagonist effects

  3. Insights into the Modulation of Dopamine Transporter Function by Amphetamine, Orphenadrine, and Cocaine Binding

    PubMed Central

    Cheng, Mary Hongying; Block, Ethan; Hu, Feizhuo; Cobanoglu, Murat Can; Sorkin, Alexander; Bahar, Ivet

    2015-01-01

    Human dopamine (DA) transporter (hDAT) regulates dopaminergic signaling in the central nervous system by maintaining the synaptic concentration of DA at physiological levels, upon reuptake of DA into presynaptic terminals. DA translocation involves the co-transport of two sodium ions and the channeling of a chloride ion, and it is achieved via alternating access between outward-facing (OF) and inward-facing states of DAT. hDAT is a target for addictive drugs, such as cocaine, amphetamine (AMPH), and therapeutic antidepressants. Our recent quantitative systems pharmacology study suggested that orphenadrine (ORPH), an anticholinergic agent and anti-Parkinson drug, might be repurposable as a DAT drug. Previous studies have shown that DAT-substrates like AMPH or -blockers like cocaine modulate the function of DAT in different ways. However, the molecular mechanisms of modulation remained elusive due to the lack of structural data on DAT. The newly resolved DAT structure from Drosophila melanogaster opens the way to a deeper understanding of the mechanism and time evolution of DAT–drug/ligand interactions. Using a combination of homology modeling, docking analysis, molecular dynamics simulations, and molecular biology experiments, we performed a comparative study of the binding properties of DA, AMPH, ORPH, and cocaine and their modulation of hDAT function. Simulations demonstrate that binding DA or AMPH drives a structural transition toward a functional form predisposed to translocate the ligand. In contrast, ORPH appears to inhibit DAT function by arresting it in the OF open conformation. The analysis shows that cocaine and ORPH competitively bind DAT, with the binding pose and affinity dependent on the conformational state of DAT. Further assays show that the effect of ORPH on DAT uptake and endocytosis is comparable to that of cocaine. PMID:26106364

  4. Positive and negative feedback learning and associated dopamine and serotonin transporter binding after methamphetamine

    PubMed Central

    Stolyarova, Alexandra; O’Dell, Steve J.; Marshall, John F.; Izquierdo, Alicia

    2014-01-01

    Learning from mistakes and prospectively adjusting behavior in response to reward feedback is an important facet of performance monitoring. Dopamine (DA) pathways play an important role in feedback learning and a growing literature has also emerged on the importance of serotonin (5HT) in reward learning, particularly during punishment or reward omission (negative feedback). Cognitive impairments resulting from psychostimulant exposure may arise from altered patterns in feedback learning, which in turn may be modulated by DA and 5HT transmission. We analyzed long-term, off-drug changes in learning from positive and negative feedback and associated striatal DA transporter (DAT) and frontocortical 5HT transporter (SERT) binding in rats pretreated with methamphetamine (mAMPH). Specifically, we assessed the reversal phase of pairwise visual discrimination learning in rats receiving single dose- (mAMPHsingle) vs. escalating-dose exposure (mAMPHescal). Using fine-grained trial-by-trial analyses, we found increased sensitivity to and reliance on positive feedback in mAMPH-pretreated animals, with the mAMPHsingle group showing more pronounced use of this type of feedback. In contrast, overall negative feedback sensitivity was not altered following any mAMPH treatment. In addition to validating the enduring effects of mAMPH on early reversal learning, we found more consecutive error commissions before the first correct response in mAMPH-pretreated rats. This behavioral rigidity was negatively correlated with subregional frontocortical SERT whereas positive feedback sensitivity negatively correlated with striatal DAT binding. These results provide new evidence for the overlapping, yet dissociable roles of DA and 5HT systems in overcoming perseveration and in learning new reward rules. PMID:24959862

  5. Positive and negative feedback learning and associated dopamine and serotonin transporter binding after methamphetamine.

    PubMed

    Stolyarova, Alexandra; O'Dell, Steve J; Marshall, John F; Izquierdo, Alicia

    2014-09-01

    Learning from mistakes and prospectively adjusting behavior in response to reward feedback is an important facet of performance monitoring. Dopamine (DA) pathways play an important role in feedback learning and a growing literature has also emerged on the importance of serotonin (5HT) in reward learning, particularly during punishment or reward omission (negative feedback). Cognitive impairments resulting from psychostimulant exposure may arise from altered patterns in feedback learning, which in turn may be modulated by DA and 5HT transmission. We analyzed long-term, off-drug changes in learning from positive and negative feedback and associated striatal DA transporter (DAT) and frontocortical 5HT transporter (SERT) binding in rats pretreated with methamphetamine (mAMPH). Specifically, we assessed the reversal phase of pairwise visual discrimination learning in rats receiving single dose- (mAMPHsingle) vs. escalating-dose exposure (mAMPHescal). Using fine-grained trial-by-trial analyses, we found increased sensitivity to and reliance on positive feedback in mAMPH-pretreated animals, with the mAMPHsingle group showing more pronounced use of this type of feedback. In contrast, overall negative feedback sensitivity was not altered following any mAMPH treatment. In addition to validating the enduring effects of mAMPH on early reversal learning, we found more consecutive error commissions before the first correct response in mAMPH-pretreated rats. This behavioral rigidity was negatively correlated with subregional frontocortical SERT whereas positive feedback sensitivity negatively correlated with striatal DAT binding. These results provide new evidence for the overlapping, yet dissociable roles of DA and 5HT systems in overcoming perseveration and in learning new reward rules.

  6. Genomic Features of the Human Dopamine Transporter Gene and Its Potential Epigenetic States: Implications for Phenotypic Diversity

    SciTech Connect

    Shumay, E.; Shumay, E.; Fowler, J.S.; Volkow, N.D.

    2010-06-01

    Human dopamine transporter gene (DAT1 or SLC6A3) has been associated with various brain-related diseases and behavioral traits and, as such, has been investigated intensely in experimental- and clinical-settings. However, the abundance of research data has not clarified the biological mechanism of DAT regulation; similarly, studies of DAT genotype-phenotype associations yielded inconsistent results. Hence, our understanding of the control of the DAT protein product is incomplete; having this knowledge is critical, since DAT plays the major role in the brain's dopaminergic circuitry. Accordingly, we reevaluated the genomic attributes of the SLC6A3 gene that might confer sensitivity to regulation, hypothesizing that its unique genomic characteristics might facilitate highly dynamic, region-specific DAT expression, so enabling multiple regulatory modes. Our comprehensive bioinformatic analyzes revealed very distinctive genomic characteristics of the SLC6A3, including high inter-individual variability of its sequence (897 SNPs, about 90 repeats and several CNVs spell out all abbreviations in abstract) and pronounced sensitivity to regulation by epigenetic mechanisms, as evident from the GC-bias composition (0.55) of the SLC6A3, and numerous intragenic CpG islands (27 CGIs). We propose that this unique combination of the genomic features and the regulatory attributes enables the differential expression of the DAT1 gene and fulfills seemingly contradictory demands to its regulation; that is, robustness of region-specific expression and functional dynamics.

  7. Replication of an association of a promoter polymorphism of the dopamine transporter gene and Attention Deficit Hyperactivity Disorder.

    PubMed

    Doyle, Christopher; Brookes, Keeley; Simpson, Jennifer; Park, Joanne; Scott, Sarah; Coghill, David R; Hawi, Ziarah; Kirley, Aiveen; Gill, Michael; Kent, Lindsey

    2009-09-22

    Genetic associations for Attention Deficit Hyperactivity Disorder (ADHD), a common highly heritable childhood behavioural disorder, require replication in order to establish whether they are true positive findings. The current study aims to replicate recent association findings from the International Multi-centre ADHD Genetics (IMAGE) project in one of the most studied genes related to ADHD, the dopamine transporter (DAT1) gene. In a family-based sample of 450 ADHD probands, three Single Nucleotide Polymorphism (SNP) markers have been genotyped using TaqMan assays. Transmission Disequilibrium Test analysis demonstrates that one of three SNP markers (rs11564750) in the 5' promoter region of the gene is significantly associated with ADHD (P=0.02). This provides further evidence that in addition to the well-known and investigated 3'UTR polymorphism associated with ADHD, there is potentially a further association signal emanating from the 5' promoter region of the gene. Further replication and functional studies are now required to fully understand the consequence of polymorphisms present at both the 5' and 3' ends of the DAT1 gene and their role in ADHD pathophysiology.

  8. Dopaminergic Control of Attentional Flexibility: Inhibition of Return is Associated with the Dopamine Transporter Gene (DAT1)

    PubMed Central

    Colzato, Lorenza S.; Pratt, Jay; Hommel, Bernhard

    2010-01-01

    Genetic variability related to the dopamine (DA) transporter gene (DAT1) has received increasing attention as a possible modulator of human cognition. The 9-repeat allele of the DAT1 gene is presumably associated with higher striatal DA levels than the 10-repeat allele, which might support inhibitory control functions. We investigated the impact of the DAT1 gene on the inhibition of return (IOR) effect, which refers to the fact that people are slower to detect a target if it appears in a previously attended location. 140 healthy adults, genotyped for the DAT1 gene, performed an IOR task with stimulus-onset asynchronies (SOAs) between attention cue and target of 150–1200 ms. Nine-repeat carriers showed more pronounced IOR effect than 10/10 homozygous at short SOAs but both groups of subjects eventually reached the same magnitude of IOR. Our findings support the idea that striatal DA levels promote IOR, presumably by biasing the interplay between prefrontal and striatal networks towards greater cognitive flexibility. PMID:20661460

  9. Sequence determinants of the Caenhorhabditis elegans dopamine transporter dictating in vivo axonal export and synaptic localization.

    PubMed

    Robinson, Sarah B; Hardaway, J Andrew; Hardie, Shannon L; Wright, Jane; Glynn, Ryan M; Bermingham, Daniel P; Han, Qiao; Sturgeon, Sarah M; Freeman, Phyllis; Blakely, Randy D

    2017-01-01

    The monoamine neurotransmitter dopamine (DA) acts across phylogeny to modulate both simple and complex behaviors. The presynaptic DA transporter (DAT) is a major determinant of DA signaling capacity in ensuring efficient extracellular DA clearance. In humans, DAT is also a major target for prescribed and abused psychostimulants. Multiple structural determinants of DAT function and regulation have been defined, though largely these findings have arisen from heterologous expression or ex vivo cell culture studies. Loss of function mutations in the gene encoding the Caenhorhabditis elegans DAT (dat-1) produces rapid immobility when animals are placed in water, a phenotype termed swimming-induced paralysis (Swip). The ability of a DA neuron-expressed, GFP-tagged DAT-1 fusion protein (GFP::DAT-1) to localize to synapses and rescue Swip in these animals provides a facile approach to define sequences supporting DAT somatic export and function in vivo. In prior studies, we found that truncation of the last 25 amino acids of the DAT-1 C-terminus (Δ25) precludes Swip rescue, supported by a deficit in GFP::DAT-1 synaptic localization. Here, we further defined the elements within Δ25 required for DAT-1 export and function in vivo. We identified two conserved motifs ((584)KW(585) and (591)PYRKR(595)) where mutation results in a failure of GFP::DAT-1 to be efficiently exported to synapses and restore DAT-1 function. The (584)KW(585) motif conforms to a sequence proposed to support SEC24 binding, ER export from the endoplasmic reticulum (ER), and surface expression of mammalian DAT proteins, whereas the (591)PYRKR(595) sequence conforms to a 3R motif identified as a SEC24 binding site in vertebrate G-protein coupled receptors. Consistent with a potential role of SEC24 orthologs in DAT-1 export, we demonstrated DA neuron-specific expression of a sec-24.2 transcriptional reporter. Mutations of the orthologous C-terminal sequences in human DAT (hDAT) significantly reduced

  10. 18F-labeled FECNT: a selective radioligand for PET imaging of brain dopamine transporters.

    PubMed

    Goodman, M M; Kilts, C D; Keil, R; Shi, B; Martarello, L; Xing, D; Votaw, J; Ely, T D; Lambert, P; Owens, M J; Camp, V M; Malveaux, E; Hoffman, J M

    2000-01-01

    Fluorine-18 labeled 2beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(2-fluoroethyl)nort ropane (FECNT) was synthesized in the development of a dopamine transporter (DAT) imaging ligand for positron emission tomography (PET). The methods of radiolabeling and ligand synthesis of FECNT, and the results of the in vitro characterization and in vivo tissue distribution in rats and in vivo PET imaging in rhesus monkeys of [18F]FECNT are described. Fluorine-18 was introduced into 2beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(2-fluoroethyl)nort ropane (4) by preparation of 1-[18F]fluoro-2-tosyloxyethane (2) followed by alkylation of 2beta-carbomethoxy-3beta-(4-chlorophenyl)nortropane (3) in 21% radiochemical yield (decay corrected to end of bombardment [EOB]). Competition binding in cells stably expressing the transfected human DAT serotonin transporter (SERT) and norepinephrine transporter (NET) labeled by [3H]WIN 35428, [3H]citalopram, and [3H]nisoxetine, respectively, indicated the following order of DAT affinity: GBR 12909 > CIT > 2beta-carbomethoxy-3beta-(4-chlorophenyl)-8-(3-fluoropropyl) nortropane (FPCT) > FECNT. The affinity of FECNT for SERT and NET was 25- and 156-fold lower, respectively, than for DAT. Blocking studies were performed in rats with a series of transporter-specific agents and demonstrated that the brain uptake of [18F]FECNT was selective and specific for DAT-rich regions. PET brain imaging studies in monkeys demonstrated high [18F]FECNT uptake in the caudate and putamen that resulted in caudate-to-cerebellum and putamen-to-cerebellum ratios of 10.5 at 60 min. [18F]FECNT uptake in the caudate/putamen peaked in less than 75 min and exhibited higher caudate- and putamen-to-cerebellum ratios at transient equilibrium than reported for 11C-WIN 35,428, [11C]CIT/RTI-55, or [18F]beta-CIT-FP. Analysis of monkey arterial plasma samples using high performance liquid chromatography determined that there was no detectable formation of lipophilic radiolabeled

  11. Pharmacological and Behavioral Characterization of D-473, an Orally Active Triple Reuptake Inhibitor Targeting Dopamine, Serotonin and Norepinephrine Transporters

    PubMed Central

    Dutta, Aloke K.; Santra, Soumava; Sharma, Horrick; Voshavar, Chandrashekhar; Xu, Liping; Mabrouk, Omar; Antonio, Tamara; Reith, Maarten E. A.

    2014-01-01

    Major depressive disorder (MDD) is a debilitating disease affecting a wide cross section of people around the world. The current therapy for depression is less than adequate and there is a considerable unmet need for more efficacious treatment. Dopamine has been shown to play a significant role in depression including production of anhedonia which has been one of the untreated symptoms in MDD. It has been hypothesized that drugs acting at all three monoamine transporters including dopamine transporter should provide more efficacious antidepressants activity. This has led to the development of triple reuptake inhibitor D-473 which is a novel pyran based molecule and interacts with all three monoamine transporters. The monoamine uptake inhibition activity in the cloned human transporters expressed in HEK-293 cells (70.4, 9.18 and 39.7 for DAT, SERT and NET, respectively) indicates a serotonin preferring triple reuptake inhibition profile for this drug. The drug D-473 exhibited good brain penetration and produced efficacious activity in rat forced swim test under oral administration. The optimal efficacy dose did not produce any locomotor activation. Microdialysis experiment demonstrated that systemic administration of D-473 elevated extracellular level of the three monoamines DA, 5-HT, and NE efficaciously in the dorsal lateral striatum (DLS) and the medial prefrontal cortex (mPFC) area, indicating in vivo blockade of all three monoamine transporters by D-473. Thus, the current biological data from D-473 indicate potent antidepressant activity of the molecule. PMID:25427177

  12. A Conserved Salt Bridge between Transmembrane Segments 1 and 10 Constitutes an Extracellular Gate in the Dopamine Transporter*

    PubMed Central

    Pedersen, Anders V.; Andreassen, Thorvald F.; Loland, Claus J.

    2014-01-01

    Neurotransmitter transporters play an important role in termination of synaptic transmission by mediating reuptake of neurotransmitter, but the molecular processes behind translocation are still unclear. The crystal structures of the bacterial homologue, LeuT, provided valuable insight 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 transporter (DAT), the corresponding residues are Arg-85 and Asp-476. Here, we present results supporting the existence of a similar interaction in DAT. The DAT R85D mutant has a complete loss of function, but the additional insertion of an arginine in opposite position (R85D/D476R), causing a charge reversal, results in a rescue of binding sites for the cocaine analogue [3H]CFT. Also, the coordination of Zn2+ between introduced histidines (R85H/D476H) caused a ∼2.5-fold increase in [3H]CFT binding (Bmax). Importantly, Zn2+ also inhibited [3H]dopamine transport in R85H/D476H, suggesting that a dynamic interaction is required for the transport process. Furthermore, cysteine-reactive chemistry shows that mutation of the gating residues causes a higher proportion of transporters to reside in the outward facing conformation. Finally, we show that charge reversal of the corresponding residues (R104E/E493R) in the serotonin transporter also rescues [3H](S)-citalopram binding, suggesting a conserved feature. Taken together, these data suggest that the extracellular thin gate is present in monoamine transporters and that a dynamic interaction is required for substrate transport. PMID:25339174

  13. Synthesis and dopamine transporter binding of 2beta-isopropyl ester analogs of cocaine.

    PubMed

    El-Moselhy, Tarek F; Avor, Kwasi S; Basmadjian, Garo P

    2002-02-01

    A series of 2beta-isopropyl ester analogs of cocaine (7-11) was synthesised and evaluated in an in vitro dopamine transporter (DAT) binding assays. Ecgonine HCl (5) was obtained from (-)-cocaine (1) by hydrolysis using 1 N HCl. Acid catalysed esterification of 5 using 2-propanol and HCl gas afforded 2beta-isopropyl ecgonine (6). Compounds 7-9 were obtained via esterification of the 3beta-hydroxyl group of 6 using the appropriate acid chloride. Compound 10 was obtained via selective hydrolysis and re-esterification of 7 using 2-propanol and HCl gas. Compound 11 was obtained by reduction of 9 using H(2)/Pd-C. Compounds 7, 10 and 11 showed high binding affinity to the DAT (as indicated from the inhibition of the binding of [(3)H]WIN 35,428 (3)) with IC(50) values (mean +/- S.E.M.) 208.5 +/- 9.5, 47.43 +/- 1.79 and 11.25 +/- 3.37 nM, respectively). Compound 7 is comparatively as active as cocaine, 10 is ca. fivefold more active than cocaine and 11 is ca. 20-fold more active than cocaine and even twice more active than the radioligand 3. Compound 11, like its methyl ester analog (2' aminococaine), exhibited the highest affinity to the DAT. These results, along with previous results, emphasise the importance of a hydrogen-bond donor group at the 2'-position of cocaine and its isopropyl ester analogs to enhance binding affinity to the DAT.

  14. Absence of age-related dopamine transporter loss in current cocaine abusers

    SciTech Connect

    Wang, G.J.; Volkow, N.D.; Fischman, M.

    1997-05-01

    The brain dopamine (DA) system appears to play a crucial role in the reinforcing properties of cocaine. Using PET we had previously shown significant decreases in DA D2 receptors but no changes in DA transporters (DAT) in detoxified cocaine abusers (>1 month after last cocaine use). This study evaluates DAT availability in current cocaine abusers (15 male and 5 female; age = 36.2{+-}5.3 years old) using PET and [C-11]cocaine, as a DAT ligand, and compares it to that in 18 male and 2 female age matched normal controls. Cocaine abusers had a history of abusing 4.2{+-}2.8 gm /week of cocaine for an average of 11.0{+-}4.9 years and their last use of cocaine was 5.4{+-}8 days prior to PET study. DAT availability was obtained using the ratio of the distribution volume in the region of interest (caudate, pulamen) to that in cerebellum which is a function of Bmax./Kd.+1. DAT availability in cocaine abusers did not differ to that in normals (N) (C= 1.78{+-}0.14, N= 1.77{+-}0.13). In addition, there were no differences between the groups in the distribution volume or the Kl (plasma to brain transfer constant) measures for [C-11]cocaine. However, in the normals but not in the abusers striatal DAT availability decreased with age (C: r = -0.07, p = 0.76; N: r = -0.55, p < 0.01). Though this study fails to show group differences in DAT availability between normals and current cocaine abusers it indicates a blunting of the age-related decline in DAT availability in the cocaine abusers. Future studies in older cocaine abusers at different time after detoxification arc required in order to assess if cocaine slows the loss of DAT with age or whether these changes reflect compensation to increased DAT blockade and recover with detoxification.

  15. Cocaine occupancy of sigma1 receptors and dopamine transporters in mice.

    PubMed

    Lever, John R; Fergason-Cantrell, Emily A; Watkinson, Lisa D; Carmack, Terry L; Lord, Sarah A; Xu, Rong; Miller, Dennis K; Lever, Susan Z

    2016-03-01

    Activation of sigma1 (σ1) receptors contributes to the behavioral and toxic effects of (-)-cocaine. We studied a key step, the ability of (-)-cocaine to occupy σ1 receptors in vivo, using CD-1(®) mice and the novel radioligand [(125) I]E-N-1-(3'-iodoallyl)-N'-4-(3",4"-dimethoxyphenethyl)-piperazine ([(125) I]E-IA-DM-PE-PIPZE). (-)-Cocaine displayed an ED50 of 68 μmol/kg for inhibition of specific radioligand binding in whole brain, with values between 73 and 80 μmol/kg for heart, lung, and spleen. For comparison, an ED50 of 26 μmol/kg for (-)-cocaine occupancy of striatal dopamine transporters (DAT) was determined by inhibition of [(125) I]3β-(4-iodophenyl)tropan-2β-carboxylic acid isopropyl ester ([(125) I]RTI-121) binding. A chief finding is the relatively small potency difference between (-)-cocaine occupancy of σ1 receptors and the DAT, although the DAT occupancy is likely underestimated. Interactions of (-)-cocaine with σ1 receptors were assessed further using [(125) I]E-IA-DM-PE-PIPZE for regional cerebral biodistribution studies and quantitative ex vivo autoradiography of brain sections. (-)-Cocaine binding to cerebral σ1 receptors proved directly proportional to the relative site densities known for the brain regions. Nonradioactive E-IA-DM-PE-PIPZE gave an ED50 of 0.23 μmol/kg for occupancy of cerebral σ1 receptors, and a 3.16 μmol/kg (i.p.) dose attenuated (-)-cocaine-induced locomotor hyperactivity by 30%. This effect did not reach statistical significance, but suggests that E-IA-DM-PE-PIPZE is a probable σ1 receptor antagonist. As groundwork for the in vivo studies, we used standard techniques in vitro to determine ligand affinities, site densities, and pharmacological profiles for the σ1 and σ2 receptors expressed in CD-1(®) mouse brain.

  16. Locomotor hyperactivity in 14-3-3ζ KO mice is associated with dopamine transporter dysfunction

    PubMed Central

    Ramshaw, H; Xu, X; Jaehne, E J; McCarthy, P; Greenberg, Z; Saleh, E; McClure, B; Woodcock, J; Kabbara, S; Wiszniak, S; Wang, Ting-Yi; Parish, C; van den Buuse, M; Baune, B T; Lopez, A; Schwarz, Q

    2013-01-01

    Dopamine (DA) neurotransmission requires a complex series of enzymatic reactions that are tightly linked to catecholamine exocytosis and receptor interactions on pre- and postsynaptic neurons. Regulation of dopaminergic signalling is primarily achieved through reuptake of extracellular DA by the DA transporter (DAT) on presynaptic neurons. Aberrant regulation of DA signalling, and in particular hyperactivation, has been proposed as a key insult in the presentation of schizophrenia and related neuropsychiatric disorders. We recently identified 14-3-3ζ as an essential component of neurodevelopment and a central risk factor in the schizophrenia protein interaction network. Our analysis of 14-3-3ζ-deficient mice now shows that baseline hyperactivity of knockout (KO) mice is rescued by the antipsychotic drug clozapine. 14-3-3ζ KO mice displayed enhanced locomotor hyperactivity induced by the DA releaser amphetamine. Consistent with 14-3-3ζ having a role in DA signalling, we found increased levels of DA in the striatum of 14-3-3ζ KO mice. Although 14-3-3ζ is proposed to modulate activity of the rate-limiting DA biosynthesis enzyme, tyrosine hydroxylase (TH), we were unable to identify any differences in total TH levels, TH localization or TH activation in 14-3-3ζ KO mice. Rather, our analysis identified significantly reduced levels of DAT in the absence of notable differences in RNA or protein levels of DA receptors D1–D5. Providing insight into the mechanisms by which 14-3-3ζ controls DAT stability, we found a physical association between 14-3-3ζ and DAT by co-immunoprecipitation. Taken together, our results identify a novel role for 14-3-3ζ in DA neurotransmission and provide support to the hyperdopaminergic basis of pathologies associated with schizophrenia and related disorders. PMID:24301645

  17. Association of Dopamine Transporter Gene Variants with Childhood ADHD Features in Bipolar Disorder

    PubMed Central

    Greenwood, Tiffany A.; Joo, Eun-Jeong; Shektman, Tatyana; Sadovnick, A. Dessa; Remick, Ronald A.; Keck, Paul E.; McElroy, Susan L.; Kelsoe, John R.

    2014-01-01

    Bipolar Disorder (BD) and Attention Deficit Hyperactivity Disorder (ADHD) exhibit remarkably high rates of comorbidity, as well as patterns of familial co-segregation. Epidemiological data suggests that these disorders either share a common genetic architecture or that ADHD features in BD may represent an etiologically distinct subtype. We previously used the Wender Utah Rating Scale (WURS) to assess ADHD features in BD families and identified three heritable factors relating to impulsivity, mood instability, and inattention. Linkage analysis revealed a LOD score of 1.33 for the inattention factor on 5p15.3 near the dopamine transporter gene (DAT1), which has been associated with both BD and ADHD. Pharmacological evidence also suggests a role for DAT in both disorders. We have now evaluated the association of ten DAT1 variants for the WURS total score and factors in an overlapping sample of 87 BD families. Significant associations for three SNPs were observed across the WURS measures, notably for a SNP in intron 8 with the WURS total score (p=0.007) and for variants in introns 9 and 13 with mood instability (p=0.009 and 0.004, respectively). Analysis of an independent sample of 52 BD cases and 46 healthy controls further supported association of the intron 8 variant with mood instability (p=0.005), and a combined analysis confirmed the associations of this SNP with WURS total score. Impulsivity, and mood instability (p= 0.002, 0.007, and 8×10−4, respectively). These data suggest that variants within DAT1 may predispose to a subtype of BD characterized by early prodromal features that include attentional deficits. PMID:23255304

  18. Reduced Dopamine Transporter Functioning Induces High-Reward Risk-Preference Consistent with Bipolar Disorder

    PubMed Central

    van Enkhuizen, Jordy; Henry, Brook L; Minassian, Arpi; Perry, William; Milienne-Petiot, Morgane; Higa, Kerin K; Geyer, Mark A; Young, Jared W

    2014-01-01

    Individuals with bipolar disorder (BD) exhibit deleterious decision making, negatively impacting their lives. Such aberrant decision making can be quantified using the Iowa Gambling Task (IGT), which requires choosing between advantageous and disadvantageous options based on different reward/punishment schedules. The mechanisms underlying this behavioral deficit are unknown, but may include the reduced dopamine transporter (DAT) functioning reported in BD patients. Using both human and mouse IGTs, we tested whether reduced DAT functioning would recreate patterns of deficient decision making of BD patients. We assessed the IGT performance of 16 BD subjects (7 female) and 17 healthy control (HC) subjects (12 female). We recorded standard IGT performance measures and novel post-reward and post-punishment decision-making strategies. We characterized a novel single-session mouse IGT using C57BL/6J mice (n=44). The BD and HC IGT performances were compared with the effects of chronic (genetic knockdown (KD; n=31) and wild-type (n=28) mice) and acute (C57BL/6J mice (n=89) treated with the DAT inhibitor GBR12909) reductions of DAT functioning in mice performing this novel IGT. BD patients exhibited impaired decision making compared with HC subjects. Both the good-performing DAT KD and GBR12909-treated mice exhibited poor decision making in the mouse IGT. The deficit of each population was driven by high-reward sensitivity. The single-session mouse IGT measures dynamic risk-based decision making similar to humans. Chronic and acute reductions of DAT functioning in mice impaired decision-making consistent with poor IGT performance of BD patients. Hyperdopaminergia caused by reduced DAT may impact poor decision making in BD patients, which should be confirmed in future studies. PMID:25005251

  19. Dopamine transporter (DAT1) VNTR polymorphism and alcoholism in two culturally different populations of south India.

    PubMed

    Bhaskar, Lakkakula V K S; Thangaraj, Kumarasamy; Wasnik, Samiksha; Singh, Lalji; Raghavendra Rao, Vadlamudi

    2012-01-01

    It is well established that the central dopaminergic reward pathway is likely involved in alcohol intake and the progression of alcohol dependence. Dopamine transporter (DAT1) mediates the active re-uptake of DA from the synapse and is a principal regulator of dopaminergic neurotransmission. The gene for the human DAT1 displays several polymorphisms, including a 40-bp variable number of tandem repeats (VNTR) ranging from 3 to 16 copies in the 3'-untranslated region (UTR) of the gene. To assess the role of this gene in alcoholism, we genotyped the VNTR of DAT1 gene in a sample of 206 subjects from the Kota population (111 alcohol dependence cases and 95 controls) and 142 subjects from Badaga population (81 alcohol dependence cases and 61 controls). Both populations inhabit a similar environmental zone, but have different ethnic histories. Phenotype was defined based on the DSM-IV criteria. Genotyping was performed using PCR and electrophoresis. The association of DAT1 with alcoholism was tested by using the Clump v1.9 program which uses the Monte Carlo method. In both Kota and Badaga populations, the allele A10 was the most frequent allele followed by allele A9. The genotypic distribution is in Hardy-Weinberg equilibrium in both cases and control groups of Kota and Badaga populations. The DAT1 VNTR was significantly associated with alcoholism in Badaga population but not in Kota population. Our results suggest that the A9 allele of the DAT gene is involved in vulnerability to alcoholism, but that these associations are population specific.

  20. Double dissociation between lab measures of inattention and impulsivity and the dopamine transporter gene (DAT1) and dopamine D4 receptor gene (DRD4).

    PubMed

    Gizer, Ian R; Waldman, Irwin D

    2012-11-01

    Studies examining the biological and neuropsychological processes underlying attention-deficit/hyperactivity disorder (ADHD) suggest that error indices from the A-X Continuous Performance Test (A-X CPT) might represent useful endophenotypes for ADHD. The current study extended such findings by evaluating the utility of these putative endophenotypes in the context of a molecular genetic study. One hundred and forty-eight clinic-referred ADHD probands and 56 siblings were recruited as part of an ongoing study. Between- and within-family tests of association were conducted to test for relations between polymorphisms in two candidate genes, the dopamine transporter gene (DAT1) and the dopamine D4 receptor gene (DRD4), and indices of inattention and impulsivity derived from the A-X CPT. Association analyses of these polymorphisms with the A-X CPT indices suggested a double dissociation such that an index of inattention was associated with DRD4 but not DAT1, and an index of impulsivity was associated with DAT1 but not DRD4. Further analyses suggested that an A-X CPT index of impulsivity partially mediated previously observed associations between hyperactive-impulsive ADHD symptoms and DAT1. Additionally, an A-X CPT index of inattention moderated the relation between inattentive ADHD symptoms and DRD4 such that children with high levels of the endophenotype showed a stronger association between inattentive symptoms and DRD4. The potential utility of endophenotypes derived from the A-X CPT in molecular genetic studies of ADHD is discussed. (PsycINFO Database Record (c) 2012 APA, all rights reserved).

  1. Effects of diet and insulin on dopamine transporter activity and expression in rat caudate-putamen, nucleus accumbens, and midbrain.

    PubMed

    Jones, Kymry T; Woods, Catherine; Zhen, Juan; Antonio, Tamara; Carr, Kenneth D; Reith, Maarten E A

    2017-03-01

    Food restriction (FR) and obesogenic (OB) diets are known to alter brain dopamine transmission and exert opposite modulatory effects on behavioral responsiveness to psychostimulant drugs of abuse. Mechanisms underlying these diet effects are not fully understood. In this study, we examined diet effects on expression and function of the dopamine transporter (DAT) in caudate-putamen (CPu), nucleus accumbens (NAc), and midbrain regions. Dopamine (DA) uptake by CPu, NAc or midbrain synapto(neuro)somes was measured in vitro with rotating disk electrode voltammetry or with [(3) H]DA uptake and was found to correlate with DAT surface expression, assessed by maximal [(3) H](-)-2-β-carbomethoxy-3-β-(4-fluorophenyl)tropane binding and surface biotinylation assays. FR and OB diets were both found to decrease DAT activity in CPu with a corresponding decrease in surface expression but had no effects in the NAc and midbrain. Diet treatments also affected sensitivity to insulin-induced enhancement of DA uptake, with FR producing an increase in CPu and NAc, likely mediated by an observed increase in insulin receptor expression, and OB producing a decrease in NAc. The increased expression of insulin receptor in NAc of FR rats was accompanied by increased DA D2 receptor expression, and the decreased DAT expression and function in CPu of OB rats was accompanied by decreased DA D2 receptor expression. These results are discussed as partial mechanistic underpinnings of diet-induced adaptations that contribute to altered behavioral sensitivity to psychostimulants that target the DAT.

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

    PubMed Central

    Rickhag, Mattias; Hansen, Freja Herborg; Sørensen, Gunnar; Strandfelt, Kristine Nørgaard; Andresen, Bjørn; Gotfryd, Kamil; Madsen, Kenneth L.; Vestergaard-Klewe, Ib; Ammendrup-Johnsen, Ina; Eriksen, Jacob; Füchtbauer, Ernst-Martin; Gomeza, Jesus; Woldbye, David P.D.; Wörtwein, Gitta; Gether, Ulrik

    2013-01-01

    The dopamine transporter (DAT) mediates reuptake of dopamine from the synaptic cleft. The cellular mechanisms controlling DAT levels in striatal nerve terminals remain poorly understood. DAT contains a C-terminal PDZ (PSD-95/Discs-large/ZO-1) domain binding sequence believed to bind synaptic scaffolding proteins, but its functional significance is uncertain. Here we demonstrate that two different DAT knock-in mice with disrupted PDZ-binding motifs (DAT-AAA and DAT+Ala) are characterized by dramatic loss of DAT expression in the striatum, causing hyperlocomotion and attenuated response to amphetamine. In cultured dopaminergic neurons and striatal slices from DAT-AAA mice, we find markedly reduced DAT surface levels and evidence for enhanced constitutive internalization. In DAT-AAA neurons, but not in wild type neurons, surface levels are rescued in part by expression of a dominant-negative dynamin mutation (K44A). Our findings suggest that PDZ domain interactions are critical for synaptic distribution of DAT in vivo and thereby for proper maintenance of dopamine homeostasis. PMID:23481388

  3. Characterization of a dopamine transporter polymorphism and behavior in Belgian Malinois

    PubMed Central

    2013-01-01

    Background The Belgian Malinois dog breed (MAL) is frequently used in law enforcement and military environments. Owners have reported seizures and unpredictable behavioral changes including dogs’ eyes “glazing over,” dogs’ lack of response to environmental stimuli, and loss of behavioral inhibition including owner-directed biting behavior. Dogs with severe behavioral changes may be euthanized as they can represent a danger to humans and other dogs. In the dog, the dopamine transporter gene (DAT) contains a 38-base pair variable number tandem repeat (DAT-VNTR); alleles have either one or two copies of the 38-base pair sequence. The objective of this study was to assess frequency of DAT-VNTR alleles, and characterize the association between DAT-VNTR alleles and behavior in MAL and other breeds. Results In an American sample of 280 dogs comprising 26 breeds, most breeds are predominantly homozygous for the DAT-VNTR two-tandem-repeat allele (2/2). The one-tandem-repeat allele is over-represented in American MAL (AM-MAL) (n = 144), both as heterozygotes (1/2) and homozygotes (1/1). All AM-MAL with reported seizures (n = 5) were 1/1 genotype. For AM-MAL with at least one “1” allele (1/1 or 1/2 genotype, n = 121), owners reported higher levels of attention, increased frequency of episodic aggression, and increased frequency of loss of responsiveness to environmental stimuli. In behavior observations, Belgian Military Working Dogs (MWD) with 1/1 or 1/2 genotypes displayed fewer distracted behaviors and more stress-related behaviors such as lower posture and increased yawning. Handlers’ treatment of MWD varied with DAT-VNTR genotype as did dogs’ responses to handlers’ behavior. For 1/1 or 1/2 genotype MWD, 1) lower posture after the first aversive stimulus given by handlers was associated with poorer obedience performance; 2) increased aversive stimuli during protection exercises were associated with decreased performance; 3) more aversive

  4. Relationship between dopamine transporter occupancy and methylphenidate induced high in humans

    SciTech Connect

    Volkow, N.D.; Wang, G.J.; Fowler, J.S. |

    1996-05-01

    The inhibition of the dopamine transporter (DAT) by cocaine has been shown to be indispensable for its reinforcing properties. The development of drugs that inibit the DAT has become a major target to prevent cocaine`s effects. However prevention of the {open_quotes}high{close_quotes} by DAT inhibitors has never been demonstrated. This study evaluates the ability to block methylphenidate (MP), a DAT inhibitor drug with similar reinforcing properties to cocaine, induced {open_quotes}high{close_quotes} by prior DAT inhibition. It uses PET and [{sup 11}C]d-threo-methylphenidate to measure the relationship between DAT occupancy prior to administration of MP and the intensity of the subjective perception of the {open_quotes}high{close_quotes} in 8 controls. MP (0.375 mg/kg iv) which was administered as a single injection and also as two sequential doses given 60 minutes apart significantly reduced the ratio of the distribution volume for [{sup 11}C]d-threo-methylphenidate in striatum to that in cerebellum from a baseline of 2.83 {plus_minus} 0.2 to 1.29 {plus_minus} 0.1 at 7 minutes and to 1.37 {plus_minus} 0.2 at 60 minutes after a single injection of MP and to 1.14 {plus_minus} 0.1 at 7 minutes after the second of two sequential MP doses. This corresponds to a DAT occupancy by MP of 84% {plus_minus} 7 at 7 minutes and of 77% {plus_minus} 6 at 60 minutes after a single injection of MP and of 93% {plus_minus} 7 at 7 after the second of two sequential MP doses. The subjective perception of {open_quotes}high{close_quotes} experienced after the second injection of MP was of a similar magnitude to that experienced after the first injection of MP was of a similar magnitude to that experienced after the first injection, in spite of the very different starting DAT occupancies (0 and 77%, respectively). DAT occupancy was not correlated with the {open_quotes}high{close_quotes}; and one subject with 100% DAT occupancy did not perceive the {open_quotes}high{close_quotes}.

  5. Quantification of dopamine transporter density with [18F]FECNT PET in healthy humans

    PubMed Central

    Nye, Jonathon A.; Votaw, John R.; Bremner, J. Douglas; Davis, Margaret R.; Voll, Ronald J.; Camp, Vernon M.; Goodman, Mark M.

    2015-01-01

    Introduction Fluorine-18 labeled 2β-carbomethoxy-3β-(4-chlorophenyl)-8-(2-fluoroethyl)nortropane ([18 F]FECNT) binds reversibly to the dopamine transporter (DAT) with high selectivity. [18 F]FECNT has been used extensively in the quantification of DAT occupancy in non-human primate brain and can distinguish between Parkinson's and healthy controls in humans. The purpose of this work was to develop a compartment model to characterize the kinetics of [18 F]FECNT for quantification of DAT density in healthy human brain. Methods Twelve healthy volunteers underwent 180 min dynamic [18 F]FECNT PET imaging including sampling of arterial blood. Regional time-activity curves were extracted from the caudate, putamen and midbrain including a reference region placed in the cerebellum. Binding potential, BPND, was calculated for all regions using kinetic parameters estimated from compartmental and Logan graphical model fits to the time-activity data. Simulations were performed to determine whether the compartment model could reliably fit time-activity data over a range of BPND values. Results The kinetics of [18 F]FECNT were well-described by the reversible 2-tissue arterial input and full reference tissue compartment models. Calculated binding potentials in the caudate, putamen and midbrain were in good agreement between the arterial input model, reference tissue model and the Logan graphical model. The distribution volume in the cerebellum did not reach a plateau over the duration of the study, which may be a result of non-specific binding in the cerebellum. Simulations that included non-specific binding show that the reference and arterial input models are able to estimate BPND for DAT densities well below that observed in normal volunteers. Conclusion The kinetics of [18 F]FECNT in human brain are well-described by arterial input and reference tissue compartment models. Measured and simulated data show that BPND calculated with reference tissue model is proportional to

  6. Cocaine Occupancy of Sigma1 Receptors and Dopamine Transporters in Mice

    PubMed Central

    LEVER, JOHN R.; FERGASON-CANTRELL, EMILY A.; WATKINSON, LISA D.; CARMACK, TERRY L.; LORD, SARAH A.; XU, RONG; MILLER, DENNIS K.; LEVER, SUSAN Z.

    2015-01-01

    Activation of sigma1 (σ1) receptors contributes to the behavioral and toxic effects of (−)-cocaine. We studied a key step, the ability of (−)-cocaine to occupy σ1 receptors in vivo, using CD-1® mice and the novel radioligand [125I]E-N-1-(3′-iodoallyl)-N′-4-(3″,4″-dimethoxyphenethyl)-piperazine ([125I]E-IA-DM-PE-PIPZE). (−)-Cocaine displayed an ED50 of 68 μmol/kg for inhibition of specific radioligand binding in whole brain, with values between 73 – 80 μmol/kg for heart, lung and spleen. For comparison, an ED50 of 26 μmol/kg for (−)-cocaine occupancy of striatal dopamine transporters (DAT) was determined by inhibition of [125I]3β-(4-iodophenyl)tropan-2β-carboxylic acid isopropyl ester ([125I]RTI-121) binding. A chief finding is the relatively small potency difference between (−)-cocaine occupancy of σ1 receptors and the DAT, although the DAT occupancy is likely underestimated. Interactions of (−)-cocaine with σ1 receptors were assessed further using [125I]E-IA-DM-PE-PIPZE for regional cerebral biodistribution studies and quantitative ex vivo autoradiography of brain sections. (−)-Cocaine binding to cerebral σ1 receptors proved directly proportional to the relative site densities known for the brain regions. Non-radioactive E-IA-DM-PE-PIPZE gave an ED50 of 0.23 μmol/kg for occupancy of cerebral σ1 receptors, and a 3.16 μmol/kg (i.p.) dose attenuated (−)-cocaine induced locomotor hyperactivity by 30%. This effect did not reach statistical significance, but suggests that E-IA-DM-PE-PIPZE is a probable σ1 receptor antagonist. As groundwork for the in vivo studies, we used standard techniques in vitro to determine ligand affinities, site densities and pharmacological profiles for the σ1 and σ2 receptors expressed in CD-1® mouse brain. PMID:26618331

  7. Effect of Gingerol on Cisplatin-Induced Pica Analogous to Emesis Via Modulating Expressions of Dopamine 2 Receptor, Dopamine Transporter and Tyrosine Hydroxylase in the Vomiting Model of Rats

    PubMed Central

    Qian, Weibin; Cai, Xinrui; Wang, Yingying; Zhang, Xinying; Zhao, Hongmin; Qian, Qiuhai; Yang, Zhihong; Liu, Zhantao; Hasegawa, Junichi

    2016-01-01

    Background Gingerol, the generic term for pungent constituents in ginger, has been used for treating vomiting in China. We are going to investigate the mechanisms of inhibitive effect of gingerol on cisplatin-induced pica behaviour by studying on both peripheral and central levels, and the effects of gingerol on homeostasis of dopamine (DA) transmission: dopamine D2 receptor (D2R), dopamine transporter (DAT) and tyrosine hydroxylase (TH). Methods The antiemetic effect of gingerol was investigated on a vomiting model in rats induced by cisplatin 3 mg·kg−1 intraperitoneal injection (i.p.). Rats were randomly divided into the normal control group (C), simple gingerol control group (CG), cisplatin control group (V), cisplatin + metoclopramide group (M), cisplatin + low-dose gingerol group (GL), cisplatin + middle-dose gingerol group (GM) and cisplatin + high-dose gingerol group (GH). In observation period, rats in Groups C and V were pretreated with sterile saline 3 mL i.g.; rats in Group CG were pretreated with gingerol 40 mg·kg−1 i.g.; rats in Group M were pretreated with metoclopramide 2.5 mg·kg−1 i.g.; rats in Groups GL, GM and GH were pretreated with gingerol 10, 20 and 40 mg·kg−1 i.g. for 3 days, respectively. Cisplatin (3 mg·kg−1, i.p.) was administered one time after each treatment with the antiemetic agent or its vehicle except the Groups C and CG. The distribution of D2R, DAT and TH in the area postrema and ileum were measured by immunohistochemistry and quantitated based on the image analysis, and the expression of DAT and TH in the area postrema and ileum were measured by RT-PCR. The weights of kaolin eaten of the remaining rats were observed in every 6 h continuously for 72 h. Results The weight of kaolin eaten in rats induced by cisplatin was significantly reduced by pretreatment with gingerol in a dose-dependent manner during the 0–24 h and 24–72 h periods (P < 0.05). Gingerol markedly improved gastric emptying induced by cisplatin in

  8. Tesofensine, a novel triple monoamine re-uptake inhibitor with anti-obesity effects: dopamine transporter occupancy as measured by PET.

    PubMed

    Appel, Lieuwe; Bergström, Mats; Buus Lassen, Jørgen; Långström, Bengt

    2014-02-01

    Tesofensine (TE) is a novel triple monoamine re-uptake inhibitor inducing a potent inhibition of the re-uptake process in the synaptic cleft of the neurotransmitters dopamine, norepinephrine, and serotonin. In recent preclinical and clinical evaluations TE showed a robust anti-obesity effect, but the specific mechanism of this triple monoamine re-uptake inhibitor still needs to be further elucidated. This positron emission tomography (PET) study, using [¹¹C]βCIT-FE, aimed to assess the degree of the dopamine transporter (DAT) occupancy, at constant TE plasma levels, following different oral, multiple doses of TE during totally 8-12 days. In addition, the relationships between DAT occupancy and TE plasma concentrations, or doses, were investigated to enable assessment of DAT occupancies in subsequent clinical trials. The results demonstrated that TE induced a dose-dependent blockade of DAT following multiple doses of 0.125-1 mg TE at anticipated steady-state conditions. The mean striatal DAT occupancy varied dose-dependently between 18% and 77%. A sigmoid E(max) model well described the relationship between striatal DAT occupancy and TE plasma concentrations or doses. It was estimated that the maximum achievable DAT occupancy was about 80% and that half of this effect was accomplished by approximately 0.25 mg TE and a plasma drug concentration of 4 ng/ml. The results indicated an important mechanism of action of TE on DAT. Further, these results suggest that the previously reported dose-dependent weight loss, in TE treated subjects, was in part mediated by an up-regulation of dopaminergic pathways due to enhanced amounts of synaptic dopamine after blockade of DAT.

  9. Choline transporter hemizygosity results in diminished basal extracellular dopamine levels in nucleus accumbens and blunts dopamine elevations following cocaine or nicotine.

    PubMed

    Dong, Yu; Dani, John A; Blakely, Randy D

    2013-10-15

    Dopamine (DA) signaling in the central nervous system mediates the addictive capacities of multiple commonly abused substances, including cocaine, amphetamine, heroin and nicotine. The firing of DA neurons residing in the ventral tegmental area (VTA), and the release of DA by the projections of these neurons in the nucleus accumbens (NAc), is under tight control by cholinergic signaling mediated by nicotinic acetylcholine (ACh) receptors (nAChRs). The capacity for cholinergic signaling is dictated by the availability and activity of the presynaptic, high-affinity, choline transporter (CHT, SLC5A7) that acquires choline in an activity-dependent matter to sustain ACh synthesis. Here, we present evidence that a constitutive loss of CHT expression, mediated by genetic elimination of one copy of the Slc5a7 gene in mice (CHT+/-), leads to a significant reduction in basal extracellular DA levels in the NAc, as measured by in vivo microdialysis. Moreover, CHT heterozygosity results in blunted DA elevations following systemic nicotine or cocaine administration. These findings reinforce a critical role of ACh signaling capacity in both tonic and drug-modulated DA signaling and argue that genetically imposed reductions in CHT that lead to diminished DA signaling may lead to poor responses to reinforcing stimuli, possibly contributing to disorders linked to perturbed cholinergic signaling including depression and attention-deficit hyperactivity disorder (ADHD).

  10. Ascorbic acid and striatal transport of (/sup 3/H)1-methyl-4-phenylpyridine (MPP/sup +/) and (/sup 3/H)dopamine

    SciTech Connect

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

    1988-01-01

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

  11. In vivo activity of modafinil on dopamine transporter measured with positron emission tomography and [¹⁸F]FE-PE2I.

    PubMed

    Kim, WooChan; Tateno, Amane; Arakawa, Ryosuke; Sakayori, Takeshi; Ikeda, Yumiko; Suzuki, Hidenori; Okubo, Yoshiro

    2014-05-01

    Modafinil, a wake-promoting drug used to treat narcolepsy, is a dopamine transporter inhibitor and is said to have very low abuse liability; this, however, is still up for debate. We conducted a dopamine transporter (DAT) occupancy study with modafinil (200 or 300 mg) in ten healthy volunteers using positron emission tomography (PET) with [¹⁸F]FE-PE2I, a new PET radioligand with high affinity and selectivity for the dopamine transporter, to characterize its relation to abuse liability. Mean striatal DAT occupancies were 51.4% at 200 mg and 56.9% at 300 mg. There was a significant correlation between occupancy and plasma concentration, indicating dose dependency of DAT inhibition by modafinil in the striatum, and especially in the nucleus accumbens. This study showed that DAT occupancy by modafinil was close to that of methylphenidate, indicating that modafinil may be near the same level as methylphenidate in relation to abuse liability in terms of dopaminergic transmission.

  12. The role of 123I-ioflupane SPECT dopamine transporter imaging in the diagnosis and treatment of patients with dementia with Lewy bodies

    PubMed Central

    Antonini, Angelo

    2007-01-01

    The diagnosis of dementia with Lewy bodies (DLB) is difficult if one relies solely on clinical features. Current International Consensus Criteria for DLB have high specificity but a significant percentage of patients might be misdiagnosed. Reasons for clinical uncertainty regard the presence of concomitant motor signs in patients with Alzheimer’s disease as well as the observation that cognitive abnormalities in DLB might develop with memory impairment without significant parkinsonism. This has clinical relevance as DLB patients may be particularly sensitive to antipsychotics and even the effectiveness of atypical neuroleptics such as quetiapine for the treatment of agitation and hallucinations has been questioned by double-blind, placebo-controlled, randomized studies. By contrast, acetyl-cholinesterase inhibitors such as rivastigmine have shown benefit not only on cognitive but also on psychiatric symptoms. Recent evidence shows that striatal dopamine transporter binding of 123I-ioflupane SPECT is reduced in DLB and this is consistent with a significant loss of nigral dopamine neurons in this disorder. Several studies have demonstrated the diagnostic accuracy of 123I-ioflupane in the differential diagnosis of parkinsonism. Given the availability of SPECT, this investigation represents a useful marker to support clinical diagnosis and can help establishing appropriate treatment for this disorder. PMID:19300562

  13. Interaction between serotonin 5-HT2A receptor gene and dopamine transporter (DAT1) gene polymorphisms influences personality trait of persistence in Austrian Caucasians.

    PubMed

    Schosser, Alexandra; Fuchs, Karoline; Scharl, Theresa; Schloegelhofer, Monika; Kindler, Jochen; Mossaheb, Nilufar; Kaufmann, Rainer M; Leisch, Friedrich; Kasper, Siegfried; Sieghart, Werner; Aschauer, Harald N

    2010-03-01

    We examined 89 normal volunteers using Cloninger's Temperament and Character Inventory (TCI). Genotyping the 102T/C polymorphism of the serotonin 5HT2A receptor gene and the ser9gly polymorphism in exon 1 of the dopamine D3 receptor (DRD3) gene was performed using PCR-RFLP, whereas the dopamine transporter (DAT1) gene variable number of tandem repeats (VNTR) polymorphism was investigated using PCR amplification followed by electrophoresis in an 8% acrylamide gel with a set of size markers. We found a nominally significant association between gender and harm avoidance (P=0.017; women showing higher scores). There was no association of either DAT1, DRD3 or 5HT2A alleles or genotypes with any dimension of the TCI applying Kruskal-Wallis rank-sum tests. Comparing homozygote and heterozygote DAT1 genotypes, we found higher novelty seeking scores in homozygotes (P=0.054). We further found a nominally significant interaction between DAT1 and 5HT2A homo-/heterozygous gene variants (P=0.0071; DAT1 and 5HT2A genotypes P value of 0.05), performing multivariate analysis of variance (MANOVA). Examining the temperamental TCI subscales, this interaction was associated with persistence (genotypes: P=0.004; homo-/heterozygous gene variants: P=0.0004). We conclude that an interaction between DAT1 and 5HT2A genes might influence the temperamental personality trait persistence.

  14. Solid metabolic waste transport and stowage investigation

    NASA Technical Reports Server (NTRS)

    Burt, R. A.; Koesterer, M. G.; Hunt, S. R., Jr.

    1974-01-01

    The basic Waste Collection System (WCS) design under consideration utilized air flow to separate the stool from the WCS user and to transport the fecal material to a slinger device for subsequent deposition on a storage bowel. The major parameters governing stool separation and transport were found to be the area of the air inlet orifices, the configuration of the air inlet orifice and the transport air flow. Separation force and transport velocity of the stool were studied. The developed inlet orifice configuration was found to be an effective design for providing fecal separation and transport. Simulated urine tests and female user tests in zero gravity established air flow rates between 0.08 and 0.25 cu sm/min (3 and 9 scfm) as satisfactory for entrapment, containment and transport of urine using an urinal. The investigation of air drying of fecal material as a substitute for vacuum drying in a WCS breadboard system showed that using baseline conditions anticipated for the shuttle cabin ambient atmosphere, flow rates of 0.14 cu sm/min (5 cfm) were adequate for drying and maintaining biological stability of the fecal material.

  15. An Investigation of Synchrony in Transport Networks

    NASA Technical Reports Server (NTRS)

    Kincaid, Rex K.; Alexandrov, Natalia M.; Holroyd, Michael J.

    2007-01-01

    The cumulative degree distributions of transport networks, such as air transportation networks and respiratory neuronal networks, follow power laws. The significance of power laws with respect to other network performance measures, such as throughput and synchronization, remains an open question. Evolving methods for the analysis and design of air transportation networks must address network performance in the face of increasing demands and the need to contain and control local network disturbances, such as congestion. Toward this end, we investigate functional relationships that govern the performance of transport networks; for example, the links between the first nontrivial eigenvalue of a network's Laplacian matrix - a quantitative measure of network synchronizability - and other global network parameters. In particular, among networks with a fixed degree distribution and fixed network assortativity (a measure of a network's preference to attach nodes based on a similarity or difference), those with the small eigenvalue are shown to be poor synchronizers, to have much longer shortest paths and to have greater clustering in comparison to those with large. A simulation of a respiratory network adds data to our investigation. This study is a beginning step in developing metrics and design variables for the analysis and active design of air transport networks.

  16. Spontaneous Inward Opening of the Dopamine Transporter Is Triggered by PIP2-Regulated Dynamics of the N-Terminus

    PubMed Central

    2015-01-01

    We present the dynamic mechanism of concerted motions in a full-length molecular model of the human dopamine transporter (hDAT), a member of the neurotransmitter/sodium symporter (NSS) family, involved in state-to-state transitions underlying function. The findings result from an analysis of unbiased atomistic molecular dynamics simulation trajectories (totaling >14 μs) of the hDAT molecule immersed in lipid membrane environments with or without phosphatidylinositol 4,5-biphosphate (PIP2) lipids. The N-terminal region of hDAT (N-term) is shown to have an essential mechanistic role in correlated rearrangements of specific structural motifs relevant to state-to-state transitions in the hDAT. The mechanism involves PIP2-mediated electrostatic interactions between the N-term and the intracellular loops of the transporter molecule. Quantitative analyses of collective motions in the trajectories reveal that these interactions correlate with the inward-opening dynamics of hDAT and are allosterically coupled to the known functional sites of the transporter. The observed large-scale motions are enabled by specific reconfiguration of the network of ionic interactions at the intracellular end of the protein. The isomerization to the inward-facing state in hDAT is accompanied by concomitant movements in the extracellular vestibule and results in the release of an Na+ ion from the Na2 site and destabilization of the substrate dopamine in the primary substrate binding S1 site. The dynamic mechanism emerging from the findings highlights the involvement of the PIP2-regulated interactions between the N-term and the intracellular loop 4 in the functionally relevant conformational transitions that are also similar to those found to underlie state-to-state transitions in the leucine transporter (LeuT), a prototypical bacterial homologue of the NSS. PMID:26255829

  17. Spontaneous inward opening of the dopamine transporter is triggered by PIP2-regulated dynamics of the N-terminus.

    PubMed

    Khelashvili, George; Stanley, Nathaniel; Sahai, Michelle A; Medina, Jaime; LeVine, Michael V; Shi, Lei; De Fabritiis, Gianni; Weinstein, Harel

    2015-11-18

    We present the dynamic mechanism of concerted motions in a full-length molecular model of the human dopamine transporter (hDAT), a member of the neurotransmitter/sodium symporter (NSS) family, involved in state-to-state transitions underlying function. The findings result from an analysis of unbiased atomistic molecular dynamics simulation trajectories (totaling >14 μs) of the hDAT molecule immersed in lipid membrane environments with or without phosphatidylinositol 4,5-biphosphate (PIP2) lipids. The N-terminal region of hDAT (N-term) is shown to have an essential mechanistic role in correlated rearrangements of specific structural motifs relevant to state-to-state transitions in the hDAT. The mechanism involves PIP2-mediated electrostatic interactions between the N-term and the intracellular loops of the transporter molecule. Quantitative analyses of collective motions in the trajectories reveal that these interactions correlate with the inward-opening dynamics of hDAT and are allosterically coupled to the known functional sites of the transporter. The observed large-scale motions are enabled by specific reconfiguration of the network of ionic interactions at the intracellular end of the protein. The isomerization to the inward-facing state in hDAT is accompanied by concomitant movements in the extracellular vestibule and results in the release of an Na(+) ion from the Na2 site and destabilization of the substrate dopamine in the primary substrate binding S1 site. The dynamic mechanism emerging from the findings highlights the involvement of the PIP2-regulated interactions between the N-term and the intracellular loop 4 in the functionally relevant conformational transitions that are also similar to those found to underlie state-to-state transitions in the leucine transporter (LeuT), a prototypical bacterial homologue of the NSS.

  18. Non-dioxin-like PCBs inhibit [(3)H]WIN-35,428 binding to the dopamine transporter: a structure-activity relationship study.

    PubMed

    Wigestrand, M B; Stenberg, M; Walaas, S I; Fonnum, F; Andersson, P L

    2013-12-01

    Non-dioxin-like polychlorinated biphenyls (NDL-PCBs) are neurotoxic compounds with known effects at the dopaminergic system in the brain. In a previous study we demonstrated that NDL-PCBs inhibit uptake of dopamine into rat brain synaptosomes, an effect most likely mediated by inhibition of the dopamine transporter (DAT). Here, using the cocaine analogue [(3)H]WIN-35,428 binding assay and synaptosomes, we directly investigate whether NDL-PCBs act via DAT and explore the structure-activity relationship of this effect. In total, thirty PCBs were investigated, including a previously selected training set of twenty PCBs covering the structural variation within tri- to hepta-chlorinated NDL-PCBs, and an additional set of ten NDL-PCB congeners selected to validate the structure-activity pattern of neurotoxic PCBs. Since previous work has demonstrated that NDL-PCBs can also inhibit the vesicular monoamine transporter 2 (VMAT2), we additionally examined whether some PCB congeners favour an effect on VMAT2 and others on DAT. Our results show that NDL-PCBs are potent inhibitors of [(3)H]WIN-35,428 binding to DAT. In fact, we identify a PCB congener (PCB 110) with similar potency for [(3)H]WIN-35,428 binding inhibition as cocaine. All active congeners were ortho-chlorinated PCBs, and in particular, tetra- and penta-chlorinated with 2-3 chlorine atoms in the ortho position were potent inhibitors of [(3)H]WIN-35,428 binding. Notably, the most active PCBs are highly prevalent in commercial mixtures of PCBs (Aroclor 1242, 1254 and 1260), which indicates that DAT inhibition could be one of the factors contributing to behavioural effects after Aroclor exposure. Derived data correlated well with the recently derived neurotoxic equivalency factors (NEQs), indicating the generality and applicability of the NEQ scheme in risk assessments of PCBs.

  19. Extended methamphetamine self-administration in rats results in a selective reduction of dopamine transporter levels in the prefrontal cortex and dorsal striatum not accompanied by marked monoaminergic depletion.

    PubMed

    Schwendt, Marek; Rocha, Angelica; See, Ronald E; Pacchioni, Alejandra M; McGinty, Jacqueline F; Kalivas, Peter W

    2009-11-01

    Chronic abuse of methamphetamine leads to cognitive dysfunction and high rates of relapse, paralleled by significant changes of brain dopamine and serotonin neurotransmission. Previously, we found that rats with extended access to methamphetamine self-administration displayed enhanced methamphetamine-primed reinstatement of drug-seeking and cognitive deficits relative to limited access animals. The present study investigated whether extended access to methamphetamine self-administration produced abnormalities in dopamine and serotonin systems in rat forebrain. Rats self-administered methamphetamine (0.02-mg/i.v. infusion) during daily 1-h sessions for 7 to 10 days, followed by either short- (1-h) or long-access (6-h) self-administration for 12 to 14 days. Lever responding was extinguished for 2 weeks before either reinstatement testing or rapid decapitation and tissue dissection. Tissue levels of monoamine transporters and markers of methamphetamine-induced toxicity were analyzed in several forebrain areas. Long-access methamphetamine self-administration resulted in escalation of daily drug intake ( approximately 7 mg/kg/day) and enhanced drug-primed reinstatement compared with the short-access group. Furthermore, long-, but not short-access to self-administered methamphetamine resulted in persistent decreases in dopamine transporter (DAT) protein levels in the prefrontal cortex and dorsal striatum. In contrast, only minor alterations in the tissue levels of dopamine or its metabolites were found, and no changes in markers specific for dopamine terminals or glial cell activation were detected. Our findings suggest that persistent methamphetamine seeking is associated with region-selective changes in DAT levels without accompanying monoaminergic neurotoxicity. Greater understanding of the neuroadaptations underlying persistent methamphetamine seeking and cognitive deficits could yield targets suitable for future therapeutic interventions.

  20. Changes in dopamine transporter binding in nucleus accumbens following chronic self-administration cocaine: heroin combinations.

    PubMed

    Pattison, Lindsey P; McIntosh, Scot; Sexton, Tammy; Childers, Steven R; Hemby, Scott E

    2014-10-01

    Concurrent use of cocaine and heroin (speedball) has been shown to exert synergistic effects on dopamine neurotransmission in the nucleus accumbens (NAc), as observed by significant increases in extracellular dopamine levels and compensatory elevations in the maximal reuptake rate of dopamine. The present studies were undertaken to determine whether chronic self-administration of cocaine, heroin or a combination of cocaine:heroin led to compensatory changes in the abundance and/or affinity of high- and low-affinity DAT binding sites. Saturation binding of the cocaine analog [(125) I] 3β-(4-iodophenyl)tropan-2β-carboxylic acid methyl ester ([(125) I]RTI-55) in rat NAc membranes resulted in binding curves that were best fit to two-site binding models, allowing calculation of dissociation constant (Kd ) and binding density (Bmax ) values corresponding to high- and low-affinity DAT binding sites. Scatchard analysis of the saturation binding curves clearly demonstrate the presence of high- and low- affinity binding sites in the NAc, with low-affinity sites comprising 85 to 94% of the binding sites. DAT binding analyses revealed that self-administration of cocaine and a cocaine:heroin combination increased the affinity of the low-affinity site for the cocaine congener RTI-55 compared to saline. These results indicate that the alterations observed following chronic speedball self-administration are likely due to the cocaine component alone; thus further studies are necessary to elaborate upon the synergistic effect of cocaine:heroin combinations on the dopamine system in the NAc.

  1. 3,4-Methylenedioxypyrovalerone prevents while methylone enhances methamphetamine-induced damage to dopamine nerve endings: β-ketoamphetamine modulation of neurotoxicity by the dopamine transporter.

    PubMed

    Anneken, John H; Angoa-Pérez, Mariana; Kuhn, Donald M

    2015-04-01

    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. METH (a) enters DA nerve endings via the DAT, causes leakage of DA into the cytoplasm and then into the synapse via DAT-mediated reverse transport. Methylone (METHY) and mephedrone (MEPH; b), like METH, are substrates for the DAT but release

  2. The interaction of methylphenidate and benztropine with the dopamine transporter is different than other substrates and ligands.

    PubMed

    Dar, Dalit E; Mayo, Cheryl; Uhl, George R

    2005-08-01

    A substantial body of evidence suggests that the dopamine transporter (DAT) is the principal site for cocaine-induced reward and euphoria. Interactions between the DAT and its substrates and ligands may therefore be of clinical relevance. The pharmacological characteristics of DAT compounds were compared in wild type (WT) and mutant DATs. The DAT mutants chosen for study were those with reduced binding and uptake activities (aspartic acid 79 mutated to alanine, termed D79A), reduced binding but normal uptake (tyrosine 251 mutated to alanine, termed Y251A; tyrosine 273 mutated to alanine, termed, Y273A), and normal binding but reduced uptake (a double mutation: serines 356 and 359 mutated to alanine, termed S356,359A). The WT and mutant DATs were transfected into COS-7 cells, and their pharmacological activities were examined 3 days later. Different patterns of pharmacological activity emerged. GBR 12909, cocaine, and mazindol each showed reduced affinity for the Y251A and the Y273A mutants, but their affinity for the S356,359A mutant was similar to that of the WT DAT. d-Amphetamine, MPP+, and dopamine each showed reduced affinity for the S356,359A mutant. Benztropine and methylphenidate had a different effect. Relative to the WT DAT, they both showed reduced affinity for the S356,359A mutant when displacing radioactive carboxyfluorotropane (CFT) binding, but similar affinity when inhibiting radioactive dopamine uptake. These results indicate that methylphenidate and benztropine may interact with the DAT in a different fashion then other substrates and ligands.

  3. No association between schizophrenia and polymorphisms within the genes for debrisoquine 4-hydroxylase (CYP2D6) and the dopamine transporter (DAT)

    SciTech Connect

    Daniels, J.; Williams, J.; Asherson, P.; McGuffin, P.; Owen, M.

    1995-02-27

    It has been suggested that the cytochrome P450 mono-oxygenase, debrisoquine 4-hydroxylase, is involved in the catabolism and processing of neurotransmitters subsequent to their reuptake into target cells. It is also thought to be related to the dopamine transporter that acts to take released dopamine back up into presynaptic terminals. The present study used the association approach to test the hypothesis that mutations in the genes for debrisoquine 4-hydroxylase (CYP2D6) and the dopamine transporter (DAT) confer susceptibility to schizophrenia. There were no differences in allele or genotype frequencies between patients and controls in the mutations causing the poor metaboliser phenotype in CYP2D6. In addition there was no association found between schizophrenia and a 48 bp repeat within the 3{prime} untranslated region of DAT. 18 refs., 2 tabs.

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

    PubMed Central

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

    2016-01-01

    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. PMID:27481941

  5. An interaction between the serotonin transporter promoter region and dopamine transporter polymorphisms contributes to harm avoidance and reward dependence traits in normal healthy subjects.

    PubMed

    Kim, S J; Kim, Y S; Lee, H S; Kim, S Y; Kim, C-H

    2006-07-01

    There is evidence for an association between polymorphisms of serotonin- and dopamine-related genes and temperamental personality traits. Recent findings have shown that interactions between allelic variants of the different genes may contribute to personality traits. We examined the effects of serotonin transporter-linked promoter region (5-HTTLPR) and dopamine transporter (DAT1) gene polymorphisms for associations with the Temperament and Character Inventory (TCI) temperament subscales in 209 Koreans. We found that the variants of 5-HTTLPR interacted with the DAT1 gene polymorphism to influence the HA and RD temperament subscales of TCI. Neither of these two genes affected any subscales of TCI alone.Controlling for the effects of gender and age, we found significant interactions between 5-HTTLPR and DAT1 genes on Harm Avoidance (HA) and Reward Dependence (RD) as measured by the TCI (Hotelling's Trace = 3.0, P = 0.02). In the presence of the DAT1 10/10 genotype, subjects of group L of 5-HTTLPR had a significantly higher HA score and significantly lower RD score than those of group S (F = 5.04, df = 1, p = 0.03 and F = 8.35, df = 1, p = 0.004, respectively). These findings suggest that the variants of 5-HTTLPR interacted with the DAT1 gene polymorphism to influence the HA and RD temperament subscales of TCI.

  6. Investigation of the reduction process of dopamine using paired pulse voltammetry

    PubMed Central

    Kim, Do Hyoung; Oh, Yoonbae; Shin, Hojin; Blaha, Charles D.; Bennet, Kevin E.; Lee, Kendall H.; Kim, In Young; Jang, Dong Pyo

    2014-01-01

    The oxidation of dopamine (DA) around +0.6V potential in anodic sweep and its reduction around −0.1V in cathodic sweep at a relatively fast scanning rate (300 V/s or greater) have been used for identification of DA oxidation in fast-scan cyclic voltammetry (FSCV). However, compared to the oxidation peak of DA, the reduction peak has not been fully examined in analytical studies, although it has been used as one of the representative features to identify DA. In this study, the reduction process of DA was investigated using paired pulse voltammetry (PPV), which consists of two identical triangle-shaped waveforms, separated by a short interval at the holding potential. Especially, the discrepancies between the magnitude of the oxidation and reduction peaks of DA were investigated based on three factors: (1) the instant desorption of the DA oxidation product (dopamine-o-quinone: DOQ) after production, (2) the effect of the holding potential on the reduction process, and (3) the rate-limited reduction process of DA. For the first test, the triangle waveform FSCV experiment was performed on DA with various scanrates (from 400 to 1000 V/s) and durations of switching potentials of the triangle waveform (from 0.0 to 6.0 ms) in order to vary the duration between the applied oxidation potential at +0.6V and the reduction potential at −0.2V. As a result, the ratio of reduction over oxidation peak current response decreased as the duration became longer. To evaluate the effect of holding potentials during the reduction process, FSCV experiments were conducted with holding potential from 0.0V to −0.8V. We found that more negative holding potentials lead to larger amount of reduction process. For evaluation of the rate-limited reduction process of DA, PPV with a 1Hz repetition rate and various delays (2, 8, 20, 40 and 80ms) between the paired scans were utilized to determine how much reduction process occurred during the holding potential (−0.4V). These tests showed that

  7. Investigation of the reduction process of dopamine using paired pulse voltammetry.

    PubMed

    Kim, Do Hyoung; Oh, Yoonbae; Shin, Hojin; Blaha, Charles D; Bennet, Kevin E; Lee, Kendall H; Kim, In Young; Jang, Dong Pyo

    2014-03-15

    The oxidation of dopamine (DA) around +0.6V potential in anodic sweep and its reduction around -0.1V in cathodic sweep at a relatively fast scanning rate (300 V/s or greater) have been used for identification of DA oxidation in fast-scan cyclic voltammetry (FSCV). However, compared to the oxidation peak of DA, the reduction peak has not been fully examined in analytical studies, although it has been used as one of the representative features to identify DA. In this study, the reduction process of DA was investigated using paired pulse voltammetry (PPV), which consists of two identical triangle-shaped waveforms, separated by a short interval at the holding potential. Especially, the discrepancies between the magnitude of the oxidation and reduction peaks of DA were investigated based on three factors: (1) the instant desorption of the DA oxidation product (dopamine-o-quinone: DOQ) after production, (2) the effect of the holding potential on the reduction process, and (3) the rate-limited reduction process of DA. For the first test, the triangle waveform FSCV experiment was performed on DA with various scanrates (from 400 to 1000 V/s) and durations of switching potentials of the triangle waveform (from 0.0 to 6.0 ms) in order to vary the duration between the applied oxidation potential at +0.6V and the reduction potential at -0.2V. As a result, the ratio of reduction over oxidation peak current response decreased as the duration became longer. To evaluate the effect of holding potentials during the reduction process, FSCV experiments were conducted with holding potential from 0.0V to -0.8V. We found that more negative holding potentials lead to larger amount of reduction process. For evaluation of the rate-limited reduction process of DA, PPV with a 1Hz repetition rate and various delays (2, 8, 20, 40 and 80ms) between the paired scans were utilized to determine how much reduction process occurred during the holding potential (-0.4V). These tests showed that

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

    SciTech Connect

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

    1989-07-25

    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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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, ...

  10. Epitope-tagged dopamine transporter knock-in mice reveal rapid endocytic trafficking and filopodia targeting of the transporter in dopaminergic axons

    PubMed Central

    Rao, Anjali; Richards, Toni L.; Simmons, Diana; Zahniser, Nancy R.; Sorkin, Alexander

    2012-01-01

    The plasma membrane dopamine (DA) transporter (DAT) is essential for reuptake of extracellular DA. DAT function in heterologous cells is regulated by subcellular targeting, endocytosis, and intracellular trafficking, but the mechanisms regulating neuronal DAT remain poorly understood. Hence, we generated a knock-in mouse expressing a hemagglutinin (HA)-epitope-tagged DAT to study endogenous transporter trafficking. Introduction of the HA tag into the second extracellular loop of mouse DAT did not perturb its expression level, distribution pattern, or substrate uptake kinetics. Live-cell fluorescence microscopy imaging using fluorescently labeled HA-specific antibody and a quantitative HA-antibody endocytosis assay demonstrated that in axons HA-DAT was primarily located in the plasma membrane and internalized mostly in growth cones and varicosities, where synaptic vesicle markers were also concentrated. Formation of varicosities was frequently preceded or accompanied by highly dynamic filopodia-like membrane protrusions. Remarkably, HA-DAT often concentrated at the tips of these filopodia. This pool of HA-DATs exhibited low lateral membrane mobility. Thus, DAT-containing filopodia may be involved in synaptogenesis in developing DA neurons. Treatment of neurons with amphetamine increased mobility of filopodial HA-DAT and accelerated HA-DAT endocytosis in axons, suggesting that chronic amphetamine may interfere with DA synapse development. Interestingly, phorbol esters did not accelerate endocytosis of axonal DAT.—Rao, A., Richards, T. L., Simmons, D., Zahniser, N. R., Sorkin, A. Epitope-tagged dopamine transporter knock-in mice reveal rapid endocytic trafficking and filopodia targeting of the transporter in dopaminergic axons. PMID:22267337

  11. Investigation of the mechanism of agonist and inverse agonist action at D2 dopamine receptors.

    PubMed

    Roberts, David J; Lin, Hong; Strange, Philip G

    2004-05-01

    This study investigated, for the D2 dopamine receptor, the relation between the ability of agonists and inverse agonists to stabilise different states of the receptor and their relative efficacies. Ki values for agonists were determined in competition versus the binding of the antagonist [3H]spiperone. Competition data were fitted best by a two-binding site model (with the exception of bromocriptine, for which a one-binding site model provided the best fit) and agonist affinities for the higher (Kh) (G protein-coupled) and lower affinity (Kl) (G protein-uncoupled) sites determined. Ki values for agonists were also determined in competition versus the binding of the agonist [3H]N-propylnorapomorphine (NPA) to provide a second estimate of Kh. Maximal agonist effects (Emax) and their potencies (EC50) were determined from concentration-response curves for agonist stimulation of guanosine-5'-O-(3-[32S]thiotriphosphate) ([35S]GTPgammaS) binding. The ability of agonists to stabilise the G protein-coupled state of the receptor (Kl/Kh determined from ligand-binding assays) did not correlate with either of two measures of relative efficacy (relative Emax, Kl/EC50) of agonists determined in [35S]GTPgammaS-binding assays, when the data for all of the compounds tested were analysed. For a subset of compounds, however, there was a relation between Kl/Kh and Emax. Competition-binding data versus [3H]spiperone and [3H]NPA for a range of inverse agonists were fitted best by a one-binding site model. Ki values for the inverse agonists tested were slightly lower in competition versus [3H]NPA compared to [3H]spiperone. These data do not provide support for the idea that inverse agonists act by binding preferentially to the ground state of the receptor.

  12. Association study of the dopamine transporter gene with personality traits and major depressive disorder in the Han Chinese population.

    PubMed

    Huang, Chang-Chih; Lu, Ru-Band; Shih, Mei-Chen; Yen, Che-Hung; Huang, San-Yuan

    2011-02-01

    Major depression is a complex psychiatric disorder involving multiple factors, including genetic and personality components. This study used 17 polymorphisms of dopamine transporter gene (DAT1) to explore whether this gene is associated with major depression and whether it influences personality traits in patients with major depression. The DAT1 polymorphisms were analyzed in 1017 unrelated individuals and 459 patients were eligible to assess personality traits. We found a borderline association between controls and total major depression and between major depression with family history versus controls; however, these differences were obscured after correction for multiple testing. Furthermore, the DAT1 polymorphisms were not associated either with major depression in haplotype analysis or with personality traits. Despite the fact that several association tendencies were found between DAT1 and major depression, we did not confirm a major role for DAT1 in the susceptibility to major depression. In addition, DAT1 does not seem to affect personality traits observed in patients with major depression.

  13. Carriers of a common variant in the dopamine transporter gene have greater dementia risk, cognitive decline, and faster ventricular expansion

    PubMed Central

    Roussotte, Florence F.; Gutman, Boris A.; Hibar, Derrek P.; Madsen, Sarah K.; Narr, Katherine L.; Thompson, Paul M.

    2015-01-01

    Background Genetic variants in DAT1, the gene encoding the dopamine transporter protein (DAT), have been implicated in many brain disorders. In a recent case-control study of Alzheimer’s disease (AD), a regulatory polymorphism in DAT1 showed a significant association with the clinical stages of dementia. Methods We tested whether this variant was associated with increased AD risk, and with measures of cognitive decline and longitudinal ventricular expansion, in a large sample of elderly participants with genetic, neurocognitive, and neuroimaging data from the Alzheimer’s Disease Neuroimaging Initiative. Results The minor allele – previously linked with increased DAT expression in vitro – was More common in AD patients than in both individuals with mild cognitive impairment and Healthy elderly controls. The same allele was also associated with poorer cognitive performance and faster ventricular expansion, independently of diagnosis. Conclusion These results may be due to reduced dopaminergic transmission in carriers of the DAT1 mutation. PMID:25496873

  14. Homeostatic mechanisms in dopamine synthesis and release: a mathematical model

    PubMed Central

    Best, Janet A; Nijhout, H Frederik; Reed, Michael C

    2009-01-01

    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 half-lives of extracellular

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

    SciTech Connect

    Gelernter, J.; Kruger, S.D.; Pakstis, A.J. |

    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.

  16. Genetic Complementation Screen Identifies a Mitogen-activated Protein Kinase Phosphatase, MKP3, as a Regulator of Dopamine Transporter Trafficking

    PubMed Central

    Larsen, Mads Breum; Prasad, Balakrishna M.; Amara, Susan G.

    2008-01-01

    The antidepressant and cocaine sensitive plasma membrane monoamine transporters are the primary mechanism for clearance of their respective neurotransmitters and serve a pivotal role in limiting monoamine neurotransmission. To identify molecules in pathways that regulate dopamine transporter (DAT) internalization, we used a genetic complementation screen in Xenopus oocytes to identify a mitogen-activated protein (MAP) kinase phosphatase, MKP3/Pyst1/DUSP6, as a molecule that inhibits protein kinase C–induced (PKC) internalization of transporters, resulting in enhanced DAT activity. The involvement of MKP3 in DAT internalization was verified using both overexpression and shRNA knockdown strategies in mammalian cell models including a dopaminergic cell line. Although the isolation of MKP3 implies a role for MAP kinases in DAT internalization, MAP kinase inhibitors have no effect on internalization. Moreover, PKC-dependent down-regulation of DAT does not correlate with the phosphorylation state of several well-studied MAP kinases (ERK1/2, p38, and SAPK/JNK). We also show that MKP3 does not regulate PKC-induced ubiquitylation of DAT but acts at a more downstream step to stabilize DAT at the cell surface by blocking dynamin-dependent internalization and delaying the targeting of DAT for degradation. These results indicate that MKP3 can act to enhance DAT function and identifies MKP3 as a phosphatase involved in regulating dynamin-dependent endocytosis. PMID:18434601

  17. Antagonist-induced conformational changes in dopamine transporter extracellular loop two involve residues in a potential salt bridge.

    PubMed

    Gaffaney, Jon D; Shetty, Madhur; Felts, Bruce; Pramod, Akula-Bala; Foster, James D; Henry, L Keith; Vaughan, Roxanne A

    2014-07-01

    Ligand-induced changes in the conformation of extracellular loop (EL) 2 in the rat (r) dopamine transporter (DAT) were examined using limited proteolysis with endoproteinase Asp-N and detection of cleavage products by epitope-specific immunoblotting. The principle N-terminal fragment produced by Asp-N was a 19kDa peptide likely derived by proteolysis of EL2 residue D174, which is present just past the extracellular end of TM3. Production of this fragment was significantly decreased by binding of cocaine and other uptake blockers, but was not affected by substrates or Zn(2+), indicating the presence of a conformational change at D174 that may be related to the mechanism of transport inhibition. DA transport activity and cocaine analog binding were decreased by Asp-N treatment, suggesting a requirement for EL2 integrity in these DAT functions. In a previous study we demonstrated that ligand-induced protease resistance also occurred at R218 on the C-terminal side of rDAT EL2. Here using substituted cysteine accessibility analysis of human (h) DAT we confirm cocaine-induced alterations in reactivity of the homologous R219 and identify conformational sensitivity of V221. Focused molecular modeling of D174 and R218 based on currently available Aquifex aeolicus leucine transporter crystal structures places these residues within 2.9Å of one another, suggesting their proximity as a structural basis for their similar conformational sensitivities and indicating their potential to form a salt bridge. These findings extend our understanding of DAT EL2 and its role in transport and binding functions.

  18. Mutational analysis of the high-affinity zinc binding site validates a refined human dopamine transporter homology model.

    PubMed

    Stockner, Thomas; Montgomery, Therese R; Kudlacek, Oliver; Weissensteiner, Rene; Ecker, Gerhard F; Freissmuth, Michael; Sitte, Harald H

    2013-01-01

    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.

  19. Characterization of reduced and oxidized dopamine and 3,4-dihydrophenylacetic acid, on brain mitochondrial electron transport chain activities.

    PubMed

    Gautam, Alpa H; Zeevalk, Gail D

    2011-07-01

    Loss of dopamine (DA) homeostasis may be a contributing factor to cell damage in Parkinson's disease (PD). Past studies showing deleterious effects of DA on mitochondrial function, however, have been inconsistent raising questions about mitochondria as a downstream target for DA. Issues such as the dopamine species i.e., reduced or oxidized, time of exposure and the effect of major metabolites such as 3,4-dihydrophenylacetic acid (DOPAC) may contribute to the disparate findings. The present study used isolated, lysed rat brain mitochondria to characterize the effects of oxidized or reduced DA and DOPAC on complex activities of the electron transport chain (ETC). Time of exposure and quantitation of reduced or oxidized catachols for DA and DOPAC were monitored for all experiments. Reduced DA and DOPAC with or without a 30min preincubation had no affect on NADH oxidase activity which monitors the activities of complexes I, III and IV. Complex II activity was inhibited by reduced DA (≥500μM), but not by reduced DOPAC and was significantly attenuated by SOD suggesting reactive oxygen species involvement. In contrast, fully oxidized DA and DOPAC dose dependently inhibited NADH oxidase, complex I and complex III activities with IC(50s) in the 50-200μM range. No preincubation was required for inhibition with the catechols when they were fully oxidized. Oxidized DA inhibited complex I only when exposure occurred during stimulated electron flow, suggesting covalent binding of quinones to proteins within active sites of the complex. In intact, well coupled mitochondria, extramitochondrial DA was shown to access the mitochondrial matrix in a dose, time and energy-dependent fashion. The findings suggest that many of the reported inconsistencies with regards to the effects of DA and DOPAC on ETC function can be attributed to the oxidized state of the catechol at the time of exposure. In addition, the findings provide possible downstream targets for DA that could contribute

  20. Dopamine transporter DAT and receptor DRD2 variants affect risk of lethal cocaine abuse: a gene–gene–environment interaction

    PubMed Central

    Sullivan, D; Pinsonneault, J K; Papp, A C; Zhu, H; Lemeshow, S; Mash, D C; Sadee, W

    2013-01-01

    Epistatic gene–gene interactions could contribute to the heritability of complex multigenic disorders, but few examples have been reported. Here, we focus on the role of aberrant dopaminergic signaling, involving the dopamine transporter DAT, a cocaine target, and the dopamine D2 receptor, which physically interacts with DAT. Splicing polymorphism rs2283265 of DRD2, encoding D2 receptors, were shown to confer risk of cocaine overdose/death (odds ratio ∼3) in subjects and controls from the Miami Dade County Brain Bank.1 Risk of cocaine-related death attributable to the minor allele of rs2283265 was significantly enhanced to OR=7.5 (P=0.0008) in homozygous carriers of the main 6-repeat allele of DAT rs3836790, a regulatory VNTR in intron8 lacking significant effect itself. In contrast, carriers of the minor 5-repeat DAT allele showed no significant risk (OR=1.1, P=0.84). DAT rs3836790 and DRD2 rs2283265 also interacted by modulating DAT protein activity in the ventral putamen of cocaine abusers. In high-linkage disequilibrium with the VNTR, DAT rs6347 in exon9 yielded similar results. Assessing the impact of DAT alone, a rare DAT haplotype formed by the minor alleles of rs3836790 and rs27072, a regulatory DAT variant in the 3′-UTR, occurred in nearly one-third of the cocaine abusers but was absent in African American controls, apparently conferring strong risk. These results demonstrate gene–gene–drug interaction affecting risk of fatal cocaine intoxication. PMID:23340505

  1. Increased impulsive behavior and risk proneness following lentivirus-mediated dopamine transporter over-expression in rats' nucleus accumbens.

    PubMed

    Adriani, W; Boyer, F; Gioiosa, L; Macrì, S; Dreyer, J-L; Laviola, G

    2009-03-03

    Multiple theories have been proposed for sensation seeking and vulnerability to impulse-control disorders [Zuckerman M, Kuhlman DM (2000) Personality and risk-taking: Common biosocial factors. J Pers 68:999-1029], and many of these rely on a dopamine system deficit. Available animal models reproduce only some behavioral symptoms and seem devoid of construct validity. We used lentivirus tools for over-expressing or silencing the dopamine transporter (DAT) and we evaluated the resulting behavioral profiles in terms of motivation and self-control. Wistar adult rats received stereotaxic inoculation of a lentivirus that allowed localized intra-accumbens delivery of a DAT gene enhancer/silencer, or the green fluorescent protein, GFP. These animals were studied for intolerance to delay, risk proneness and novelty seeking. As expected, controls shifted their demanding from a large reward toward a small one when the delivery of the former was increasingly delayed (or uncertain). Interestingly, in the absence of general locomotor effects, DAT over-expressing rats showed increased impulsivity (i.e. a more marked shift of demanding from the large/delayed toward the small/soon reward), and increased risk proneness (i.e. a less marked shift from the large/uncertain toward the small/sure reward), compared with controls. Rats with enhanced or silenced DAT expression did not show any significant preference for a novel environment. In summary, consistent with literature on comorbidity between attention-deficit/hyperactivity disorder and pathological gambling, we demonstrate that DAT over-expression in rats' nucleus accumbens leads to impulsive and risk prone phenotype. Thus, a reduced dopaminergic tone following altered accumbal DAT function may subserve a sensation-seeker phenotype and the vulnerability to impulse-control disorders.

  2. Valeriana officinalis does not alter the orofacial dyskinesia induced by haloperidol in rats: role of dopamine transporter.

    PubMed

    Fachinetto, Roselei; Villarinho, Jardel G; Wagner, Caroline; Pereira, Romaiana P; Avila, Daiana Silva; Burger, Marilise E; Calixto, João Batista; Rocha, João B T; Ferreira, Juliano

    2007-10-01

    Chronic treatment with classical neuroleptics in humans can produce a serious side effect, known as tardive dyskinesia (TD). Here, we examined the effects of V. officinalis, a medicinal herb widely used as calming and sleep-promoting, in an animal model of orofacial dyskinesia (OD) induced by long-term treatment with haloperidol. Adult male rats were treated during 12 weeks with haloperidol decanoate (38 mg/kg, i.m., each 28 days) and with V. officinalis (in the drinking water). Vacuous chewing movements (VCMs), locomotor activity and plus maze performance were evaluated. Haloperidol treatment produced VCM in 40% of the treated rats and the concomitant treatment with V. officinalis did not alter either prevalence or intensity of VCMs. The treatment with V. officinalis increased the percentage of the time spent on open arm and the number of entries into open arm in the plus maze test. Furthermore, the treatment with haloperidol and/or V. officinalis decreased the locomotor activity in the open field test. We did not find any difference among the groups when oxidative stress parameters were evaluated. Haloperidol treatment significantly decreased [(3)H]-dopamine uptake in striatal slices and V. officinalis was not able to prevent this effect. Taken together, our data suggest a mechanism involving the reduction of dopamine transport in the maintenance of chronic VCMs in rats. Furthermore, chronic treatment with V. officinalis seems not produce any oxidative damage to central nervous system (CNS), but it also seems to be devoid of action to prevent VCM, at least in the dose used in this study.

  3. Mutational Analysis of the High-Affinity Zinc Binding Site Validates a Refined Human Dopamine Transporter Homology Model

    PubMed Central

    Stockner, Thomas; Montgomery, Therese R.; Kudlacek, Oliver; Weissensteiner, Rene; Ecker, Gerhard F.; Freissmuth, Michael; Sitte, Harald H.

    2013-01-01

    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. PMID:23436987

  4. Occupational exposure to PCBs reduces striatal dopamine transporter densities only in women: A β-CIT imaging study

    PubMed Central

    Seegal, Richard F.; Marek, Kenneth L.; Seibyl, John P.; Jennings, Danna L.; Molho, Eric S.; Higgins, Donald S.; Factor, Stewart A.; Fitzgerald, Edward F.; Hills, Elaine A.; Korrick, Susan A.; Wolff, Mary S.; Haase, Richard F.; Todd, Andrew C.; Parsons, Patrick; McCaffrey, Robert F.

    2010-01-01

    We hypothesize that occupational exposure to PCBs is associated with a reduction in central dopamine (DA) similar to changes previously seen in PCB exposed adult non-human primates. To test that hypothesis we used [123I]β-CIT SPECT imaging to estimate basal ganglia DA transporter density in former capacitor workers. Women, but not men, showed an inverse relationship between lipid-adjusted total serum PCB concentrations and DA transporter densities in the absence of differences in serum PCB concentrations. These sex differences may reflect age-related reductions in the levels of gonadal hormones since these hormones have been shown experimentally to alter response to DA neurotoxicants. These findings may aid in better understanding the roles that sex and age play in modifying central DA function following exposure, not only to PCBs, but also to other DA neurotoxicants as well as further elucidating the role of gonadal hormones in influencing the initiation and/or progression of neurodegenerative disorders. PMID:20096358

  5. Knocking out the dopamine reuptake transporter (DAT) does not change the baseline brain arachidonic acid signal in the mouse

    PubMed Central

    Ramadan, Epolia; Chang, Lisa; Chen, Mei; Ma, Kaizong; Hall, F. Scott; Uhl, George R.; Rapoport, Stanley I.; Basselin, Mireille

    2012-01-01

    Background Dopamine transporter (DAT) homozygous knockout (DAT−/−) mice have a 10-fold higher extracellular DA concentration in the caudate-putamen and nucleus accumbens than do wildtype (DAT+/+) mice, but show reduced presynaptic DA synthesis and fewer postsynaptic D2 receptors. One aspect of neurotransmission involves DA binding to postsynaptic D2-like receptors coupled to cytosolic phospholipase A2 (cPLA2), releasing second messenger arachidonic acid (AA) from synaptic membrane phospholipid. We hypothesized that tonic overactivation of D2-like receptors in DAT−/− mice due to elevated DA would not increase brain AA signaling, because of compensatory downregulation of postsynaptic signaling mechanisms. Methods [1-14C]AA was infused intravenously for 3 min in unanesthetized DAT+/+, heterozygous (DAT+/−) and DAT−/− mice. AA incorporation coefficients k* and rates Jin, markers of AA metabolism and signaling, were imaged in 83 brain regions using quantitative autoradiography brain cPLA2-IV activity also was measured. Results Neither k* nor Jin for AA in any brain region, or in brain cPLA2-IV activity, differed significantly between DAT−/−, DAT+/− and DAT+/+ mice. Conclusions These results differ from reported increases in k* and Jin for AA, and brain cPLA2 expression, in serotonin reuptake transporter (5-HTT) knockout mice, and suggest that postsynaptic dopaminergic neurotransmission mechanisms involving AA are downregulated despite elevated DA in DAT−/− mice. PMID:22376027

  6. Occupancy of the Zinc-binding Site by Transition Metals Decreases the Substrate Affinity of the Human Dopamine Transporter by an Allosteric Mechanism*

    PubMed Central

    Li, Yang; Mayer, Felix P.; Hasenhuetl, Peter S.; Burtscher, Verena; Schicker, Klaus; Sitte, Harald H.; Freissmuth, Michael; Sandtner, Walter

    2017-01-01

    The human dopamine transporter (DAT) has a tetrahedral Zn2+-binding site. Zn2+-binding sites are also recognized by other first-row transition metals. Excessive accumulation of manganese or of copper can lead to parkinsonism because of dopamine deficiency. Accordingly, we examined the effect of Mn2+, Co2+, Ni2+, and Cu2+ on transport-associated currents through DAT and DAT-H193K, a mutant with a disrupted Zn2+-binding site. All transition metals except Mn2+ modulated the transport cycle of wild-type DAT with affinities in the low micromolar range. In this concentration range, they were devoid of any action on DAT-H193K. The active transition metals reduced the affinity of DAT for dopamine. The affinity shift was most pronounced for Cu2+, followed by Ni2+ and Zn2+ (= Co2+). The extent of the affinity shift and the reciprocal effect of substrate on metal affinity accounted for the different modes of action: Ni2+ and Cu2+ uniformly stimulated and inhibited, respectively, the substrate-induced steady-state currents through DAT. In contrast, Zn2+ elicited biphasic effects on transport, i.e. stimulation at 1 μm and inhibition at 10 μm. A kinetic model that posited preferential binding of transition metal ions to the outward-facing apo state of DAT and a reciprocal interaction of dopamine and transition metals recapitulated all experimental findings. Allosteric activation of DAT via the Zn2+-binding site may be of interest to restore transport in loss-of-function mutants. PMID:28096460

  7. Low dose pramipexole is neuroprotective in the MPTP mouse model of Parkinson's disease, and downregulates the dopamine transporter via the D3 receptor

    PubMed Central

    Joyce, Jeffrey N; Woolsey, Cheryl; Ryoo, Han; Borwege, Sabine; Hagner, Diane

    2004-01-01

    Background Our aim was to determine if pramipexole, a D3 preferring agonist, effectively reduced dopamine neuron and fiber loss in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model when given at intraperitoneal doses corresponding to clinical doses. We also determined whether subchronic treatment with pramipexole regulates dopamine transporter function, thereby reducing intracellular transport of the active metabolite of MPTP, 1-methyl-4-phenylpyridinium (MPP+). Methods Ten 12-month old C57BL/6 mice were treated with MPTP (or saline) twice per day at 20 mg/kg s.c. (4 injections over 48 h). Mice were pretreated for 3 days and during the 2-day MPTP regimen with pramipexole (0.1 mg/kg/day) or saline. Stereological quantification of dopamine neuron number and optical density measurement of dopamine fiber loss were carried out at 1 week after treatment, using immunostaining for dopamine transporter (DAT) and tyrosine hydroxylase (TH). Additional wild-type (WT) and D3 receptor knockout (KO) mice were treated for 5 days with pramipexole (0.1 mg/kg/day) or vehicle. The kinetics of [3H]MPP+ and [3H]DA uptake (Vmax and Km) were determined 24 h later; and at 24 h and 14 days dopamine transporter density was measured by quantitative autoradiography. Results Pramipexole treatment completely antagonized the neurotoxic effects of MPTP, as measured by substantia nigra and ventral tegmental area TH-immunoreactive cell counts. MPTP- induced loss of striatal innervation, as measured by DAT-immunoreactivity, was partially prevented by pramipexole, but not with regard to TH-IR. Pramipexole also reduced DAT- immunoreactivity in non-MPTP treated mice. Subchronic treatment with pramipexole lowered the Vmax for [3H]DA and [3H]MPP+ uptake into striatal synaptosomes of WT mice. Pramipexole treatment lowered Vmax in WT but not D3 KO mice; however, D3 KO mice had lower Vmax for [3H]DA uptake. There was no change in DAT number in WT with pramipexole treatment or D3 KO mice at

  8. Ctr9, a Protein in the Transcription Complex Paf1, Regulates Dopamine Transporter Activity at the Plasma Membrane*

    PubMed Central

    De Gois, Stéphanie; Slama, Patrick; Pietrancosta, Nicolas; Erdozain, Amaia M.; Louis, Franck; Bouvrais-Veret, Caroline; Daviet, Laurent; Giros, Bruno

    2015-01-01

    Dopamine (DA) is a major regulator of sensorimotor and cognitive functions. The DA transporter (DAT) is the key protein that regulates the spatial and temporal activity of DA release into the synaptic cleft via the rapid reuptake of DA into presynaptic termini. Several lines of evidence have suggested that transporter-interacting proteins may play a role in DAT function and regulation. Here, we identified the tetratricopeptide repeat domain-containing protein Ctr9 as a novel DAT binding partner using a yeast two-hybrid system. We showed that Ctr9 is expressed in dopaminergic neurons and forms a stable complex with DAT in vivo via GST pulldown and co-immunoprecipitation assays. In mammalian cells co-expressing both proteins, Ctr9 partially colocalizes with DAT at the plasma membrane. This interaction between DAT and Ctr9 results in a dramatic enhancement of DAT-mediated DA uptake due to an increased number of DAT transporters at the plasma membrane. We determined that the binding of Ctr9 to DAT requires residues YKF in the first half of the DAT C terminus. In addition, we characterized Ctr9, providing new insight into this protein. Using three-dimensional modeling, we identified three novel tetratricopeptide repeat domains in the Ctr9 sequence, and based on deletion mutation experiments, we demonstrated the role of the SH2 domain of Ctr9 in nuclear localization. Our results demonstrate that Ctr9 localization is not restricted to the nucleus, as previously described for the transcription complex Paf1. Taken together, our data provide evidence that Ctr9 modulates DAT function by regulating its trafficking. PMID:26048990

  9. Amphetamine elevates nucleus accumbens dopamine via an action potential-dependent mechanism that is modulated by endocannabinoids.

    PubMed

    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.

  10. [18F]CFT [(18F)WIN 35,428], a radioligand to study the dopamine transporter with PET: characterization in human subjects.

    PubMed

    Laakso, A; Bergman, J; Haaparanta, M; Vilkman, H; Solin, O; Hietala, J

    1998-03-01

    We have characterized the usage of [18F]CFT (also known as [18F]WIN 35,428) as a radioligand for in vivo studies of human dopamine transporter by PET. CFT was labeled with 18F to a high specific activity, and dynamic PET scans were conducted in healthy volunteers at various time points up to 5 h from [18F]CFT injection. The regional distribution of [18F]CFT uptake correlated well with the known distribution of dopaminergic nerve terminals in the human brain and also with that of other dopamine transporter radioligands. Striatal binding peaked at 225 min after injection and declined thereafter, demonstrating the reversible nature of the binding to the dopamine transporter. Therefore, due to the relatively long half-life of 18F (109.8 min), PET scans with [18F]CFT could easily be conducted during the binding equilibrium, allowing estimation of Bmax/Kd values (i.e., binding potential). Binding potentials for putamen and caudate measured at equilibrium were 4.79+/-0.11 and 4.50+/-0.23, respectively. We were able to also visualize midbrain dopaminergic neurons (substantia nigra) with [18F]CFT in some subjects. In conclusion, the labeling of CFT with 18F allows PET scans to be conducted at binding equilibrium, and therefore a high signal-to-noise ratio and reliable quantification of binding potential can be achieved. With a high resolution 3D PET scanner, the quantification of extrastriatal dopamine transporters should become possible.

  11. Differential Internalization Rates and Postendocytic Sorting of the Norepinephrine and Dopamine Transporters Are Controlled by Structural Elements in the N Termini*

    PubMed Central

    Vuorenpää, Anne; Jørgensen, Trine N.; Newman, Amy H.; Madsen, Kenneth L.; Scheinin, Mika

    2016-01-01

    The norepinephrine transporter (NET) mediates reuptake of synaptically released norepinephrine in central and peripheral noradrenergic neurons. The molecular processes governing availability of NET in the plasma membrane are poorly understood. Here we use the fluorescent cocaine analogue JHC 1-64, as well as several other approaches, to investigate the trafficking itinerary of NET in live noradrenergic neurons. Confocal imaging revealed extensive constitutive internalization of JHC 1-64-labeled NET in the neuronal somata, proximal extensions and presynaptic boutons. Phorbol 12-myristate 13-acetate increased intracellular accumulation of JHC 1-64-labeled NET and caused a parallel reduction in uptake capacity. Internalized NET strongly colocalized with the “long loop” recycling marker Rab11, whereas less overlap was seen with the “short loop” recycling marker Rab4 and the late endosomal marker Rab7. 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. PMID:26786096

  12. Differential Internalization Rates and Postendocytic Sorting of the Norepinephrine and Dopamine Transporters Are Controlled by Structural Elements in the N Termini.

    PubMed

    Vuorenpää, Anne; Jørgensen, Trine N; Newman, Amy H; Madsen, Kenneth L; Scheinin, Mika; Gether, Ulrik

    2016-03-11

    The norepinephrine transporter (NET) mediates reuptake of synaptically released norepinephrine in central and peripheral noradrenergic neurons. The molecular processes governing availability of NET in the plasma membrane are poorly understood. Here we use the fluorescent cocaine analogue JHC 1-64, as well as several other approaches, to investigate the trafficking itinerary of NET in live noradrenergic neurons. Confocal imaging revealed extensive constitutive internalization of JHC 1-64-labeled NET in the neuronal somata, proximal extensions and presynaptic boutons. Phorbol 12-myristate 13-acetate increased intracellular accumulation of JHC 1-64-labeled NET and caused a parallel reduction in uptake capacity. Internalized NET strongly colocalized with the "long loop" recycling marker Rab11, whereas less overlap was seen with the "short loop" recycling marker Rab4 and the late endosomal marker Rab7. 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.

  13. Orthostatic hypotension, non-dipping and striatal dopamine in Parkinson disease.

    PubMed

    Oh, Yoon-Sang; Kim, Joong-Seok; Chung, Yong-An; You, Ie Ryung; Yang, Dong-Won; Chung, Sung-Woo; Park, Jeong-Wook; Kim, Yeong-In; Lee, Kwang-Soo

    2013-04-01

    Orthostatic hypotension and non-dipping are relatively common autonomic dysfunctions in patients with Parkinson disease (PD). These abnormalities have been thought to occur independently of striatal dopaminergic depletion; however, only little preliminary information is available. In this study, we investigated the association of neurocirculatory changes with striatal dopamine transporter status in 69 patients with early PD. Seventeen patients had orthostatic hypotension and 55 patients were non-dippers. A comparison between cases with and without orthostatic hypotension was insignificant for striatal dopamine transporter uptake. These insignificances continued in a comparison of dippers and non-dippers. These results suggest that sympathetic noradrenergic dysfunctions in PD are independent of striatal dopamine transporter depletion.

  14. Candidate-gene approach in posttraumatic stress disorder after urban violence: association analysis of the genes encoding serotonin transporter, dopamine transporter, and BDNF.

    PubMed

    Valente, Nina Leão Marques; Vallada, Homero; Cordeiro, Quirino; Miguita, Karen; Bressan, Rodrigo Affonseca; Andreoli, Sergio Baxter; Mari, Jair Jesus; Mello, Marcelo Feijó

    2011-05-01

    Posttraumatic stress disorder (PTSD) is a prevalent, disabling anxiety disorder marked by behavioral and physiologic alterations which commonly follows a chronic course. Exposure to a traumatic event constitutes a necessary, but not sufficient, factor. There is evidence from twin studies supporting a significant genetic predisposition to PTSD. However, the precise genetic loci still remain unclear. The objective of the present study was to identify, in a case-control study, whether the brain-derived neurotrophic factor (BDNF) val66met polymorphism (rs6265), the dopamine transporter (DAT1) three prime untranslated region (3'UTR) variable number of tandem repeats (VNTR), and the serotonin transporter (5-HTTPRL) short/long variants are associated with the development of PTSD in a group of victims of urban violence. All polymorphisms were genotyped in 65 PTSD patients as well as in 34 victims of violence without PTSD and in a community control group (n = 335). We did not find a statistical significant difference between the BDNF val66met and 5-HTTPRL polymorphism and the traumatic phenotype. However, a statistical association was found between DAT1 3'UTR VNTR nine repeats and PTSD (OR = 1.82; 95% CI, 1.20-2.76). This preliminary result confirms previous reports supporting a susceptibility role for allele 9 and PTSD.

  15. [123I]beta-CIT SPECT imaging of dopamine transporter availability after mazindol administration in human cocaine addicts.

    PubMed

    Malison, R T; McCance, E; Carpenter, L L; Baldwin, R M; Seibyl, J P; Price, L H; Kosten, T R; Innis, R B

    1998-06-01

    The in vivo potency of mazindol for binding to striatal dopamine transporters (DAT) was assessed by [123I]beta-CIT ([123I]2beta-carbomethoxy-3beta-(4-iodophenyl)tropane) single photon emission computed tomography (SPECT). Cocaine-dependent subjects (n = 12) underwent three SPECT scans; one before, between, and after subchronic (1 week) administration of 2 mg/day and 4 mg/day mazindol. For each scan, subjects were injected with [123I]beta-CIT and imaged 24 h later under equilibrium conditions. Results showed a statistically significant main effect of mazindol dose (df = 2, F = 10.30, P < 0.001, repeated measures ANOVA) in reducing the specific to non-displaceable equilibrium partition coefficient, V3'' (a measure proportional to DAT binding potential). Regression analysis of the logit transformed data enabled estimation of the 50% displacement dose of mazindol (ED50 = 30mg/day). These data suggest that low doses of mazindol (i.e., 2-4 mg) occupy a small percentage (i.e., < 25%) of DAT in human cocaine abusers and that much higher, potentially intolerable doses (i.e., > or = 30 mg/day) may be required to antagonize significantly cocaine binding in vivo.

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

    SciTech Connect

    Volkow, N.D. |; Wang, G.J.; Fowler, J.S.

    1999-05-28

    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 [{sup 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 [{sup 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{sub 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.

  17. A one-step automated synthesis of the dopamine transporter ligand [(18)F]FECNT from the chlorinated precursor.

    PubMed

    Pijarowska-Kruszyna, Justyna; Jaron, Antoni; Kachniarz, Artur; Malkowski, Bogdan; Garnuszek, Piotr; Mikolajczak, Renata

    2016-03-01

    The use of [(18)F]labelled nortropane derivative 2β-carbomethoxy-3β-(4-chlorophenyl)-8-(2-fluoroethyl)-nortropane (FECNT) as a dopamine transporter ligand for PET imaging is dependent on efficient radiosynthesis method. Herein, the automated synthesis of [(18)F]FECNT from its chlorinated precursor in commercially available SynChrom [(18)F] R&D module has been developed. The synthesis unit was readily configured for the one-step synthesis from corresponding chlorinated precursor. The radiolabeling process involved a classical [(18)F]fluoride nucleophilic substitution performed at 110 °C for 12 min and finally HPLC and SPE purification. Crude [(18)F]FECNT was obtained with a radiolabeling yield of 59 ± 12% (n = 5). The average uncorrected amount of [(18)F]FECNT in the final formulated dose was 2.0 ± 0.5 GBq (32 ± 7% overall decay-corrected yields) obtained with radiochemical purity over 99% and specific activity of 55 GBq/µmol. The total duration of the procedure was 80-90 min. An automated radiosynthesis of [(18)F]FECNT with high radiochemical purity may provide a simple and robust method of radiopharmaceutical preparation for routine clinical applications.

  18. From linked open data to molecular interaction: studying selectivity trends for ligands of the human serotonin and dopamine transporter.

    PubMed

    Zdrazil, Barbara; Hellsberg, Eva; Viereck, Michael; Ecker, Gerhard F

    2016-09-14

    Retrieval of congeneric and consistent SAR data sets for protein targets of interest is still a laborious task to do if no appropriate in-house data set is available. However, combining integrated open data sources (such as the Open PHACTS Discovery Platform) with workflow tools now offers the possibility of querying across multiple domains and tailoring the search to the given research question. Starting from two phylogenetically related protein targets of interest (the human serotonin and dopamine transporters), the whole chemical compound space was explored by implementing a scaffold-based clustering of compounds possessing biological measurements for both targets. In addition, potential hERG blocking liabilities were included. The workflow allowed studying the selectivity trends of scaffold series, identifying potentially harmful compound series, and performing SAR, docking studies and molecular dynamics (MD) simulations for a consistent data set of 56 cathinones. This delivered useful insights into driving determinants for hDAT selectivity over hSERT. With respect to the scaffold-based analyses it should be noted that the cathinone data set could be retrieved only when Murcko scaffold analyses were combined with similarity searches such as a common substructure search.

  19. “Deconstruction” of the Abused Synthetic Cathinone Methylenedioxypyrovalerone (MDPV) and an Examination of Effects at the Human Dopamine Transporter

    PubMed Central

    2013-01-01

    Synthetic cathinones, β-keto analogues of amphetamine (or, more correctly, of phenylalkylamines), represent a new and growing class of abused substances. Several such analogues have been demonstrated to act as dopamine (DA) releasing agents. Methylenedioxypyrovalerone (MDPV) was the first synthetic cathinone shown to act as a cocaine-like DA reuptake inhibitor. MDPV and seven deconstructed analogues were examined to determine which of MDPV’s structural features account(s) for uptake inhibition. In voltage-clamped (−60 mV) Xenopus oocytes transfected with the human DA transporter (hDAT), all analogues elicited inhibitor-like behavior shown as hDAT-mediated outward currents. Using hDAT-expressing mammalian cells we determined the affinities of MDPV and its analogues to inhibit uptake of [3H]DA by hDAT that varied over a broad range (IC50 values ca. 135 to >25 000 nM). The methylenedioxy group of MDPV made a minimal contribution to affinity, the carbonyl group and a tertiary amine are more important, and the extended α-alkyl group seems most important. Either a tertiary amine, or the extended α-alkyl group (but not both), are required for the potent nature of MDPV as an hDAT inhibitor. PMID:24116392

  20. [123I]beta-CIT SPECT demonstrates decreased brain dopamine and serotonin transporter levels in untreated parkinsonian patients.

    PubMed

    Haapaniemi, T H; Ahonen, A; Torniainen, P; Sotaniemi, K A; Myllylä, V V

    2001-01-01

    Striatal dopamine transporters (DATs) and serotonin transporters (SERTs) were evaluated in untreated patients with Parkinson's disease (PD) and controls using single-photon emission computed tomography (SPECT) with 2beta-carboxymethoxy-3beta-(4-iodophenyl)tropane ([123I]beta-CIT). The striatal DAT specific to non-displaceable uptake ratios of 29, and the SERT uptake measurements of 27, PD patients were compared with those of 21 and 16 controls, respectively. The results were correlated with Unified Parkinson's Disease Rating Scale (UPDRS) scores, the Hoehn & Yahr stage, age, duration of the disease, and the major PD signs. The specific DAT binding in the caudate, the putamen and the caudate/putamen ratio were measured. In all of the PD patients the striatal uptake values were bilaterally reduced, being 36.9% (P < 0.001) lower than those of the controls. In the hemiparkinsonian patients the reduction was greater on the side contralateral to the initial symptoms (33.3% vs. 27.8%) and the uptake ratios indicated a more pronounced deficit in the putamen (39.1%) than in the caudate (27.9%). The DAT uptake correlated with the UPDRS total score and activities of daily living (ADL) and motor subscores, the Hoehn & Yahr stage, and rigidity score. PD patients had significantly higher caudate to putamen ratios than the controls. In the PD patients the SERT values were lower in the thalamic and frontal regions. The SERT uptake ratio of the frontal area correlated with the UPDRS subscore I. [123I]beta-CIT SPECT provides a useful method for confirming the clinical diagnosis of PD with correlation to disease severity. Additionally, this technique allows the simultaneous measurement of SERT uptake and shows that PD patients, interestingly, seem to have decreased SERT availability in the thalamic and frontal areas.

  1. Norepinephrine transporter inhibition with desipramine exacerbates L-DOPA-induced dyskinesia: role for synaptic dopamine regulation in denervated nigrostriatal terminals.

    PubMed

    Chotibut, Tanya; Fields, Victoria; Salvatore, Michael F

    2014-12-01

    Pharmacological dopamine (DA) replacement with Levodopa [L-dihydroxyphenylalanine (L-DOPA)] is the gold standard treatment of Parkinson's disease (PD). However, long-term L-DOPA treatment is complicated by eventual debilitating abnormal involuntary movements termed L-DOPA-induced dyskinesia (LID), a clinically significant obstacle for the majority of patients who rely on L-DOPA to alleviate PD-related motor symptoms. The manifestation of LID may in part be driven by excessive extracellular DA derived from L-DOPA, but potential involvement of DA reuptake in LID severity or expression is unknown. We recently reported that in 6-hydroxydopamine (6-OHDA)-lesioned striatum, norepinephrine transporter (NET) expression increases and may play a significant role in DA transport. Furthermore, L-DOPA preferentially inhibits DA uptake in lesioned striatum. Therefore, we hypothesized that desipramine (DMI), a NET antagonist, could affect the severity of LID in an established LID model. Whereas DMI alone elicited no dyskinetic effects in lesioned rats, DMI + L-DOPA-treated rats gradually expressed more severe dyskinesia compared with L-DOPA alone over time. At the conclusion of the study, we observed reduced NET expression and norepinephrine-mediated inhibition of DA uptake in the DMI + L-DOPA group compared with L-DOPA-alone group in lesioned striatum. LID severity positively correlated with striatal extracellular signal-regulated protein kinase phosphorylation among the three treatment groups, with increased ppERK1/2 in DMI + L-DOPA group compared with the L-DOPA- and DMI-alone groups. Taken together, these results indicate that the combination of chronic L-DOPA and NET-mediated DA reuptake in lesioned nigrostriatal terminals may have a role in LID severity in experimental Parkinsonism.

  2. Differences of Various Region-of-Interest Methods for Measuring Dopamine Transporter Availability Using 99mTc-TRODAT-1 SPECT

    PubMed Central

    Yin, Tang-Kai; Lee, Bi-Fang; Yang, Yen Kuang; Chiu, Nan-Tsing

    2014-01-01

    This study was to investigate whether various region-of-interest (ROI) methods for measuring dopamine transporter (DAT) availabilities by single photon emission computed tomography (SPECT) are statistically different, whether results of medical research are thereby influenced, and causes of these differences. Eighty-four healthy adults with 99mTc-TRODAT-1 SPECT and magnetic resonance imaging (MRI) scans were included. Six major analysis approaches were compared: (1) ROI drawn on the coregistered MRI; (2) ROIs drawn on the SPECT images; (3) standard ROI templates; (4) threshold-ROIs; (5) atlas-based mappings with coregistered MRI; and (6) atlas-based mappings with SPECT images. Using the atlas-based approaches we assessed the influence of striatum ROIs by slice-wise and voxel-wise comparisons. In (5) and (6), three partial-volume correction (PVC) methods were also explored. The results showed that DAT availabilities obtained from different methods were closely related but quite different and leaded to significant differences in determining the declines of DAT availability per decade (range: 5.95–11.99%). Use of 3D whole-striatum or more transverse slices could avoid biases in measuring the striatal DAT declines per decade. Atlas-based methods with PVC may be the preferable methods for medical research. PMID:25101323

  3. Chinese Medicine Formula “Jian-Pi-Zhi-Dong Decoction” Attenuates Tourette Syndrome via Downregulating the Expression of Dopamine Transporter in Mice

    PubMed Central

    Wang, Dao-han; Li, Wei; Liu, Xiao-fang; Zhang, Jin-ming; Wang, Su-mei

    2013-01-01

    Jian-Pi-Zhi-Dong Decoction (JPZDD) is dedicated to the treatment for Tourette syndrome (TS) with the guidance of the theories of Traditional Chinese Medicine (TCM). This study aims to investigate the expression of dopamine transporter (DAT) in the striatum and stereotyped behavior of TS mice model by intervention of JPZDD. Mice were induced by 3,3′-iminodipropionitrile (IDPN, 350 mg kg−1 day−1, i.p.) for 7 days and divided into 4 groups (n = 20, each): control and IDPN groups were gavaged with saline and the remaining 2 groups with Tiapride (Tia, 50 mg kg−1 day−1) and JPZDD (20 g kg−1 day−1), respectively. The results showed that the scores of stereotyped behavior in IDPN+JPZDD group were significantly reduced. A noticeably increased 11C-β-CFT binding at bilateral striatum was observed after administration of JPZDD versus that of IDPN or Tia. Immunohistochemistry and in situ hybridization studies manifested higher levels of DAT protein and mRNA in IDPN+JPZDD group. These findings not only demonstrated that JPZDD could effectively inhibit the abnormal behaviors of TS mice model, but also increase the level of DAT in striatum. Therefore, JPZDD could be one of potential treatments of patients with TS. PMID:23431337

  4. Graphical, kinetic, and equilibrium analyses of in vivo [123I] beta-CIT binding to dopamine transporters in healthy human subjects.

    PubMed

    Laruelle, M; Wallace, E; Seibyl, J P; Baldwin, R M; Zea-Ponce, Y; Zoghbi, S S; Neumeyer, J L; Charney, D S; Hoffer, P B; Innis, R B

    1994-11-01

    The in vivo kinetics of the dopamine (DA) transporter probe 123I-labeled 2 beta-carboxymethoxy-3 beta-(4-iodophenyl) tropane ([123I] beta-CIT) in striatum was investigated with single-photon emission computerized tomography (SPECT) in five healthy human subjects. The aim of this study was to derive an adequate measure of the DA transporter density that would not be affected by regional cerebral blood flow or peripheral clearance of the tracer. SPECT data were acquired on the day of injection (day 1) from 0 to 7 h and on the following day (day 2) from 19 to 25 h. Arterial sampling on day 1 was used to measure the input function. Graphical, kinetic, and equilibrium analyses were evaluated. Graphical analysis of day 1 data, with the assumption of negligible dissociation of the tracer-receptor complex (k4 = 0), was found to be blood flow-dependent. A three-compartment kinetic analysis of day 1 data were performed using a three (k4 = 0)- and a four (k4 > 0)-parameter model. The three-parameter model estimated the konBmax product at 0.886 +/- 0.087 min-1. The four-parameter model gave a binding potential (BP) of 476 ml g-1, a value consistent with in vitro measurements. The stability of the regional uptake on day 2 allowed direct measurement of the specific to nonspecific equilibrium partition coefficient (V3" = k3/k4 = 6.66 +/- 1.54). Results of day 1 kinetic analysis and day 2 equilibrium analysis were well correlated among subjects. Simulations indicated that the error associated with the day 2 equilibrium analysis was acceptable for plasma tracer terminal half-lives > 10 h. We propose the equilibrium analysis on day 2 as the method of choice for clinical studies since it does not require multiple scans or the measurement of the arterial plasma tracer concentrations.

  5. Investigation of the binding and functional properties of extended length D3 dopamine receptor-selective antagonists.

    PubMed

    Furman, Cheryse A; Roof, Rebecca A; Moritz, Amy E; Miller, Brittney N; Doyle, Trevor B; Free, R Benjamin; Banala, Ashwini K; Paul, Noel M; Kumar, Vivek; Sibley, Christopher D; Newman, Amy Hauck; Sibley, David R

    2015-09-01

    The D3 dopamine receptor represents an important target in drug addiction in that reducing receptor activity may attenuate the self-administration of drugs and/or disrupt drug or cue-induced relapse. Medicinal chemistry efforts have led to the development of D3 preferring antagonists and partial agonists that are >100-fold selective vs. the closely related D2 receptor, as best exemplified by extended-length 4-phenylpiperazine derivatives. Based on the D3 receptor crystal structure, these molecules are known to dock to two sites on the receptor where the 4-phenylpiperazine moiety binds to the orthosteric site and an extended aryl amide moiety docks to a secondary binding pocket. The bivalent nature of the receptor binding of these compounds is believed to contribute to their D3 selectivity. In this study, we examined if such compounds might also be "bitopic" such that their aryl amide moieties act as allosteric modulators to further enhance the affinities of the full-length molecules for the receptor. First, we deconstructed several extended-length D3-selective ligands into fragments, termed "synthons", representing either orthosteric or secondary aryl amide pharmacophores and investigated their effects on D3 receptor binding and function. The orthosteric synthons were found to inhibit radioligand binding and to antagonize dopamine activation of the D3 receptor, albeit with lower affinities than the full-length compounds. Notably, the aryl amide-based synthons had no effect on the affinities or potencies of the orthosteric synthons, nor did they have any effect on receptor activation by dopamine. Additionally, pharmacological investigation of the full-length D3-selective antagonists revealed that these compounds interacted with the D3 receptor in a purely competitive manner. Our data further support that the 4-phenylpiperazine D3-selective antagonists are bivalent and that their enhanced affinity for the D3 receptor is due to binding at both the orthosteric site as

  6. Investigation of the binding and functional properties of extended length D3 dopamine receptor-selective antagonists☆

    PubMed Central

    Furman, Cheryse A.; Roof, Rebecca A.; Moritz, Amy E.; Miller, Brittney N.; Doyle, Trevor B.; Free, R. Benjamin; Banala, Ashwini K.; Paul, Noel M.; Kumar, Vivek; Sibley, Christopher D.; Newman, Amy Hauck; Sibley, David R.

    2015-01-01

    The D3 dopamine receptor represents an important target in drug addiction in that reducing receptor activity may attenuate the self-administration of drugs and/or disrupt drug or cue-induced relapse. Medicinal chemistry efforts have led to the development of D3 preferring antagonists and partial agonists that are >100-fold selective vs. the closely related D2 receptor, as best exemplified by extended-length 4-phenylpiperazine derivatives. Based on the D3 receptor crystal structure, these molecules are known to dock to two sites on the receptor where the 4-phenylpiperazine moiety binds to the orthosteric site and an extended aryl amide moiety docks to a secondary binding pocket. The bivalent nature of the receptor binding of these compounds is believed to contribute to their D3 selectivity. In this study, we examined if such compounds might also be “bitopic” such that their aryl amide moieties act as allosteric modulators to further enhance the affinities of the full-length molecules for the receptor. First, we deconstructed several extended-length D3-selective ligands into fragments, termed “synthons”, representing either orthosteric or secondary aryl amide pharmacophores and investigated their effects on D3 receptor binding and function. The orthosteric synthons were found to inhibit radioligand binding and to antagonize dopamine activation of the D3 receptor, albeit with lower affinities than the full-length compounds. Notably, the aryl amide-based synthons had no effect on the affinities or potencies of the orthosteric synthons, nor did they have any effect on receptor activation by dopamine. Additionally, pharmacological investigation of the full-length D3-selective antagonists revealed that these compounds interacted with the D3 receptor in a purely competitive manner. Our data further support that the 4-phenylpiperazine D3-selective antagonists are bivalent and that their enhanced affinity for the D3 receptor is due to binding at both the orthosteric

  7. Comparison of two I-123 labeled SPECT probes, for the dopamine transporter in non-human primate brain

    SciTech Connect

    Gandelman, M.S.; Scanley, B.E.; Al-Tikrite, M.S.

    1994-05-01

    A comparative SPECT evaluation of the regional uptake of 28-carboisopropoxy-3{beta}-(4-iodophenyl)tropane (IP-CIT) and 2{beta}-carbomethoxy-3{beta}-(4-iodophenyl)tropane ({beta}-CIT) was performed to assess the improved specificity of IP-CIT over {beta}-CIT for the dopamine (DE) transporter, as shown previously by in vitro studies (n=10), ranging from 7 to 10 hours with 6.9 to 15 mCi injected dose, were completed in 3 baboons. Peripheral metabolism of the two ligands were similar The SPECT images utilized ROIs over striatum (which reflect DA transporters), midbrain (previously shown for {beta}-CIT to reflect primarily serotonin transporters), and the occipital lobe (a region of non-specific uptake). The time to peak specific striatal uptake (striatal minus occipital activity) was similar for IP-CIT and {beta}-CIT (377{plus_minus}60 and 410{plus_minus}60 min, respectively); whereas midbrain peak activity occurred at a significantly earlier time for IP-CIT (21{plus_minus}4 min) as compared to {beta}-CIT (60{plus_minus}17 min). At time of peak specific striatal activity, striatal to occipital ratios were 2.7+0.6 for IP-CIT and 7.6{plus_minus}0.7 for {beta}-CIT, and at time of peak midbrain activity, midbrain to occipital ratios were 1.1{plus_minus}0.1 for IP-CIT, and 1.7{plus_minus}0.2 for {beta}-CIT. At peak specific striatal time, normalized regional uptake values ({mu}Ci/cc per {mu}Ci injected dose per g body mass) for the striatum were 4.9{plus_minus}1.1 IP-CIT and 5.2{plus_minus}0.7 {beta}-CIT, whereas for the occipital lobe normalized regional uptake values were 1.9{plus_minus}0.4 IP-CIT and 0.7{plus_minus}0.2 for {beta}-CIT. Similar regional kinetics in the striatum were observed, as both ligands demonstrate comparable peak striatal uptake and time to peak.

  8. SLC6A3 coding variant Ala559Val found in two autism probands alters dopamine transporter function and trafficking.

    PubMed

    Bowton, E; Saunders, C; Reddy, I A; Campbell, N G; Hamilton, P J; Henry, L K; Coon, H; Sakrikar, D; Veenstra-VanderWeele, J M; Blakely, R D; Sutcliffe, J; Matthies, H J G; Erreger, K; Galli, A

    2014-10-14

    Emerging evidence associates dysfunction in the dopamine (DA) transporter (DAT) with the pathophysiology of autism spectrum disorder (ASD). The human DAT (hDAT; SLC6A3) rare variant with an Ala to Val substitution at amino acid 559 (hDAT A559V) was previously reported in individuals with bipolar disorder or attention-deficit hyperactivity disorder (ADHD). We have demonstrated that this variant is hyper-phosphorylated at the amino (N)-terminal serine (Ser) residues and promotes an anomalous DA efflux phenotype. Here, we report the novel identification of hDAT A559V in two unrelated ASD subjects and provide the first mechanistic description of its impaired trafficking phenotype. DAT surface expression is dynamically regulated by DAT substrates including the psychostimulant amphetamine (AMPH), which causes hDAT trafficking away from the plasma membrane. The integrity of DAT trafficking directly impacts DA transport capacity and therefore dopaminergic neurotransmission. Here, we show that hDAT A559V is resistant to AMPH-induced cell surface redistribution. This unique trafficking phenotype is conferred by altered protein kinase C β (PKCβ) activity. Cells expressing hDAT A559V exhibit constitutively elevated PKCβ activity, inhibition of which restores the AMPH-induced hDAT A559V membrane redistribution. Mechanistically, we link the inability of hDAT A559V to traffic in response to AMPH to the phosphorylation of the five most distal DAT N-terminal Ser. Mutation of these N-terminal Ser to Ala restores AMPH-induced trafficking. Furthermore, hDAT A559V has a diminished ability to transport AMPH, and therefore lacks AMPH-induced DA efflux. Pharmacological inhibition of PKCβ or Ser to Ala substitution in the hDAT A559V background restores AMPH-induced DA efflux while promoting intracellular AMPH accumulation. Although hDAT A559V is a rare variant, it has been found in multiple probands with neuropsychiatric disorders associated with imbalances in DA neurotransmission

  9. The dopamine transporter gene, a spectrum of most common risky behaviors, and the legal status of the behaviors.

    PubMed

    Guo, Guang; Cai, Tianji; Guo, Rui; Wang, Hongyu; Harris, Kathleen Mullan

    2010-02-22

    This study tests the specific hypothesis that the 9R/9R genotype in the VNTR of the dopamine transporter gene (DAT1) exerts a general protective effect against a spectrum of risky behaviors in comparison to the 10R/9R and 10R/10R genotypes, drawing on three-time repeated measures of risky behaviors in adolescence and young adulthood on about 822 non-Hispanic white males from the Add Health study. Our data have established two empirical findings. The first is a protective main effect in the DAT1 gene against risky behaviors. The second finding is that the protective effect varies over age, with the effect prominent at ages when a behavior is illegal and the effect largely vanished at ages when the behavior becomes legal or more socially tolerated. Both the protective main effect and the gene-lifecourse interaction effect are replicated across a spectrum of most common risky behaviors: delinquency, variety of sexual partners, binge drinking, drinking quantity, smoking quantity, smoking frequency, marijuana use, cocaine use, other illegal drug use, and seatbelt non-wearing. We also compared individuals with the protective genotype and individuals without it in terms of age, physical maturity, verbal IQ, GPA, received popularity, sent popularity, church attendance, two biological parents, and parental education. These comparisons indicate that the protective effect of DAT1*9R/9R cannot be explained away by these background characteristics. Our work demonstrates how legal/social contexts can enhance or reduce a genetic effect on risky behaviors.

  10. Interaction of Dopamine Transporter Gene and Observed Parenting Behaviors on Attention-Deficit/Hyperactivity Disorder: A Structural Equation Modeling Approach

    PubMed Central

    Li, James J.; Lee, Steve S.

    2012-01-01

    Objective Emerging evidence suggests that some individuals may be simultaneously more responsive to the effects from environmental adversity and enrichment (i.e., differential susceptibility). Given that parenting behavior and a variable number tandem repeat polymorphism in the 3′untranslated region of the dopamine transporter (DAT1) gene are each independently associated with ADHD, our goal was to evaluate the potential interactive effects of child DAT1 genotype with positive and negative parenting behaviors on childhood ADHD. Method We recruited an ethnically-diverse sample of 150 six to nine year-old boys and girls with and without ADHD. Children were genotyped for a common polymorphism of the DAT1 gene, and objective counts of observed parenting behavior (i.e., negativity and praise) were obtained from a valid parent-child interaction task. Structural equation modeling was used to examine the interactive effects of DAT1 and observed parenting with a latent ADHD factor. Results We detected a significant interaction between observed praise and child DAT1 (coded additively) which suggested that praise was associated with increased ADHD, but only among youth with the 9/10 genotype. In addition, a marginally significant interaction between DAT1 (coded additively and recessively) and observed negativity emerged for ADHD, such that negativity was positively associated with ADHD but only for youth with the 9/9 genotype. Conclusions Although differential susceptibility theory was not fully supported, These preliminary results suggest that interactive exchanges between parenting behavior and child genotype potentially contribute to the development of ADHD. Clinical implications for interactions between parenting behavior and child genotype are discussed. PMID:23153115

  11. Influence of CT-based attenuation correction on dopamine transporter SPECT with [(123)I]FP-CIT.

    PubMed

    Lapa, Constantin; Spehl, Timo S; Brumberg, Joachim; Isaias, Ioannis U; Schlögl, Susanne; Lassmann, Michael; Herrmann, Ken; Meyer, Philipp T

    2015-01-01

    Dopamine transporter (DAT) imaging using single-photon emission computed tomography (SPECT) and (123)I-labelled radiopharmaceuticals like [(123)I]FP-CIT is an established part in the diagnostic work-up of parkinsonism. Guidelines recommend attenuation correction (AC), either by a calculated uniform attenuation matrix (calAC) or by a measured attenuation map (nowadays done by low-dose CT; CTAC). We explored the impact of CTAC compared to conventional calAC on diagnostic accuracy and the use of DAT availability as a biomarker of nigrostriatal integrity.Integrated SPECT/CT studies with [(123)I]FP-CIT were performed in patients with Parkinson's disease (PD; n = 15) and essential tremor (ET; n = 15). SPECT data was reconstructed with calAC, CTAC and without AC (noAC). Regional DAT availability was assessed by uniform volume-of-interest analyses providing striatal binding potential (BP ND) estimates. BP ND values were compared among methods and correlated with clinical parameters. Compared to calAC, both CTAC and noAC provided significantly lower, but highly linearly correlated BP ND estimates (R (2) = 0.96). Diagnostic performance to distinguish between patients with PD and those with ET was very high and did not differ between AC methods. CTAC and noAC data tended so show a stronger correlation with severity and duration of disease in PD and age in ET than did calAC. Defining the reference region on low-dose CT instead of SPECT did not consistently alter findings. [(123)I]FP-CIT SPECT provides a very high diagnostic accuracy for differentiation between PD and ET that is not dependent on the employed AC method. Preliminary correlations analyses suggest that BP ND estimates derived from CTAC represent a superior biomarker of nigrostriatal integrity.

  12. Heterogeneity of Monosymptomatic Resting Tremor in a Prospective Study: Clinical Features, Electrophysiological Test, and Dopamine Transporter Positron Emission Tomography

    PubMed Central

    Zheng, Hua-Guang; Zhang, Rong; Li, Xin; Li, Fang-Fei; Wang, Ya-Chen; Wang, Xue-Mei; Lu, Ling-Long; Feng, Tao

    2015-01-01

    Background: The relationship between monosymptomatic resting tremor (mRT) and Parkinson's disease (PD) remains controversial. In this study, we aimed to assess the function of presynaptic dopaminergic neurons in patients with mRT by dopamine transporter positron emission tomography (DAT-PET) and to evaluate the utility of clinical features or electrophysiological studies in differential diagnosis. Methods: Thirty-three consecutive patients with mRT were enrolled prospectively. The Unified Parkinson's Disease Rating Scale and electromyography were tested before DAT-PET. Striatal asymmetry index (SAI) was calculated, and a normal DAT-PET was defined as a SAI of <15%. Scans without evidence of dopaminergic deficits (SWEDDs) were diagnosed in patients with a subsequent normal DAT-PET and structural magnetic resonance imaging. Results: Twenty-eight mRT patients with a significant reduction in uptake of DAT binding in the striatum were diagnosed with PD, while the remained 5 with a normal DAT-PET scan were SWEDDs. As for UPRDS, the dressing and hygiene score, walking in motor experiences of daily living (Part II) and motor examination (Part III) were significant different between two groups (P < 0.05 and P < 0.01, respectively). Bilateral tremor was more frequent in the SWEDDs group (P < 0.05). The frequency of resting tremor and the amplitude of postural tremor tend to be higher in the SWEDDs group (P = 0.08 and P = 0.05, respectively). Conclusions: mRT is heterogeneous in presynaptic nigrostriatal dopaminergic degeneration, which can be determined by DAT-PET brain imaging. Clinical and electrophysiological features may provide clues to distinguish PD from SWEDDs. PMID:26112718

  13. Substrates and inhibitors display different sensitivity to expression level of the dopamine transporter in heterologously expressing cells.

    PubMed

    Chen, Nianhang; Reith, Maarten E A

    2007-04-01

    The use of heterologous expression systems for studying dopamine (DA) transporter (DAT) function has provided important information corroborating and complementing in situ obtained knowledge. Preliminary experiments with human embryonic kidney cells (HEK293) heterologously expressing varying amounts of DAT suggested fluctuations in the potency of cocaine in inhibiting DA uptake and led to the present systematic assessment of the impact of the density of DAT on its function. Transiently expressing intact HEK293 cells, transfected with increasing amounts of DAT cDNA, displayed increasing levels of surface DAT, binding of the cocaine analog [(3)H]2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane ([(3)H]CFT), and uptake of [(3)H]DA, [(3)H]N-methyl-4-phenylpyridinium ([(3)H]MPP(+)), [(3)H]norepinephrine, and [(3)H]serotonin. However, the amount of DAT cDNA and the DAT expression level required to produce 50% of maximal activity was threefold higher for CFT binding than for DA uptake. Increased DAT expression was accompanied by weakened potency in inhibiting [(3)H]DA uptake for cocaine, CFT, benztropine, and its analog JHW025, GBR 12909 and mazindol; their potency in inhibiting [(3)H]CFT binding was unaffected. Inhibition of uptake by the substrates DA, m-tyramine, d-amphetamine, or MPP(+) was also unaffected. Increasing DAT in stably expressing HEK293 cells by stimulation of gene expression with sodium butyrate also decreased the uptake inhibitory potency of a number of the above blockers without affecting the interaction between substrates and DAT. The present results prompt discussion of models explaining how factors regulating DAT expression at the plasma membrane can regulate DAT function and pharmacology.

  14. 2-Substituted 3β-Aryltropane Cocaine Analogs Produce Atypical Effects without Inducing Inward-Facing Dopamine Transporter Conformations

    PubMed Central

    Hong, Weimin C.; Kopajtic, Theresa A.; Xu, Lifen; Lomenzo, Stacey A.; Jean, Bernandie; Madura, Jeffry D.; Surratt, Christopher K.; Trudell, Mark L.

    2016-01-01

    Previous structure-activity relationship studies indicate that a series of cocaine analogs, 3β-aryltropanes with 2β-diarylmethoxy substituents, selectively bind to the dopamine transporter (DAT) with nanomolar affinities that are 10-fold greater than the affinities of their corresponding 2α-enantiomers. The present study compared these compounds to cocaine with respect to locomotor effects in mice, and assessed their ability to substitute for cocaine (10 mg/kg, i.p.) in rats trained to discriminate cocaine from saline. Despite nanomolar DAT affinity, only the 2β-Ph2COCH2-3β-4-Cl-Ph analog fully substituted for cocaine-like discriminative effects. Whereas all of the 2β compounds increased locomotion, only the 2β-(4-ClPh)PhCOCH2-3β-4-Cl-Ph analog had cocaine-like efficacy. None of the 2α-substituted compounds produced either of these cocaine-like effects. To explore the molecular mechanisms of these drugs, their effects on DAT conformation were probed using a cysteine-accessibility assay. Previous reports indicate that cocaine binds with substantially higher affinity to the DAT in its outward (extracellular)- compared with inward-facing conformation, whereas atypical DAT inhibitors, such as benztropine, have greater similarity in affinity to these conformations, and this is postulated to explain their divergent behavioral effects. All of the 2β- and 2α-substituted compounds tested altered cysteine accessibility of DAT in a manner similar to cocaine. Furthermore, molecular dynamics of in silico inhibitor-DAT complexes suggested that the 2-substituted compounds reach equilibrium in the binding pocket in a cocaine-like fashion. These behavioral, biochemical, and computational results show that aryltropane analogs can bind to the DAT and stabilize outward-facing DAT conformations like cocaine, yet produce effects that differ from those of cocaine. PMID:26769919

  15. Computational and Biochemical Docking of the Irreversible Cocaine Analog RTI 82 Directly Demonstrates Ligand Positioning in the Dopamine Transporter Central Substrate-binding Site*

    PubMed Central

    Dahal, Rejwi Acharya; Pramod, Akula Bala; Sharma, Babita; Krout, Danielle; Foster, James D.; Cha, Joo Hwan; Cao, Jianjing; Newman, Amy Hauck; Lever, John R.; Vaughan, Roxanne A.; Henry, L. Keith

    2014-01-01

    The dopamine transporter (DAT) functions as a key regulator of dopaminergic neurotransmission via re-uptake of synaptic dopamine (DA). Cocaine binding to DAT blocks this activity and elevates extracellular DA, leading to psychomotor stimulation and addiction, but the mechanisms by which cocaine interacts with DAT and inhibits transport remain incompletely understood. Here, we addressed these questions using computational and biochemical methodologies to localize the binding and adduction sites of the photoactivatable irreversible cocaine analog 3β-(p-chlorophenyl)tropane-2β-carboxylic acid, 4′-azido-3′-iodophenylethyl ester ([125I]RTI 82). Comparative modeling and small molecule docking indicated that the tropane pharmacophore of RTI 82 was positioned in the central DA active site with an orientation that juxtaposed the aryliodoazide group for cross-linking to rat DAT Phe-319. This prediction was verified by focused methionine substitution of residues flanking this site followed by cyanogen bromide mapping of the [125I]RTI 82-labeled mutants and by the substituted cysteine accessibility method protection analyses. These findings provide positive functional evidence linking tropane pharmacophore interaction with the core substrate-binding site and support a competitive mechanism for transport inhibition. This synergistic application of computational and biochemical methodologies overcomes many uncertainties inherent in other approaches and furnishes a schematic framework for elucidating the ligand-protein interactions of other classes of DA transport inhibitors. PMID:25179220

  16. Computational and biochemical docking of the irreversible cocaine analog RTI 82 directly demonstrates ligand positioning in the dopamine transporter central substrate-binding site.

    PubMed

    Dahal, Rejwi Acharya; Pramod, Akula Bala; Sharma, Babita; Krout, Danielle; Foster, James D; Cha, Joo Hwan; Cao, Jianjing; Newman, Amy Hauck; Lever, John R; Vaughan, Roxanne A; Henry, L Keith

    2014-10-24

    The dopamine transporter (DAT) functions as a key regulator of dopaminergic neurotransmission via re-uptake of synaptic dopamine (DA). Cocaine binding to DAT blocks this activity and elevates extracellular DA, leading to psychomotor stimulation and addiction, but the mechanisms by which cocaine interacts with DAT and inhibits transport remain incompletely understood. Here, we addressed these questions using computational and biochemical methodologies to localize the binding and adduction sites of the photoactivatable irreversible cocaine analog 3β-(p-chlorophenyl)tropane-2β-carboxylic acid, 4'-azido-3'-iodophenylethyl ester ([(125)I]RTI 82). Comparative modeling and small molecule docking indicated that the tropane pharmacophore of RTI 82 was positioned in the central DA active site with an orientation that juxtaposed the aryliodoazide group for cross-linking to rat DAT Phe-319. This prediction was verified by focused methionine substitution of residues flanking this site followed by cyanogen bromide mapping of the [(125)I]RTI 82-labeled mutants and by the substituted cysteine accessibility method protection analyses. These findings provide positive functional evidence linking tropane pharmacophore interaction with the core substrate-binding site and support a competitive mechanism for transport inhibition. This synergistic application of computational and biochemical methodologies overcomes many uncertainties inherent in other approaches and furnishes a schematic framework for elucidating the ligand-protein interactions of other classes of DA transport inhibitors.

  17. [{sup 11}C]d-threo-Methylphenidate, a new radiotracer for the dopamine transporter. Characterization in baboon and human brain

    SciTech Connect

    Ding, Y.S.; Volkow, N.D.; Fowler, J.S.

    1995-05-01

    dl-threo Methylphenidate (MP, Ritalin) is a psychostimulant drug which binds to the dopamine transporter (DAT). We evaluated [{sup 11}C]d-threo-methylphenidate ([{sup 11}C]d-MP), the more active enantiomer, as a radiotracer for the DAT in baboons and human brain. Stereoselectivity, saturability and pharmacological specificity and reproducibility were examined. Stereoselectivity was examined in baboons by comparing [{sup 11C}]d-MP,[{sup 11}C]l-MP and [{sup 11}C]dl-MP. Unlabeled MP was used to assess the reversibility and saturability of the binding. GBR 12909,{beta}-(4-iodophenyl)tropane-2-carboxylic acid methyl ester ({beta}-CIT), tomoxetine and citalopram were used to assess the specificity of the binding. The ratios between the radioactivity in the striatum to that in cerebellum (ST/CB) were 3.3,2.2 and 1.1 for [{sup 11}C]d-MP,[{sup 11}C]dl-MP and [{sup 11}C]l-MP respectively. Most of the striatal binding of [{sup 11}C]d-threo-MP was displaced by injection of nonradioactive MP demonstrating reversibility. Pretreatment with MP (0.5 mg/kg), GBR12909 (1.5 mg/kg) or {beta}-CIT (0.3 mg/kg) reduced ST/CB by about 60% and the ratios of distribution volumes at the steady-state for the triatum to cerebellum (DV{sub st/}DV{sub cb}) by about 50%. Pretreatment with tomoxetine (3.0 mg/kg) or citalopram (2.0 mg/kg), inhibitors of the norepinephrine and serotonin transporter, had no effect. Studies of [{sup 11}C]d-MP in the human brain showed highest uptake in basal ganglia with a half clearance time of about 60 minutes. Repeated studies in 6 normal human subjects showed differences in DV{sub st/}DV{sub cb} between -7% and 8%. MP pretreatment decreased BG but no cortical or cerebellar binding and reduced Bmax/Kd by 91%.

  18. Investigation of Tropical Transport with UARS Data

    NASA Technical Reports Server (NTRS)

    Dunkerton, Timothy J.

    1999-01-01

    Measurements of trace constituents obtained by instruments aboard the Upper Atmosphere Research Satellite (UARS) have been used to study transport processes associated with the quasi-biennial oscillation, laterally propagating Rossby waves, and upward propagating Kelvin waves in the tropical and subtropical upper troposphere and stratosphere. Mean vertical motions, vertical diffusivities and in-mixing rates were inferred from observations of the 'tape recorder' signal in near-equatorial stratospheric water vapor. The effect of the quasi-biennial oscillation (QBO) on tracer distributions in the upper half of the stratosphere was seen in a spectacular 'staircase' pattern, predominantly in the winter hemisphere, revealing the latitudinally asymmetric nature of QBO transport due to induced mean meridional circulations and modulation of lateral mixing associated with planetary Rossby waves. The propagation of Rossby waves across the equator in the westerly phase of the QBO was seen in tracer fields and corroborating United Kingdom Meteorological Office (UKMO) analyses; a modeling study of the effect of these waves on typical QBO wind profiles was performed. Water vapor in the upper troposphere and lower stratosphere was found to exhibit signatures of the tropical intraseasonal oscillation (TIO) and faster Kelvin waves in the two regions, respectively.

  19. Caffeine regulates frontocorticostriatal dopamine transporter density and improves attention and cognitive deficits in an animal model of attention deficit hyperactivity disorder.

    PubMed

    Pandolfo, Pablo; Machado, Nuno J; Köfalvi, Attila; Takahashi, Reinaldo N; Cunha, Rodrigo A

    2013-04-01

    Attention deficit hyperactivity disorder (ADHD) likely involves dopaminergic dysfunction in the frontal cortex and striatum, resulting in cognitive and motor abnormalities. Since both adenosine and dopamine modulation systems are tightly intertwined, we tested if caffeine (a non-selective adenosine receptor antagonist) attenuated the behavioral and neurochemical changes in adolescent spontaneously hypertensive rats (SHR, a validated ADHD animal model) compared to their control strain (Wistar Kyoto rats, WKY). SHR were hyperactive and had poorer performance in the attentional set-shifting and Y-maze paradigms and also displayed increased dopamine transporter (DAT) density and increased dopamine uptake in frontocortical and striatal terminals compared with WKY rats. Chronic caffeine treatment was devoid of effects in WKY rats while it improved memory and attention deficits and also normalized dopaminergic function in SHR. Additionally, we provide the first direct demonstration for the presence of adenosine A2A receptors (A2AR) in frontocortical nerve terminals, whose density was increased in SHR. These findings underscore the potential for caffeine treatment to normalize frontocortical dopaminergic function and to abrogate attention and cognitive changes characteristic of ADHD.

  20. The primate thalamus is a key target for brain dopamine.

    PubMed

    Sánchez-González, Miguel Angel; García-Cabezas, Miguel Angel; Rico, Beatriz; Cavada, Carmen

    2005-06-29

    The thalamus relays information to the cerebral cortex from subcortical centers or other cortices; in addition, it projects to the striatum and amygdala. The thalamic relay function is subject to modulation, so the flow of information to the target regions may change depending on behavioral demands. Modulation of thalamic relay by dopamine is not currently acknowledged, perhaps because dopamine innervation is reportedly scant in the rodent thalamus. We show that dopaminergic axons profusely target the human and macaque monkey thalamus using immunolabeling with three markers of the dopaminergic phenotype (tyrosine hydroxylase, dopamine, and the dopamine transporter). The dopamine innervation is especially prominent in specific association, limbic, and motor thalamic nuclei, where the densities of dopaminergic axons are as high as or higher than in the cortical area with the densest dopamine innervation. We also identified the dopaminergic neurons projecting to the macaque thalamus using retrograde tract-tracing combined with immunohistochemistry. The origin of thalamic dopamine is multiple, and thus more complex, than in any other dopaminergic system defined to date: dopaminergic neurons of the hypothalamus, periaqueductal gray matter, ventral mesencephalon, and the lateral parabrachial nucleus project bilaterally to the monkey thalamus. We propose a novel dopaminergic system that targets the primate thalamus and is independent from the previously defined nigrostriatal, mesocortical, and mesolimbic dopaminergic systems. Investigating this "thalamic dopaminergic system" should further our understanding of higher brain functions and conditions such as Parkinson's disease, schizophrenia, and drug addiction.

  1. Delivery of dopamine transporter tracer (PE2I) through blood brain barrier with ultrasound and microbubbles

    NASA Astrophysics Data System (ADS)

    Serrière, Sophie; Escoffre, Jean-Michel; Bodard, Sylvie; Novell, Anthony; Vergote, Jackie; Vercouillie, Johnny; Thiéry, Jean-Claude; Chalon, Sylvie; Bouakaz, Ayache

    2012-10-01

    The blood-brain barrier plays a major role in controlling the delivery of therapeutic and imaging agents to the brain. The aim of this study was to investigate the use of ultrasound and microbubbles to increase its delivery through the BBB and by determining the optimal experimental conditions that achieve a transient and safe BBB disruption. First, we established the ultrasound conditions that achieved a transient BBB disruption in rats using a non-permeant marker, Evans blue. Hence SonoVue® (450 μL/kg) and Evans blue (100 mg/kg) were intravenously administered. BBB leakage was obtained using ultrasound insonation through the rat skull at 1.6 MPa, PRF 1 Hz, duty cycle 12%, burst 10 ms during 120 sec. BBB disruption was observed in all treated animals (N=4) by histological analysis. The same experimental conditions were applied to enhance brain uptake of PE2I. Biological samples were analyzed using a scintillation counter apparatus. The results showed 50% and 20% increase of 125I-PE2I uptake in the striatum and cerebral cortex, respectively, in the treated rats (N=5) versus control (N=4). Similar enhancements were observed using SonoVue® at half concentration. This innovative method provides a great potential for intracerebral delivery of molecular ligands that could be used for the therapy of brain diseases.

  2. Introducing Thermal Wave Transport Analysis (TWTA): A Thermal Technique for Dopamine Detection by Screen-Printed Electrodes Functionalized with Molecularly Imprinted Polymer (MIP) Particles.

    PubMed

    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.

  3. Optimal Acquisition Time Window and Simplified Quantification of Dopamine Transporter Availability Using 18F-FE-PE2I in Healthy Controls and Parkinson Disease Patients.

    PubMed

    Sonni, Ida; Fazio, Patrik; Schain, Martin; Halldin, Christer; Svenningsson, Per; Farde, Lars; Varrone, Andrea

    2016-10-01

    (18)F-(E)-N-(3-iodoprop-2-enyl)-2β-carbofluoroethoxy-3β-(4'methylphenyl)nortropane ((18)F-FE-PE2I) is a newly developed dopamine transporter (DAT) PET radioligand. Full quantification methods rely on dynamic acquisition of (18)F-FE-PE2I, but in a clinical setting a simplified protocol is preferable. The aims of this study were to identify the optimal acquisition time window for (18)F-FE-PE2I and to validate the specific binding ratio (SBR) as a simplified quantification method.

  4. The presence of both serotonin 1A receptor (HTR1A) and dopamine transporter (DAT1) gene variants increase the risk of borderline personality disorder

    PubMed Central

    Joyce, Peter R.; Stephenson, John; Kennedy, Martin; Mulder, Roger T.; McHugh, Patrick C.

    2014-01-01

    Dysfunction in the dopaminergic and serotonergic neurotransmitter systems has been demonstrated to be important in the etiology of borderline personality disorder (BPD). We investigated the relationship of two BPD risk factors, the HTR1A promoter polymorphism -1019C > G (rs6295) and the dopamine transporter (DAT1) repeat allele, with BPD in a major depressive disorder cohort of 367 patients. Out-patients with major depressive disorder were recruited for two treatment trials and assessed for personality disorders, including BPD. DNA samples were collected and the rs6295 polymorphism was detected with a TaqMan® assay. The DAT1 repeat allele was genotyped using a modified PCR method. The impact of polymorphisms on BPD was statistically analyzed using uncontrolled logistic and multiple logistic regression models. BPD patients had higher frequencies of the DAT1 9,9 (OR = 2.67) and 9,10 (OR = 3.67) genotypes and also those homozygous HTR1A G allele (OR = 2.03). No significant interactions between HTR1A and DAT1 genotypes, were observed; however, an increased risk of BPD was observed for those patients who were either 9,10; G,G (OR = 6.64) and 9,9; C,G (OR = 5.42). Furthermore, the odds of BPD in patients exhibiting high-risk variants of these two genes differed from those of patients in low-risk groups by up to a factor of 9. Our study provides evidence implicating the importance of the serotonergic and dopaminergic systems in BPD and that the interaction between genes from different neurotransmitters may play a role in the susceptibility to BPD. PMID:24432029

  5. Dopamine transporter occupancy by RTI-55 determined using labeled cocaine, and displacement of RTI-55 with unlabeled cocaine

    SciTech Connect

    Gatley, S.J.; Volkow, N.D.; Fowler, J.S.

    1995-05-01

    We have previously visualized dopamine transporters (DAT) in human and baboon striatum using PET and C-11 cocaine. Cocaine analogs such as 3{beta}-(4-iodophenyl) tropane-2{beta}-carboxylic acid methyl ester (RTI-55 or {beta}CIT) with a higher affinity for the DAT may be potentially useful in interfering with cocaine`s actions in brain. We evaluated the time course of the effects of RTI-55 on C-11 cocaine binding in baboon brain prior to and 90 minutes, 24 hours, 4-5 days and 11-13 days after RTI-55(0.3 mg/kg iv). RTI-55 significantly inhibited C-11 cocaine binding at 90 minutes and 24 hours after administration. The half life for the clearance of RTI-55 from the DAT was estimated to be 2 to 3 days in the baboon brain. Parallel studies with H-3 cocaine and RTI-55 (0.5 mg/kg iv or 2 mg/kg ip) were performed in mice, where RTI-55 significantly inhibited 5 minute striatum-to-cerebellium ratios (S/C) at 60 and 180 minutes after administration, and recovery was obtained at 12 hours. However, unlabeled cocaine (20 mg/Kg, i/p) given 60 minutes after RTI-55 led to a greater recovery of H-3 cocaine uptake measured at 180 minutes (S/C = 1.23 {plus_minus} 0.07, n= 5), than in control animals given saline after RTI-55 (S/C = 9.5{plus_minus}0.08). Animals given saline instead of RTI-55 had S/C = 1.45{plus_minus}0.04. These results document long lasting inhibition of cocaine binding by RTI-55 and corroborate the assumption that the binding kinetics of RTI-55 in striatum observed in SPECT imaging studies with I-123 RTI-55 represents binding to DAT`s. However, a pharmacological dose of cocaine is able to displace a fraction of the previously bound RTI-55 from the DAT. These findings have implications for drug development strategies for cocaine abuse.

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

    PubMed

    Sirova, Jana; Kristofikova, Zdenka; Vrajova, Monika; Fujakova-Lipski, Michaela; Ripova, Daniela; Klaschka, Jan; Slamberova, Romana

    2016-08-01

    Methamphetamine (MA) is the most commonly used psychostimulant drug, the chronic abuse of which leads to neurodegenerative changes in the brain. The global use of MA is increasing, including in pregnant women. Since MA can cross both placental and haematoencephalic barriers and is also present in maternal milk, children of chronically abused mothers are exposed prenatally as well as postnatally. Women seem to be more vulnerable to some aspects of MA abuse than men. MA is thought to exert its effects among others via direct interactions with dopamine transporters (DATs) in the brain tissue. Sexual dimorphism of the DAT system could be a base of sex-dependent actions of MA observed in behavioural and neurochemical studies. Possible sex differences in the DATs of preadolescent offspring exposed to MA prenatally and/or postnatally have not yet been evaluated. We examined the striatal synaptosomal DATs (the activity and density of surface expressed DATs and total DAT expression) in preadolescent male and female Wistar rats (31-35-day old animals) exposed prenatally and/or postnatally to MA (daily 5 mg/kg, s.c. to mothers during pregnancy and lactation). To distinguish between specific and nonspecific effects of MA on DATs, we also evaluated the in vitro effects of lipophilic MA on the fluidity of striatal membranes isolated from preadolescent and young adult rats of both sexes. We observed similar changes in the DATs of preadolescent rats exposed prenatally or postnatally (MA-mediated drop in the reserve pool but no alterations in surface-expressed DATs). However, prenatal exposure evoked significant changes in males and postnatal exposure in females. A significant decrease in the activity of surface-expressed DATs was found only in postnatally exposed females sensitized to MA via prenatal exposure. MA applied in vitro increased the fluidity of striatal membranes of preadolescent female but not male rats. In summary, DATs of preadolescent males are more sensitive to

  7. Usefulness of a dopamine transporter PET ligand [18F]β-CFT in assessing disability in Parkinson's disease

    PubMed Central

    Rinne, J.; Ruottinen, H.; Bergman, J.; Haaparanta, M.; Sonninen, P.; Solin, O.

    1999-01-01

    OBJECTIVES—The usefulness of a novel dopamine transporter PET ligand, [18F]β-CFT in assessing disability in Parkinson's disease was studied.
METHODS—Twenty seven patients with Parkinson's disease in different disability stages (of which nine were patients with early disease) and nine healthy controls were studied. The regions of interest were drawn on a magnetic resonance image resliced according to the PET image.
RESULTS—There was a significant reduction in [18F]β-CFT uptake in the posterior putamen (to 18% of the control mean, p<0.00001), anterior putamen (28%, p<0.00001), and caudate nucleus (51%, p<0.00001) in the total population of patients with Parkinson's disease. The reduction in [18F]β-CFT uptake was more pronounced with more severe disability of the patients, the correlations between the total motor score of the unified Parkinson's disease rating scale (UPDRS) and [18F]β-CFT uptake being significant in the posterior putamen (r=−0.62 p=0.0005), anterior putamen (r=-0.64, p=0.0003), and the caudate nucleus (r=−0.62, p=0.0006). There was a significant negative correlation with putaminal [18F]β-CFT uptake and the hypokinesia and rigidity scores, but not with the tremor score of the UPDRS motor part. In nine patients with early disease and without any antiparkinsonian medication the reduction in the [18F]β-CFT uptake (average of ipsilateral and contralateral side) was reduced in the total putamen to 34% of the mean control value (p<0.00001). The corresponding figures in the other brain areas were: posterior putamen 21% (p<0.00001), anterior putamen 43% (p<0.00001), and caudate nucleus 76% (p<0.01). The reductions in [18F]β-CFT uptake were more severe in the contralateral than in the ipsilateral side. Individually, [18F]β-CFT uptake in the putamen in all patients was below 3 SD from the control mean. 
CONCLUSIONS—[18F]β-CFT is a sensitive marker of nigrostriatal dopaminergic dysfunction in Parkinson's disease and can be used in the

  8. Characterisation of [11C]PR04.MZ in Papio anubis baboon: A selective high-affinity radioligand for quantitative imaging of the dopamine transporter

    SciTech Connect

    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.

  9. Iron chelation down-regulates dopamine transporter expression by decreasing mRNA stability and increasing endocytosis in N2a cells.

    PubMed

    Hegde, Narasimha V; Jensen, Gordon L; Unger, Erica L

    2011-02-15

    Cell surface expression of the dopamine transporter (DAT) is determined by the relative rates of its internalization and recycling. Changes in the cellular labile iron pool (LIP) affect many cellular mechanisms including those that regulate DAT trafficking. In this study, we analyzed DAT expression and posttranslational modifications in response to changes in cellular iron in transfected neuroblastoma cells (N2a). Iron chelation by desferrioxamine (DFO) altered DAT protein levels by decreasing the stability of DAT mRNA. Increased phosphorylation and ubiquitination of this transporter protein following DFO treatment were also observed. Cellular iron depletion elevated protein levels of the early endosomal marker Rab5. Moreover, confocal microscopy studies showed increased localization of DAT into the endosomal compartment in DFO-treated cells compared to control. Together, these findings suggest that cellular iron depletion regulates DAT expression through reducing mRNA stability as well as an increasing in endocytosis.

  10. Ethylenedioxy homologs of N-methyl-(3,4-methylenedioxyphenyl)-2-aminopropane (MDMA) and its corresponding cathinone analog methylenedioxymethcathinone: Interactions with transporters for serotonin, dopamine, and norepinephrine.

    PubMed

    Del Bello, Fabio; Sakloth, Farhana; Partilla, John S; Baumann, Michael H; Glennon, Richard A

    2015-09-01

    N-Methyl-(3,4-methylenedioxyphenyl)-2-aminopropane (MDMA; 'Ecstasy'; 1) and its β-keto analog methylone (MDMC; 2) are popular drugs of abuse. Little is known about their ring-expanded ethylenedioxy homologs. Here, we prepared N-methyl-(3,4-ethylenedioxyphenyl)-2-aminopropane (EDMA; 3), both of its optical isomers, and β-keto EDMA (i.e., EDMC; 4) to examine their effects at transporters for serotonin (SERT), dopamine (DAT), and norepinephrine (NET). In general, ring-expansion of the methylenedioxy group led to a several-fold reduction in potency at all three transporters. With respect to EDMA (3), S(+)3 was 6-fold, 50-fold, and 8-fold more potent than its R(-) enantiomer at SERT, DAT, and NET, respectively. Overall, in the absence of a β-carbonyl group, the ethylenedioxy (i.e., 1,4-dioxane) substituent seems better accommodated at SERT than at DAT and NET.

  11. Azido-iodo-N-benzyl derivatives of threo-methylphenidate (Ritalin, Concerta): Rational design, synthesis, pharmacological evaluation, and dopamine transporter photoaffinity labeling.

    PubMed

    Lapinsky, David J; Velagaleti, Ranganadh; Yarravarapu, Nageswari; Liu, Yi; Huang, Yurong; Surratt, Christopher K; Lever, John R; Foster, James D; Acharya, Rejwi; Vaughan, Roxanne A; Deutsch, Howard M

    2011-01-01

    In contrast to tropane-based compounds such as benztropine and cocaine, non-tropane-based photoaffinity ligands for the dopamine transporter (DAT) are relatively unexplored. Towards addressing this knowledge gap, ligands were synthesized in which the piperidine nitrogen of 3- and 4-iodomethylphenidate was substituted with a benzyl group bearing a photoreactive azide. Analog (±)-3a demonstrated modest DAT affinity and a radioiodinated version was shown to bind covalently to rat striatal DAT and hDAT expressed in cultured cells. Co-incubation of (±)-3a with nonradioactive d-(+)-methylphenidate or (-)-2-β-carbomethoxy-3-β-(4-fluorophenyl)tropane (β-CFT, WIN-35,428, a cocaine analog) blocked DAT labeling. Compound (±)-3a represents the first successful example of a DAT photoaffinity ligand based on the methylphenidate scaffold. Such ligands are expected to assist in mapping non-tropane ligand-binding pockets within plasma membrane monoamine transporters.

  12. Azido-Iodo-N-Benzyl Derivatives of threo-Methylphenidate (Ritalin, Concerta): Rational Design, Synthesis, Pharmacological Evaluation, and Dopamine Transporter Photoaffinity Labeling

    PubMed Central

    Lapinsky, David J.; Velagaleti, Ranganadh; Yarravarapu, Nageswari; Liu, Yi; Huang, Yurong; Surratt, Christopher K.; Lever, John R.; Foster, James D.; Acharya, Rejwi; Vaughan, Roxanne A.; Deutsch, Howard M.

    2010-01-01

    In contrast to tropane-based compounds such as benztropine and cocaine, non-tropane-based photoaffinity ligands for the dopamine transporter (DAT) are relatively unexplored. Towards addressing this knowledge gap, ligands were synthesized in which the piperidine nitrogen of 3- and 4-iodomethylphenidate was substituted with a benzyl group bearing a photoreactive azide. Analog (±)-3a demonstrated modest DAT affinity and a radioiodinated version was shown to bind covalently to rat striatal DAT and hDAT expressed in cultured cells. Co-incubation of (±)-3a with nonradioactive D-(+)-methylphenidate or (−)-2-β-carbomethoxy-3-β-(4-fluorophenyl)tropane (β-CFT, WIN-35,428, a cocaine analog) blocked DAT labeling. Compound (±)-3a represents the first successful example of a DAT photoaffinity ligand based on the methylphenidate scaffold. Such ligands are expected to assist in mapping non-tropane ligand-binding pockets within plasma membrane monoamine transporters. PMID:21129986

  13. Single-quantum-dot tracking reveals altered membrane dynamics of an attention-deficit/hyperactivity-disorder-derived dopamine transporter coding variant.

    PubMed

    Kovtun, Oleg; Sakrikar, Dhananjay; Tomlinson, Ian D; Chang, Jerry C; Arzeta-Ferrer, Xochitl; Blakely, Randy D; Rosenthal, Sandra J

    2015-04-15

    The presynaptic, cocaine- and amphetamine-sensitive dopamine (DA) transporter (DAT, SLC6A3) controls the intensity and duration of synaptic dopamine signals by rapid clearance of DA back into presynaptic nerve terminals. Abnormalities in DAT-mediated DA clearance have been linked to a variety of neuropsychiatric disorders, including addiction, autism, and attention deficit/hyperactivity disorder (ADHD). Membrane trafficking of DAT appears to be an important, albeit incompletely understood, post-translational regulatory mechanism; its dysregulation has been recently proposed as a potential risk determinant of these disorders. In this study, we demonstrate a link between an ADHD-associated DAT mutation (Arg615Cys, R615C) and variation on DAT transporter cell surface dynamics, a combination only previously studied with ensemble biochemical and optical approaches that featured limited spatiotemporal resolution. Here, we utilize high-affinity, DAT-specific antagonist-conjugated quantum dot (QD) probes to establish the dynamic mobility of wild-type and mutant DATs at the plasma membrane of living cells. Single DAT-QD complex trajectory analysis revealed that the DAT 615C variant exhibited increased membrane mobility relative to DAT 615R, with diffusion rates comparable to those observed after lipid raft disruption. This phenomenon was accompanied by a loss of transporter mobilization triggered by amphetamine, a common component of ADHD medications. Together, our data provides the first dynamic imaging of single DAT proteins, providing new insights into the relationship between surface dynamics and trafficking of both wild-type and disease-associated transporters. Our approach should be generalizable to future studies that explore the possibilities of perturbed surface DAT dynamics that may arise as a consequence of genetic alterations, regulatory changes, and drug use that contribute to the etiology or treatment of neuropsychiatric disorders.

  14. Dopamine Transporter Regulation during Four Nights of REM Sleep Deprivation Followed by Recovery – An in vivo Molecular Imaging Study in Humans

    PubMed Central

    Martins, RCS; Andersen, ML; Garbuio, SA; Bittencourt, LR; Guindalini, C; Shih, MC; Hoexter, MQ; Bressan, RA; Castiglioni, MLV; Tufik, S

    2010-01-01

    Objectives: To assess the influence of total or selective REM sleep deprivation on the dopamine transporter (DAT) densities and sleep patterns of healthy volunteers. Design: Prospective study. Setting: Evaluation of polysomnography recordings and DAT density after 4 nights of selective REM sleep deprivation followed by 3 nights of sleep recovery compared to a control group and a group that was subjected to 2 nights of total sleep deprivation. Single positron emission computed tomography and [99mTc]TRODAT-1 were used to assess the cerebral DAT density in the striatum at baseline, after REM sleep deprivation and total sleep deprivation as well as after sleep recovery. Blood was collected daily to examine prolactin and estradiol levels, which were correlated with dopaminergic activity. Patients or Participants: Thirty healthy male volunteers ranging from 19 to 29 years of age were randomly assigned to one of three experimental groups after giving written informed consent (10 non-sleep deprived, 10 total sleep deprived, and 10 REM sleep deprived). Measurements and Results: Four nights of REM sleep deprivation and 2 nights of total sleep deprivation induced distinct and heterogeneous patterns of sleep recovery. No significant modulation of DAT availability was observed within groups. In the recovery nights, changes in cortisol, prolactin and estradiol concentrations were significantly correlated with specific sleep stages in the total and REM sleep deprived groups. In addition, DAT density was positively correlated with estradiol concentration and inversely associated with SWS latency only after total sleep deprivation. Conclusion: Our study demonstrates that although sleep deprivation did not promote significant alterations in DAT density within the striatum, there were significant correlations among transporter availability, hormonal concentrations and sleep parameters. Citation: Martins, RCS; Andersen ML; Garbuio SA; Bittencourt LR: Guindalini C; Shih MC; Hoexter MQ

  15. Metabolic and Cardiovascular Benefits and Risks of EMD386088—A 5-HT6 Receptor Partial Agonist and Dopamine Transporter Inhibitor

    PubMed Central

    Kotańska, Magdalena; Śniecikowska, Joanna; Jastrzębska-Więsek, Magdalena; Kołaczkowski, Marcin; Pytka, Karolina

    2017-01-01

    Since 5-HT6 receptors play role in controlling feeding and satiety and dopamine is essential for normal feeding behavior, we evaluated the ability of EMD 386088—5-HT6 receptor partial agonist and dopamine transporter inhibitor—to reduce body weight in obese rats, as well as its anorectic properties (calorie intake reduction) in rat model of excessive eating and the influence on metabolism (plasma glucose and glycerol levels). We also determined the effect of the studied compound on pica behavior in rats and its influence on blood pressure after single administration. EMD 386088 reduced body weight in obese rats fed high-fat diet and decreased calorie intake in both models applied (rat model of obesity and of excessive eating). In both models EMD 386088 regulated plasma glucose and increased plasma glycerol levels. The latter proves that the compound reduced body fat. We think that it might have increased lipolysis, but this requires further studies. The reduction in glucose levels is the first symptom of metabolic disorders compensation. EMD 386088 did not cause pica behavior in rats but increased blood pressure after single administration. We think that partial 5-HT6 agonists might have potential in the treatment of obesity. Thus, EMD 386088 requires extended studies. PMID:28228713

  16. Population pharmacokinetics, brain distribution, and pharmacodynamics of 2nd generation dopamine transporter selective benztropine analogs developed as potential substitute therapeutics for treatment of cocaine abuse.

    PubMed

    Syed, Shariq A; Newman, Amy H; Othman, Ahmed A; Eddington, Natalie D

    2008-05-01

    A second generation of N-substituted 3alpha-[bis(4'-fluorophenyl)methoxy]-tropanes (GA 1-69, JHW 005 and JHW 013) binds with high affinity to the dopamine transporter (DAT) and are highly selective toward DAT compared to muscarinic receptor binding (M1). The objective of this study was to characterize brain distribution, pharmacokinetics, and pharmacodynamics [extracellular brain dopamine (DA) levels] of three novel N-substituted benztropine (BZT) analogs in male Sprague-Dawley rats. The BZT analogs displayed a higher distribution (Vd = 8.69-34.3 vs. 0.9 L/kg) along with longer elimination (t l/2: 4.1-5.4 vs. 0.5 h) than previously reported for cocaine. Brain-to-plasma partition coefficients were 1.3-2.5 vs. 2.1 for cocaine. The effect of the BZT analogs on extracellular brain (DA) levels ranged from minimal effects (GA 1-69) to several fold elevation (approximately 850% of basal DA for JHW 013) at the highest dose evaluated. PK/PD analysis of exposure-response data resulted in lower IC50 values for the BZT analogs compared to cocaine indicating their higher potency to inhibit DA reuptake (0.1-0.3 vs. 0.7 mg/L). These BZT analogs possess significantly different PK and PD profiles as compared to cocaine suggesting that further evaluation as cocaine abuse therapeutics is warranted.

  17. Time course of changes in striatal dopamine transporters and D2 receptors with specific iodinated markers in a rat model of Parkinson's disease.

    PubMed

    Chalon, S; Emond, P; Bodard, S; Vilar, M P; Thiercelin, C; Besnard, J C; Guilloteau, D

    1999-02-01

    The time course of the loss in presynaptic dopamine transporters (DAT) and of the increase in postsynaptic dopamine D2 receptors (D2R) was studied in a rat model of Parkinson's disease. For this, in vitro autoradiographic experiments were performed in the striatum using (E)-N-(3-iodoprop-2-enyl)-2beta-carbomethoxy-3beta-(4'-methy lphenyl) nortropane (PE2I), a new single photon emission tomography (SPET) ligand for DAT, and iodobenzamide (IBZM), a SPET ligand for D2R. A significant decrease in [125I]PE2I binding was observed as early as 24 h after 6-hydroxydopamine lesion, whereas no change occurred in [125I]IBZM binding. At 48 h postlesion, PE2I binding was 50% decreased, while IBZM binding was 30% increased. Between 3 and 14 days postlesion, PE2I binding had almost totally disappeared and IBZM binding remained increased by around 40-50%. From these animal experiments, it can be assumed that PE2I would be very efficient for the detection of a reduction in the number of DAT reflecting neuronal loss, thus allowing early diagnosis of Parkinson's disease. The exploration of both DAT and D2R would improve follow-up of this disease.

  18. Investigation of air transportation technology at Princeton University, 1986

    NASA Technical Reports Server (NTRS)

    Stengel, Robert F.

    1988-01-01

    The Air Transportation Technology Program at Princeton proceeded along four avenues: Guidance and control strategies for penetration of microbursts and wind shear; Application of artificial intelligence in flight control systems; Computer aided control system design; and Effects of control saturation on closed loop stability and response of open loop unstable aircraft. Areas of investigation relate to guidance and control of commercial transports as well as general aviation aircraft. Interaction between the flight crew and automatic systems is a subject of prime concern.

  19. Untangling Basal Ganglia Network Dynamics and Function: Role of Dopamine Depletion and Inhibition Investigated in a Spiking Network Model

    PubMed Central

    2016-01-01

    Abstract The basal ganglia are a crucial brain system for behavioral selection, and their function is disturbed in Parkinson’s disease (PD), where neurons exhibit inappropriate synchronization and oscillations. We present a spiking neural model of basal ganglia including plausible details on synaptic dynamics, connectivity patterns, neuron behavior, and dopamine effects. Recordings of neuronal activity in the subthalamic nucleus and Type A (TA; arkypallidal) and Type I (TI; prototypical) neurons in globus pallidus externa were used to validate the model. Simulation experiments predict that both local inhibition in striatum and the existence of an indirect pathway are important for basal ganglia to function properly over a large range of cortical drives. The dopamine depletion–induced increase of AMPA efficacy in corticostriatal synapses to medium spiny neurons (MSNs) with dopamine receptor D2 synapses (CTX-MSN D2) and the reduction of MSN lateral connectivity (MSN–MSN) were found to contribute significantly to the enhanced synchrony and oscillations seen in PD. Additionally, reversing the dopamine depletion–induced changes to CTX–MSN D1, CTX–MSN D2, TA–MSN, and MSN–MSN couplings could improve or restore basal ganglia action selection ability. In summary, we found multiple changes of parameters for synaptic efficacy and neural excitability that could improve action selection ability and at the same time reduce oscillations. Identification of such targets could potentially generate ideas for treatments of PD and increase our understanding of the relation between network dynamics and network function. PMID:28101525

  20. Investigation of air transportation technology at Princeton University, 1984

    NASA Technical Reports Server (NTRS)

    Stengel, Robert F.

    1987-01-01

    The Air Transportation Technology Program at Princeton University, a program emphasizing graduate and undergraduate student research, proceeded along four avenues during 1984: (1) guidance and control strategies for penetration of microbursts and wind shear; (2) application of artificial intelligence in flight control systems; (3) effects of control saturation on closed loop stability; and (4) response of open loop unstable aircraft. Areas of investigation relate to guidance and control of commercial transports as well as to general aviation aircraft. Interaction between the flight crew and automatic systems is a subject of principle concern. These areas of investigation are briefly discussed.

  1. Three modality image registration of brain SPECT/CT and MR images for quantitative analysis of dopamine transporter imaging

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yuzuho; Takeda, Yuta; Hara, Takeshi; Zhou, Xiangrong; Matsusako, Masaki; Tanaka, Yuki; Hosoya, Kazuhiko; Nihei, Tsutomu; Katafuchi, Tetsuro; Fujita, Hiroshi

    2016-03-01

    Important features in Parkinson's disease (PD) are degenerations and losses of dopamine neurons in corpus striatum. 123I-FP-CIT can visualize activities of the dopamine neurons. The activity radio of background to corpus striatum is used for diagnosis of PD and Dementia with Lewy Bodies (DLB). The specific activity can be observed in the corpus striatum on SPECT images, but the location and the shape of the corpus striatum on SPECT images only are often lost because of the low uptake. In contrast, MR images can visualize the locations of the corpus striatum. The purpose of this study was to realize a quantitative image analysis for the SPECT images by using image registration technique with brain MR images that can determine the region of corpus striatum. In this study, the image fusion technique was used to fuse SPECT and MR images by intervening CT image taken by SPECT/CT. The mutual information (MI) for image registration between CT and MR images was used for the registration. Six SPECT/CT and four MR scans of phantom materials are taken by changing the direction. As the results of the image registrations, 16 of 24 combinations were registered within 1.3mm. By applying the approach to 32 clinical SPECT/CT and MR cases, all of the cases were registered within 0.86mm. In conclusions, our registration method has a potential in superimposing MR images on SPECT images.

  2. MPA-capped CdTe quantum dots exposure causes neurotoxic effects in nematode Caenorhabditis elegans by affecting the transporters and receptors of glutamate, serotonin and dopamine at the genetic level, or by increasing ROS, or both

    NASA Astrophysics Data System (ADS)

    Wu, Tianshu; He, Keyu; Zhan, Qinglin; Ang, Shengjun; Ying, Jiali; Zhang, Shihan; Zhang, Ting; Xue, Yuying; Tang, Meng

    2015-12-01

    As quantum dots (QDs) are widely used in biomedical applications, the number of studies focusing on their biological properties is increasing. While several studies have attempted to evaluate the toxicity of QDs towards neural cells, the in vivo toxic effects on the nervous system and the molecular mechanisms are unclear. The aim of the present study was to investigate the neurotoxic effects and the underlying mechanisms of water-soluble cadmium telluride (CdTe) QDs capped with 3-mercaptopropionic acid (MPA) in Caenorhabditis elegans (C. elegans). Our results showed that exposure to MPA-capped CdTe QDs induced behavioral defects, including alterations to body bending, head thrashing, pharyngeal pumping and defecation intervals, as well as impaired learning and memory behavior plasticity, based on chemotaxis or thermotaxis, in a dose-, time- and size-dependent manner. Further investigations suggested that MPA-capped CdTe QDs exposure inhibited the transporters and receptors of glutamate, serotonin and dopamine in C. elegans at the genetic level within 24 h, while opposite results were observed after 72 h. Additionally, excessive reactive oxygen species (ROS) generation was observed in the CdTe QD-treated worms, which confirmed the common nanotoxicity mechanism of oxidative stress damage, and might overcome the increased gene expression of neurotransmitter transporters and receptors in C. elegans induced by long-term QD exposure, resulting in more severe behavioral impairments.

  3. Investigation of air transportation technology at Princeton University

    NASA Technical Reports Server (NTRS)

    Stengel, R. F.

    1983-01-01

    The Air Transportation Technology Program at Princeton University, a program emphasizing graduate and undergraduate student research, proceeded along six avenues during the past year: investigation of fuel use characteristics of general aviation aircraft, experimentation with an ultrasonic altimeter, single pilot instrument flight, application of fiber optics in flight control systems, voice recognition inputs for navigation/communication receiver tuning, and computer aided aircraft design.

  4. First evidence of epithelial transport in tardigrades: a comparative investigation of organic anion transport.

    PubMed

    Halberg, Kenneth Agerlin; Møbjerg, Nadja

    2012-02-01

    We investigated transport of the organic anion Chlorophenol Red (CPR) in the tardigrade Halobiotus crispae using a new method for quantifying non-fluorescent dyes. We compared the results acquired from the tardigrade with CPR transport data obtained from Malpighian tubules of the desert locust Schistocerca gregaria. CPR accumulated in the midgut lumen of H. crispae, indicating that organic anion transport takes place here. Our results show that CPR transport is inhibited by the mitochondrial un-coupler DNP (1 mmol l(-1); 81% reduction), the Na(+)/K(+)-ATPase inhibitor ouabain (10 mmol l(-1); 21% reduction) and the vacuolar H(+)-ATPase inhibitor bafilomycin (5 μmol l(-1); 21% reduction), and by the organic anions PAH (10 mmol l(-1); 44% reduction) and probenecid (10 mmol l(-1); 61% reduction, concentration-dependent inhibition). Transport by locust Malpighian tubules exhibits a similar pharmacological profile, albeit with markedly higher concentrations of CPR being reached in S. gregaria. Immunolocalization of the Na(+)/K(+)-ATPase α-subunit in S. gregaria revealed that this transporter is abundantly expressed and localized to the basal cell membranes. Immunolocalization data could not be obtained from H. crispae. Our results indicate that organic anion secretion by the tardigrade midgut is transporter mediated with likely candidates for the basolateral entry step being members of the Oat and/or Oatp transporter families. From our results, we cautiously suggest that apical H(+) and possibly basal Na(+)/K(+) pumps provide the driving force for the transport; the exact coupling between electrochemical gradients generated by the pumps and transport of ions, as well as the nature of the apical exit step, are unknown. This study is, to our knowledge, the first to show active epithelial transport in tardigrades.

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

    PubMed

    Sotnikova, Tatyana D; Beaulieu, Jean-Martin; Barak, Larry S; Wetsel, William C; Caron, Marc G; Gainetdinov, Raul R

    2005-08-01

    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.

  6. The effects of dopamine receptor agonists and antagonists on the secretory rate of cockroach (Periplaneta americana) salivary glands.

    PubMed

    Marg, Susanna; Walz, Bernd; Blenau, Wolfgang

    2004-09-01

    The acinar salivary glands of the cockroach, Periplaneta americana, are innervated by dopaminergic and serotonergic nerve fibers. Serotonin stimulates the secretion of protein-rich saliva, whereas dopamine causes the production of protein-free saliva. This suggests that dopamine acts selectively on ion-transporting peripheral cells within the acini and the duct cells, and that serotonin acts on the protein-producing central cells of the acini. We have investigated the pharmacology of the dopamine-induced secretory activity of the salivary gland of Periplaneta americana by testing several dopamine receptor agonists and antagonists. The effects of dopamine can be mimicked by the non-selective dopamine receptor agonist 6,7-ADTN and, less effectively, by the vertebrate D1 receptor-selective agonist chloro-APB. The vertebrate D1 receptor-selective agonist SKF 38393 and vertebrate D2 receptor-selective agonist R(-)-TNPA were ineffective. R(+)-Lisuride induces a secretory response with a slower onset and a lower maximal response compared with dopamine-induced secretion. However, lisuride-stimulated glands continue secreting saliva, even after lisuride-washout. Dopamine-induced secretions can be blocked by the vertebrate dopamine receptor antagonists cis(Z)-flupenthixol, chlorpromazine, and S(+)-butaclamol. Our pharmacological data do not unequivocally indicate whether the dopamine receptors on the Periplaneta salivary glands belong to the D1 or D2 subfamily of dopamine receptors, but we can confirm that the pharmacology of invertebrate dopamine receptors is remarkably different from that of their vertebrate counterparts.

  7. The conditioning of intervention effects on early adolescent alcohol use by maternal involvement and dopamine receptor D4 (DRD4) and serotonin transporter linked polymorphic region (5-HTTLPR) genetic variants.

    PubMed

    Cleveland, H Harrington; Schlomer, Gabriel L; Vandenbergh, David J; Feinberg, Mark; Greenberg, Mark; Spoth, Richard; Redmond, Cleve; Shriver, Mark D; Zaidi, Arslan A; Hair, Kerry L

    2015-02-01

    Data drawn from the in-home subsample of the PROSPER intervention dissemination trial were used to investigate the moderation of intervention effects on underage alcohol use by maternal involvement and candidate genes. The primary gene examined was dopamine receptor D4 (DRD4). Variation in this gene and maternal involvement were hypothesized to moderate the influence of intervention status on alcohol use. The PROSPER data used were drawn from 28 communities randomly assigned to intervention or comparison conditions. Participating youth were assessed in five in-home interviews from sixth to ninth grades. A main effect of sixth-grade pretest maternal involvement on ninth-grade alcohol use was found. Neither intervention status nor DRD4 variation was unconditionally linked to ninth-grade drinking. However, moderation analyses revealed a significant three-way interaction among DRD4 status, maternal involvement, and intervention condition. Follow-up analyses revealed that prevention reduced drinking risk, but only for youth with at least one DRD4 seven-repeat allele who reported average or greater pretest levels of maternal involvement. To determine if this conditional pattern was limited to the DRD4 gene, we repeated analyses using the serotonin transporter linked polymorphic region site near the serotonin transporter gene. The results for this supplemental analysis revealed a significant three-way interaction similar but not identical to that found for DRD4.

  8. An initial investigation of associations between dopamine-linked genetic variation and smoking motives in African Americans.

    PubMed

    Bidwell, L C; McGeary, J E; Gray, J C; Palmer, R H C; Knopik, V S; MacKillop, J

    2015-11-01

    Nicotine dependence (ND) is a heterogeneous phenotype with complex genetic influences that may vary across ethnicities. The use of intermediate phenotypes may clarify genetic influences and reveal specific etiological pathways. Prior work in European Americans has found that the four Primary Dependence Motives (PDM) subscales (Automaticity, Craving, Loss of Control, and Tolerance) of the Wisconsin Inventory of Smoking Motives represent core features of nicotine dependence and are promising intermediate phenotypes for understanding genetic pathways to ND. However, no studies have examined PDM as an intermediate phenotype in African American smokers, an ethnic population that displays unique patterns of smoking and genetic variation. In the current study, 268 African American daily smokers completed a phenotypic assessment and provided a sample of DNA. Associations among haplotypes in the NCAM1-TTC12-ANKK1-DRD2 gene cluster, a dopamine-related gene region associated with ND, PDM intermediate phenotypes, and ND were examined. Dopamine-related genetic variation in the DBH and COMT genes was also considered on an exploratory basis. Mediational analysis was used to test the indirect pathway from genetic variation to smoking motives to nicotine dependence. NCAM1-TTC12-ANKK1-DRD2 region variation was significantly associated with the Automaticity subscale and, further, Automaticity significantly mediated associations among NCAM1-TTC12-ANKK1-DRD2 cluster variants and ND. DBH was also significantly associated with Automaticity, Craving, and Tolerance; Automaticity and Tolerance also served as mediators of the DBH-ND relationship. These results suggest that PDM, Automaticity in particular, may be a viable intermediate phenotype for understanding dopamine-related genetic influences on ND in African American smokers. Findings support a model in which putatively dopaminergic variants exert influence on ND through an effect on patterns of automatic routinized smoking.

  9. Laboratory experimental investigation of heat transport in fractured media

    NASA Astrophysics Data System (ADS)

    Cherubini, Claudia; Pastore, Nicola; Giasi, Concetta I.; Allegretti, Nicoletta Maria

    2017-01-01

    Low enthalpy geothermal energy is a renewable resource that is still underexploited nowadays in relation to its potential for development in society worldwide. Most of its applications have already been investigated, such as heating and cooling of private and public buildings, road defrosting, cooling of industrial processes, food drying systems or desalination. Geothermal power development is a long, risky and expensive process. It basically consists of successive development stages aimed at locating the resources (exploration), confirming the power generating capacity of the reservoir (confirmation) and building the power plant and associated structures (site development). Different factors intervene in influencing the length, difficulty and materials required for these phases, thereby affecting their cost. One of the major limitations related to the installation of low enthalpy geothermal power plants regards the initial development steps that are risky and the upfront capital costs that are huge. Most of the total cost of geothermal power is related to the reimbursement of invested capital and associated returns. In order to increase the optimal efficiency of installations which use groundwater as a geothermal resource, flow and heat transport dynamics in aquifers need to be well characterized. Especially in fractured rock aquifers these processes represent critical elements that are not well known. Therefore there is a tendency to oversize geothermal plants. In the literature there are very few studies on heat transport, especially on fractured media. This study is aimed at deepening the understanding of this topic through heat transport experiments in fractured networks and their interpretation. Heat transfer tests have been carried out on the experimental apparatus previously employed to perform flow and tracer transport experiments, which has been modified in order to analyze heat transport dynamics in a network of fractures. In order to model the obtained

  10. Investigation of electron beam transport in a helical undulator

    SciTech Connect

    Jeong, Y.U.; Lee, B.C.; Kim, S.K.

    1995-12-31

    Lossless transport of electrons through the undulator is essential for CW operation of the FELs driven by recirculating electrostatic accelerators. We calculate the transport ratio of an electron beam in a helical undulator by using a 3-D simulation code and compare the results with the experimental results. The energy and the current of the electron beam are 400 keV and 2 A, respectively. The 3-D distribution of the magnetic field of a practical permanent-magnet helical undulator is measured and is used in the calculations. The major parameters of the undutlator are : period = 32 mm, number of periods = 20, number of periods in adiabatic region = 3.5, magnetic field strength = 1.3 kG. The transport ratio is very sensitive to the injection condition of the electron beam such as the emittance, the diameter, the divergence, etc.. The injection motion is varied in the experiments by changing the e-gun voltage or the field strength of the focusing magnet located at the entrance of the undulator. It is confirmed experimentally and with simulations that most of the beam loss occurs at the adiabatic region of the undulator regardless of the length of the adiabatic region The effect of axial guiding magnetic field on the beam finish is investigated. According to the simulations, the increase of the strength of axial magnetic field from 0 to 1 kG results in the increase of the transport ratio from 15 % to 95%.

  11. Investigating water transport through the xylem network in vascular plants.

    PubMed

    Kim, Hae Koo; Park, Joonghyuk; Hwang, Ildoo

    2014-04-01

    Our understanding of physical and physiological mechanisms depends on the development of advanced technologies and tools to prove or re-evaluate established theories, and test new hypotheses. Water flow in land plants is a fascinating phenomenon, a vital component of the water cycle, and essential for life on Earth. The cohesion-tension theory (CTT), formulated more than a century ago and based on the physical properties of water, laid the foundation for our understanding of water transport in vascular plants. Numerous experimental tools have since been developed to evaluate various aspects of the CTT, such as the existence of negative hydrostatic pressure. This review focuses on the evolution of the experimental methods used to study water transport in plants, and summarizes the different ways to investigate the diversity of the xylem network structure and sap flow dynamics in various species. As water transport is documented at different scales, from the level of single conduits to entire plants, it is critical that new results be subjected to systematic cross-validation and that findings based on different organs be integrated at the whole-plant level. We also discuss the functional trade-offs between optimizing hydraulic efficiency and maintaining the safety of the entire transport system. Furthermore, we evaluate future directions in sap flow research and highlight the importance of integrating the combined effects of various levels of hydraulic regulation.

  12. Spin transport in Au films: An investigation by spin pumping

    NASA Astrophysics Data System (ADS)

    Montoya, Eric; Kardasz, Bartek; Burrowes, Capucine; Huttema, Wendell; Girt, Erol; Heinrich, Bret

    2012-04-01

    The thickness and temperature dependence of spin transport in Au has been investigated in multilayer films via the spin pumping effect. To study spin transport in Au, single layer GaAs/16Fe/(d)Au(001) and double layer GaAs/16Fe/(d)Au/12Fe/20Au(001) were investigated using ferromagnetic resonance (FMR), where d = 20, 300, and the numerals preceding Fe and Au indicate the layer thickness in atomic layers (AL). FMR measurements were performed at frequencies ranging from 27.3 to 40.6 GHz and at temperatures ranging from 88 to 295 K. By measuring the total Gilbert damping in the 16Fe layer as a function of d and temperature for both single and double magnetic layer structures and by utilizing the spin diffusion equation, one is able to determine the spin mixing conductance, g↑↓, at the Fe/Au interface, and the spin flip relaxation time, τsf, in Au as a function of temperature. The temperature dependence of the momentum relaxation time, τm, in Au was measured independently by means of electron transport measurements in a van der Pauw configuration. It has been found that the spin flip relaxation time, τsf, in Au is dominated by phonon interactions.

  13. The cooperative roles of the dopamine receptors, D1R and D5R, on the regulation of renal sodium transport.

    PubMed

    Gildea, John J; Shah, Ishan T; Van Sciver, Robert E; Israel, Jonathan A; Enzensperger, Christoph; McGrath, Helen E; Jose, Pedro A; Felder, Robin A

    2014-07-01

    Determining the individual roles of the two dopamine D1-like receptors (D1R and D5R) on sodium transport in the human renal proximal tubule has been complicated by their structural and functional similarity. Here we used a novel D5R-selective antagonist (LE-PM436) and D1R- or D5R-specific gene silencing to determine second messenger coupling pathways and heterologous receptor interaction between the two receptors. D1R and D5R colocalize in renal proximal tubule cells and physically interact, as determined by co-immunoprecipitation and fluorescent resonance energy transfer microscopy. Stimulation of renal proximal tubule cells with fenoldopam (D1R/D5R agonist) led to both adenylyl cyclase and phospholipase C (PLC) activation using real-time fluorescent resonance energy transfer biosensors ICUE3 and CYPHR, respectively. Fenoldopam increased cAMP accumulation and PLC activity and inhibited both NHE3 and NaKATPase activities. LE-PM436 and D5R siRNA blocked the fenoldopam-stimulated PLC pathway but not cAMP accumulation, whereas D1R siRNA blocked both fenoldopam-stimulated cAMP accumulation and PLC signaling. Either D1R or D5R siRNA, or LE-PM436 blocked the fenoldopam-dependent inhibition of sodium transport. Further studies using the cAMP-selective D1R/D5R agonist SKF83822 and PLC-selective D1R/D5R agonist SKF83959 confirmed the cooperative influence of the two pathways on sodium transport. Thus, D1R and D5R interact in the inhibition of NHE3 and NaKATPase activity, the D1R primarily by cAMP, whereas the D1R/D5R heteromer modulates the D1R effect through a PLC pathway.

  14. The cooperative roles of the dopamine receptors, D1R and D5R, on the regulation of renal sodium transport

    PubMed Central

    Gildea, John J.; Shah, Ishan T.; Van Sciver, Robert; Israel, Jonathan A.; Enzensperger, Christoph; McGrath, Helen E.; Jose, Pedro A.; Felder, Robin A.

    2014-01-01

    Determining the individual roles of the two dopamine D1-like receptors (D1R and D5R) on sodium transport in the human renal proximal tubule has been complicated by their structural and functional similarity. Here we used a novel D5R-selective antagonist (LE-PM436) and D1R or D5R-specific gene silencing to determine second messenger coupling pathways and heterologous receptor interaction between the two receptors. D1R and D5R co-localized in renal proximal tubule cells and physically interact, as determined by co-immunoprecipitation and FRET microscopy. Stimulation of renal proximal tubule cells with fenoldopam (D1R/D5R agonist) led to both adenylyl cyclase and phospholipase C (PLC) activation using real-time FRET biosensors ICUE3 and CYPHR, respectively. Fenoldopam increased cAMP accumulation and PLC activity and inhibited both NHE3 and NaKATPase activities. LE-PM436 and D5R siRNA blocked the fenoldopam-stimulated PLC pathway but not cAMP accumulation, while D1R siRNA blocked both fenoldopam-stimulated cAMP accumulation and PLC signaling. Either D1R or D5R siRNA, or LE-PM436 blocked the fenoldopam dependent inhibition of sodium transport. Further studies using the cAMP-selective D1R/D5R agonist SKF83822 and PLC-selective D1R/D5R agonist SKF83959 confirmed the cooperative influence of the two pathways on sodium transport. Thus, D1R and D5R interact in the inhibition of NHE3 and NaKATPase activity, the D1R primarily by cAMP, while the D1R/D5R heteromer modulates the D1R effect through a PLC pathway. PMID:24552847

  15. Further investigations into hormone-directed transport in stems.

    PubMed

    Bowen, M R; Wareing, P F

    1971-06-01

    The effect of IAA and three synthetic auxins on the upward movement of (32)P-orthophosphate and (14)C-sucrose has been investigated in decapitated stems of Phaseolus vulgaris L., Pisum sativum L., Coleus blumci L. and Helianthus annuus L. IAA greatly enhanced the accumulation of (32)P-orthophosphate in Phaseolus vulgaris and Pisum sativum, whereas in C. blumei and H. annuus it did not. 2,4-D like IAA, caused an increase in (14)C-sucrose and (32)P-orthophosphate accumulation in Phaseolus vulgaris but, unlike IAA, caused no increase in Pisum sativum. The downward transport of (14)C-IAA, (14)C-NAA, (14)C-2,4-D and (14)C-2,4,5-T from the decapitated apex was also studied. Results are discussed in terms of current theories of hormone-directed transport.

  16. Orchestration of salivary secretion mediated by two different dopamine receptors in the blacklegged tick Ixodes scapularis

    PubMed Central

    Kim, Donghun; Šimo, Ladislav; Park, Yoonseong

    2014-01-01

    Salivary secretion is crucial for successful tick feeding, and it is the mediator of pathogen transmission. Salivation functions to inhibit various components of the host immune system and remove excess water and ions during the ingestion of large blood meals. Control of salivary glands involves autocrine/paracrine dopamine, which is the most potent inducer of tick salivation. Previously, we reported the presence of two dopamine receptors in the salivary glands of the blacklegged tick (Ixodes scapularis): dopamine receptor (D1) and invertebrate specific D1-like dopamine receptor (InvD1L). Here, we investigated the different physiological roles of the dopamine receptors in tick salivary glands by using pharmacological tools that discriminate between the two distinct receptors. Heterologous expressions followed by reporter assays of the dopamine receptors identified receptor-specific antagonists and agonists. These pharmacological tools were further used to discriminate the physiological role of each receptor by using in vitro assays: measuring salivary secretions of isolated salivary glands and monitoring dynamic changes in the size of individual salivary gland acini. We propose that the D1 receptor acts on salivary gland acini epithelial cells for inward fluid transport. InvD1L controls (or modulates) each acinus for expelling saliva from the acini to the salivary ducts, presumably through the actions of myoepithelial cells and valves for pumping/gating. We conclude that dopamine acts on the D1 and the InvD1L receptors and leads different physiological actions to orchestrate tick salivary secretion. PMID:25320269

  17. Investigation of spin transport and accumulation in aluminum gallium arsenide

    NASA Astrophysics Data System (ADS)

    Misuraca, Jennifer

    This dissertation describes spin injection, transport, and detection experiments from Fe electrodes into a bulk AlGaAs channel. This semiconducting alloy is one of a class of persistent photoconductors, chosen as the spin transport medium because its carrier density can be tuned in a controlled manner via photoexcitation through the metal to insulator transition (MIT) in situ. This allows one to determine the dependence of spin lifetime on a variety of external parameters including carrier density, all on one sample. This research represents the first electrical spin-dependent measurements in this material and describes the dependence of the Hanle signal size and spin lifetime on bias, temperature, and carrier density. The photoexcitation needed to change the carrier density in this material comes from an infrared light-emitting diode (IR LED). The first step of this project was to characterize the new, highly Si doped Al0.3Ga 0.7As heterostructures, in order to determine how the illumination of the sample will affect the parameters of the material. To complete this study, Hall crosses were fabricated from the AlGaAs material and the transport properties were measured between 350 mK and 165 K. The resistivity, carrier density, and mobility were determined as a function of temperature for a variety of different illumination times. From this data, the MIT, scattering mechanisms, and the shape of the band tail of the density of states (DOS) were investigated. In fact, this is the first work to electrically probe the DOS in AlGaAs. Once the materials were characterized, they were used to fabricate lateral spin transport devices. Spin transport and accumulation were studied in detail via Hanle effect measurements, which measure the dephasing of electron spins in a perpendicular magnetic field. From these measurements, the spin lifetime of the material can be calculated, and is in the nanosecond range for all measured carrier densities. The spin lifetimes are measured

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

    PubMed

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

    2016-04-12

    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.

  19. Exchange diffusion of dopamine induced in planar lipid bilayer membranes by the ionophore X537A

    PubMed Central

    Holz, RW

    1977-01-01

    The ionophore X537A causes a large increase in the [(14)C]dopamine (a catecholamine) permeability of planar bilayer membranes. Dopamine transport increases linearly with the ionophore concentration. At relatively high concentrations in the presence of dopamine, the ionophore omdices a conductance which is nearly ideally selective for the dopamine cation. However, the total dopamine flux as determined in tracer experiments is not affected by an electric field and is over 10(5) times larger than predicted from the estimated dopamine conductance. Increasing the dopamine concentration on the side containing radioactive dopamine (the cis side) saturates the dopamine transport. This saturation is relieved by trans addition of nonradioactive dopamine, tyramine, H(+), or K(+). With unequal concentrations of dopamine cis and trans (49 and 12.5 mM), the unidirectional dopamine fluxes are equal. Increasing H(+) cis and trans decreases dopamine transport. It is concluded that at physiological pH, the X537A-induced transport of dopamine occurs via an electrically silent exchange diffusion of dopamine cation with another cation (e.g., dopamine(+), H(+), or K(+)). X537A induces a Ca(++)-independent release of catecholamines from sympathetic nerves by interfering with intracellular storage within storage vesicles (R.W. Holz. 1975. Biochim. Biophys. Acta. 375:138-152). It is suggested that X537A causes an exchange of intravesicular catecholamine with a cytoplasmic cation (perhaps K(+) or H(+)) across the storage vesicle membrane. PMID:16982

  20. Multiple functions of Na/K-ATPase in dopamine-induced salivation of the Blacklegged tick, Ixodes scapularis

    PubMed Central

    Kim, Donghun; Urban, Joshua; Boyle, Daniel L.; Park, Yoonseong

    2016-01-01

    Control of salivary secretion in ticks involves autocrine dopamine activating two dopamine receptors: D1 and Invertebrate-specific D1-like dopamine receptors. In this study, we investigated Na/K-ATPase as an important component of the secretory process. Immunoreactivity for Na/K-ATPase revealed basal infolding of lamellate cells in type-I, abluminal interstitial (epithelial) cells in type-II, and labyrinth-like infolding structures opening towards the lumen in type-III acini. Ouabain (10 μmol l−1), a specific inhibitor of Na/K-ATPase, abolished dopamine-induced salivary secretion by suppressing fluid transport in type III acini. At 1 μmol l−1, ouabain, the secreted saliva was hyperosmotic. This suggests that ouabain also inhibits an ion resorptive function of Na/K-ATPase in the type I acini. Dopamine/ouabain were not involved in activation of protein secretion, while dopamine-induced saliva contained constitutively basal level of protein. We hypothesize that the dopamine-dependent primary saliva formation, mediated by Na/K-ATPase in type III and type II acini, is followed by a dopamine-independent resorptive function of Na/K-ATPase in type I acini located in the proximal end of the salivary duct. PMID:26861075

  1. Multiple functions of Na/K-ATPase in dopamine-induced salivation of the Blacklegged tick, Ixodes scapularis.

    PubMed

    Kim, Donghun; Urban, Joshua; Boyle, Daniel L; Park, Yoonseong

    2016-02-10

    Control of salivary secretion in ticks involves autocrine dopamine activating two dopamine receptors: D1 and Invertebrate-specific D1-like dopamine receptors. In this study, we investigated Na/K-ATPase as an important component of the secretory process. Immunoreactivity for Na/K-ATPase revealed basal infolding of lamellate cells in type-I, abluminal interstitial (epithelial) cells in type-II, and labyrinth-like infolding structures opening towards the lumen in type-III acini. Ouabain (10 μmol l(-1)), a specific inhibitor of Na/K-ATPase, abolished dopamine-induced salivary secretion by suppressing fluid transport in type III acini. At 1 μmol l(-1), ouabain, the secreted saliva was hyperosmotic. This suggests that ouabain also inhibits an ion resorptive function of Na/K-ATPase in the type I acini. Dopamine/ouabain were not involved in activation of protein secretion, while dopamine-induced saliva contained constitutively basal level of protein. We hypothesize that the dopamine-dependent primary saliva formation, mediated by Na/K-ATPase in type III and type II acini, is followed by a dopamine-independent resorptive function of Na/K-ATPase in type I acini located in the proximal end of the salivary duct.

  2. The divalent metal transporter homologues SMF-1/2 mediate dopamine neuron sensitivity in caenorhabditis elegans models of manganism and parkinson disease.

    PubMed

    Settivari, Raja; Levora, Jennifer; Nass, Richard

    2009-12-18

    Parkinson disease (PD) and manganism are characterized by motor deficits and a loss of dopamine (DA) neurons in the substantia nigra pars compacta. Epidemiological studies indicate significant correlations between manganese exposure and the propensity to develop PD. The vertebrate divalent metal transporter-1 (DMT-1) contributes to maintaining cellular Mn(2+) homeostasis and has recently been implicated in Fe(2+)-mediated neurodegeneration in PD. In this study we describe a novel model for manganism that incorporates the genetically tractable nematode Caenorhabditis elegans. We show that a brief exposure to Mn(2+) increases reactive oxygen species and glutathione production, decreases oxygen consumption and head mitochondria membrane potential, and confers DA neuronal death. DA neurodegeneration is partially dependent on a putative homologue to DMT-1, SMF-1, as genetic knockdown or deletion partially inhibits the neuronal death. Mn(2+) also amplifies the DA neurotoxicity of the PD-associated protein alpha-synuclein. Furthermore, both SMF-1 and SMF-2 are expressed in DA neurons and contribute to PD-associated neurotoxicant-induced DA neuron death. These studies describe a C. elegans model for manganism and show that DMT-1 homologues contribute to Mn(2+)- and PD-associated DA neuron vulnerability.

  3. Striatal dopamine transporter binding for predicting the development of delayed neuropsychological sequelae in suicide attempters by carbon monoxide poisoning: A SPECT study.

    PubMed

    Yang, Kai-Chun; Ku, Hsiao-Lun; Wu, Chia-Liang; Wang, Shyh-Jen; Yang, Chen-Chang; Deng, Jou-Fang; Lee, Ming-Been; Chou, Yuan-Hwa

    2011-12-30

    Carbon monoxide poisoning (COP) after charcoal burning results in delayed neuropsychological sequelae (DNS), which show clinical resemblance to Parkinson's disease, without adequate predictors at present. This study examined the role of dopamine transporter (DAT) binding for the prediction of DNS. Twenty-seven suicide attempters with COP were recruited. Seven of them developed DNS, while the remainder did not. The striatal DAT binding was measured by single photon emission computed tomography with (99m)Tc-TRODAT. The specific uptake ratio was derived based on a ratio equilibrium model. Using a logistic regression model, multiple clinical variables were examined as potential predictors for DNS. COP patients with DNS had a lower binding on left striatal DAT binding than patients without DNS. Logistic regression analysis showed that a combination of initial loss of consciousness and lower left striatal DAT binding predicted the development of DNS. Our data indicate that the left striatal DAT binding could help to predict the development of DNS. This finding not only demonstrates the feasibility of brain imaging techniques for predicting the development of DNS but will also help clinicians to improve the quality of care for COP patients.

  4. [A comparative study of hemantane and amantadine effects on dopamine transporter expression in brain of normal and MPTP-treated C57BL/6 mice].

    PubMed

    Zimin, I A; Logvinov, I O; Antipova, T A; Kovalev, G I

    2011-01-01

    The effects of acute and subchronic administration of antiparkinsonian drugs hemantane and amantadine on dopamine transporter (DAT) content in the brain of normal and MPTP-treated mice have been studied. MPTP treatment (30 mg/kg, daily for 2 days, i.p.) led to an insignificant decrease of the DAT level in striatum, while not influencing the DAT content in the frontal cortex of mice. The acute administration of hemantane (20 mg/kg, i.p.) failed to influence the DAT levels in the tested structures of mice brain, while amantadine (13.9 mg/kg, i.p) decreased the DAT level but only in striatum. The acute administration of a drug (hemantane or amantadine) simultaneously with MPTP toxin reduced the DAT levels in striatum but did change the DAT concentration in the frontal cortex. On the contrary, the subchronic injection of hemantane alone (7 x 20 mg/kg, i.p.) and in combination with the toxin increased the DAT levels in the brain structures, while amantadine (7 x 13.9 mg/kg, i.p.) led to a pronounced increase of DAT concentration only in the striatum. Thus, both similar and dissimilar trends in the neurochemical effects of hemantane and amantadine have been experimentally revealed.

  5. Subchronic administration of short-acting naltrexone has no effect on striatal dopamine transporter availability, food intake or body weight gain in rats.

    PubMed

    Zaaijer, Eline R; de Bruin, Kora; la Fleur, Susanne E; Goudriaan, Anna E; van den Brink, Wim; Booij, Jan

    2015-03-01

    The opioid receptor antagonist naltrexone is successfully used in the treatment of opioid and alcohol dependence. However, questions have been raised about possible anhedonic side effects, because the opioid system is directly involved in hedonic responses to natural rewarding activities, possibly due to its indirect effects on the striatal dopamine transporter (DAT). In order to test this hypothesis, 30 rats were randomized to either a 10-day treatment with 3 mg/kg short-acting naltrexone or vehicle. No significant differences between the groups were found in striatal DAT availability, cumulative food intake (for 48 or 72 h), body weight gain and abdominal fatpad weight. Thus, the results of this study suggest that (sub)chronic treatment with short-acting naltrexone does not induce possible anhedonic effects. However, it cannot be ruled out the anhedonic effect of naltrexone is only short-lived and thus not detected in the current study. Therefore, future studies are needed to study possible acute anhedonic effects at several time points shortly after short-acting naltrexone administration and to directly compare the possible anhedonic effects of long-acting with those of short-acting opioid antagonists.

  6. Clinical utility of dopamine transporter single photon emission CT (DaT-SPECT) with (123I) ioflupane in diagnosis of parkinsonian syndromes

    PubMed Central

    Bajaj, Nin; Hauser, Robert A; Grachev, Igor D

    2013-01-01

    The diagnosis of movement disorders including Parkinson's disease (PD) and essential tremor is determined through clinical assessment. The difficulty with diagnosis of early PD has been highlighted in several recent clinical trials. Studies have suggested relatively high clinical diagnostic error rates for PD and essential tremor. This review was undertaken to clarify the utility of DaT-SPECT imaging with (123I)ioflupane (DaTSCAN or DaTscan or (123I)FP-CIT) in assisting practitioners in their clinical decision making by visualising the dopamine transporter in parkinsonian cases. In some patients with suspected parkinsonian syndromes, SPECT imaging with (123I)ioflupane is useful to assist in the diagnosis and to help guide prognosis and treatment decisions, including avoiding medications that are unlikely to provide benefit. Clinicians ordering (123I)ioflupane SPECT should be aware of its limitations and pitfalls and should order scans when there is diagnostic uncertainty or when the scan will be helpful in clinical decision making. PMID:23486993

  7. Involvement of estrogen receptors in the resveratrol-mediated increase in dopamine transporter in human dopaminergic neurons and in striatum of female mice.

    PubMed

    Di Liberto, Valentina; Mäkelä, Johanna; Korhonen, Laura; Olivieri, Melania; Tselykh, Timofey; Mälkiä, Annika; Do Thi, Hai; Belluardo, Natale; Lindholm, Dan; Mudò, Giuseppa

    2012-02-01

    Treatment with resveratrol (RSV) has been shown to protect vulnerable neurons after various brain injuries and in neurodegenerative diseases. The mechanisms for the effects of RSV in brain are not fully understood, but RSV may affect the expression of various gene products. RSV is structurally related to the synthetic estrogen, diethylstilbestrol so the effects of RSV may be gender-specific. Here we studied the role of RSV in the regulation of dopamine transporter (DAT) in the striatum using male and female mice. The basic levels of DAT in the striatum showed no sex difference, but the levels increased significantly by RSV (20 mg/kg i.p.) in female but not in male mice. Pretreatment of mice with the selective estrogen receptor (ER), ERα- and ERβ antagonist ICI 182,780, led to a complete block of RSV effect on DAT protein levels, suggesting that ERs are involved in the up-regulation of DAT by RSV. Similar data was also obtained in culture using human MESC2.10 and mouse SN4741 dopaminergic cells after treatment with RSV. Data further showed that RSV specifically induced gene transcription of DAT in the dopaminergic cells. These results show that estrogen receptors are involved in the up-regulation of DAT by RSV in the dopaminergic neurons, demonstrating a sex-dependent effect of RSV in the brain that may be of clinical importance. This article is part of a Special Issue entitled 'Post-Traumatic Stress Disorder'.

  8. Rats classified as low or high cocaine locomotor responders: A unique model involving striatal dopamine transporters that predicts cocaine addiction-like behaviors

    PubMed Central

    Yamamoto, Dorothy J.; Nelson, Anna M.; Mandt, Bruce H.; Larson, Gaynor A.; Rorabaugh, Jacki M.; Ng, Christopher M.C.; Barcomb, Kelsey M.; Richards, Toni L.; Allen, Richard M.; Zahniser, Nancy R.

    2013-01-01

    Individual differences are a hallmark of drug addiction. Here, we describe a rat model based on differential initial responsiveness to low dose cocaine. Despite similar brain cocaine levels, individual outbred Sprague-Dawley rats exhibit markedly different magnitudes of acute cocaine-induced locomotor activity and, thereby, can be classified as low or high cocaine responders (LCRs or HCRs). LCRs and HCRs differ in drug-induced, but not novelty-associated, hyperactivity. LCRs have higher basal numbers of striatal dopamine transporters (DATs) than HCRs and exhibit marginal cocaine inhibition of in vivo DAT activity and cocaine-induced increases in extracellular DA. Importantly, lower initial cocaine response predicts greater locomotor sensitization, conditioned place preference and greater motivation to self-administer cocaine following low dose acquisition. Further, outbred Long-Evans rats classified as LCRs, versus HCRs, are more sensitive to cocaine’s discriminative stimulus effects. Overall, results to date with the LCR/HCR model underscore the contribution of striatal DATs to individual differences in initial cocaine responsiveness and the value of assessing the influence of initial drug response on subsequent expression of addiction-like behaviors. PMID:23850581

  9. Investigation of air transportation technology at Princeton University, 1985

    NASA Technical Reports Server (NTRS)

    Stengel, Robert F.

    1987-01-01

    The program proceeded along five avenues during 1985. Guidance and control strategies for penetration of microbursts and wind shear, application of artificial intelligence in flight control and air traffic control systems, the use of voice recognition in the cockpit, the effects of control saturation on closed-loop stability and response of open-loop unstable aircraft, and computer aided control system design are among the topics briefly considered. Areas of investigation relate to guidance and control of commercial transports as well as general aviation aircraft. Interaction between the flight crew and automatic systems is the subject of principal concern.

  10. X-linked dystonia parkinsonism syndrome (XDP, lubag): disease-specific sequence change DSC3 in TAF1/DYT3 affects genes in vesicular transport and dopamine metabolism.

    PubMed

    Herzfeld, Thilo; Nolte, Dagmar; Grznarova, Maria; Hofmann, Andrea; Schultze, Joachim L; Müller, Ulrich

    2013-03-01

    X-chromosomal dystonia parkinsonism syndrome (XDP, 'lubag') is associated with sequence changes within the TAF1/DYT3 multiple transcript system. Although most sequence changes are intronic, one, disease-specific single-nucleotide change 3 (DSC3), is located within an exon (d4). Transcribed exon d4 occurs as part of multiple splice variants. These variants include exons d3 and d4 spliced to exons of TAF1, and an independent transcript composed of exons d2-d4. Location of DSC3 in exon d4 and utilization of this exon in multiple splice variants suggest an important role of DSC3 in the XDP pathogenesis. To test this hypothesis, we transfected neuroblastoma cells with four expression constructs, including exons d2-d4 [d2-d4/wild-type (wt) and d2-d4/DSC3] and d3-d4 (d3-d4/wt and d3-d4/DSC3). Expression profiling revealed a dramatic effect of DSC3 on overall gene expression. Three hundred and sixty-two genes differed between cells containing d2-d4/wt and d2-d4/DSC3. Annotation clustering revealed enrichment of genes related to vesicular transport, dopamine metabolism, synapse function, Ca(2+) metabolism and oxidative stress. Two hundred and eleven genes were differentially expressed in d3-d4/wt versus d3-d4/DSC3. Annotation clustering highlighted genes in signal transduction and cell-cell interaction. The data show an important role of physiologically occurring transcript d2-d4 in normal brain function. Interference with this role by DSC3 is a likely pathological mechanism in XDP. Disturbance of dopamine function and of Ca(2+) metabolism can explain abnormal movement; loss of protection against reactive oxygen species may account for the neurodegenerative changes in XDP. Although d3-d4 also affect genes potentially related to neurodegenerative processes, their physiologic role as splice variants of TAF1 awaits further exploration.

  11. Novel N-1,2-dihydroxypropyl analogs of lobelane inhibit vesicular monoamine transporter-2 function and methamphetamine-evoked dopamine release.

    PubMed

    Horton, David B; Siripurapu, Kiran B; Zheng, Guangrong; Crooks, Peter A; Dwoskin, Linda P

    2011-10-01

    Lobelane, a chemically defunctionalized saturated analog of lobeline, has increased selectivity for the vesicular monoamine transporter 2 (VMAT2) compared with the parent compound. Lobelane inhibits methamphetamine-evoked dopamine (DA) release and decreases methamphetamine self-administration. Unfortunately, tolerance develops to the ability of lobelane to decrease these behavioral effects of methamphetamine. Lobelane has low water solubility, which is problematic for drug development. The aim of the current study was to determine the pharmacological effect of replacement of the N-methyl moiety with a chiral N-1,2-dihydroxypropyl (N-1,2-diol) moiety, which enhances water solubility, altering the configuration of the N-1,2-diol moiety and incorporating phenyl ring substituents into the analogs. To determine VMAT2 selectivity, structure-activity relationships also were generated for inhibition of DA and serotonin transporters. Analogs with the highest potency for inhibiting DA uptake at VMAT2 and at least 10-fold selectivity were evaluated further for ability to inhibit methamphetamine-evoked DA release from superfused striatal slices. (R)-3-[2,6-cis-di(4-methoxyphenethyl)piperidin-1-yl]propane-1,2-diol (GZ-793A), the (R)-4-methoxyphenyl-N-1,2-diol analog, and (R)-3-[2,6-cis-di(1-naphthylethyl)piperidin-1-yl]propane-1,2-diol (GZ-794A), the (R)-1-naphthyl-N-1,2-diol analog, exhibited the highest potency (K(i) ∼30 nM) inhibiting VMAT2, and both analogs inhibited methamphetamine-evoked endogenous DA release (IC(50) = 10.6 and 0.4 μM, respectively). Thus, the pharmacophore for VMAT2 inhibition accommodates the N-1,2-diol moiety, which improves drug-likeness and enhances the potential for the development of these clinical candidates as treatments for methamphetamine abuse.

  12. N-Substituted Benztropine Analogs: Selective Dopamine Transporter Ligands with a Fast Onset of Action and Minimal Cocaine-Like Behavioral Effects

    PubMed Central

    Li, Su-Min; Kopajtic, Theresa A.; O'Callaghan, Matthew J.; Agoston, Gregory E.; Cao, Jianjing; Newman, Amy Hauck

    2011-01-01

    Previous studies suggested that differences between the behavioral effects of cocaine and analogs of benztropine were related to the relatively slow onset of action of the latter compounds. Several N-substituted benztropine analogs with a relatively fast onset of effects were studied to assess whether a fast onset of effects would render the effects more similar to those of cocaine. Only one of the compounds increased locomotor activity, and the increases were modest compared with those of 10 to 20 mg/kg cocaine. In rats trained to discriminate 10 mg/kg cocaine from saline none of the compounds produced more than 40% cocaine-like responds up to 2 h after injection. None of the compounds produced place-conditioning when examined up to 90 min after injection, indicating minimal abuse liability. The compounds had 5.6 to 30 nM affinities at the dopamine transporter (DAT), with uniformly lower affinities at norepinephrine and serotonin transporters (from 490-4600 and 1420–7350 nM, respectively). Affinities at muscarinic M1 receptors were from 100- to 300-fold lower than DAT affinities, suggesting minimal contribution of those sites to the behavioral effects of the compounds. Affinities at histaminic H1 sites were from 11- to 43-fold lower than those for the DAT. The compounds also had affinity for sigma, 5-hydroxytryptamine1 (5-HT1), and 5-HT2 receptors that may have contributed to their behavioral effects. Together, the results indicate that a slow onset of action is not a necessary condition for reduced cocaine-like effects of atypical DAT ligands and suggest several mechanisms that may contribute to the reduced cocaine-like efficacy of these compounds. PMID:21088247

  13. A numerical investigation of fine sediment transport at intertidal flat

    NASA Astrophysics Data System (ADS)

    Hsu, T.; Chen, S.; Ogston, A. S.

    2010-12-01

    A detailed numerical model is developed to study the hydrodynamic and fine sediment transport processes at tidal flats. The critical science issues to be investigated here are to quantify the main mechanisms causing landward and seaward transports. Prior modeling studies have identified the settling-lag effects as the main mechanism causing landward fine sediment transport. Field studies have also observed pronounced landward transport due to the movement of shallow-water’s turbid edge which is associated with bed erodibility and wetting-drying process. Recent 3D coastal numerical modeling of Skagit tidal flat (Chen et al. 2010, J. Geophys. Res., in press) is able to model settling-lag-induced landward transport. However, the observed short residence time for river-delivered sediment cannot be reproduced by the model, suggesting that a key offshore transport mechanism is not captured by the exiting coastal models. Field studies carried out in the ongoing Tidal Flat DRI have observed the so-called ebb tide sediment pulse, which seems to support the export of sediment through channels (Nowacki et al. 2010, this meeting) that balances landward fluxes. Both the bed erosion at water’s edge and ebb tide sediment pulse occur at a very shallow water depths. Conventional coastal models have difficulties in resolving the shallow flow at the wetting and drying seabed and some numerical approximations, such as specifying a minimum artificial flow depth, are often adopted. Therefore, a small-scale study is necessary before an appropriate parameterization for these transport mechanisms can be adopted by an estuarine/coastal model. In this study, a two-dimensional-vertical numerical model solving Reynolds-averaged Navier-Stokes equations with a Volume of Fluid (VOF) scheme to track the free surface evolution is adopted. The VOF scheme allows a more realistic simulation of the wetting and drying processes. For the simulation of tidal flow over a flat of constant slope (slope

  14. 75 FR 37435 - Fact Finding Investigation No. 27; Potentially Unlawful, Unfair or Deceptive Ocean Transportation...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-29

    ... Fact Finding Investigation No. 27; Potentially Unlawful, Unfair or Deceptive Ocean Transportation... from unlawful, unfair or deceptive ocean transportation practices and resolving shipping disputes in... nature, scope and frequency of potentially unlawful, unfair or deceptive ocean transportation...

  15. Transport of bacteria in porous media; 1: An experimental investigation

    SciTech Connect

    Sarkar, A.K.; Georgiou, G.; Sharma, M.M. )

    1994-08-05

    The convective transport of concentrated suspensions of bacteria in porous media is of interest for several processes such as microbial enhanced oil recovery and in situ bioremediation. The parameters which affect the transport of the bacterium Bacillus licheniformis JF-2, a candidate microorganism for microbial enhanced oil recovery, were investigated experimentally in sandpacks. Bacteria retention and permeability reduction occurred primarily in the first few centimeters upon entering the porous medium. In downstream sections of the sandpack, the permeability reduction was low, even in cases in which high cell concentrations were detected in the effluent. The effects of (1) addition of a dispersant, (2) linear velocity of injection, (3) cell concentration, (4) salinity, (5) temperature, and (6) the presence of a residual oleic phase were determined experimentally. A lower reduction in permeability and a higher effluent bacterial concentration were obtained in the presence of dispersant, high injection velocities, low salinities, and at a higher temperature. Macroscopic measurements at different linear velocities and in the presence or absence of dispersants suggest that the formation of reversible microaggregates and multiparticle hydrodynamic exclusion may be the primary mechanisms for bacterial retention and permeability reduction.

  16. [C-11]{beta}CNT: A new monoamine uptake ligand for studying serotonin and dopamine transporter sites in the living brain with PET

    SciTech Connect

    Mulholland, G.K.; Zheng, Q.H.; Zhou, F.C.

    1996-05-01

    There is considerable interest in measuring serotonin (5HT) and dopamine (DA) function in the human brain. Altered levels of 5HT and DA are recognized in drug abuse, neurotoxicities, psychiatric disorders, and neurodegenerative conditions including Alzheimer`s and Parkinson`s disease. Several phenyltropane analogs of cocaine bind tightly to both DA and 5HT uptake proteins. We have made a new agent from this class called {beta}CNT, 2{beta}-carboxymethyl-3{beta}-(2-naphthyl)-tropane, the isosteric O-for-CH{sub 2} analog of a compound reported to have among the highest measured affinities for DA and 5HT transporters and studied its in vivo brain distributions in animals for the first time. Optically pure {beta}CNT was made from cocaine, and labeled at the O-methyl position by esterification of {beta}CNT-acid with [C-11]CH{sub 3}OTfl under conditions similar to Wilson`s. HPLC-purified (99+%) final products (15-50% eob yield from CO{sub 2}, 40 min synth) had specific activities 0.1-1.2 Ci/{mu}mol at the time of injection. Preliminary [C-11]{beta}{beta}CNT rodent distribution showed very high brain uptake (3% ID at 60 min) and localization (striat: fr cort: hypo: cer: blood, 11: 5: 4: 1: 06). {beta}CNT-PET studies in juvenile pigs (5-20 mCi, 20-35 kg) found rapid brain uptake, and prominent retention (85 min) in midbrain, anterior brainstem and striatum, followed by cortex and olfactory bulb. Paroxetine pretreatment (5HT uptake blocker, 2mg/kg), diminished retention in most brain areas; nomifensine (DA/NE uptake blocker, 6 mg/kg) reduced striatum selectively. Direct comparisons of [C-11]{beta}CNT with other PET transporter radioligands {beta}CFT, {beta}CIT, and {beta}CTT (RTI-32) in the same pig found {beta}CNT had highest overall brain uptake among the agents. These initial results suggest {beta}CNT has favorable properties for imaging both 5HT and DA transporters in vivo, and further evaluation of its potential as a human PET agent is warranted.

  17. Growth of dopamine crystals

    NASA Astrophysics Data System (ADS)

    Patil, Vidya; Patki, Mugdha

    2016-05-01

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  18. Frequency of 3' VNTR Polymorphism in the Dopamine Transporter Gene SLC6A3 in Humans Predisposed to Antisocial Behavior.

    PubMed

    Cherepkova, E V; Aftanas, L I; Maksimov, N; Menshanov, P N

    2016-11-01

    Predisposition to antisocial behavior can be related to the presence of certain polymorphic variants of genes encoding dopaminergic system proteins. We studied the frequencies of allele variants and genotypes of variable number tandem repeat polymorphism in 3' untranslated region (3' VTNR) of the dopaminergic transporter SLC6A3 gene in Caucasian men committed socially dangerous violent and non-violent crimes. Alleles with 9 and 10 repeats were most frequent in both the control group and group of men predisposed to antisocial behavior. At the same time, the 10/10 genotype was more frequently observed in the group of men prone to antisocial non-violent behavior. Hence, the presence of certain variants of 3' VTNR polymorphism of SLC6A3 gene in men is associated with predisposition to certain forms of antisocial behavior.

  19. Investigation of anisotropic thermal transport in cross-linked polymers

    NASA Astrophysics Data System (ADS)

    Simavilla, David Nieto

    Thermal transport in lightly cross-linked polyisoprene and polybutadine subjected to uniaxial elongation is investigated experimentally. We employ two experimental techniques to assess the effect that deformation has on this class of materials. The first technique, which is based on Forced Rayleigh Scattering (FRS), allows us to measure the two independent components of the thermal diffusivity tensor as a function of deformation. These measurements along with independent measurements of the tensile stress and birefringence are used to evaluate the stress-thermal and stress-optic rules. The stress-thermal rule is found to be valid for the entire range of elongations applied. In contrast, the stress-optic rule fails for moderate to large stretch ratios. This suggests that the degree of anisotropy in thermal conductivity depends on both orientation and tension in polymer chain segments. The second technique, which is based on infrared thermography (IRT), allows us to measure anisotropy in thermal conductivity and strain induced changes in heat capacity. We validate this method measurements of anisotropic thermal conductivity by comparing them with those obtained using FRS. We find excellent agreement between the two techniques. Uncertainty in the infrared thermography method measurements is estimated to be about 2-5 %. The accuracy of the method and its potential application to non-transparent materials makes it a good alternative to extend current research on anisotropic thermal transport in polymeric materials. A second IRT application allows us to investigate the dependence of heat capacity on deformation. We find that heat capacity increases with stretch ratio in polyisoprene specimens under uniaxial extension. The deviation from the equilibrium value of heat capacity is consistent with an independent set of experiments comparing anisotropy in thermal diffusivity and conductivity employing FRS and IRT techniques. We identify finite extensibility and strain

  20. Interaction between serotonin transporter and dopamine D2/D3 receptor radioligand measures is associated with harm avoidant symptoms in anorexia and bulimia nervosa

    PubMed Central

    Bailer, Ursula F.; Frank, Guido K.; Price, Julie C.; Meltzer, Carolyn C.; Becker, Carl; Mathis, Chester A.; Wagner, Angela; Barbarich-Marsteller, Nicole C.; Bloss, Cinnamon S.; Putnam, Karen; Schork, Nicholas J.; Gamst, Anthony; Kaye, Walter H.

    2013-01-01

    Rationale Individuals with anorexia nervosa (AN) and bulimia nervosa (BN) have alterations of measures of serotonin (5-HT) and dopamine (DA) function, which persist after long-term recovery and are associated with elevated harm avoidance (HA), a measure of anxiety and behavioral inhibition. Objective Based on theories that 5-HT is an aversive motivational system that may oppose a DA-related appetitive system, we explored interactions of positron emission tomography (PET) radioligand measures that reflect portions of these systems. Methods Twenty-seven individuals recovered (REC) from eating disorders (EDs) (7 AN-BN, 11 AN, 9 BN) and 9 control women (CW) were analyzed for correlations between [11C]McN5652 and [11C]raclopride binding. Results There was a positive correlation between [11C]McN5652 binding potential BPnon displaceable(ND)) and [11C]raclopride BPND for the dorsal caudate (r(27) = .62; p < .001), antero-ventral striatum (r(27) = .55, p = .003), middle caudate (r(27) = .68; p < .001), ventral (r(27) = .64; p < .001) and dorsal putamen (r(27) = .42; p = .03). No significant correlations were found in CW. [11C]raclopride BPND, but not [11C]McN5652 BPND, was significantly related to HA in REC EDs. A linear regression analysis showed that the interaction between [11C]McN5652 BPND and [11C]raclopride BPND in the dorsal putamen significantly (b = 140.04; t (22) = 2.21; p = .04) predicted HA. Conclusions This is the first study using PET and the radioligands [11C]McN5652 and [11C]raclopride to show a direct relationship between 5-HT transporter and striatal DA D2/D3 receptor binding in humans, supporting the possibility that 5-HT and DA interactions contribute to HA behaviors in EDs. PMID:23154100

  1. Differential patterns of dopamine transporter loss in the basal ganglia of progressive supranuclear palsy and Parkinson's disease: analysis with [(123)I]IPT single photon emission computed tomography.

    PubMed

    Im, Joo-Hyuk; Chung, Sun J; Kim, Jae-Seung; Lee, Myoung C

    2006-05-15

    We evaluated the patterns of dopamine transporter loss in the striatum of ten controls, twenty patients with Parkinson's disease (PD), and nine with progressive supranuclear palsy (PSP) using (123)I-IPT single photon emission tomography (SPECT). Four ROIs in the striatum correspond to the head of caudate nucleus (ROI 1), a transitional region between head of caudate and putamen (ROI 2), anterior putamen (ROI 3), and posterior putamen (ROI 4). A striatal ratio of specific to nondisplaceable uptake (V3'') was calculated normalizing the activity of the ROIs to that of occipital cortex. V3'' values were significantly reduced in all ROIs of PD and PSP patients, compared with controls (p=0.001). V3'' value in ROI 2 was significantly lower in PSP group, compared with PD group (p=0.02). The percent reductions of striatal uptake in ROI 1, ROI 2, ROI 3 and ROI 4 were 56%, 53%, 64% and 78% in PD patients, whereas 75%, 72%, 75% and 77% in PSP patients, respectively. The reduction patterns of uptake were significantly different between PD and PSP groups (p=0.001). In PD patients, the percent reductions of (123)I-IPT uptake were significantly greater in ROI 3 and 4 compared with ROI 1 or 2, whereas those were similar in all ROIs of PSP patients. In addition, PD patients showed a significantly higher posterior putamen/caudate ratio of reduced (123)I-IPT uptake than the anterior putamen/caudate ratio (p=0.005). Our results implicate that (123)I-IPT SPECT is a relatively simple and reliable technique that may be useful in differentiating PD from PSP.

  2. Dissecting the attention deficit hyperactivity disorder (ADHD) phenotype: sustained attention, response variability and spatial attentional asymmetries in relation to dopamine transporter (DAT1) genotype.

    PubMed

    Bellgrove, Mark A; Hawi, Ziarah; Kirley, Aiveen; Gill, Michael; Robertson, Ian H

    2005-01-01

    ADHD is a childhood-onset behavioural disorder with a heterogeneous profile of neuropsychological impairment. Neuropsychological heterogeneity may, in part, reflect underlying genetic differences. Here we examined sustained attention, response variability and spatial attentional asymmetries in a sample of children and adolescents with ADHD (n=22) in relation to dopamine transporter genotype (DAT1) and also controls (n=20). Participants performed the sustained attention to response task (SART) (testing sustained attention and response variability) and the greyscales task (a perceptual measure of attentional bias). The latter has previously been shown to yield a robust leftward attentional asymmetry in healthy subjects. The 10-repeat allele of the DAT1 gene has been associated with ADHD in a number of studies and appears to have biological significance. The ADHD group was sub-divided into those individuals with two copies of the "high-risk" 10-repeat allele (high-risk DAT1) versus those with one or no copies of this allele (low-risk DAT1). The high-risk DAT1 ADHD group displayed greater response variability on the SART than either the low-risk DAT1 group or healthy controls, whereas the latter two groups did not differ. Further, the high-risk DAT1 group showed an attenuated spatial asymmetry, relative to the low-risk DAT1 ADHD group, who showed the typical leftward attentional asymmetry. Our results suggest that the 10-repeat DAT1 allele may mediate neuropsychological impairment in ADHD. The application of molecular genetics may help to define neuropsychological impaired subgroups of ADHD.

  3. The dopamine transporter gene and the impulsivity phenotype in attention deficit hyperactivity disorder: a case-control association study in a Korean sample.

    PubMed

    Kim, Jae-won; Kim, Boong-nyun; Cho, Soo-churl

    2006-12-01

    The dopamine transporter gene (DAT1) has been extensively studied as one of the candidate genes in attention-deficit/hyperactivity disorder (ADHD). Several studies have reported on the association between the DAT1 10-repeat allele and cognitive variables in ADHD. However, few studies have been designed to ascertain the association between DAT1 genotypes other than the 10-repeat allele and cognitive endophenotypes in ADHD. The aim of this study was to examine the relationship between the DAT1 genotypes and the candidate endophenotypes, inattention and impulsivity symptoms, as measured by the continuous performance test (CPT), in a Korean sample of 85 children diagnosed with DSM-IV ADHD. Compared to the normal control group, the frequencies of the 9/10 genotype were significantly higher in the ADHD probands (chi(2)=13.45, p=0.02, OR=4.12, 95% CI: 2.21-12.34) and parents of probands (chi(2)=11.60, p=0.03). The 9-repeat allele frequencies were significantly higher in the ADHD probands (chi(2)=11.55, p=0.03, OR=4.43, 95% CI: 1.55-11.78) and parents of probands (chi(2)=12.70,p=0.03) than the normal control group. Compared to the ADHD probands without the 9-repeat allele (n=74), the mean T-score, with regard to the commission errors of the CPT, was significantly higher (p<0.05) in the ADHD probands with the 9-repeat allele (n=11). Compared to the ADHD probands with other DAT1 genotypes, the mean T-score, with respect to the commission errors of the CPT, was significantly higher in the ADHD probands with the 9/10 genotype (p<0.05). The results of this study suggest the possibility of an association between the DAT1 9-repeat allele and the impulsivity phenotype of ADHD.

  4. Association between dopamine transporter (DAT1) genotype, left-sided inattention, and an enhanced response to methylphenidate in attention-deficit hyperactivity disorder.

    PubMed

    Bellgrove, Mark A; Hawi, Ziarih; Kirley, Aiveen; Fitzgerald, Michael; Gill, Michael; Robertson, Ian H

    2005-12-01

    A polymorphism of the dopamine transporter gene (DAT1, 10-repeat) is associated with attention-deficit hyperactivity disorder (ADHD) and has been linked to an enhanced response to methylphenidate (MPH). One aspect of the attention deficit in ADHD includes a subtle inattention to left space, resembling that seen after right cerebral hemisphere damage. Since left-sided inattention in ADHD may resolve when treated with MPH, we asked whether left-sided inattention in ADHD was related to DAT1 genotype and the therapeutic efficacy of MPH. A total of 43 ADHD children and their parents were genotyped for the DAT1 3' variable number of tandem repeats polymorphism. The children performed the Landmark Test, a well-validated measure yielding a spatial attentional asymmetry index (leftward to rightward attentional bias). Parents rated their child's response to MPH retrospectively using a three-point scale (no, mediocre or very good response). Additionally, parents used a symptom checklist to rate behavior while on and off medication. A within-family control design determined whether asymmetry indices predicted biased transmission of 10-repeat parental DAT1 alleles and/or response to MPH. It was found that left-sided inattention predicted transmission of the 10-repeat allele from parents to probands and was associated with the severity of ADHD symptomatology. Children rated as achieving a very good response to MPH displayed left-sided inattention, while those rated as achieving a poorer response did not. Our results suggest a subgroup of children with ADHD for whom the 10-repeat DAT1 allele is associated with left-sided inattention. MPH may be most efficacious in this group because it ameliorates a DAT1-mediated hypodopaminergic state.

  5. Radiosynthesis and validation of 18F-FP-CMT, a phenyltropane with superior properties for imaging the dopamine transporter in living brain

    PubMed Central

    Cumming, Paul; Maschauer, Simone; Riss, Patrick J; Tschammer, Nuska; Fehler, Stefanie K; Heinrich, Markus R; Kuwert, Torsten; Prante, Olaf

    2014-01-01

    To date there is no validated, 18F-labeled dopamine transporter (DAT) radiotracer with a rapid kinetic profile suitable for preclinical small-animal positron emission tomography (PET) studies in rodent models of human basal ganglia disease. Herein we report radiosynthesis and validation of the phenyltropane 18F-FP-CMT. Dynamic PET recordings were obtained for 18F-FP-CMT in six untreated rats, and six rats pretreated with the high-affinity DAT ligand GBR 12909; mean parametric maps of binding potential (BPND) relative to the cerebellum reference region, and maps of total distribution volume (VT) relative to the metabolite-corrected arterial input were produced. 18F-FP-CMT BPND maps showed peak values of ∼4 in the striatum, versus ∼0.4 in the vicinity of the substantia nigra. Successive truncation of the PET recordings indicated that stable BPND estimates could be obtained with recordings lasting only 45 minutes, reflecting rapid kinetics of 18F-FP-CMT. Pretreatment with GBR 12909 reduced the striatal binding by 72% to 76%. High-performance liquid chromatography analysis revealed rapid metabolism of 18F-FP-CMT to a single, non-brain penetrant hydrophilic metabolite. Total distribution of volume calculated relative to the metabolite-corrected arterial input was 4.4 mL/g in the cerebellum. The pharmacological selectivity of 18F-FP-CMT, rapid kinetic profile, and lack of problematic metabolites constitute optimal properties for quantitation of DAT in rat, and may also predict applicability in human PET studies. PMID:24714035

  6. Dopamine Transporter Correlates and Occupancy by Modafinil in Cocaine-Dependent Patients: A Controlled Study With High-Resolution PET and [(11)C]-PE2I.

    PubMed

    Karila, Laurent; Leroy, Claire; Dubol, Manon; Trichard, Christian; Mabondo, Audrey; Marill, Catherine; Dubois, Albertine; Bordas, Nadège; Martinot, Jean-Luc; Reynaud, Michel; Artiges, Eric

    2016-08-01

    Modafinil is a candidate compound for the treatment of cocaine addiction that binds to the dopamine transporter (DAT) in healthy humans, as observed by positron emission tomography (PET). This mechanism, analogous to that of cocaine, might mediate a putative therapeutic effect of modafinil on cocaine dependence, though the binding of modafinil to DAT has never been assessed in cocaine-dependent patients. We aimed at quantifying the DAT availability during a controlled treatment by modafinil, and its clinical and psychometric correlates in cocaine-dependent patients at the onset of abstinence initiation. Twenty-nine cocaine-dependent male patients were enrolled in a 3-month trial for cocaine abstinence. Modafinil was used in a randomized double-blind placebo-controlled design and was administered as follows: 400 mg/day for 26 days, then 300 mg/day for 30 days, and 200 mg/day for 31 days. Participants were examined twice during a 17-day hospitalization for their DAT availability using PET and [(11)C]-PE2I and for assessments of craving, depressive symptoms, working memory, and decision-making. Cocaine abstinence was further assessed during a 10-week outpatient follow-up period. Baseline [(11)C]-PE2I-binding potential covaried with risk taking and craving index in striatal and extrastriatal regions. A 65.6% decrease of binding potential was detected in patients receiving modafinil for 2 weeks, whereas placebo induced no significant change. During hospitalization, an equivalent improvement in clinical outcomes was observed in both treatment groups, and during the outpatient follow-up there were more therapeutic failures in the modafinil-treated group. Therefore, these results do not support the usefulness of modafinil to treat cocaine addiction.

  7. Increased dopamine uptake in striatal synaptosomes after treatment of rats with amantadine.

    PubMed

    Page, G; Peeters, M; Maloteaux, J M; Hermans, E

    2000-09-01

    The aim of the present study was to investigate the effect of short- and long-term treatments with amantadine on the activity of the neuronal dopamine transporter (DAT) in the rat striatum. For this purpose, the [3H]dopamine uptake was measured in striatal synaptosomes prepared from rats treated for 2, 7 and 14 days with amantadine (40 mg/kg; i.p.). After 7 days of treatment, amantadine increased the apparent V(max) by 30% without modification of the apparent K(m) of dopamine uptake whereas no change in these parameters was observed after 2 and 14 days treatment. Binding assays conducted with [3H]GBR-12935 on membranes prepared from animals treated with amantadine revealed no difference in the density and the affinity of striatal DAT binding sites as compared to control. This indicates that the increased dopamine uptake was not reflecting a modification at the level of the DAT expression. The activity of the DAT is regulated by phosphorylation and one may propose that ionotropic glutamate receptors present on presynaptic terminals directly modulate this phosphorylation. An indirect mechanism would involve presynaptic dopamine receptors that control the activity of the DAT in response to the increased dopamine concentration in the synaptic cleft.

  8. Dopamine receptors – IUPHAR Review 13

    PubMed Central

    Beaulieu, Jean-Martin; Espinoza, Stefano; Gainetdinov, Raul R

    2015-01-01

    The variety of physiological functions controlled by dopamine in the brain and periphery is mediated by the D1, D2, D3, D4 and D5 dopamine GPCRs. Drugs acting on dopamine receptors are significant tools for the management of several neuropsychiatric disorders including schizophrenia, bipolar disorder, depression and Parkinson's disease. Recent investigations of dopamine receptor signalling have shown that dopamine receptors, apart from their canonical action on cAMP-mediated signalling, can regulate a myriad of cellular responses to fine-tune the expression of dopamine-associated behaviours and functions. Such signalling mechanisms may involve alternate G protein coupling or non-G protein mechanisms involving ion channels, receptor tyrosine kinases or proteins such as β-arrestins that are classically involved in GPCR desensitization. Another level of complexity is the growing appreciation of the physiological roles played by dopamine receptor heteromers. Applications of new in vivo techniques have significantly furthered the understanding of the physiological functions played by dopamine receptors. Here we provide an update of the current knowledge regarding the complex biology, signalling, physiology and pharmacology of dopamine receptors. PMID:25671228

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

    DTIC Science & Technology

    2001-05-01

    disease (Hornykiewicz, 1979) and attention deficit hyperactivity disorder (Ernst et al., 1998). DAT is of particular interest because it is believed to be...Cohen R. M. (1998) DOPA decarboxylase activity in attention deficit hyperactivity disorder adults. A [fluorine-18] fluorodopa positron emission

  10. Impedimetric DNA-biosensor for the study of dopamine induces DNA damage and investigation of inhibitory and repair effects of some antioxidants.

    PubMed

    Ensafi, Ali A; Kazemnadi, Narges; Amini, Maryam; Rezaei, B

    2015-08-01

    A simple and inexpensive methodology was used to develop a new method in order to inspect the DNA damage due to dopamine and some ionic metals. In addition, the inhibitory and repair effects of some antioxidant such as glutathione and ascorbic acid were studied and compared with each other using electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). In this work a pencil graphite electrode (PGE) was modified with multiwall carbon nanotubes (MWCNTs) and chitosan (CHIT), then it was decorated with a ds-DNA (ds-DNA/CHIT-MWCNTs/PGE). Due to interaction of ds-DNA and the damaging agents (dopamine+metallic ions), electrochemical and spectroscopy properties of ds-DNA at the surface of the modified electrode was changed, and these changes are followed with EIS and DPV methods. Our study showed that dopamine, Cu(II) and Fe(III) alone could not destroy DNA, but dopamine + Cu(II) and dopamine + Fe(III) can damage DNA. In addition, the ability of dopamine-Cu(II) was greater than dopamine-Fe(III). Moreover, some antioxidant such as glutathione and ascorbic acid can overcome and/or minimize the influence of these damaging interactions.

  11. Investigations of Particle Transport in the Texas Helimak

    NASA Astrophysics Data System (ADS)

    Taylor, E. I.; Rowan, W. L.; Gentle, K. W.; Huang, H.; Williams, C. B.

    2016-10-01

    The correlation between electrostatic turbulence and particle flux is investigated in a simple magnetic torus, the Helimak. The Helimak is an experimental realization of a sheared cylindrical slab that generates and heats a plasma with microwaves at 2.45 GHz and confines it in a helical magnetic field. Although it is MHD stable, the plasma is always in a nonlinearly saturated state of microturbulence. The causes of this turbulence are diverse and it is thought that it is either due to drift wave instabilities or interchange instabilites. The local particle flux is estimated over most of the plasma cross section by measuring the particle source using filtered cameras. Plasma flow along the field lines is physically similar to SOL flows in tokamaks. It is significant and can be measured directly as well as inferred from asymmetries in the electron density. The cross field transport due to electrostatic turbulence is measured as the cross correlation of radial electric field fluctuations with electron density fluctuations with the data acquired using Langmuir probes. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences under Award Number DE-FG02-04ER54766.

  12. National Transportation Safety Board Aircraft Accident Investigation Supported

    NASA Technical Reports Server (NTRS)

    Reehorst, Andrew L.

    1999-01-01

    The main purpose of this investigation was for NASA to help the National Transportation Safety Board (NTSB) gain better understanding of the events that led to the loss of Comair Flight 3272 over Monroe, Michigan, on January 9, 1997. In-flight icing was suspected as being the primary cause of this accident. Of particular interest to the Safety Board was what NASA could learn about the potential performance degradation of the wing of the Embraer EMB-120 twin-turboprop commuter aircraft with various levels of ice contamination. NASA agreed to undertake (1) ice-accretion prediction computations with NASA s LEWICE program to bound the kind of contaminations that the vehicle may have developed, (2) testing in the NASA Lewis Research Center's Icing Research Tunnel to verify and refine the ice shapes developed by LEWICE, (3) a two-dimensional Navier- Stokes analysis to determine the performance degradation that those ice shapes could have caused, and (4) an examination using three-dimensional Navier-Stokes codes to study the three-dimensional effects of ice contamination.

  13. Numerical Investigation of Laser Propulsion for Transport in Water Environment

    SciTech Connect

    Han Bing; Li Beibei; Zhang Hongchao; Chen Jun; Shen Zhonghua; Lu Jian; Ni Xiaowu

    2010-10-08

    Problems that cumber the development of the laser propulsion in atmosphere and vacuum are discussed. Based on the theory of interaction between high-intensity laser and materials, as air and water, it is proved that transport in water environment can be impulsed by laser. The process of laser propulsion in water is investigated theoretically and numerically. It shows that not only the laser induced plasma shock wave, but also the laser induced bubble oscillation shock waves and the pressure induced by the collapsing bubble can be used. Many experimental results show that the theory and the numerical results are valid. The numerical result of the contribution of every propulsion source is given in percentage. And the maximum momentum coupling coefficient Cm is given. Laser propulsion in water environment can be applied in many fields. For example, it can provide highly controllable forces of the order of micro-Newton ({mu}N) in microsystems, such as the MEMS (Micro-electromechanical Systems). It can be used as minimally invasive surgery tools of high temporal and spatial resolution. It can be used as the propulsion source in marine survey and exploitation.

  14. Investigations for Supersonic Transports at Transonic and Supersonic Conditions

    NASA Technical Reports Server (NTRS)

    Rivers, S. Melissa B.; Owens, Lewis R.; Wahls, Richard A.

    2007-01-01

    Several computational studies were conducted as part of NASA s High Speed Research Program. Results of turbulence model comparisons from two studies on supersonic transport configurations performed during the NASA High-Speed Research program are given. The effects of grid topology and the representation of the actual wind tunnel model geometry are also investigated. Results are presented for both transonic conditions at Mach 0.90 and supersonic conditions at Mach 2.48. A feature of these two studies was the availability of higher Reynolds number wind tunnel data with which to compare the computational results. The transonic wind tunnel data was obtained in the National Transonic Facility at NASA Langley, and the supersonic data was obtained in the Boeing Polysonic Wind Tunnel. The computational data was acquired using a state of the art Navier-Stokes flow solver with a wide range of turbulence models implemented. The results show that the computed forces compare reasonably well with the experimental data, with the Baldwin-Lomax with Degani-Schiff modifications and the Baldwin-Barth models showing the best agreement for the transonic conditions and the Spalart-Allmaras model showing the best agreement for the supersonic conditions. The transonic results were more sensitive to the choice of turbulence model than were the supersonic results.

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

    PubMed Central

    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

  16. The nature of dopamine dysfunction in schizophrenia and what this means for treatment

    PubMed Central

    Howes, Oliver D; Kambeitz, Joseph; Kim, Euitae; Stahl, Daniel; Slifstein, Mark; Abi-Dargham, Anissa; Kapur, Shitij

    2013-01-01

    Context Current drug treatments for schizophrenia are inadequate for many patients and, despite five decades of drug discovery, all use the same mechanism-dopamine D2 receptor blockade. Understanding the pathophysiology of the disorder is thus likely to be critical to the rational development of new treatments for schizophrenia. Objective To investigate the nature of the dopaminergic dysfunction in schizophrenia using meta-analysis of in vivo studies. Data sources The MEDLINE, EMBASE and PsychINFO databases were searched for studies from January 1, 1960, to July 1, 2011. Study selection Forty-four studies were identified that compared in vivo striatal dopaminergic function in 618 patients with schizophrenia with 606 controls using positron emission tomography or single photon emission computed tomography. Data extraction Demographic, clinical and imaging variables were extracted from each study and effect sizes determined for the measures of dopaminergic function. Studies were grouped into those of presynaptic function, and dopamine transporter and receptor availability. Sensitivity analyses were conducted to explore the consistency of effects and the effect of clinical and imaging variables. Data synthesis There was a highly significant elevation (p<0.0001) in presynaptic dopaminergic function in schizophrenia with a large effect size (Cohen’s d=0.79). There was no evidence of alterations in dopamine transporter availability. There was a small elevation in D2/3 receptor availability (Cohen’s d=0.26), but this was not evident in drug-naïve patients and was influenced by the imaging approach used. Conclusions The locus of the largest dopaminergic abnormality in schizophrenia is presynaptic-affecting dopamine synthesis capacity, baseline synaptic dopamine levels and dopamine release. Current drug treatments - which primarily act at D2/3 receptors - fail to target these abnormalities. Future drug development should focus on the control of presynaptic dopamine

  17. Principal Component Analysis of Multimodal Neuromelanin MRI and Dopamine Transporter PET Data Provides a Specific Metric for the Nigral Dopaminergic Neuronal Density

    PubMed Central

    Kawaguchi, Hiroshi; Shimada, Hitoshi; Kodaka, Fumitoshi; Suzuki, Masayuki; Shinotoh, Hitoshi; Hirano, Shigeki; Kershaw, Jeff; Inoue, Yuichi; Nakamura, Masaki; Sasai, Taeko; Kobayashi, Mina; Suhara, Tetsuya; Ito, Hiroshi

    2016-01-01

    The loss of dopaminergic (DA) neurons in the substantia nigra (SN) is a major pathophysiological feature of patients with Parkinson's disease (PD). As nigral DA neurons contain both neuromelanin (NM) and dopamine transporter (DAT), decreased intensities in both NM-sensitive MRI and DAT PET reflect decreased DA neuronal density. This study demonstrates that a more specific metric for the nigral DA neuronal density can be derived with multimodal MRI and PET. Participants were 11 clinically diagnosed PD patients and 10 age and gender matched healthy controls (HCs). Two quantities, the NM-related index (RNM) and the binding potential of the radiotracer [18F]FE-PE2I to DAT (BPND) in SN, were measured for each subject using MRI and PET, respectively. Principal component analysis (PCA) was applied to the multimodal data set to estimate principal components. One of the components, PCP, corresponds to a basis vector oriented in a direction where both BPND and RNM increase. The ability of BPND, RNM and PCP to discriminate between HC and PD groups was compared. Correlation analyses between the motor score of the unified Parkinson's disease rating scale and each metric were also performed. PCP, BPND and RNM for PD patients were significantly lower than those for HCs (F = 16.26, P<0.001; F = 6.05, P = 0.008; F = 7.31, P = 0.034, respectively). The differential diagnostic performance between the HC and PD groups as assessed by the area under the receiver-operating characteristic curve was best for PCP (0.94, 95% CI: 0.66–1.00). A significant negative correlation was found between the motor severity score and PCp (R = -0.70, P<0.001) and RNM (R = -0.52, P = 0.015), but not for BPND (R = -0.36, P = 0.110). PCA of multimodal NM-sensitive MRI and DAT PET data provides a metric for nigral DA neuronal density that will help illuminate the pathophysiology of PD in SN. Further studies are required to explore whether PCA is useful for other parkinsonian syndromes. PMID:26954690

  18. Investigation on the co-luminescence effect of europium (III)-lanthanum(III)-dopamine-sodium dodecylbenzene sulfonate system and its application.

    PubMed

    Si, Hailin; Zhao, Fang; Cai, Huan

    2013-01-01

    A novel luminescence, enhancement phenomenon in the europium(III)-dopamine-sodium dodecylbenzene sulfonate system was observed when lanthanum(III) was added. Based on this, a sensitive co-luminescence method was established for the determination of dopamine. The luminescence signal for the europium (III)-lanthanum(III)-dopamine-sodium dodecylbenzene sulfonate system was monitored at λ(ex) = 300 nm, λ(em) = 618 nm and pH 8.3. Under optimized conditions, the enhanced luminescence signal responded linearly to the concentration of dopamine in the range 1.0 × 10(-10)-5.0 × 10(-7) mol/L with a correlation coefficient of 0.9993 (n = 11). The detection limit (3σ) was 2.7 × 10(-11) mol/L and the relative standard deviation for 11 parallel measurements of 3.0 × 10(-8) mol/L dopamine was 1.9%. The presented method was successfully applied for the estimation of dopamine in samples of pharmaceutical preparations, human serum and urine. The possible luminescence enhancement mechanism of the system is discussed briefly.

  19. Investigations into a potential laser-NASP transport technology

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Laser propelled flight/transport technology is surveyed. A detailed conceptual design is presented for an on-place Mercury-Lightcraft: other designs are briefly explored for larger, 15-place Executive Lightcraft, and 150 to 350 passenger Jumbo Lightcraft.

  20. An Investigation of Landing-Contact Conditions for Two Large Turbojet Transports and a Turboprop Transport During Routine Daylight Operations

    NASA Technical Reports Server (NTRS)

    Stickle, Joseph W.

    1961-01-01

    The National Aeronautics and Space Administration has recently completed a statistical investigation of landing-contact conditions for two large turbojet transports and a turboprop transport landing on a dry runway during routine daylight operations at the Los Angeles International Airport. Measurements were made to obtain vertical velocity, airspeed, rolling velocity, bank angle, and distance from the runway threshold, just prior to ground contact. The vertical velocities at touchdown for one of the turbojet airplanes measured in this investigation were essentially the same as those measured on the same type of airplane during a similar investigation (see NASA Technical Note D-527) conducted approximately 8 months earlier. Thus, it appeared that 8 months of additional pilot experience has had no noticeable tendency toward lowering the vertical velocities of this transport. Distributions of vertical velocities for the turbojet transports covered in this investigation were similar and considerably higher than'those for the turboprop transport. The data for the turboprop transport were in good agreement with the data for the piston-engine transports (see NACA Report 1214 and NASA Technical Note D-147) for all the measured parameters. For the turbojet transports, 1 landing in 100 would be expected to equal or exceed a vertical velocity of approximately 4.2 ft/sec; whereas, for the turboprop transport, 1 landing in 100 would be expected to equal or exceed 3.2 ft/sec. The mean airspeeds at touchdown for the three transports ranged from 22.5 percent to 26.6 percent above the stalling speed. Rolling velocities for the turbojet transports were considerably higher than those for the turboprop transport. Distributions of bank angles at contact for the three transports were similar. For each type of airplane, 1 landing in 100 would be expected to equal or exceed a bank angle at touchdown of approximately 3.0 deg. Distributions of touchdown distances for the three transports

  1. Dopamine-melanin nanofilms for biomimetic structural coloration.

    PubMed

    Wu, Tong-Fei; Hong, Jong-Dal

    2015-02-09

    This article describes the formation of dopamine-melanin thin films (50-200 nm thick) at an air/dopamine solution interface under static conditions. Beneath these films, spherical melanin granules formed in bulk liquid phase. The thickness of dopamine-melanin films at the interface relied mainly on the concentration of dopamine solution and the reaction time. A plausible mechanism underlining dopamine-melanin thin film formation was proposed based on the hydrophobicity of dopamine-melanin aggregates and the mass transport of the aggregates to the air/solution interface as a result of convective flow. The thickness of the interfacial films increased linearly with the dopamine concentration and the reaction time. The dopamine-melanin thin film and granules (formed in bulk liquid phase) with a double-layered structure were transferred onto a solid substrate to mimic the (keratin layer)/(melanin granules) structure present in bird plumage, thereby preparing full dopamine-melanin thin-film reflectors. The reflected color of the thin-film reflectors depended on the film thickness, which could be adjusted according to the dopamine concentration. The reflectance of the resulted reflectors exhibited a maximal reflectance value of 8-11%, comparable to that of bird plumage (∼11%). This study provides a useful, simple, and low-cost approach to the fabrication of biomimetic thin-film reflectors using full dopamine-melanin materials.

  2. The role of dopamine transporter (SLC6A3) and dopamine D2 receptor/ankyrin repeat and kinase domain containing 1 (DRD2/ANKK1) gene polymorphisms in personality traits.

    PubMed

    Kazantseva, A; Gaysina, D; Malykh, S; Khusnutdinova, E

    2011-06-01

    Variations in personality traits are caused by interactions between multiple genes of small effect and environmental factors. To date, gender- and ethnicity-specific variations in personality have been established. In the present study, we aimed to test: (1) the effects of four polymorphisms of dopamine system genes: ANKK1/DRD2 Taq1A, DRD2 rs6275, SLC6A3 40-bp VNTR and rs27072, on personality traits; (2) whether these effects differ between men and women and between Russians and Tatars. A sample of 652 healthy individuals (222 men and 430 women) of Caucasian origin (233 Russians and 419 Tatars) from Russia was subjected to personality traits assessment with Eysenck Personality Inventory (EPI) and Temperament and Character Inventory-125 (TCI-125). The associations between each personality trait and polymorphisms were assessed with regression models adjusted for gender and ethnicity. There were significant effects of ANKK1/DRD2 Taq1A on Neuroticism (p=0.016) and of SLC6A3 rs27072 on Persistence (p=0.021) in both genders. The association between ANKK1/DRD2 Taq1A A2/A2-genotype and higher Novelty Seeking and lower Reward Dependence was shown in men only (p for gender interaction=0.018). In women only, there was a significant association between SLC6A3 10R*G-haplotype and higher Persistence (p=0.002). Our findings provide evidence for a modifying effect of gender on the associations between dopamine system genes and approach-related traits (in men) and Persistence (in women).

  3. Investigation of transport processes in a large urban estuary

    NASA Astrophysics Data System (ADS)

    Caplow, T.; Schlosser, P.; Ho, D. T.; Santella, N.

    2003-04-01

    The Hudson River drains an area of 35 000 km^2 and terminates in a complex of waterways surrounding New York City. These waterways support the largest metropolitan area and third busiest seaport in the U.S., absorbing a large flux of industrial contaminants and wastewater, as well as accidental spills of oil and chemicals. Traditional approaches to the study of transport processes in New York Harbor include fluorescent dyes, moored current profilers, and numerical models, but these methods are limited by low temporal and spatial resolution and/or uncertain accuracy, particularly with regard to mixing. In July 2001, sulfur hexafluoride (SF_6) was injected into the Hudson River estuary near Newburgh, NY, about 100 km upstream from New York City. The resulting tracer patch was surveyed by boat (average resolution: 400 m) with an automated measurement system. After 13 days, the tracer patch was more than 100 km long. Net advection (0.5 km d-1), longitudinal dispersion (70 ± 4 m^2 s-1) and gas transfer velocity (6.5 ± 0.5 cm h-1) were determined from the tracer data. Tidal motions dominated river flow, and considerable quantities of tracer propagated upstream from the injection site. In July 2002, SF_6 was injected in the inner harbor, a complex of estuarine channels adjacent to the city. The tracer was tracked for 11 days. Due to tidal mixing, the shorter of two channels (9 km and 20 km) that connect with the outer harbor was the dominant seaward pathway, despite subtidal circulation in the opposite direction. As a result of gas transfer and seaward flushing, tracer mass in the inner harbor declined quasi-exponentially with a loss term of 0.29 ± 0.03 day-1. The loss term due to flushing alone (0.13 ± 0.02 day-1) indicated a mean residence time for water and solutes in the inner harbor of 8 days (without gas transfer). Further projects, including an investigation of wastewater fate, are planned within the lower estuary.

  4. Transport Properties of Metallic Ruthenates: A DFT +DMFT Investigation

    NASA Astrophysics Data System (ADS)

    Deng, Xiaoyu; Haule, Kristjan; Kotliar, Gabriel

    2016-06-01

    We present a systematical theoretical study on the transport properties of an archetypal family of Hund's metals, Sr2RuO4 , Sr3 Ru2 O7 , SrRuO3 , and CaRuO3 , within the combination of first principles density functional theory and dynamical mean field theory. The agreement between theory and experiments for optical conductivity and resistivity is good, which indicates that electron-electron scattering dominates the transport of ruthenates. We demonstrate that in the single-site dynamical mean field approach the transport properties of Hund's metals fall into the scenario of "resilient quasiparticles." We explain why the single layered compound Sr2 RuO4 has a relative weak correlation with respect to its siblings, which corroborates its good metallicity.

  5. Modeling transport in the kidney: investigating function and dysfunction

    PubMed Central

    2010-01-01

    Mathematical models of water and solute transport in the kidney have significantly expanded our understanding of renal function in both health and disease. This review describes recent theoretical developments and emphasizes the relevance of model findings to major unresolved questions and controversies. These include the fundamental processes by which urine is concentrated in the inner medulla, the ultrastructural basis of proteinuria, irregular flow oscillation patterns in spontaneously hypertensive rats, and the mechanisms underlying the hypotensive effects of thiazides. Macroscopic models of water, NaCl, and urea transport in populations of nephrons have served to test, confirm, or refute a number of hypotheses related to the urine concentrating mechanism. Other macroscopic models focus on the mechanisms, role, and irregularities of renal hemodynamic control and on the regulation of renal oxygenation. At the mesoscale, models of glomerular filtration have yielded significant insight into the ultrastructural basis underlying a number of disorders. At the cellular scale, models of epithelial solute transport and pericyte Ca2+ signaling are being used to elucidate transport pathways and the effects of hormones and drugs. Areas where further theoretical progress is conditional on experimental advances are also identified. PMID:19889951

  6. Computational Investigation of the Transport of Burning Particles

    NASA Astrophysics Data System (ADS)

    Matvienko, O. V.; Fil'kov, A. I.; Grishin, A. M.

    2016-09-01

    Computational modeling of the dynamics of the convective column formed by a low forest fire and of the transport of particles burning in it has been carried out. At the initial stage of formation of a thermal column, medium- and large-size particles move with the ascending air flow to its upper boundary; then they are entrained by the torroidal vortex and carried out of the combustion zone to the outer boundary of the circulation flow where they settle to the underlying surface. With increasing size of particles the maximum rise height of particles and the distance for which they are transported by the vortex flow decrease. The temperature of large particles at the moment of their landing is above the critical one, which can initiate ignition of the underlying surface and the formation of a secondary site of fire.

  7. Investigation of air transportation technology at Princeton University, 1981

    NASA Technical Reports Server (NTRS)

    Stengel, R. F.

    1982-01-01

    A summary of the air transportation technology program is presented. The following topics were examined: (1) fuel use characteristics of general aviation aircraft; (2) dead-reckoning concept incorporating a fluidic rate sensor; (3) experimentation with an ultrasonic altimeter; (4) development of laser-based collision avoidance systems; (5) flight path reconstruction from sequential DME data; (6) application of fiber optics in flight control systems; and (7) voice recognition inputs for navigation/communication receiver tuning.

  8. Investigation of air transportation technology at Ohio University, 1984

    NASA Technical Reports Server (NTRS)

    Mcfarland, Richard H.

    1987-01-01

    The operational development of Loran-C for enroute navigation and nonprecision approaches was studied, and is only one of the many projects funded by the Joint University Program for Air Transportation at Ohio University. Other projects included work on the DATAC data bus monitor, global positioning system test bed receiver development, fiber optic data bus application in general aviation aircraft, and advanced remote monitoring techniques.

  9. PKCβ Inhibitors Attenuate Amphetamine-Stimulated Dopamine Efflux.

    PubMed

    Zestos, Alexander G; Mikelman, Sarah R; Kennedy, Robert T; Gnegy, Margaret E

    2016-06-15

    Amphetamine abuse afflicts over 13 million people, and there is currently no universally accepted treatment for amphetamine addiction. Amphetamine serves as a substrate for the dopamine transporter and reverses the transporter to cause an increase in extracellular dopamine. Activation of the beta subunit of protein kinase C (PKCβ) enhances extracellular dopamine in the presence of amphetamine by facilitating the reverse transport of dopamine and internalizing the D2 autoreceptor. We previously demonstrated that PKCβ inhibitors block amphetamine-stimulated dopamine efflux in synaptosomes from rat striatum in vitro. In this study, we utilized in vivo microdialysis in live, behaving rats to assess the effect of the PKCβ inhibitors, enzastaurin and ruboxistaurin, on amphetamine-stimulated locomotion and increases in monoamines and their metabolites. A 30 min perfusion of the nucleus accumbens core with 1 μM enzastaurin or 1 μM ruboxistaurin reduced efflux of dopamine and its metabolite 3-methoxytyramine induced by amphetamine by approximately 50%. The inhibitors also significantly reduced amphetamine-stimulated extracellular levels of norepinephrine. The stimulation of locomotor behavior by amphetamine, measured simultaneously with the analytes, was comparably reduced by the PKCβ inhibitors. Using a stable isotope label retrodialysis procedure, we determined that ruboxistaurin had no effect on basal levels of dopamine, norepinephrine, glutamate, or GABA. In addition, normal uptake function through the dopamine transporter was unaltered by the PKCβ inhibitors, as measured in rat synaptosomes. Our results support the utility of using PKCβ inhibitors to reduce the effects of amphetamine.

  10. Endogenous dopamine increases extracellular concentrations of glutamate and GABA in striatum of the freely moving rat: involvement of D1 and D2 dopamine receptors.

    PubMed

    Expósito, I; Del Arco, A; Segovia, G; Mora, F

    1999-07-01

    Interactions between endogenous dopamine, glutamate, GABA, and taurine were investigated in striatum of the freely moving rat by using microdialysis. Intrastriatal infusions of the selective dopamine uptake inhibitor nomifensine (NMF) were used to increase the endogenous extracellular dopamine. NMF produced a dose-related increase in extracellular dopamine and also increased extracellular concentrations of glutamate, GABA, and taurine. Extracellular increases of dopamine were significantly correlated with extracellular increases of glutamate and GABA, but not taurine. To investigate whether the increased extracellular dopamine produced by NMF was responsible for the concomitant increase of glutamate and GABA, D1, and D2 receptor antagonists were used. Dopamine receptor antagonists D1 (SCH23390) and D2 (sulpiride) significantly attenuated the increases of glutamate and GABA produced by NMF. These data suggest that endogenous dopamine, through both D1 and D2 dopamine receptors, plays a role in releasing glutamate and GABA in striatum of the freely moving rat.

  11. Investigation of diamond deposition by chemical vapor transport with hydrogen

    NASA Astrophysics Data System (ADS)

    Piekarczyk, Wladyslaw; Messier, Russell F.; Roy, Rustum; Engdahl, Chris

    1990-12-01

    The carbon-hydrogen chemical vapor transport system was examined in accordance with a four-stage transport model. A result of this examination is that graphite co-deposition could be avoided when diamond is deposited from gas solutions under-saturated with respect to diamond. Actual deposition experiments showed that this unusual requirement can be fulfilled but only for the condition that the transport distance between the carbon source and the substrate surface is short. In such a case diamond can be deposited equally from super-saturated as well as from under-saturated gas solutions. On the basis of thermodynamic considerations a possible explanation of this unusual phenomenon is given. It is shown that there is a possibility of deposition of diamond from both super-saturated as well as under-saturated gas solutions but only on the condition that they are in a non-equilibrium state generally called the activated state. A model of the diamond deposition process consisting of two steps is proposed. In the first step diamond and graphite are deposited simultaneously. The most important carbon deposition reaction is C2H2(g) + 2 H(g) C(diamond graphite) + CH(g). The amount of co-deposited graphite is not a direct function of the saturation state of the gas phase. In the second step graphite is etched according to the most probable reaction C(graphite) + 4 H(g) CH4(g). Atomic hydrogen in a super-equilibrium concentration is necessary not only to etch graphite but also to precipitate and graphite. 1.

  12. Acoustic charge transport technology investigation for advanced development transponder

    NASA Technical Reports Server (NTRS)

    Kayalar, S.

    1993-01-01

    Acoustic charge transport (ACT) technology has provided a basis for a new family of analog signal processors, including a programmable transversal filter (PTF). Through monolithic integration of ACT delay lines with GaAs metal semiconductor field effect transistor (MESFET) digital memory and controllers, these devices significantly extend the performance of PTF's. This article introduces the basic operation of these devices and summarizes their present and future specifications. The production and testing of these devices indicate that this new technology is a promising one for future space applications.

  13. Angular neutron transport investigation in the HZETRN free-space ion and nucleon transport and shielding computer program

    SciTech Connect

    Singleterry, R.C. Jr.; Wilson, J.W.

    1997-05-01

    Extension of the high charge and energy (HZE) transport computer program HZETRN for angular transport of neutrons is considered. For this paper, only light ion transport, He{sup 4} and lighter, will be analyzed using a pure solar proton source. The angular transport calculator is the ANISN/PC program which is being controlled by the HZETRN program. The neutron flux values are compared for straight-ahead transport and angular transport in one dimension. The shield material is aluminum and the target material is water. The thickness of these materials is varied; however, only the largest model calculated is reported which is 50 gm/cm{sup 2} of aluminum and 100 gm/cm{sup 2} of water. The flux from the ANISN/PC calculation is about two orders of magnitude lower than the flux from HZETRN for very low energy neutrons. It is only a magnitude lower for the neutrons in the 10 to 20 MeV range in the aluminum and two orders lower in the water. The major reason for this difference is in the transport modes: straight-ahead versus angular. The angular treatment allows a longer path length than the straight-ahead approximation. Another reason is the different cross section sets used by the ANISN/PC-BUGLE-80 mode and the HZETRN mode. The next step is to investigate further the differences between the two codes and isolate the differences to just the angular versus straight-ahead transport mode. Then, create a better coupling between the angular neutron transport and the charged particle transport.

  14. Angular neutron transport investigation in the HZETRN free-space ion and nucleon transport and shielding computer program

    NASA Technical Reports Server (NTRS)

    Singleterry, R. C., Jr.; Wilson, J. W.

    1997-01-01

    Extension of the high charge and energy (HZE) transport computer program HZETRN for angular transport of neutrons is considered. For this paper, only light ion transport, He4 and lighter, will be analyzed using a pure solar proton source. The angular transport calculator is the ANISN/PC program which is being controlled by the HZETRN program. The neutron flux values are compared for straight-ahead transport and angular transport in one dimension. The shield material is aluminum and the target material is water. The thickness of these materials is varied; however, only the largest model calculated is reported which is 50 gm/sq cm of aluminum and 100 gm/sq cm of water. The flux from the ANISN/PC calculation is about two orders of magnitude lower than the flux from HZETRN for very low energy neutrons. It is only a magnitude lower for the neutrons in the 10 to 20 MeV range in the aluminum and two orders lower in the water. The major reason for this difference is in the transport modes: straight-ahead versus angular. The angular treatment allows a longer path length than the straight-ahead approximation. Another reason is the different cross section sets used by the ANISN/PC-BUGLE-80 mode and the HZETRN mode. The next step is to investigate further the differences between the two codes and isolate the differences to just the angular versus straight-ahead transport mode. Then, create a better coupling between the angular neutron transport and the charged particle transport.

  15. Distinct Effects of Nalmefene on Dopamine Uptake Rates and Kappa Opioid Receptor Activity in the Nucleus Accumbens Following Chronic Intermittent Ethanol Exposure.

    PubMed

    Rose, Jamie H; Karkhanis, Anushree N; Steiniger-Brach, Björn; Jones, Sara R

    2016-07-27

    The development of pharmacotherapeutics that reduce relapse to alcohol drinking in patients with alcohol dependence is of considerable research interest. Preclinical data support a role for nucleus accumbens (NAc) κ opioid receptors (KOR) in chronic intermittent ethanol (CIE) exposure-induced increases in ethanol intake. Nalmefene, a high-affinity KOR partial agonist, reduces drinking in at-risk patients and relapse drinking in rodents, potentially due to its effects on NAc KORs. However, the effects of nalmefene on accumbal dopamine transmission and KOR function are poorly understood. We investigated the effects of nalmefene on dopamine transmission and KORs using fast scan cyclic voltammetry in NAc brain slices from male C57BL/6J mice following five weeks of CIE or air exposure. Nalmefene concentration-dependently reduced dopamine release similarly in air and CIE groups, suggesting that dynorphin tone may not be present in brain slices. Further, nalmefene attenuated dopamine uptake rates to a greater extent in brain slices from CIE-exposed mice, suggesting that dopamine transporter-KOR interactions may be fundamentally altered following CIE. Additionally, nalmefene reversed the dopamine-decreasing effects of a maximal concentration of a KOR agonist selectively in brain slices of CIE-exposed mice. It is possible that nalmefene may attenuate withdrawal-induced increases in ethanol consumption by modulation of dopamine transmission through KORs.

  16. Distinct Effects of Nalmefene on Dopamine Uptake Rates and Kappa Opioid Receptor Activity in the Nucleus Accumbens Following Chronic Intermittent Ethanol Exposure

    PubMed Central

    Rose, Jamie H.; Karkhanis, Anushree N.; Steiniger-Brach, Björn; Jones, Sara R.

    2016-01-01

    The development of pharmacotherapeutics that reduce relapse to alcohol drinking in patients with alcohol dependence is of considerable research interest. Preclinical data support a role for nucleus accumbens (NAc) κ opioid receptors (KOR) in chronic intermittent ethanol (CIE) exposure-induced increases in ethanol intake. Nalmefene, a high-affinity KOR partial agonist, reduces drinking in at-risk patients and relapse drinking in rodents, potentially due to its effects on NAc KORs. However, the effects of nalmefene on accumbal dopamine transmission and KOR function are poorly understood. We investigated the effects of nalmefene on dopamine transmission and KORs using fast scan cyclic voltammetry in NAc brain slices from male C57BL/6J mice following five weeks of CIE or air exposure. Nalmefene concentration-dependently reduced dopamine release similarly in air and CIE groups, suggesting that dynorphin tone may not be present in brain slices. Further, nalmefene attenuated dopamine uptake rates to a greater extent in brain slices from CIE-exposed mice, suggesting that dopamine transporter-KOR interactions may be fundamentally altered following CIE. Additionally, nalmefene reversed the dopamine-decreasing effects of a maximal concentration of a KOR agonist selectively in brain slices of CIE-exposed mice. It is possible that nalmefene may attenuate withdrawal-induced increases in ethanol consumption by modulation of dopamine transmission through KORs. PMID:27472317

  17. Effect of cocaine and sucrose withdrawal period on extinction behavior, cue-induced reinstatement, and protein levels of the dopamine transporter and tyrosine hydroxylase in limbic and cortical areas in rats

    PubMed Central

    Grimm, J.W.; Shaham, Y.; Hope, B.T.

    2010-01-01

    Lever pressing during tests for resistance to extinction and cue-induced reinstatement of cocaine seeking in rats progressively increases over the first 2 months of withdrawal. In the present report, we investigated the generality of these findings in rats trained to self-administer sucrose, a non-drug reinforcer. We also examined whether the time-dependent changes in cocaine seeking correlate with the levels of the dopamine transporter (DAT) and tyrosine hydroxylase (TH) proteins in the amygdala, nucleus accumbens, prefrontal cortex and orbitofrontal cortex. Rats were trained to self-administer cocaine (0.5 mg/kg/i.v. infusion) or 10% sucrose (0.2 ml/infusion into a liquid drop receptacle) for 10 days (6 h/day); each reward delivery was paired with a tone+light cue. Tests for cocaine seeking were conducted following 1 or 15 reward-free days. On the test day, rats were initially tested for resistance to extinction during 6–7 60-min extinction sessions in the absence of the tone–light cue, until they reached the extinction criterion of less than 15 responses/60 min. Subsequently, rats were tested for cue-induced reinstatement during a 60-min session in which each lever press led to a contingent presentation of the tone–light cue. Lever pressing during the tests for reward seeking was significantly greater on day 15 than on day 1 following withdrawal from both cocaine and sucrose self-administration training. The levels of DAT, but not TH, were greater in the prefrontal cortex of cocaine-trained rats than in sucrose-trained rats on both days 1 and 15 of withdrawal. The levels of DAT and TH in other brain areas were not altered following withdrawal from cocaine or sucrose self-administration. These data suggest that the withdrawal period can modulate reward seeking of both drug and non-drug reinforcers, and that alterations in DAT and TH levels in the brain regions examined do not mediate this effect. PMID:12394414

  18. Investigation of stochastic radiation transport methods in random heterogeneous mixtures

    NASA Astrophysics Data System (ADS)

    Reinert, Dustin Ray

    Among the most formidable challenges facing our world is the need for safe, clean, affordable energy sources. Growing concerns over global warming induced climate change and the rising costs of fossil fuels threaten conventional means of electricity production and are driving the current nuclear renaissance. One concept at the forefront of international development efforts is the High Temperature Gas-Cooled Reactor (HTGR). With numerous passive safety features and a meltdown-proof design capable of attaining high thermodynamic efficiencies for electricity generation as well as high temperatures useful for the burgeoning hydrogen economy, the HTGR is an extremely promising technology. Unfortunately, the fundamental understanding of neutron behavior within HTGR fuels lags far behind that of more conventional water-cooled reactors. HTGRs utilize a unique heterogeneous fuel element design consisting of thousands of tiny fissile fuel kernels randomly mixed with a non-fissile graphite matrix. Monte Carlo neutron transport simulations of the HTGR fuel element geometry in its full complexity are infeasible and this has motivated the development of more approximate computational techniques. A series of MATLAB codes was written to perform Monte Carlo simulations within HTGR fuel pebbles to establish a comprehensive understanding of the parameters under which the accuracy of the approximate techniques diminishes. This research identified the accuracy of the chord length sampling method to be a function of the matrix scattering optical thickness, the kernel optical thickness, and the kernel packing density. Two new Monte Carlo methods designed to focus the computational effort upon the parameter conditions shown to contribute most strongly to the overall computational error were implemented and evaluated. An extended memory chord length sampling routine that recalls a neutron's prior material traversals was demonstrated to be effective in fixed source calculations containing

  19. The dopamine-related polymorphisms BDNF, COMT, DRD2, DRD3, and DRD4 are not linked with changes in CSF dopamine levels and frequency of HIV infection.

    PubMed

    Horn, Anne; Scheller, C; du Plessis, S; Burger, R; Arendt, G; Joska, J; Sopper, S; Maschke, C M; Obermann, M; Husstedt, I W; Hain, J; Riederer, P; Koutsilieri, E

    2017-04-01

    We showed previously that higher levels in CSF dopamine in HIV patients are associated with the presence of the dopamine transporter (DAT) 10/10-repeat allele which was also detected more frequently in HIV-infected individuals compared to uninfected subjects. In the current study, we investigated further whether other genetic dopamine (DA)-related polymorphisms may be related with changes in CSF DA levels and frequency of HIV infection in HIV-infected subjects. Specifically, we studied genetic polymorphisms of brain-derived neurotrophic factor, catechol-O-methyltransferase, and dopamine receptors DRD2, DRD3, and DRD4 genetic polymorphisms in uninfected and HIV-infected people in two different ethnical groups, a German cohort (Caucasian, 72 individuals with HIV infection and 22 individuals without HIV infection) and a South African cohort (Xhosan, 54 individuals with HIV infection and 19 individuals without HIV infection). We correlated the polymorphisms with CSF DA levels, HIV dementia score, CD4(+) T cell counts, and HIV viral load. None of the investigated DA-related polymorphisms was associated with altered CSF DA levels, CD4(+) T cell count, viral load, and HIV dementia score. The respective allele frequencies were equally distributed between HIV-infected patients and controls. Our findings do not show any influence of the studied genetic polymorphisms on CSF DA levels and HIV infection. This is in contrast to what we found previously for the DAT 3'UTR VNTR and highlights the specific role of the DAT VNTR in HIV infection and disease.

  20. Comparative investigation of electronic transport across three-dimensional nanojunctions

    NASA Astrophysics Data System (ADS)

    Wang, Yun-Peng; Zhang, X.-G.; Fry, J. N.; Cheng, Hai-Ping

    2017-02-01

    We show the thickness-dependent transition from metallic conduction to tunneling in three-dimensional (3D) Ag/Si/Ag nanojunctions through layer-by-layer electronic structure and quantum transport calculations. The transmission coefficients are calculated quantum mechanically within the framework of density functional theory in conjunction with nonequilibrium Green's function techniques. Thin junctions show nearly metallic character with no energy gap opening in Si layers due to the metal-induced interface states, and the transmission is independent of the stacking order of Si layers. An energy gap reemerges for Si layers deeply buried within thick junction, and the decay rate of transmission in this insulating region depends on the stacking order. Complex band analysis indicates that the decay of transmission is not determined by a single exponential constant but also depends on the available number of evanescent states. Calculating the electric resistance from the transmission coefficient requires a 3D generalization of the Landauer formula, which is not unique. We examine two approaches, the Landauer-Büttiker formula, with and without subtraction of the Sharvin resistance, and a semiclassical Boltzmann equation with boundary conditions defined by the transmission coefficients at the junction. We identify an empirical upper limit of ˜0.05 per channel in the transmission coefficient, below which the Landauer-Büttiker formula without the Sharvin resistance correction remains a good approximation. In the high transmission limit, the Landauer-Büttiker formula with Sharvin correction and the semiclassical Boltzmann method reach fair agreement.

  1. Investigation of air transportation technology at Ohio University, 1981. [loran

    NASA Technical Reports Server (NTRS)

    Mcfarland, R. H.

    1982-01-01

    The increased availability of Loran signals in the United States encouraged consideration of Loran for airborne applications. High quality signal processing to obtain effective signal-to-noise ratios which permit good reliability in position determination consistent with airborne applications is considered. Techniques for deriving air navigation quality information from Loran-C were investigated.

  2. Investigation of Laser Optical Biasing on the Quantum Transport Properties of n-InSb.

    DTIC Science & Technology

    1979-10-01

    Af-01578 NOTH TEXAS STATE UNIV DENTON DEPT OF PHYSICS FIG 20/12 INVESTIGATION OF LASER OPTICAL BIASING ON THE QUANTUM TRANSPORT -ETC(U) OCT 79 0 6...SEILER NOOO-76-C-0319 NCLASSIFIED NL MEEEEEEE4N VEt IC?) ’ ,~CUAL)SUMMARY E’--. C Ii Investigation of Laser Optical Biasing on the Quantum Transport Properties...the investigation of laser optical biasing ef- fects on the quantum transport properties of n-InSb is given for the period October 1, 1978 - September

  3. Rail accelerators for space transportation: An experimental investigation

    NASA Technical Reports Server (NTRS)

    Zana, L. M.; Kerslake, W. R.; Sturman, J. L.

    1986-01-01

    An experimental program was conducted at the Lewis Research Center with the objective of investigating the technical feasibility of rail accelerators for propulsion applications. Single-stage, plasma driven rail accelerators of small (4 by 6 mm) and medium (12.5 by 12.5 mm) bores were tested at peak accelerating currents of 50 to 450 kA. Streak-camera photography was used to provide a qualitative description of plasma armature acceleration. The effects of plasma blowby and varying bore pressure on the behavior of plasma armatures were studied.

  4. Measuring dopamine release in the human brain with PET

    SciTech Connect

    Volkow, N.D. |; Fowler, J.S.; Logan, J.; Wang, G.J.

    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.

  5. An investigation of turbulent transport in the extreme lower atmosphere

    NASA Technical Reports Server (NTRS)

    Koper, C. A., Jr.; Sadeh, W. Z.

    1975-01-01

    A model in which the Lagrangian autocorrelation is expressed by a domain integral over a set of usual Eulerian autocorrelations acquired concurrently at all points within a turbulence box is proposed along with a method for ascertaining the statistical stationarity of turbulent velocity by creating an equivalent ensemble to investigate the flow in the extreme lower atmosphere. Simultaneous measurements of turbulent velocity on a turbulence line along the wake axis were carried out utilizing a longitudinal array of five hot-wire anemometers remotely operated. The stationarity test revealed that the turbulent velocity is approximated as a realization of a weakly self-stationary random process. Based on the Lagrangian autocorrelation it is found that: (1) large diffusion time predominated; (2) ratios of Lagrangian to Eulerian time and spatial scales were smaller than unity; and, (3) short and long diffusion time scales and diffusion spatial scales were constrained within their Eulerian counterparts.

  6. Structure and transport investigations on lithium-iron-phosphate glasses

    NASA Astrophysics Data System (ADS)

    Banday, Azeem; Sharma, Monika; Murugavel, Sevi

    2016-05-01

    Cathode materials for Lithium Ion Batteries (LIB's) are being constantly studied and reviewed especially in the past few decades. LiFePO4 (LFP) is one of the most potential candidates in the pedigree of cathode materials and has been under extensive study ever since. In this work, we report the synthesis of amorphous analogs of crystallite LFP by conventional melt quenching method. Thermal study by using differential scanning calorimetry (DSC) was used to determine the glass transition Tg and crystallization Tc temperatures on the obtained glass sample Fourier transform infrared (FTIR) absorption spectroscopy is being used to investigate the structural properties of the glass sample. The intrinsic electrical conductivity measurements were done using broad-band impedance spectroscopy with wide different temperature ranges. The conduction mechanism is described by non-adiabatic small polaron hopping between nearest neighbors. Based on the obtained results, we suggest that the glassy LFP is more suitable cathode material as compared to its crystalline counterpart.

  7. An Investigation of a Thermal Ice-Prevention System for a Twin-Engine Transport Airplane

    NASA Technical Reports Server (NTRS)

    Jones, Alun R

    1946-01-01

    Several previously published reports on a comprehensive investigation of a thermal ice-prevention system for a typical twin-engine transport airplane are correlated with some unpublished data to present the entire investigation in one publication. Several previously published reports on a comprehensive investigation of a thermal ice-prevention system for a typical twin-engine transport airplane are correlated with some unpublished data to present the entire investigation in one publication. The thermal system investigated was based upon the transfer of heat from the engine exhaust gas to air, which is then caused to flow along the inner surface of any portion of the airplane for which protection is desired.

  8. Investigation of hydrate formation and transportability in multiphase flow systems

    NASA Astrophysics Data System (ADS)

    Grasso, Giovanny A.

    cohesion force (3.32 mN/m). These measurements prove the importance of natural surfactants in crude oil for particle dispersion. An experimental methodology was provided to determine the effectiveness of asphaltenes as a dispersant. Even though hydrate deposition was inferred from the flowloop tests, it could not be verified from these measurements. Custom-made experimental set-ups (a recirculation liquid system, a rocking cell and a lab-scale mini-loop) were used to isolate the hydrate deposi- tion investigation. Besides water, mineral oil 70T and King Ranch condensate were used in combination with water for the deposition investigation. One of the most important deliverables of this thesis was the construction of a lab-scale flowloop that provides insight on deposition phenomenon in multiphase flow, representing the only set-up, reported in the literature, suitable for this investigation. The miniloop can handle gas-liquid flow (maximum flow rates of 10 Nm3/m for gas and 22 GPM for liquid) through a 10 ft. long straight section (2 in. standard tubing). The testing section (30 in. long) was designed to observe hydrate deposition on the wall. Three mechanisms of hydrate deposition were identified: film growth, particles adhering and particle bedding. The maximum water conversions were: 27.5 ml in the rocking cell, 2400 ml in the miniloop with 100 % WC and 250 ml in the miniloop for dispersed water in mineral oil 70T. The measured DP across to the testing section ranged from 0 to 8 in. H2O. Deposits were obtained for different flow regimes, including 100 % LL, stratified, stratified- wavy and slug flow. The maximum deposit thickness was 1.5 in., obtained in the gas flowing section. When deposits form from particle cohesion, they were easy to slough. From all the experimental worked in this thesis, hydrates accumulated depending on the degrees of subcooling of the bulk fluid, film growth (between 3 to 5 F), deposition from a combination of film growth and particle cohesion

  9. Exposure to the polybrominated diphenyl ether mixture DE-71 damages the nigrostriatal dopamine system: role of dopamine handling in neurotoxicity.

    PubMed

    Bradner, Joshua M; Suragh, Tiffany A; Wilson, W Wyatt; Lazo, Carlos R; Stout, Kristen A; Kim, Hye Mi; Wang, Min Z; Walker, Douglas I; Pennell, Kurt D; Richardson, Jason R; Miller, Gary W; Caudle, W Michael

    2013-03-01

    In the last several decades polybrominated diphenyl ethers (PBDEs) have replaced the previously banned polychlorinated biphenyls (PCBs) in multiple flame retardant utilities. As epidemiological and laboratory studies have suggested PCBs as a risk factor for Parkinson's disease (PD), the similarities between PBDEs and PCBs suggest that PBDEs have the potential to be neurotoxic to the dopamine system. The purpose of this study was to evaluate the neurotoxic effects of the PBDE mixture, DE-71, on the nigrostriatal dopamine system and address the role of altered dopamine handling in mediating this neurotoxicity. Using an in vitro model system we found DE-71 effectively caused cell death in a dopaminergic cell line as well as reducing the number of TH+ neurons isolated from VMAT2 WT and LO animals. Assessment of DE-71 neurotoxicity in vivo demonstrated significant deposition of PBDE congeners in the brains of mice, leading to reductions in striatal dopamine and dopamine handling, as well as reductions in the striatal dopamine transporter (DAT) and VMAT2. Additionally, DE-71 elicited a significant locomotor deficit in the VMAT2 WT and LO mice. However, no change was seen in TH expression in dopamine terminal or in the number of dopamine neurons in the substantia nigra pars compacta (SNpc). To date, these are the first data to demonstrate that exposure to PBDEs disrupts the nigrostriatal dopamine system. Given their similarities to PCBs, additional laboratory and epidemiological research should be considered to assess PBDEs as a potential risk factor for PD and other neurological disorders.

  10. How does fiction reading influence empathy? An experimental investigation on the role of emotional transportation.

    PubMed

    Bal, P Matthijs; Veltkamp, Martijn

    2013-01-01

    The current study investigated whether fiction experiences change empathy of the reader. Based on transportation theory, it was predicted that when people read fiction, and they are emotionally transported into the story, they become more empathic. Two experiments showed that empathy was influenced over a period of one week for people who read a fictional story, but only when they were emotionally transported into the story. No transportation led to lower empathy in both studies, while study 1 showed that high transportation led to higher empathy among fiction readers. These effects were not found for people in the control condition where people read non-fiction. The study showed that fiction influences empathy of the reader, but only under the condition of low or high emotional transportation into the story.

  11. How Does Fiction Reading Influence Empathy? An Experimental Investigation on the Role of Emotional Transportation

    PubMed Central

    Bal, P. Matthijs; Veltkamp, Martijn

    2013-01-01

    The current study investigated whether fiction experiences change empathy of the reader. Based on transportation theory, it was predicted that when people read fiction, and they are emotionally transported into the story, they become more empathic. Two experiments showed that empathy was influenced over a period of one week for people who read a fictional story, but only when they were emotionally transported into the story. No transportation led to lower empathy in both studies, while study 1 showed that high transportation led to higher empathy among fiction readers. These effects were not found for people in the control condition where people read non-fiction. The study showed that fiction influences empathy of the reader, but only under the condition of low or high emotional transportation into the story. PMID:23383160

  12. Investigation of Thermal Creep and Thermal Stress Effects in Microgravity Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Mackowski, D. W. (Principal Investigator); Knight, R. W. (Principal Investigator)

    1996-01-01

    Reported here are the results of our numerical investigation into the mechanisms which affect the transport and growth processes in physical vapor transport (PVT) crystal growth ampoules. The first part of the report consists of a brief summary of the major accomplishments and conclusions of our work. The second part consists of two manuscripts, submitted to the Journal of Crystal Growth, which provided a detailed description of the findings in our investigation.

  13. HIV-1 transgenic rats display an increase in [3H]dopamine uptake in the prefrontal cortex and striatum

    PubMed Central

    Zhu, Jun; Yuan, Yaxia; Midde, Narasimha M.; Gomez, Adrian M.; Sun, Wei-Lun; Quizon, Pamela M.; Zhan, Chang-Guo

    2017-01-01

    HIV viral proteins within the central nervous system are associated with the development of neurocognitive impairments in HIV-infected individuals. Dopamine transporter (DAT)-mediated dopamine transport is critical for normal dopamine homeostasis. Abnormal dopaminergic transmission has been implicated as a risk determinant of HIV-induced neurocognitive impairments. Our published work has demonstrated that Tat-induced inhibition of DAT is mediated by allosteric binding site(s) on DAT, not the interaction with the dopamine uptake site. The present study investigated whether impaired DAT function induced by Tat exposure in vitro can be documented in HIV-1 transgenic (HIV-1Tg) rats. We assessed kinetic analyses of [3H]dopamine uptake into prefrontal and striatal synaptosomes of HIV-1Tg and Fisher 344 rats. Compared with Fisher 344 rats, the capacity of dopamine transport in the prefrontal cortex (PFC) and striatum of HIV-1Tg rats was increased by 34% and 32%, respectively. Assessment of surface biotinylation indicated that DAT expression in the plasma membrane was reduced in PFC and enhanced in striatum, respectively, of HIV-1Tg rats. While the maximal binding sites (Bmax) of [3H]WIN 35,428 was decreased in striatum of HIV-1Tg rats, an increase in DAT turnover proportion was found, relative to Fisher 344 rats. Together, these findings suggest that neuroadaptive changes in DAT function are evidenced in the HIV-1Tg rats, perhaps compensating for viral protein-induced abnormal dopaminergic transmission. Thus, our study provides novel insights into understanding mechanism underlying neurocognitive impairment evident in neuroAIDS. PMID:26501780

  14. What Mechanisms Are Responsible for the Reuptake of Levodopa-Derived Dopamine in Parkinsonian Striatum?

    PubMed Central

    Nishijima, Haruo; Tomiyama, Masahiko

    2016-01-01

    Levodopa is the most effective medication for motor symptoms in Parkinson's disease. However, various motor and non-motor complications are associated with levodopa treatment, resulting from altered levodopa-dopamine metabolism with disease progression and long-term use of the drug. The present review emphasizes the role of monoamine transporters other than the dopamine transporter in uptake of extracellular dopamine in the dopamine-denervated striatum. When dopaminergic neurons are lost and dopamine transporters decreased, serotonin and norepinephrine transporters compensate by increasing uptake of excessive extracellular dopamine in the striatum. Organic cation transporter-3 and plasma membrane monoamine transporter, low affinity, and high capacity transporters, also potentially uptake dopamine when high-affinity transporters do not work normally. Selective serotonin reuptake inhibitors and serotonin norepinephrine reuptake inhibitors are often administered to patients with Parkinson's disease presenting with depression, pain or other non-motor symptoms. Thus, it is important to address the potential of these drugs to modify dopamine metabolism and uptake through blockade of the compensatory function of these transporters, which could lead to changes in motor symptoms of Parkinson's disease. PMID:28018168

  15. How Addictive Drugs Disrupt Presynaptic Dopamine Neurotransmission

    PubMed Central

    Sulzer, David

    2011-01-01

    The fundamental principle that unites addictive drugs appears to be that each enhances synaptic dopamine by means that dissociate it from normal behavioral control, so that they act to reinforce their own acquisition. This occurs via the modulation of synaptic mechanisms involved in learning, including enhanced excitation or disinhibition of dopamine neuron activity, blockade of dopamine reuptake, and altering the state of the presynaptic terminal to enhance evoked over basal transmission. Amphetamines offer an exception to such modulation in that they combine multiple effects to produce non-exocytic stimulation-independent release of neurotransmitter via reverse transport independent from normal presynaptic function. Questions on the molecular actions of addictive drugs, prominently including the actions of alcohol and solvents, remain unresolved, but their ability to co-opt normal presynaptic functions helps to explain why treatment for addiction has been challenging. PMID:21338876

  16. Methylphenidate normalizes elevated dopamine transporter densities in an animal model of the attention-deficit/hyperactivity disorder combined type, but not to the same extent in one of the attention-deficit/hyperactivity disorder inattentive type.

    PubMed

    Roessner, V; Sagvolden, T; Dasbanerjee, T; Middleton, F A; Faraone, S V; Walaas, S I; Becker, A; Rothenberger, A; Bock, N

    2010-06-02

    The spontaneously hypertensive rat (SHR/NCrl) is a validated model of attention-deficit/hyperactivity disorder (ADHD) combined subtype, whereas a recently identified substrain of the Wistar Kyoto rat (WKY/NCrl) is a model of ADHD inattentive subtype. In this study, we first examined the expression of genes involved in dopamine signaling and metabolism in the dorsal striatum and ventral mesencephalon of these two rat strains, as well as three reference control strains (WKY/NHsd, WK/HanTac, and SD/NTac) using quantitative real time RT-PCR. Next, striatal dopamine transporter (DAT) density was determined by ligand binding assay in the two ADHD-like strains at different developmental stages and after methylphenidate treatment. In adult rats, the mRNA expression of DAT and tyrosine hydroxylase was elevated in SHR/NCrl and WKY/NCrl rats compared to control strains, with differences between SHR/NCrl and WKY/NCrl rats also evident. During normal development, changes of striatal DAT densities occurred in both strains with lower densities in WKY/NCrl compared to SHR/NCrl after day 25. Two-weeks methylphenidate treatment during different developmental stages was associated with decreased striatal DAT density in both rat strains compared to the non-treated rats with more pronounced effects followed prepubertal treatment. These results suggest differences in the pathophysiology of the combined versus the predominantly inattentive animal model of ADHD. Finally, treatment with methylphenidate might reduce elevated DAT levels more effectively in the combined subtype especially when applied before puberty.

  17. ILLICIT DOPAMINE TRANSIENTS: RECONCILING ACTIONS OF ABUSED DRUGS

    PubMed Central

    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

  18. In-situ Investigation of Vanadium Ion Transport in Redox Flow Battery

    SciTech Connect

    Luo, Qingtao; Li, Liyu; Nie, Zimin; Wang, Wei; Wei, Xiaoliang; Li, Bin; Chen, Baowei; Yang, Zhenguo

    2012-06-27

    We will show a new method to differentiate the vanadium transport from concentration gradient and that from electric field. Flow batteries with vanadium and iron redox couples as the electro-active species were employed to investigate the transport behavior of vanadium ions in the presence of electric field. It was shown that electric field accelerated the positive-to-negative and reduced the negative-to-positive vanadium ions transport in charge process and affected the vanadium ions transport in an opposite way in discharge process. In addition, a method was designed to differentiate the concentration gradient-driven vanadium ions diffusion and electric field-driven vanadium ions migration. Simplified mathematical model was established to simulate the vanadium ions transport in real charge-discharge operation of flow battery. The concentration gradient diffusion coefficients and electric-migration coefficients of V2+, V3+, VO2+, and VO2+ across Nafion membrane were obtained by fitting the experimental data.

  19. Sex and temporally-dependent effects of methamphetamine toxicity on dopamine markers and signaling pathways.

    PubMed

    Bourque, Mélanie; Dluzen, Dean E; Di Paolo, Thérèse

    2012-06-01

    Methamphetamine induces a greater neurodegenerative effect in male versus female mice. In order to investigate this sex difference we studied the involvement of Akt and extracellular signal-regulated kinase (ERK1/2) in methamphetamine toxicity as a function of time post-treatment (30 min, 1 and 3 days). Methamphetamine-induced decreases in dopamine concentrations and dopamine transporter (DAT) specific binding in the medial striatum were similar in female and male mice when evaluated 1 day post-methamphetamine (40 mg/kg). At 3 days post-methamphetamine, striatal dopamine concentration and DAT specific binding continued to decline in males, whereas females showed a recovery with increases in dopamine content and DAT specific binding in medial striatum at day 3 versus day 1 post-methamphetamine. The reduction in striatal vesicular monoamine transporter 2 specific binding observed at 1 and 3 days post-methamphetamine showed neither a sex- nor temporal-dependent effect. Under the present experimental conditions, methamphetamine treatments had modest effects on dopamine markers measured in the substantia nigra. Proteins assessed by Western blots showed similar reductions in both female and male mice for DAT proteins at 1 and 3 days post-methamphetamine. An increase in the phosphorylation of striatal Akt (after 1 day), glycogen synthase kinase 3β (at 1 and 3 days) and ERK1/2 (30 min post-methamphetamine) was only observed in females. Striatal glial fibrillary acidic protein levels were augmented in both females and males at 3 days post-methamphetamine. These results reveal some of the sex- and temporally-dependent effects of methamphetamine toxicity on dopaminergic markers and suggest some of the signaling pathways associated with these responses.

  20. Plasmalogen Augmentation Reverses Striatal Dopamine Loss in MPTP Mice

    PubMed Central

    Miville-Godbout, Edith; Bourque, Mélanie; Morissette, Marc; Al-Sweidi, Sara; Smith, Tara; Mochizuki, Asuka; Senanayake, Vijitha; Jayasinghe, Dushmanthi; Wang, Li; Goodenowe, Dayan; Di Paolo, Thérèse

    2016-01-01

    Plasmalogens are a class of glycerophospholipids shown to play critical roles in membrane structure and function. Decreased plasmalogens are reported in the brain and blood of Parkinson’s disease (PD) patients. The present study investigated the hypothesis that augmenting plasmalogens could protect striatal dopamine neurons that degenerate in response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment in mice, a PD model. First, in a pre-treatment experiment male mice were treated for 10 days with the docosahexaenoic acid (DHA)-plasmalogen precursor PPI-1011 (10, 50 and 200 mg/kg). On day 5 mice received MPTP and were killed on day 11. Next, in a post-treatment study, male mice were treated with MPTP and then received daily for 5 days PPI-1011 (5, 10 and 50 mg/kg). MPTP treatment reduced serum plasmalogen levels, striatal contents of dopamine (DA) and its metabolites, serotonin, DA transporter (DAT) and vesicular monoamine transporter 2 (VMAT2). Pre-treatment with PPI-1011 (10 and 50 mg/kg) prevented all MPTP-induced effects. Positive correlations were measured between striatal DA contents and serum plasmalogen levels as well as striatal DAT and VMAT2 specific binding. Post-treatment with PPI-1011 prevented all MPTP-induced effects at 50 mg/kg but not at lower doses. Positive correlations were measured between striatal DA contents and serum plasmalogen levels as well as striatal DAT and VMAT2 specific binding in the post-treatment experiment. PPI-1011 treatment (10 days at 5, 10 and 50 mg/kg) of intact mice left unchanged striatal biogenic amine contents. These data demonstrate that treatment with a plasmalogen precursor is capable of protecting striatal dopamine markers in an animal model of PD. PMID:26959819