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Federici M, Latagliata EC, Ledonne A, Rizzo FR, Feligioni M, Sulzer D, Dunn M, Sames D, Gu H, Nisticò R, Puglisi-Allegra S, Mercuri NB. Paradoxical abatement of striatal dopaminergic transmission by cocaine and methylphenidate. J Biol Chem 2013; 289:264-74. [PMID: 24280216 DOI: 10.1074/jbc.m113.495499] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We combined in vitro amperometric, optical analysis of fluorescent false neurotransmitters and microdialysis techniques to unveil that cocaine and methylphenidate induced a marked depression of the synaptic release of dopamine (DA) in mouse striatum. In contrast to the classical dopamine transporter (DAT)-dependent enhancement of the dopaminergic signal observed at concentrations of cocaine lower than 3 μM, the inhibitory effect of cocaine was found at concentrations higher than 3 μM. The paradoxical inhibitory effect of cocaine and methylphenidate was associated with a decrease in synapsin phosphorylation. Interestingly, a cocaine-induced depression of DA release was only present in cocaine-insensitive animals (DAT-CI). Similar effects of cocaine were produced by methylphenidate in both wild-type and DAT-CI mice. On the other hand, nomifensine only enhanced the dopaminergic signal either in wild-type or in DAT-CI mice. Overall, these results indicate that cocaine and methylphenidate can increase or decrease DA neurotransmission by blocking reuptake and reducing the exocytotic release, respectively. The biphasic reshaping of DA neurotransmission could contribute to different behavioral effects of psychostimulants, including the calming ones, in attention deficit hyperactivity disorder.
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Affiliation(s)
- Mauro Federici
- From the Laboratorio di Neurologia Sperimentale, Istituto Ricovero e Cura a carattere scientifico (IRCCS) Fondazione Santa Lucia, 00143 Rome, Italy
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52
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Park SY, Kang UG. Hypothetical dopamine dynamics in mania and psychosis--its pharmacokinetic implications. Prog Neuropsychopharmacol Biol Psychiatry 2013; 43:89-95. [PMID: 23268190 DOI: 10.1016/j.pnpbp.2012.12.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 11/28/2012] [Accepted: 12/18/2012] [Indexed: 11/27/2022]
Abstract
The symptoms of psychosis and mania are both related to dopaminergic hyperactivity. In psychosis, it is proposed that post-synaptic receptor sensitization causes dysfunctional salience processing, leading to the development of delusional symptoms. In various animal models of psychosis, the mechanism of post-synaptic sensitization is related to the increased proportion of high-affinity D2 receptors. On the other hand, psychostimulant-induced increase in synaptic dopamine can serve as a model for manic distractibility. In this study, brief models were constructed to identify the differences in dopaminergic hyperactivity between psychosis and mania, and the effects of antipsychotics were sought in terms of the dynamics of dopamine receptor occupancy. According to the study, it was found that antipsychotics with small Koff value had advantages in restoring the receptor occupancy to normal level in the psychosis model, while in the mania model, those with large Koff value showed a better profile.
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Affiliation(s)
- Seo Yeon Park
- Department of Neuropsychiatry, Seoul National University Hospital, Seoul, Republic of Korea
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53
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Vickrey TL, Xiao N, Venton BJ. Kinetics of the dopamine transporter in Drosophila larva. ACS Chem Neurosci 2013; 4:832-7. [PMID: 23600464 DOI: 10.1021/cn400019q] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Dopamine transporters (DAT) regulate neurotransmission and are important in diseases such as addiction and attention deficit hyperactivity disorder. The Drosophila dopamine transporter (dDAT) is analogous to the mammalian DAT, but Michaelis-Menten kinetic parameters have not been characterized in vivo. In this study, dopamine clearance kinetics were measured in a Drosophila larval CNS using an implanted carbon-fiber microelectrode and fast-scan cyclic voltammetry. Dopamine was pressure ejected from a micropipet implanted 15-20 μm from the microelectrode. Clearance of exogenously applied dopamine was significantly reduced in dDAT null (fumin) mutants, and kinetic constants in these mutants were used to determine clearance by other mechanisms including diffusion. After correction for diffusion, the maximal rate of uptake, Vmax, was estimated to be 0.11 ± 0.02 μM/s and Km was 1.3 ± 0.6 μM in wild-type flies. The clearance rate was significantly reduced following treatment with the DAT inhibitor cocaine in wild-type flies, but not in fumin mutants, which indicates that serotonin transporter is not contributing significantly to dopamine clearance in these larvae. Clearance of endogenous dopamine, evoked by optical stimulation in flies expressing Channelrhodopsin2, was similar to clearance of exogenous dopamine, but it was not possible to evoke concentrations that were close to saturation. The ability to quickly assess the role of the dopamine transporter in any Drosophila larva will be useful for future studies of how transporters regulate neurotransmission and to understand the underlying mechanisms of drug addiction.
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Affiliation(s)
- Trisha L. Vickrey
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Ning Xiao
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - B. Jill Venton
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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54
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Wood KM, Hashemi P. Fast-scan cyclic voltammetry analysis of dynamic serotonin reponses to acute escitalopram. ACS Chem Neurosci 2013; 4:715-20. [PMID: 23597074 DOI: 10.1021/cn4000378] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The treatment of depression with selective serotonin reuptake inhibitors, SSRIs, is important to study on a neurochemical level because of the therapeutic variability experienced by many depressed patients. We employed the rapid temporal capabilities of fast scan cyclic voltammetry at carbon fiber microelectrodes to study the effects of a popular SSRI, escitalopram (ESCIT), marketed as Lexapro, on serotonin in mice. We report novel, dynamic serotonin behavior after acute ESCIT doses, characterized by a rapid increase in stimulated serotonin release and a gradual rise in serotonin clearance over 120 min. Dynamic changes after acute SSRI doses may be clinically relevant to the pathology of increased depression or suicidality after onset of antidepressant treatment. Due to the short-term variability of serotonin responses after acute ESCIT, we outline difficulties in creating dose response curves and we suggest effective means to visualize dynamic serotonin changes after SSRIs. Correlating chemical serotonin patterns to clinical findings will allow a finer understanding of SSRI mechanisms, ultimately providing a platform for reducing therapeutic variability.
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Affiliation(s)
- Kevin M. Wood
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States
| | - Parastoo Hashemi
- Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, United States
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55
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Ferris MJ, Calipari ES, Yorgason JT, Jones SR. Examining the complex regulation and drug-induced plasticity of dopamine release and uptake using voltammetry in brain slices. ACS Chem Neurosci 2013; 4:693-703. [PMID: 23581570 DOI: 10.1021/cn400026v] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Fast scan cyclic voltammetry in brain slices (slice voltammetry) has been used over the last several decades to increase substantially our understanding of the complex local regulation of dopamine release and uptake in the striatum. This technique is routinely used for the study of changes that occur in the dopamine system associated with various disease states and pharmacological treatments, and to study mechanisms of local circuitry regulation of dopamine terminal function. In the context of this Review, we compare the relative advantages of voltammetry using striatal slice preparations versus in vivo preparations, and highlight recent advances in our understanding of dopamine release and uptake in the striatum specifically from studies that use slice voltammetry in drug-naïve animals and animals with a history of psychostimulant self-administration.
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Affiliation(s)
- Mark J. Ferris
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Erin S. Calipari
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Jordan T. Yorgason
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Sara R. Jones
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
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56
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Covey DP, Juliano SA, Garris PA. Amphetamine elicits opposing actions on readily releasable and reserve pools for dopamine. PLoS One 2013; 8:e60763. [PMID: 23671560 PMCID: PMC3643976 DOI: 10.1371/journal.pone.0060763] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 03/02/2013] [Indexed: 11/18/2022] Open
Abstract
Amphetamine, a highly addictive drug with therapeutic efficacy, exerts paradoxical effects on the fundamental communication modes employed by dopamine neurons in modulating behavior. While amphetamine elevates tonic dopamine signaling by depleting vesicular stores and driving non-exocytotic release through reverse transport, this psychostimulant also activates phasic dopamine signaling by up-regulating vesicular dopamine release. We hypothesized that these seemingly incongruent effects arise from amphetamine depleting the reserve pool and enhancing the readily releasable pool. This novel hypothesis was tested using in vivo voltammetry and stimulus trains of varying duration to access different vesicular stores. We show that amphetamine actions are stimulus dependent in the dorsal striatum. Specifically, amphetamine up-regulated vesicular dopamine release elicited by a short-duration train, which interrogates the readily releasable pool, but depleted release elicited by a long-duration train, which interrogates the reserve pool. These opposing actions of vesicular dopamine release were associated with concurrent increases in tonic and phasic dopamine responses. A link between vesicular depletion and tonic signaling was supported by results obtained for amphetamine in the ventral striatum and cocaine in both striatal sub-regions, which demonstrated augmented vesicular release and phasic signals only. We submit that amphetamine differentially targeting dopamine stores reconciles the paradoxical activation of tonic and phasic dopamine signaling. Overall, these results further highlight the unique and region-distinct cellular mechanisms of amphetamine and may have important implications for its addictive and therapeutic properties.
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Affiliation(s)
- Dan P. Covey
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Steven A. Juliano
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Paul A. Garris
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
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57
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An H, Sohn H, Chung S. Phentermine, sibutramine and affective disorders. CLINICAL PSYCHOPHARMACOLOGY AND NEUROSCIENCE 2013; 11:7-12. [PMID: 23678348 PMCID: PMC3650299 DOI: 10.9758/cpn.2013.11.1.7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 11/12/2012] [Accepted: 12/04/2012] [Indexed: 12/16/2022]
Abstract
A safe and effective way to control weight in patients with affective disorders is needed, and phentermine is a possible candidate. We performed a PubMed search of articles pertaining to phentermine, sibutramine, and affective disorders. We compared the studies of phentermine with those of sibutramine. The search yielded a small number of reports. Reports concerning phentermine and affective disorders reported that i) its potency in the central nervous system may be comparatively low, and ii) it may induce depression in some patients. We were unable to find more studies on the subject; thus, it is unclear presently whether phentermine use is safe in affective disorder patients. Reports regarding the association of sibutramine and affective disorders were slightly more abundant. A recent study that suggested that sibutramine may have deleterious effects in patients with a psychiatric history may provide a clue for future phentermine research. Three explanations are possible concerning the association between phentermine and affective disorders: i) phentermine, like sibutramine, may have a depression-inducing effect that affects a specific subgroup of patients, ii) phentermine may have a dose-dependent depression-inducing effect, or iii) phentermine may simply not be associated with depression. Large-scale studies with affective disorder patients focusing on these questions are needed to clarify this matter before investigation of its efficacy may be carried out and it can be used in patients with affective disorders.
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Affiliation(s)
- Hoyoung An
- Department of Psychiatry, Jeju Medical Center, Jeju, Korea
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58
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Abstract
Drugs of abuse hijack brain-reward circuitry during the addiction process by augmenting action potential-dependent phasic dopamine release events associated with learning and goal-directed behavior. One prominent exception to this notion would appear to be amphetamine (AMPH) and related analogs, which are proposed instead to disrupt normal patterns of dopamine neurotransmission by depleting vesicular stores and promoting nonexocytotic dopamine efflux via reverse transport. This mechanism of AMPH action, though, is inconsistent with its therapeutic effects and addictive properties, which are thought to be reliant on phasic dopamine signaling. Here we used fast-scan cyclic voltammetry in freely moving rats to interrogate principal neurochemical responses to AMPH in the striatum and relate these changes to behavior. First, we showed that AMPH dose-dependently enhanced evoked dopamine responses to phasic-like current pulse trains for up to 2 h. Modeling the data revealed that AMPH inhibited dopamine uptake but also unexpectedly potentiated vesicular dopamine release. Second, we found that AMPH increased the amplitude, duration, and frequency of spontaneous dopamine transients, the naturally occurring, nonelectrically evoked, phasic increases in extracellular dopamine. Finally, using an operant sugar reward paradigm, we showed that low-dose AMPH augmented dopamine transients elicited by sugar-predictive cues. However, operant behavior failed at high-dose AMPH, which was due to phasic dopamine hyperactivity and the decoupling of dopamine transients from the reward predictive cue. These findings identify upregulation of exocytotic dopamine release as a key AMPH action in behaving animals and support a unified mechanism of abused drugs to activate phasic dopamine signaling.
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59
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Baumann MH, Partilla JS, Lehner KR, Thorndike EB, Hoffman AF, Holy M, Rothman RB, Goldberg SR, Lupica CR, Sitte HH, Brandt SD, Tella SR, Cozzi NV, Schindler CW. Powerful cocaine-like actions of 3,4-methylenedioxypyrovalerone (MDPV), a principal constituent of psychoactive 'bath salts' products. Neuropsychopharmacology 2013; 38:552-62. [PMID: 23072836 PMCID: PMC3572453 DOI: 10.1038/npp.2012.204] [Citation(s) in RCA: 316] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The abuse of psychoactive 'bath salts' containing cathinones such as 3,4-methylenedioxypyrovalerone (MDPV) is a growing public health concern, yet little is known about their pharmacology. Here, we evaluated the effects of MDPV and related drugs using molecular, cellular, and whole-animal methods. In vitro transporter assays were performed in rat brain synaptosomes and in cells expressing human transporters, while clearance of endogenous dopamine was measured by fast-scan cyclic voltammetry in mouse striatal slices. Assessments of in vivo neurochemistry, locomotor activity, and cardiovascular parameters were carried out in rats. We found that MDPV blocks uptake of [(3)H]dopamine (IC(50)=4.1 nM) and [(3)H]norepinephrine (IC(50)=26 nM) with high potency but has weak effects on uptake of [(3)H]serotonin (IC(50)=3349 nM). In contrast to other psychoactive cathinones (eg, mephedrone), MDPV is not a transporter substrate. The clearance of endogenous dopamine is inhibited by MDPV and cocaine in a similar manner, but MDPV displays greater potency and efficacy. Consistent with in vitro findings, MDPV (0.1-0.3 mg/kg, intravenous) increases extracellular concentrations of dopamine in the nucleus accumbens. Additionally, MDPV (0.1-3.0 mg/kg, subcutaneous) is at least 10 times more potent than cocaine at producing locomotor activation, tachycardia, and hypertension in rats. Our data show that MDPV is a monoamine transporter blocker with increased potency and selectivity for catecholamines when compared with cocaine. The robust stimulation of dopamine transmission by MDPV predicts serious potential for abuse and may provide a mechanism to explain the adverse effects observed in humans taking high doses of 'bath salts' preparations.
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Affiliation(s)
- Michael H Baumann
- Medicinal Chemistry Section of the Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD 21224, USA.
| | - John S Partilla
- Medicinal Chemistry Section of the Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Kurt R Lehner
- Medicinal Chemistry Section of the Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Eric B Thorndike
- Preclinical Pharmacology Section of the Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Alexander F Hoffman
- Electrophysiology Research Section of the Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Marion Holy
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Richard B Rothman
- Medicinal Chemistry Section of the Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Steven R Goldberg
- Preclinical Pharmacology Section of the Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Carl R Lupica
- Electrophysiology Research Section of the Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
| | - Harald H Sitte
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Simon D Brandt
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Liverpool, UK
| | - Srihari R Tella
- Drug and Chemical Evaluation Section, Office of Diversion Control, Drug Enforcement Administration, Springfield, VA, USA
| | - Nicholas V Cozzi
- Neuropharmacology Laboratory, Department of Cell and Regenerative Biology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA
| | - Charles W Schindler
- Preclinical Pharmacology Section of the Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, USA
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60
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Yorgason JT, España RA, Konstantopoulos JK, Weiner JL, Jones SR. Enduring increases in anxiety-like behavior and rapid nucleus accumbens dopamine signaling in socially isolated rats. Eur J Neurosci 2013; 37:1022-31. [PMID: 23294165 DOI: 10.1111/ejn.12113] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 11/15/2012] [Accepted: 11/28/2012] [Indexed: 01/02/2023]
Abstract
Social isolation (SI) rearing, a model of early life stress, results in profound behavioral alterations, including increased anxiety-like behavior, impaired sensorimotor gating and increased self-administration of addictive substances. These changes are accompanied by alterations in mesolimbic dopamine function, such as increased dopamine and metabolite tissue content, increased dopamine responses to cues and psychostimulants, and increased dopamine neuron burst firing. Using voltammetric techniques, we examined the effects of SI rearing on dopamine transporter activity, vesicular release and dopamine D2-type autoreceptor activity in the nucleus accumbens core. Long-Evans rats were housed in group (GH; 4/cage) or SI (1/cage) conditions from weaning into early adulthood [postnatal day (PD) 28-77]. After this initial housing period, rats were assessed on the elevated plus-maze for an anxiety-like phenotype, and then slice voltammetry experiments were performed. To study the enduring effects of SI rearing on anxiety-like behavior and dopamine terminal function, another cohort of similarly reared rats was isolated for an additional 4 months (until PD 174) and then tested. Our findings demonstrate that SI rearing results in lasting increases in anxiety-like behavior, dopamine release and dopamine transporter activity, but not D2 activity. Interestingly, GH-reared rats that were isolated as adults did not develop the anxiety-like behavior or dopamine changes seen in SI-reared rats. Together, our data suggest that early life stress results in an anxiety-like phenotype, with lasting increases in dopamine terminal function.
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Affiliation(s)
- Jordan T Yorgason
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA
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61
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Espana RA, Jones SR. Presynaptic dopamine modulation by stimulant self-administration. Front Biosci (Schol Ed) 2013; 5:261-76. [PMID: 23277050 DOI: 10.2741/s371] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The mesolimbic dopamine system is an essential participant in the initiation and modulation of various forms of goal-directed behavior, including drug reinforcement and addiction processes. Dopamine neurotransmission is increased by acute administration of all drugs of abuse, including the stimulants cocaine and amphetamine. Chronic exposure to these drugs via voluntary self-administration provides a model of stimulant abuse that is useful in evaluating potential behavioral and neurochemical adaptations that occur during addiction. This review describes commonly used methodologies to measure dopamine and baseline parameters of presynaptic dopamine regulation, including exocytotic release and reuptake through the dopamine transporter in the nucleus accumbens core, as well as dramatic adaptations in dopamine neurotransmission and drug sensitivity that occur with acute non-contingent and chronic, contingent self-administration of cocaine and amphetamine.
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Affiliation(s)
- Rodrigo A Espana
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
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62
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Dreyer JK, Hounsgaard J. Mathematical model of dopamine autoreceptors and uptake inhibitors and their influence on tonic and phasic dopamine signaling. J Neurophysiol 2012; 109:171-82. [PMID: 23054599 DOI: 10.1152/jn.00502.2012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Dopamine (DA) D2-like autoreceptors are an important component of the DA system, but their influence on postsynaptic DA signaling is not well understood. They are, directly or indirectly, involved in drug abuse and in treatment of schizophrenia and attention deficit hyperactive disorder: DA autoreceptors influence the behavioral effect of cocaine and methylphenidate and may be the target of antipsychotic medications such as haloperidol. DA autoreceptors are active at two levels: Somatodendritic autoreceptors mainly influence firing rate of DA neurons, and presynaptic autoreceptors control release of neurotransmitter at axonal terminals. Here we develop a mathematical model that captures the dynamics of this dual autoregulation system. Our model predicts a biphasic autoreceptor response between DA terminals and somatodendritic regions that influences the postsynaptic integration of DAergic firing patterns. We applied our model to study how DA uptake inhibition affects the translation of DA cell firing into activation of postsynaptic DA receptors. While uptake inhibition increased tonic activation of low-affinity postsynaptic receptors, high-affinity state receptors saturated and thus became insensitive to phasic DA signaling. This effect had remarkable regional specificity: While high-affinity DA receptors saturated at low levels of uptake inhibition in nucleus accumbens, they only saturated at higher levels of uptake inhibition in dorsal striatum. Based on high-affinity receptor saturation, the model predicted that removal of autoreceptor control would lead to cocaine hypersensitivity.
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Affiliation(s)
- Jakob Kisbye Dreyer
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
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63
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Chadchankar H, Yavich L. Characterization of a 32 μm diameter carbon fiber electrode for in vivo fast-scan cyclic voltammetry. J Neurosci Methods 2012; 211:218-26. [PMID: 22995525 DOI: 10.1016/j.jneumeth.2012.09.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 09/09/2012] [Accepted: 09/11/2012] [Indexed: 10/27/2022]
Abstract
Carbon fiber electrodes (CFE) are commonly used for in vivo detection of catecholamines due to their excellent electrochemical properties and biocompatibility. Fast-scan cyclic voltammetry (FSCV) combined with CFEs permits the detection of catecholamines such as dopamine (DA) with high specificity and reliability. However, advances in neuroscience constantly demand sensors with greater sensitivities and selectivities. This study investigated an untreated CFE of 32 μm diameter and 300 μm exposed length for detection of DA using FSCV. Despite the larger area of the working electrode, we observed only a small increase in the background current in comparison with the commonly used CFE of 7 μm diameter and 100 μm exposed length. The sensitivity of the 32 μm CFE was 9 times greater than that of the 7 μm CFE. These larger electrodes exhibited good linearity and a 6 fold higher signal-to-noise ratio than 7 μm CFEs in vitro. The 32 μm CFE showed significantly better selectivity for DA in preference to 3,4-dihydroxyphenylacetic acid than the 7 μm CFE and similar selectivity to the 7 μm CFE for ascorbic and homovanillic acid. The electrodes displayed good temporal resolution and electrochemical stability in both in vitro and in vivo tests.
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Affiliation(s)
- Heramb Chadchankar
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Yliopistonranta 1, P.O. Box 1627, Kuopio 70211, Finland.
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64
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Ferris MJ, Calipari ES, Mateo Y, Melchior JR, Roberts DCS, Jones SR. Cocaine self-administration produces pharmacodynamic tolerance: differential effects on the potency of dopamine transporter blockers, releasers, and methylphenidate. Neuropsychopharmacology 2012; 37:1708-16. [PMID: 22395730 PMCID: PMC3358740 DOI: 10.1038/npp.2012.17] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The dopamine transporter (DAT) is the primary site of action for psychostimulant drugs such as cocaine, methylphenidate, and amphetamine. Our previous work demonstrated a reduced ability of cocaine to inhibit the DAT following high-dose cocaine self-administration (SA), corresponding to a reduced ability of cocaine to increase extracellular dopamine. However, this effect had only been demonstrated for cocaine. Thus, the current investigations sought to understand the extent to which cocaine SA (1.5 mg/kg/inf × 40 inf/day × 5 days) altered the ability of different dopamine uptake blockers and releasers to inhibit dopamine uptake, measured using fast-scan cyclic voltammetry in rat brain slices. We demonstrated that, similar to cocaine, the DAT blockers nomifensine and bupropion were less effective at inhibiting dopamine uptake following cocaine SA. The potencies of amphetamine-like dopamine releasers such as 3,4-methylenedioxymethamphetamine, methamphetamine, amphetamine, and phentermine, as well as a non-amphetamine releaser, 4-benzylpiperidine, were all unaffected. Finally, methylphenidate, which blocks dopamine uptake like cocaine while being structurally similar to amphetamine, shared characteristics of both, resembling an uptake blocker at low concentrations and a releaser at high concentrations. Combined, these experiments demonstrate that after high-dose cocaine SA, there is cross-tolerance of the DAT to other uptake blockers, but not releasers. The reduced ability of psychostimulants to inhibit dopamine uptake following cocaine SA appears to be contingent upon their functional interaction with the DAT as a pure blocker or releaser rather than their structural similarity to cocaine. Further, methylphenidate's interaction with the DAT is unique and concentration-dependent.
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Affiliation(s)
- Mark J Ferris
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA.
| | - Erin S Calipari
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Yolanda Mateo
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - James R Melchior
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - David CS Roberts
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Sara R Jones
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA
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65
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Kile BM, Walsh PL, McElligott ZA, Bucher ES, Guillot TS, Salahpour A, Caron MG, Wightman RM. Optimizing the Temporal Resolution of Fast-Scan Cyclic Voltammetry. ACS Chem Neurosci 2012; 3:285-292. [PMID: 22708011 DOI: 10.1021/cn200119u] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Electrochemical detection with carbon-fiber microelectrodes has become an established method to monitor directly the release of dopamine from neurons and its uptake by the dopamine transporter. With constant potential amperometry (CPA) the measured current provides a real time view of the rapid concentration changes, but the method lacks chemical identification of the monitored species and markedly increases the difficulty of signal calibration. Monitoring with fast-scan cyclic voltammetry (FSCV) allows species identification and concentration measurements, but often exhibits a delayed response time due to the time-dependent adsorption/desorption of electroactive species at the electrode. We sought to improve the temporal resolution of FSCV to make it more comparable to CPA by increasing the waveform repetition rate from 10 to 60 Hz with uncoated carbon-fiber electrodes. The faster acquisition led to diminished time delays of the recordings that tracked more closely with CPA measurements. The measurements reveal that FSCV at 10 Hz underestimates the normal rate of dopamine uptake by about 18%. However, FSCV collection at 10 Hz and 60 Hz provide identical results when a dopamine transporter (DAT) blocker such as cocaine is bath applied. To verify further the utility of this method, we used transgenic mice that over-express DAT. After accounting for the slight adsorption delay time, FSCV at 60 Hz adequately monitored the increased uptake rate that arose from overexpression of DAT and, again, was similar to CPA results. Furthermore, the utility of collecting data at 60 Hz was verified in an anesthetized rat by using a higher scan rate (2400 V/s) to increase sensitivity and the overall signal.
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Affiliation(s)
- Brian M. Kile
- Department of Chemistry and
Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United
States
| | - Paul L. Walsh
- Department of Chemistry and
Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United
States
| | - Zoé A. McElligott
- Department of Chemistry and
Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United
States
| | - Elizabeth S. Bucher
- Department of Chemistry and
Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United
States
| | - Thomas S. Guillot
- Department of Chemistry and
Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United
States
| | - Ali Salahpour
- Department of Pharmacology
and
Toxicology, University of Toronto, Toronto,
Ontario M5S 1A8, Canada
| | - Marc G. Caron
- Department
of Cell Biology, Duke University, Durham,
North Carolina 27710, United
States
| | - R. Mark Wightman
- Department of Chemistry and
Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United
States
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66
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Umezu T. Unusual effects of nicotine as a psychostimulant on ambulatory activity in mice. ISRN PHARMACOLOGY 2012; 2012:170981. [PMID: 22530136 PMCID: PMC3317018 DOI: 10.5402/2012/170981] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 12/26/2011] [Indexed: 01/08/2023]
Abstract
The present study examined the effect of nicotine, alone and in combination with various drugs that act on the CNS, on ambulatory activity, a behavioral index for locomotion, in ICR (CD-1) strain mice. Nicotine at 0.25–2 mg/kg acutely reduced ambulatory activity of ICR mice. The effect of nicotine was similar to that of haloperidol and fluphenazine but distinct from that of bupropion and methylphenidate. ICR mice developed tolerance against the inhibitory effect of nicotine on ambulatory activity when nicotine was repeatedly administered. This effect was also distinct from bupropion and methylphenidate as they produced augmentation of their ambulation-stimulating effects in ICR mice. Nicotine reduced the ambulation-stimulating effects of bupropion and methylphenidate as well as haloperidol and fluphenazine. Taken together, nicotine exhibited unusual effects as a psychostimulant on ambulatory activity in ICR mice.
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Affiliation(s)
- Toyoshi Umezu
- Biological Imaging and Analysis Section, Center for Environmental Measurement and Analysis, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506, Japan
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67
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Selective bilateral lesion to caudate nucleus modulates the acute and chronic methylphenidate effects. Pharmacol Biochem Behav 2012; 101:208-16. [PMID: 22260871 DOI: 10.1016/j.pbb.2012.01.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 12/29/2011] [Accepted: 01/04/2012] [Indexed: 11/21/2022]
Abstract
The psychostimulant methylphenidate (MPD) is currently the most prescribed drug therapy for attention deficit hyperactivity disorder (ADHD) and is used by students as a cognitive enhancer. The caudate nucleus (CN) is a structure within the motive circuit where MPD exerts its effects, it is known to contain high levels of dopaminergic cells and directly influence motor activity. The objective of this study was to understand the role of CN in response to acute and chronic administration of MPD. Specific and non-specific bilateral ablations were created in the CN using electrolytic lesion and 6-Hydoxydopamine (6-OHDA). Four groups of rats were used: control (n=4), sham (n=4), CN electrolytic lesion group (n=8) and CN 6-OHDA injected group (n=8). On experimental day one (ED 1) all rats received a saline injection and baseline locomotive activity was recorded. On ED 2 and ED 3 CN sham, electrolytic lesion and/or 6-OHDA injected groups were made followed by four to five days recovery (ED 3-7), followed by six daily 2.5 mg/kg MPD injections (ED 9-14), three days of washout (ED 15-17) and an MPD re-challenge of drug proceeding the washout days (ED 18). Locomotor activity was obtained at ED 1, 8, 9, and 18 using an open field assay. The results show that the CN electrolytic lesion group responded to the acute and chronic MPD administration similar to the control and sham group, while the CN 6-OHDA injected group prevented the acute and the chronic effects of MPD administration. One possible interpretation why nonspecific electroyltic lesioning of the CN failed to prevent acute and chronic effects of MPD administration is due to destruction of both the direct and the indirect CN pathways which act as an inhibitory/excitatory balance, electroylticelectroyltic. The selective dopaminergic lesioning prevented the effects of MPD administration suggesting that dopaminergic pathways in CN play a significant role in the effects of MPD.
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68
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Bosse KE, Maina FK, Birbeck JA, France MM, Roberts JJP, Colombo ML, Mathews TA. Aberrant striatal dopamine transmitter dynamics in brain-derived neurotrophic factor-deficient mice. J Neurochem 2011; 120:385-95. [PMID: 21988371 DOI: 10.1111/j.1471-4159.2011.07531.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Brain-derived neurotrophic factor (BDNF) modulates the synaptic transmission of several monoaminergic neuronal systems, including forebrain dopamine-containing neurons. Recent evidence shows a strong correlation between neuropsychiatric disorders and BDNF hypofunction. The aim of the present study was to characterize the effect of low endogenous levels of BDNF on dopamine system function in the caudate-putamen using heterozygous BDNF (BDNF(+/-) ) mice. Apparent extracellular dopamine levels in the caudate-putamen, determined by quantitative microdialysis, were significantly elevated in BDNF(+/-) mice compared with wildtype controls (12 vs. 5 nM, respectively). BDNF(+/-) mice also had a potentiated increase in dopamine levels following potassium (120 mM)-stimulation (10-fold) relative to wildtype controls (6-fold). Slice fast-scan cyclic voltammetry revealed that BDNF(+/-) mice had reductions in both electrically evoked dopamine release and dopamine uptake rates in the caudate-putamen. Superfusion of BDNF led to partial recovery of the electrically stimulated dopamine release response in BDNF(+/-) mice. Conversely, tissue accumulation of L-3,4-dihydroxyphenylalanine, extracellular levels of dopamine metabolites, and spontaneous locomotor activity were unaltered. Together, this study indicates that endogenous BDNF influences dopamine system homeostasis by regulating the release and uptake dynamics of pre-synaptic dopamine transmission.
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Affiliation(s)
- Kelly E Bosse
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
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69
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Hashemi P, Dankoski EC, Wood KM, Ambrose RE, Wightman RM. In vivo electrochemical evidence for simultaneous 5-HT and histamine release in the rat substantia nigra pars reticulata following medial forebrain bundle stimulation. J Neurochem 2011; 118:749-59. [PMID: 21682723 PMCID: PMC3155665 DOI: 10.1111/j.1471-4159.2011.07352.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Exploring the mechanisms of serotonin [5-hydroxytryptamine (5-HT)] in the brain requires an in vivo method that combines fast temporal resolution with chemical selectivity. Fast-scan cyclic voltammetry is a technique with sufficient temporal and chemical resolution for probing dynamic 5-HT neurotransmission events; however, traditionally it has not been possible to probe in vivo 5-HT mechanisms. Recently, we optimized fast-scan cyclic voltammetry for measuring 5-HT release and uptake in vivo in the substantia nigra pars reticulata (SNR) with electrical stimulation of the dorsal raphe nucleus (DRN) in the rat brain. Here, we address technical challenges associated with rat DRN surgery by electrically stimulating 5-HT projections in the medial forebrain bundle (MFB), a more accessible anatomical location. MFB stimulation elicits 5-HT in the SNR; furthermore, we find simultaneous release of an additional species. We use electrochemical and pharmacological methods and describe physiological, anatomical and independent chemical analyses to identify this species as histamine. We also show pharmacologically that increasing the lifetime of extracellular histamine significantly decreases 5-HT release, most likely because of increased activation of histamine H-3 receptors that inhibit 5-HT release. Despite this, under physiological conditions, we find by kinetic comparisons of DRN and MFB stimulations that the simultaneous release of histamine does not interfere with the quantitative 5-HT concentration profile. We therefore present a novel and robust electrical stimulation of the MFB that is technically less challenging than DRN stimulation to study 5-HT and histamine release in the SNR.
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Affiliation(s)
- Parastoo Hashemi
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, 27599
| | - Elyse C. Dankoski
- Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, 27599
| | - Kevin M. Wood
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, 27599
| | - R. Ellen Ambrose
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, 27599
| | - R. Mark Wightman
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, 27599
- Curriculum in Neurobiology, University of North Carolina at Chapel Hill, Chapel Hill, 27599
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70
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Ramsson ES, Howard CD, Covey DP, Garris PA. High doses of amphetamine augment, rather than disrupt, exocytotic dopamine release in the dorsal and ventral striatum of the anesthetized rat. J Neurochem 2011; 119:1162-72. [PMID: 21806614 DOI: 10.1111/j.1471-4159.2011.07407.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
High doses of amphetamine (AMPH) are thought to disrupt normal patterns of action potential-dependent dopaminergic neurotransmission by depleting vesicular stores of dopamine (DA) and inducing robust non-exocytotic DA release or efflux via dopamine transporter (DAT) reversal. However, these cardinal AMPH actions have been difficult to establish definitively in vivo. Here, we use fast-scan cyclic voltammetry (FSCV) in the urethane-anesthetized rat to evaluate the effects of 10 and 20 mg/kg AMPH on vesicular DA release and DAT function in dorsal and ventral striata. An equivalent high dose of cocaine (40 mg/kg) was also examined for comparison to psychostimulants acting preferentially by DAT inhibition. Parameters describing exocytotic DA release and neuronal DA uptake were determined from dynamic DA signals evoked by mild electrical stimulation previously established to be reinforcing. High-sensitivity FSCV with nanomolar detection was used to monitor changes in the background voltammetric signal as an index of DA efflux. Both doses of AMPH and cocaine markedly elevated evoked DA levels over the entire 2-h time course in the dorsal and ventral striatum. These increases were mediated by augmented vesicular DA release and diminished DA uptake typically acting concurrently. AMPH, but not cocaine, induced a slow, DA-like rise in some baseline recordings. However, this effect was highly variable in amplitude and duration, modest, and generally not present at all. These data thus describe a mechanistically similar activation of action potential-dependent dopaminergic neurotransmission by AMPH and cocaine in vivo. Moreover, DA efflux appears to be a unique, but secondary, AMPH action.
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Affiliation(s)
- Eric S Ramsson
- School of Biological Sciences, Illinois State University, Normal, IL, USA
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71
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Singh YS, Sawarynski LE, Dabiri PD, Choi WR, Andrews AM. Head-to-head comparisons of carbon fiber microelectrode coatings for sensitive and selective neurotransmitter detection by voltammetry. Anal Chem 2011; 83:6658-66. [PMID: 21770471 DOI: 10.1021/ac2011729] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Voltammetry is widely used to investigate neurotransmission and other biological processes but is limited by poor chemical selectivity and fouling of commonly used carbon fiber microelectrodes (CFMs). We performed direct comparisons of three key coating materials purported to impart selectivity and fouling resistance to electrodes: Nafion, base-hydrolyzed cellulose acetate (BCA), and fibronectin. We systematically evaluated the impact on a range of electrode parameters. Fouling due to exposure to brain tissue was investigated using an approach that minimizes the use of animals while enabling evaluation of statistically significant populations of electrodes. We find that BCA is relatively fouling-resistant. Moreover, detection at BCA-coated CFMs can be tuned by altering hydrolysis times to minimize the impact on sensitivity losses while maintaining fouling resistance. Fibronectin coating is associated with moderate losses in sensitivity after coating and fouling. Nafion imparts increased sensitivity for dopamine and norepinephrine but not serotonin, as well as the anticipated selectivity for cationic neurotransmitters over anionic metabolites. Although Nafion has been suggested to resist fouling, both dip-coating and electrodeposition of Nafion are associated with substantial fouling, similar to levels observed at bare electrodes after exposure to brain tissue. Direct comparisons of these coatings identified unique electroanalytical properties of each that can be used to guide selection tailored to the goals and environment of specific studies.
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Affiliation(s)
- Yogesh S Singh
- Semel Institute for Neuroscience & Human Behavior, David Geffen School of Medicine and California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, USA
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72
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Khalid M, Aoun RA, Mathews TA. Altered striatal dopamine release following a sub-acute exposure to manganese. J Neurosci Methods 2011; 202:182-91. [PMID: 21740928 DOI: 10.1016/j.jneumeth.2011.06.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Revised: 05/05/2011] [Accepted: 06/20/2011] [Indexed: 12/30/2022]
Abstract
Certain metals that are necessary for regulating biological function at trace levels hold the potential to become neurotoxic when in excess. Specifically, chronic exposure to high levels of manganese leads to manganism, a neurological disorder that exhibits both motor and learning deficits similar to Parkinson's disease. Since Parkinson's disease symptomatology is primarily attributed to dopamine neurodegeneration in the striatum, dopamine system dysfunction has been implicated in the onset of manganism. In this study, dopamine system function in the dorsal striatum was evaluated in C57Bl/6 mice, 1, 7, and 21 days following repeated injections of manganese(II) chloride (50 mg/kg, subcutaneous) intermittently for 7 days. Tissue content analysis confirmed the presence of persistent accumulation of manganese in the striatum up to 21 days after cessation of treatment. In vitro fast scan cyclic voltammetry examined the effect of sub-acute manganese on electrically stimulated dopamine release and uptake in the striatum. While no difference was observed in uptake rates following manganese treatment, dopamine release was attenuated on days 7 and 21, compared to control levels. Basal levels of extracellular dopamine determined by the zero net flux microdialysis method were significantly lower in manganese-treated mice at 7 days post-treatment. On the other hand, potassium stimulated increases in extracellular dopamine were attenuated at all three time points. Together, these findings indicate that repeated manganese exposure has long-term effects on the regulation of exocytotic dopamine release in the striatum, which may be involved in the mechanism underlying manganese toxicity.
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Affiliation(s)
- Madiha Khalid
- Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, MI 48202, USA
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73
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Ramsson ES, Covey DP, Daberkow DP, Litherland MT, Juliano SA, Garris PA. Amphetamine augments action potential-dependent dopaminergic signaling in the striatum in vivo. J Neurochem 2011; 117:937-48. [PMID: 21443523 DOI: 10.1111/j.1471-4159.2011.07258.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Amphetamine (AMPH) is thought to disrupt normal patterns of action potential-dependent dopaminergic signaling by depleting dopamine (DA) vesicular stores and promoting non-exocytotic DA efflux. Voltammetry in brain slices concurrently demonstrates these key drug effects, along with competitive inhibition of neuronal DA uptake. Here, we perform comparable kinetic and voltammetric analyses in vivo to determine whether AMPH acts qualitatively and quantitatively similar in the intact brain. Fast-scan cyclic voltammetry measured extracellular DA in dorsal and ventral striata of urethane-anesthetized rats. Electrically evoked recordings were analyzed to determine K(m) and V(max) for DA uptake and vesicular DA release, while background voltammetric current indexed basal DA concentration. AMPH (0.5, 3, and 10 mg/kg i.p.) robustly increased evoked DA responses in both striatal subregions. The predominant contributor to these elevated levels was competitive uptake inhibition, as exocytotic release was unchanged in the ventral striatum and only modestly decreased in the dorsal striatum. Increases in basal DA levels were not detected. These results are consistent with AMPH augmenting action potential-dependent dopaminergic signaling in vivo across a wide, behaviorally relevant dose range. Future work should be directed at possible causes for the distinct in vitro and in vivo pharmacology of AMPH.
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Affiliation(s)
- Eric S Ramsson
- School of Biological Sciences, Illinois State University, Normal, Illinois 61790-4120, USA
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74
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Yorgason JT, Jones SR, España RA. Low and high affinity dopamine transporter inhibitors block dopamine uptake within 5 sec of intravenous injection. Neuroscience 2011; 182:125-32. [PMID: 21402130 DOI: 10.1016/j.neuroscience.2011.03.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2010] [Revised: 03/03/2011] [Accepted: 03/08/2011] [Indexed: 11/25/2022]
Abstract
Extensive evidence suggests that the reinforcing effects of cocaine involve inhibition of dopamine transporters (DAT) and subsequent increases in dopamine (DA) levels in the striatum. We have previously reported that cocaine inhibits the DAT within 4-5 s of i.v. injection, matching the temporal profile of the behavioral and subjective effects of cocaine. Intravenous injection of GBR-12909, a high affinity, long-acting DAT inhibitor, also inhibits DA uptake within 5 s. Given that high affinity, long-acting drugs are considered to have relatively low abuse potential, we found it intriguing that GBR-12909 had an onset profile similar to that of cocaine. To further explore the onset kinetics of both low and high affinity DAT inhibitors, we examined the effects of i.v. cocaine (1.5 mg/kg), methylphenidate (1.5 mg/kg), nomifensine (1.5 mg/kg), GBR-12909 (1.5 mg/kg), PTT (0.5 mg/kg), and WF23 (0.5 mg/kg) on electrically-evoked DA release and uptake in the nucleus accumbens core. Results indicate that all of the DAT inhibitors significantly inhibited DA uptake within 5 s of injection. However, the timing of peak uptake inhibition varied greatly between the low and high affinity uptake inhibitors. Uptake inhibition following cocaine, methylphenidate, and nomifensine peaked 30 s following injection. In contrast, peak effects for GBR-12909, PTT, and WF23 occurred between 20 and 60 min following injection. These observations suggest that the initial onset for i.v. DAT inhibitors is extremely rapid and does not appear to be dictated by a drug's affinity.
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Affiliation(s)
- J T Yorgason
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC 27157, USA
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75
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Yorgason JT, España RA, Jones SR. Demon voltammetry and analysis software: analysis of cocaine-induced alterations in dopamine signaling using multiple kinetic measures. J Neurosci Methods 2011; 202:158-64. [PMID: 21392532 DOI: 10.1016/j.jneumeth.2011.03.001] [Citation(s) in RCA: 245] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2011] [Revised: 02/26/2011] [Accepted: 03/01/2011] [Indexed: 10/18/2022]
Abstract
The fast sampling rates of fast scan cyclic voltammetry make it a favorable method for measuring changes in brain monoamine release and uptake kinetics in slice, anesthetized, and freely moving preparations. The most common analysis technique for evaluating changes in dopamine signaling uses well-established Michaelis-Menten kinetic methods that can accurately model dopamine release and uptake parameters across multiple experimental conditions. Nevertheless, over the years, many researchers have turned to other measures to estimate changes in dopamine release and uptake, yet to our knowledge no systematic comparison amongst these measures has been conducted. To address this lack of uniformity in kinetic analyses, we have created the Demon Voltammetry and Analysis software suite, which is freely available to academic and non-profit institutions. Here we present an explanation of the Demon Voltammetry acquisition and analysis features, and demonstrate its utility for acquiring voltammetric data under in vitro, in vivo anesthetized, and freely moving conditions. Additionally, the software was used to compare the sensitivity of multiple kinetic measures of release and uptake to cocaine-induced changes in electrically evoked dopamine efflux in nucleus accumbens core slices. Specifically, we examined and compared tau, full width at half height, half-life, T₂₀, T₈₀, slope, peak height, calibrated peak dopamine concentration, and area under the curve to the well-characterized Michaelis-Menten parameters, dopamine per pulse, maximal uptake rate, and apparent affinity. Based on observed results we recommend tau for measuring dopamine uptake and calibrated peak dopamine concentration for measuring dopamine release.
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Affiliation(s)
- Jordan T Yorgason
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Medical Center Boulevard, Winston-Salem, NC 27157, USA
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76
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Wooters TE, Bardo MT, Dwoskin LP, Midde NM, Gomez AM, Mactutus CF, Booze RM, Zhu J. Effect of environmental enrichment on methylphenidate-induced locomotion and dopamine transporter dynamics. Behav Brain Res 2011; 219:98-107. [PMID: 21219939 DOI: 10.1016/j.bbr.2011.01.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 12/14/2010] [Accepted: 01/03/2011] [Indexed: 01/01/2023]
Abstract
Rats raised in an enriched condition (EC) are less sensitive to the locomotor effects of stimulant drugs than rats raised in an impoverished condition (IC). Methylphenidate (MPD), a primary pharmacotherapy for attention-deficit/hyperactivity disorder, has abuse potential. This study determined whether environmental enrichment differentially altered the effects of MPD on locomotor activity and dopamine (DA) transporter (DAT) function. Acute and repeated MPD (3 or 10 mg/kg, s.c.) increased locomotion in EC, IC and social condition (SC) rats; however, EC rats showed a blunted response to repeated MPD (3 mg/kg). The maximal velocity (V(max)) of [(3)H]DA uptake in the presence of the combination of phorbol 12-myristate 13-acetate, a protein kinase C (PKC) activator and okadaic acid, a protein phosphatase inhibitor was decreased in EC and IC rats by 68% and 40%, respectively, indicating that DAT in prefrontal cortex (PFC) is more sensitive to PKC-mediated down-regulation in EC rats. Acute MPD (10 mg/kg) administration decreased the V(max) of [(3)H]DA uptake in PFC and striatum in EC rats, but not in IC rats. Furthermore, [(3)H]WIN 35,428 binding density was decreased in PFC of EC and IC rats, and in striatum of EC rats given repeated MPD (10 mg/kg). These results demonstrate that environmental enrichment modulates DAT dynamics in PFC. However, since the change in DAT function was observed only following the high dose of MPH (10 mg/kg), the attenuated locomotor response to repeated MPD (3 mg/kg) in EC rats is not likely due to a specific DAT alteration in the brain regions examined.
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Affiliation(s)
- Thomas E Wooters
- Department of Psychology, University of Kentucky, Lexington, KY 40506, USA
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77
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Abstract
Tonic and phasic dopamine release is implicated in learning, motivation, and motor functions. However, the relationship between spike patterns in dopaminergic neurons, the extracellular concentration of dopamine, and activation of dopamine receptors remains unresolved. In the present study, we develop a computational model of dopamine signaling that give insight into the relationship between the dynamics of release and occupancy of D(1) and D(2) receptors. The model is derived from first principles using experimental data. It has no free parameters and offers unbiased estimation of the boundaries of dopaminergic volume transmission. Bursts primarily increase occupancy of D(1) receptors, whereas pauses translate into low occupancy of D(1) and D(2) receptors. Phasic firing patterns, composed of bursts and pauses, reduce the average D(2) receptor occupancy and increase average D(1) receptor occupancy compared with equivalent tonic firing. Receptor occupancy is crucially dependent on synchrony and the balance between tonic and phasic firing modes. Our results provide quantitative insight in the dynamics of volume transmission and complement experimental data obtained with electrophysiology, positron emission tomography, microdialysis, amperometry, and voltammetry.
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78
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Hagan CE, Neumaier JF, Schenk JO. Rotating disk electrode voltammetric measurements of serotonin transporter kinetics in synaptosomes. J Neurosci Methods 2010; 193:29-38. [PMID: 20713085 PMCID: PMC2952731 DOI: 10.1016/j.jneumeth.2010.08.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 08/06/2010] [Accepted: 08/06/2010] [Indexed: 12/13/2022]
Abstract
Altered serotonin (5-HT) signaling is implicated in several neuropsychiatric disorders, including depression, anxiety, obsessive-compulsive disorder, and autism. The 5-HT transporter (SERT) modulates 5-HT neurotransmission strength and duration. This is the first study using rotating disk electrode voltammetry (RDEV) to measure 5-HT clearance. SERT kinetics were measured in whole brain synaptosomes. Uptake kinetics of exogenous 5-HT were measured using glassy carbon electrodes rotated in 500 μL glass chambers containing synaptosomes from SERT-knockout (-/-), heterozygous (+/-), or wild-type (+/+) mice. RDEV detected 5-HT concentrations of 5nM and higher. Initial velocities were kinetically resolved with K(m) and V(max) values of 99±35 standard error of regression (SER) nM and 181±11 SER fmol/(s×mg protein), respectively in wild-type synaptosomes. The method enables control over drug and chemical concentrations, facilitating interpretation of results. Results are compared in detail to other techniques used to measure SERT kinetics, including tritium labeled assays, chronoamperometry, and fast scan cyclic voltammetry. RDEV exhibits decreased 5-HT detection limits, decreased vulnerability to 5-HT oxidation products that reduce electrode sensitivity, and also overcomes diffusion limitations via forced convection by providing a continuous, kinetically resolved signal. Finally, RDEV distinguishes functional differences between genotypes, notably, between wild-type and heterozygous mice, an experimental problem with other experimental approaches.
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Affiliation(s)
- Catherine E Hagan
- Department of Comparative Medicine, University of Washington, Seattle, WA 98195, USA.
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79
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Abstract
Synapsins are a family of synaptic vesicle proteins that are important for neurotransmitter release. Here we have used triple knock-out (TKO) mice lacking all three synapsin genes to determine the roles of synapsins in the release of two monoamine neurotransmitters, dopamine and serotonin. Serotonin release evoked by electrical stimulation was identical in substantia nigra pars reticulata slices prepared from TKO and wild-type mice. In contrast, release of dopamine in response to electrical stimulation was approximately doubled in striatum of TKO mice, both in vivo and in striatal slices, in comparison to wild-type controls. This was due to loss of synapsin III, because deletion of synapsin III alone was sufficient to increase dopamine release. Deletion of synapsins also increased the sensitivity of dopamine release to extracellular calcium ions. Although cocaine did not affect the release of serotonin from nigral tissue, this drug did enhance dopamine release. Cocaine-induced facilitation of dopamine release was a function of external calcium, an effect that was reduced in TKO mice. We conclude that synapsins play different roles in the control of release of dopamine and serotonin, with release of dopamine being negatively regulated by synapsins, specifically synapsin III, while serotonin release appears to be relatively independent of synapsins. These results provide further support for the concept that synapsin function in presynaptic terminals varies according to the neurotransmitter being released.
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Roitman MF, Wescott S, Cone JJ, McLane MP, Wolfe HR. MSI-1436 reduces acute food intake without affecting dopamine transporter activity. Pharmacol Biochem Behav 2010; 97:138-43. [PMID: 20478327 DOI: 10.1016/j.pbb.2010.05.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 04/15/2010] [Accepted: 05/10/2010] [Indexed: 01/16/2023]
Abstract
Many therapies designed to reduce food intake and body weight act, in part, by blocking the dopamine transporter (DAT) - a protein responsible for clearing extracellular dopamine (DA) after release thereby terminating its action. Here, we found that a single injection of the drug trodusquemine (MSI-1436) decreased food intake in rats. To assess the effects of MSI-1436 on DAT function, fast-scan cyclic voltammetry was used to measure DA concentration changes in the ventral striatum. DA release was evoked by electrical stimulation of the ventral tegmental area every 5 min. After 3 baseline measurements, rats were injected with MSI-1436 (10 mg/kg), the known DAT blocker bupropion (80 mg/kg) or saline and evoked DA release and reuptake were monitored for an additional hour. Neither saline nor MSI-1436 caused a significant change in the magnitude of evoked release from baseline values whereas bupropion caused a significant increase. In addition, neither saline nor MSI-1436 significantly increased DA decay rates while such an increase was observed with bupropion. Thus, over a time course when MSI-1436 suppresses food intake it does not affect DAT function. The results support MSI-1436 as an anti-obesity treatment which spares DAT.
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Affiliation(s)
- Mitchell F Roitman
- Department of Psychology, University of Illinois, Chicago, IL 60607, USA.
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81
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Podet A, Lee MJ, Swann AC, Dafny N. Nucleus accumbens lesions modulate the effects of methylphenidate. Brain Res Bull 2010; 82:293-301. [PMID: 20470871 DOI: 10.1016/j.brainresbull.2010.05.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2010] [Accepted: 05/04/2010] [Indexed: 01/08/2023]
Abstract
The psychostimulant methylphenidate (MPD, Ritalin) is the prescribed drug of choice for treatment of ADHD. In recent years, the diagnosis rate of ADHD has increased dramatically, as have the number of MPD prescriptions. Repeated exposure to psychostimulants produces behavioral sensitization in rats, an experimental indicator of a drug's potential liability. In studies on cocaine and amphetamine, this effect has been reported to involve the nucleus accumbens (NAc), one of the nuclei belonging to the motive circuit. The aim of this study was to investigate the role of the NAc on the expression of behavioral sensitization as a response to MPD exposure. In the present study, 20 male Sprague-Dawley rats were divided randomly into three groups: an intact control group, a sham-operated group, and a NAc bilateral electrical lesion group. Locomotor activity was assessed for the first 2h following 2.5mg/kg MPD injection, using open field monitoring systems. Recordings were made during 6 days of continuous MPD administration, and then upon re-challenge with the same dose following 3 days of washout. Acute MPD exposure elicited an increase in locomotor activity in all three groups. However, the NAc lesion group exhibited significantly increased locomotor activity in comparison to sham and control groups. Chronic MPD did not elicit sensitization in the NAc lesion group, while both sham and control groups did exhibit behavioral sensitization to repetitive MPD administration. These findings suggest that the NAc plays a significant role in eliciting locomotor activity as an acute effect of MPD, and in the expression of sensitization due to chronic MPD exposure.
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Affiliation(s)
- Adam Podet
- Department of Neurobiology and Anatomy, The University of Texas-Medical School at Houston, P.O. Box 20708, Houston, TX 77225, United States
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82
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Maina FK, Mathews TA. A functional fast scan cyclic voltammetry assay to characterize dopamine D2 and D3 autoreceptors in the mouse striatum. ACS Chem Neurosci 2010; 1:450-462. [PMID: 20567609 DOI: 10.1021/cn100003u] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Dopamine D2 and D3 autoreceptors are located on pre-synaptic terminals and are known to control the release and synthesis of dopamine. Dopamine D3 receptors have a fairly restricted pattern of expression in the mammalian brain. Their localization in the nucleus accumbens core and shell is of particular interest because of their association with the rewarding properties of drugs of abuse. Using background subtracted fast scan cyclic voltammetry, we investigated the effects of dopamine D2 and D3 agonists on electrically stimulated dopamine release and uptake rates in the mouse caudate-putamen and nucleus accumbens core and shell. The dopamine D2 agonists (-)-quinpirole hydrochloride and 5,6,7,8-Tetrahydro-6-(2-propen-1-yl)-4H-thiazolo[4,5-d]azepin-2-amine dihydrochloride (B-HT 920) had the same dopamine release inhibition effects on caudate-putamen and nucleus accumbens (core and shell) based on their EC(50) and efficacies. This suggests that the dopamine D2 autoreceptor functionality is comparable in all three striatal regions investigated. The dopamine D3 agonists (4aR,10bR)-3,4a,4,10b-Tetrahydro-4-propyl-2H,5H-[1]benzopyrano-[4,3-b]-1,4-oxazin-9-ol hydrochloride ((+)-PD 128907) and (+/-)-7-Hydroxy-2-dipropylaminotetralin hydrobromide (7-OH-DPAT) had a significantly greater effect on dopamine release inhibition in the nucleus accumbens shell than in caudate-putamen. This study confirms that, the dopamine D3 autoreceptor functionality is greater in the nucleus accumbens shell followed by the nucleus accumbens core, with the caudate-putamen having the least. Neither dopamine D2 nor D3 agonists affected the uptake rates in nucleus accumbens but concentrations greater than 0.3 muM lowered the uptake rate in caudate-putamen. To validate our method of evaluating dopamine D2 and D3 autoreceptors, sulpiride (D2 antagonist) and nafadotride (D3 antagonist) were used to reverse the effects of the dopamine agonists to approximately 100% of the pre-agonist dopamine release concentration. Finally, these results demonstrate a functional voltammetric assay that characterizes dopamine D2-like agonist as either D2- or D3-preferring agonists by taking advantage of the unique receptor density within the striatum.
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Affiliation(s)
- Francis K. Maina
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202
| | - Tiffany A. Mathews
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202
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83
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Enhanced striatal dopamine transmission and motor performance with LRRK2 overexpression in mice is eliminated by familial Parkinson's disease mutation G2019S. J Neurosci 2010; 30:1788-97. [PMID: 20130188 DOI: 10.1523/jneurosci.5604-09.2010] [Citation(s) in RCA: 267] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
PARK8/LRRK2 (leucine-rich repeat kinase 2) was recently identified as a causative gene for autosomal dominant Parkinson's disease (PD), with LRRK2 mutation G2019S linked to the most frequent familial form of PD. Emerging in vitro evidence indicates that aberrant enzymatic activity of LRRK2 protein carrying this mutation can cause neurotoxicity. However, the physiological and pathophysiological functions of LRRK2 in vivo remain elusive. Here we characterize two bacterial artificial chromosome (BAC) transgenic mouse strains overexpressing LRRK2 wild-type (Wt) or mutant G2019S. Transgenic LRRK2-Wt mice had elevated striatal dopamine (DA) release with unaltered DA uptake or tissue content. Consistent with this result, LRRK2-Wt mice were hyperactive and showed enhanced performance in motor function tests. These results suggest a role for LRRK2 in striatal DA transmission and the consequent motor function. In contrast, LRRK2-G2019S mice showed an age-dependent decrease in striatal DA content, as well as decreased striatal DA release and uptake. Despite increased brain kinase activity, LRRK2-G2019S overexpression was not associated with loss of DAergic neurons in substantia nigra or degeneration of nigrostriatal terminals at 12 months. Our results thus reveal a pivotal role for LRRK2 in regulating striatal DA transmission and consequent control of motor function. The PD-associated mutation G2019S may exert pathogenic effects by impairing these functions of LRRK2. Our LRRK2 BAC transgenic mice, therefore, could provide a useful model for understanding early PD pathological events.
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84
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Borue X, Condron B, Venton BJ. Both synthesis and reuptake are critical for replenishing the releasable serotonin pool in Drosophila. J Neurochem 2010; 113:188-99. [PMID: 20070864 DOI: 10.1111/j.1471-4159.2010.06588.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The two main sources of serotonin available for release are expected to be newly synthesized serotonin and serotonin recycled after reuptake by the serotonin transporter. However, their relative importance for maintaining release and the time course of regulation are unknown. We studied serotonin signaling in the ventral nerve cord of the larval Drosophila CNS. Fast-scan cyclic voltammetry at implanted microelectrodes was used to detect serotonin elicited by channelrhodopsin2-mediated depolarization. The effects of reuptake were probed by incubating in cocaine, which is selective for the serotonin transporter in Drosophila. p-chlorophenylalanine, an inhibitor of tryptophan hydroxylase2, was used to investigate the effects of synthesis. Stimulations were repeated at various intervals to assess the time course of recovery of the releasable pool. Reuptake is important for the rapid replenishment of the releasable pool, on the 1 min time scale. Synthesis is critical to the longer-term replenishment (10 min) of the releasable pool, especially when reuptake is also inhibited. Concurrent synthesis and reuptake inhibition decreased both serotonin tissue content measured by immunohistochemistry (by 50%) and the initial amount of evoked serotonin (by 65%). Decreases in evoked serotonin are rescued by inhibiting action potential propagation with tetrodotoxin, implicating endogenous activity in the depletion. These results show synthesis is necessary to replenish part of the releasable serotonin pool that is depleted after reuptake inhibition, suggesting that regulation of synthesis may modulate the effects of serotonin reuptake inhibitors.
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Affiliation(s)
- Xenia Borue
- Medical Scientist Training Program, University of Virginia, Charlottesville, VA 22904, USA
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85
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España RA, Oleson EB, Locke JL, Brookshire BR, Roberts DCS, Jones SR. The hypocretin-orexin system regulates cocaine self-administration via actions on the mesolimbic dopamine system. Eur J Neurosci 2009; 31:336-48. [PMID: 20039943 DOI: 10.1111/j.1460-9568.2009.07065.x] [Citation(s) in RCA: 187] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent evidence suggests that the hypocretin-orexin system participates in the regulation of reinforcement processes. The current studies examined the extent to which hypocretin neurotransmission regulates behavioral and neurochemical responses to cocaine, and behavioral responses to food reinforcement. These studies used a combination of fixed ratio, discrete trials, progressive ratio and threshold self-administration procedures to assess whether the hypocretin 1 receptor antagonist, SB-334867, reduces cocaine self-administration in rats. Progressive ratio sucrose self-administration procedures were also used to assess the extent to which SB-334867 reduces responding to a natural reinforcer in food-restricted and food-sated rats. Additionally, these studies used microdialysis and in vivo voltammetry in rats to examine whether SB-334867 attenuates the effects of cocaine on dopamine signaling within the nucleus accumbens core. Furthermore, in vitro voltammetry was used to examine whether hypocretin knockout mice display attenuated dopamine responses to cocaine. Results indicate that when SB-334867 was administered peripherally or within the ventral tegmental area, it reduced the motivation to self-administer cocaine and attenuated cocaine-induced enhancement of dopamine signaling. SB-334867 also reduced the motivation to self-administer sucrose in food-sated but not food-restricted rats. Finally, hypocretin knockout mice displayed altered baseline dopamine signaling and reduced dopamine responses to cocaine. Combined, these studies suggest that hypocretin neurotransmission participates in reinforcement processes, likely through modulation of the mesolimbic dopamine system. Additionally, the current observations suggest that the hypocretin system may provide a target for pharmacotherapies to treat cocaine addiction.
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Affiliation(s)
- Rodrigo A España
- Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA.
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86
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Kita JM, Kile BM, Parker LE, Wightman RM. In vivo measurement of somatodendritic release of dopamine in the ventral tegmental area. Synapse 2009; 63:951-60. [PMID: 19593821 DOI: 10.1002/syn.20676] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The ventral tegmental area (VTA), the locus of mesolimbic dopamine cell bodies, contains dopamine. Experiments in brain slices have demonstrated that VTA dopamine can be released by local electrical stimulation. Measurements with both push-pull cannula and microdialysis in intact animals have also obtained evidence for releasable dopamine. Here we demonstrate that dopamine release in the VTA can be evoked by remote stimulations of the medial forebrain bundle (MFB) in the anesthetized rat. In initial experiments, the MFB was electrically stimulated while a carbon-fiber electrode was lowered to the VTA, with recording by fast-scan cyclic voltammetry. While release was not observed with the carbon fiber 4-6 mm below dura, a voltammetric response was observed at 6-8 mm below dura, but the voltammogram was poorly defined. At lower depths, in the VTA, dopamine release was evoked. Immunohistochemistry experiments with antibodies for tyrosine hydroxylase (TH) confirmed that dopamine processes were primarily found below 8 mm. Similarly, tissue content determined by liquid chromatography revealed serotonin but not dopamine dorsal to 8 mm with both dopamine and serotonin at lower depths. Evaluation of the VTA signal by pharmacological means showed that it increased with inhibitors of dopamine uptake, but release was not altered by D2 agents. Dopamine release in the VTA was frequency dependent and could be exhausted by stimulations longer than 5 s. Thus, VTA dopamine release can be evoked in vivo by remote stimulations and it resembles release in terminal regions, possessing a similar uptake mechanism and a finite releasable storage pool.
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Affiliation(s)
- Justin M Kita
- Department of Chemistry and Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA
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87
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Hashemi P, Dankoski EC, Petrovic J, Keithley RB, Wightman RM. Voltammetric detection of 5-hydroxytryptamine release in the rat brain. Anal Chem 2009; 81:9462-71. [PMID: 19827792 PMCID: PMC2783829 DOI: 10.1021/ac9018846] [Citation(s) in RCA: 201] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
5-Hydroxytryptamine (5-HT) is an important molecule in the brain that is implicated in mood and emotional processes. In vivo, its dynamic release and uptake kinetics are poorly understood due to a lack of analytical techniques for its rapid measurement. Whereas fast-scan cyclic voltammetry with carbon fiber microelectrodes is used frequently to monitor subsecond dopamine release in freely moving and anesthetized rats, the electrooxidation of 5-HT forms products that quickly polymerize and irreversibly coat the carbon electrode surface. Previously described modifications of the electrochemical waveform allow stable and sensitive 5-HT measurements in mammalian tissue slice preparations and in the brain of fruit fly larvae. For in vivo applications in mammals, however, the problem of electrode deterioration persists. We identify the root of this problem to be fouling by extracellular metabolites such as 5-hydoxyindole acetic acid (5-HIAA), which is present in 200-1000 times the concentration of 5-HT and displays similar electrochemical properties, including filming of the electrode surface. To impede access of the 5-HIAA to the electrode surface, a thin layer of Nafion, a cation exchange polymer, has been electrodeposited onto cylindrical carbon-fiber microelectrodes. The presence of the Nafion film was confirmed with environmental scanning electron microscopy and was demonstrated by the diminution of the voltammetric signals for 5-HIAA as well as other common anionic species. The modified microelectrodes also display increased sensitivity to 5-HT, yielding a characteristic cyclic voltammogram that is easily distinguishable from other common electroactive brain species. The thickness of the Nafion coating and a diffusion coefficient (D) in the film for 5-HT were evaluated by measuring permeation through Nafion. In vivo, we used physiological, anatomical, and pharmacological evidence to validate the signal as 5-HT. Using Nafion-modified microelectrodes, we present the first endogenous recording of 5-HT in the mammalian brain.
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Affiliation(s)
- Parastoo Hashemi
- Department of Chemistry and Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA
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88
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Real-time voltammetric detection of cocaine-induced dopamine changes in the striatum of freely moving mice. Neurosci Lett 2009; 467:144-6. [PMID: 19822192 DOI: 10.1016/j.neulet.2009.10.025] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Revised: 10/06/2009] [Accepted: 10/07/2009] [Indexed: 11/22/2022]
Abstract
In the present voltammetric study, we have characterized cocaine-induced changes in evoked dopamine release and uptake in the striatum of freely moving mice in real time. Cocaine induced marked dopamine uptake inhibition measured as apparent K(m) changes, producing a maximal effect 20min following a single injection (15mg/kg, i.p.). Changes in uptake were paralleled by increases in evoked dopamine release per stimulus pulse, revealing a high correlation between these two parameters following cocaine administration. This initial characterization of cocaine effects on striatal dopamine transmission in the commonly used C57BL/6 mouse strain provides a basis for future voltammetric studies using genetic mouse models.
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89
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Ethanol-induced hyperactivity is associated with hypodopaminergia in the 22-TNJ ENU-mutated mouse. Alcohol 2009; 43:421-31. [PMID: 19801272 DOI: 10.1016/j.alcohol.2009.04.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 04/22/2009] [Accepted: 04/29/2009] [Indexed: 11/23/2022]
Abstract
Characterization of neurochemical and behavioral responses to ethanol in phenotypically distinct mouse strains can provide insight into the mechanisms of ethanol stimulant actions. Increases in striatal dopamine (DA) levels have often been linked to ethanol-induced hyperactivity. We examined the functional status of the DA system and behavioral responsiveness to ethanol, cocaine, and a DA-receptor agonist in an N-ethyl-N-nitrosourea-mutagenized mouse strain, 22-TNJ, generated by the Integrative Neuroscience Initiative on Alcoholism Consortium. The 22-TNJ mouse strain exhibited greater locomotor responses to 2.25g/kg ethanol and 10mg/kg cocaine, compared with control mice. In vivo microdialysis showed low-baseline DA levels and a larger DA increase with both 2.25g/kg ethanol and 10mg/kg cocaine. In in vitro voltammetry studies, the 22-TNJ mice displayed increased V(max) rates for DA uptake, possibly contributing to the low-baseline DA levels found with microdialysis. Finally, 22-TNJ mice showed enhanced in vitro autoreceptor sensitivity to the D2/D3 agonist, quinpirole, and greater locomotor responses to both autoreceptor-selective and postsynaptic receptor-selective doses of apomorphine compared with controls. Taken together, these results indicate that the dopaminergic system of the 22-TNJ mouse is low functioning compared with control, with consequent receptor supersensitivity, such that mutant animals exhibit enhanced behavioral responses to DA-activating drugs, such as ethanol. Thus, the 22-TNJ mouse represents a model for a relatively hypodopaminergic system, and could provide important insights into the mechanisms of hyper-responsiveness to ethanol's stimulant actions.
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90
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Ledonne A, Sebastianelli L, Federici M, Bernardi G, Mercuri NB. The anorexic agents, sibutramine and fenfluramine, depress GABA(B)-induced inhibitory postsynaptic potentials in rat mesencephalic dopaminergic cells. Br J Pharmacol 2009; 156:962-9. [PMID: 19298257 DOI: 10.1111/j.1476-5381.2008.00081.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Nutrition is the result of a complex interaction among environmental, homeostatic and reward-related processes. Accumulating evidence supports key roles for the dopaminergic neurons of the ventral midbrain in regulating feeding behaviour. For this reason, in the present study, we have investigated the electrophysiological effects of two centrally acting anorexic agents, fenfluramine and sibutramine, on these cells. EXPERIMENTAL APPROACH Rat midbrain slices were used to make intracellular recordings from dopaminergic neurons of the substantia nigra and the ventral tegmental area. Gamma-aminobutyric acid (GABA)-mediated synaptic transmission was assessed from the inhibitory postsynaptic potentials (IPSPs) mediated by GABA(A) and GABA(B) receptors. KEY RESULTS Fenfluramine and sibutramine reduced, concentration-dependently, the GABA(B) IPSPs, without affecting the GABA(A)-mediated potentials. This effect is presynaptic, as postsynaptic membrane responses induced by application of a GABA(B) receptor agonist, baclofen, were not affected by the two drugs. Furthermore, the selective 5-hydroxytriptamine 1B (5-HT(1B)) receptor antagonist, SB216641, blocked the reduction of GABA(B) IPSPs caused by fenfluramine and sibutramine, indicating that the receptor mediating this effect is 5-HT(1B). CONCLUSIONS AND IMPLICATIONS Two anorexic agents, fenfluramine and sibutramine, induced the activation of 5-HT(1B) receptors located on presynaptic GABAergic terminals, thus reducing the release of GABA. This action can alter the strength of synaptic afferents that modify the activity of dopaminergic neurons, inducing neuronal excitation. Our results reveal an additional mechanism of action for fenfluramine and sibutramine that might contribute to reducing food intake, by influencing the pleasurable and motor aspects of feeding behaviour.
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Affiliation(s)
- Ada Ledonne
- Università della Calabria, Dipartimento Farmaco-Biologico, Arcavacata di Rende, Cosenza, Italy
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91
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Zhu J, Reith MEA. Role of the dopamine transporter in the action of psychostimulants, nicotine, and other drugs of abuse. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2009; 7:393-409. [PMID: 19128199 DOI: 10.2174/187152708786927877] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
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.
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Affiliation(s)
- J Zhu
- Department of Psychology, University of South Carolina, Columbia, SC 29208, USA.
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92
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Borue X, Cooper S, Hirsh J, Condron B, Venton BJ. Quantitative evaluation of serotonin release and clearance in Drosophila. J Neurosci Methods 2009; 179:300-8. [PMID: 19428541 DOI: 10.1016/j.jneumeth.2009.02.013] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2008] [Revised: 02/19/2009] [Accepted: 02/19/2009] [Indexed: 10/21/2022]
Abstract
Serotonin signaling plays a key role in the regulation of development, mood and behavior. Drosophila is well suited for the study of the basic mechanisms of serotonergic signaling, but the small size of its nervous system has previously precluded the direct measurements of neurotransmitters. This study demonstrates the first real-time measurements of changes in extracellular monoamine concentrations in a single larval Drosophila ventral nerve cord. Channelrhodopsin-2-mediated, neuronal type-specific stimulation is used to elicit endogenous serotonin release, which is detected using fast-scan cyclic voltammetry at an implanted microelectrode. Release is decreased when serotonin synthesis or packaging are pharmacologically inhibited, confirming that the detected substance is serotonin. Similar to tetanus-evoked serotonin release in mammals, evoked serotonin concentrations are 280-640nM in the fly, depending on the stimulation length. Extracellular serotonin signaling is prolonged after administering cocaine or fluoxetine, showing that transport regulates the clearance of serotonin from the extracellular space. When ChR2 is targeted to dopaminergic neurons, dopamine release is measured demonstrating that this method is broadly applicable to other neurotransmitter systems. This study shows that the dynamics of serotonin release and reuptake in Drosophila are analogous to those in mammals, making this simple organism more useful for the study of the basic physiological mechanisms of serotonergic signaling.
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Affiliation(s)
- Xenia Borue
- Medical Scientist Training Program, University of Virginia, Charlottesville, VA 22904, USA
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93
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Microelectrodes for studying neurobiology. Curr Opin Chem Biol 2009; 12:491-6. [PMID: 18675377 DOI: 10.1016/j.cbpa.2008.06.035] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2008] [Revised: 06/09/2008] [Accepted: 06/16/2008] [Indexed: 01/09/2023]
Abstract
Microelectrodes have emerged as an important tool used by scientists to study biological changes in the brain and in single cells. This review briefly summarizes the ways in which microelectrodes as chemical sensors have furthered the field of neurobiology by reporting on changes that occur on the subsecond time scale. Microelectrodes have been used in a variety of fields including their use by electrophysiologists to characterize neuronal action potentials and develop neural prosthetics. Here we restrict our review to microelectrodes that have been used as chemical sensors. They have played a major role in many important neurobiological findings.
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94
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Goodwin JS, Larson GA, Swant J, Sen N, Javitch JA, Zahniser NR, De Felice LJ, Khoshbouei H. Amphetamine and methamphetamine differentially affect dopamine transporters in vitro and in vivo. J Biol Chem 2008; 284:2978-2989. [PMID: 19047053 DOI: 10.1074/jbc.m805298200] [Citation(s) in RCA: 152] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The psychostimulants d-amphetamine (AMPH) and methamphetamine (METH) release excess dopamine (DA) into the synaptic clefts of dopaminergic neurons. Abnormal DA release is thought to occur by reverse transport through the DA transporter (DAT), and it is believed to underlie the severe behavioral effects of these drugs. Here we compare structurally similar AMPH and METH on DAT function in a heterologous expression system and in an animal model. In the in vitro expression system, DAT-mediated whole-cell currents were greater for METH stimulation than for AMPH. At the same voltage and concentration, METH released five times more DA than AMPH and did so at physiological membrane potentials. At maximally effective concentrations, METH released twice as much [Ca(2+)](i) from internal stores compared with AMPH. [Ca(2+)](i) responses to both drugs were independent of membrane voltage but inhibited by DAT antagonists. Intact phosphorylation sites in the N-terminal domain of DAT were required for the AMPH- and METH-induced increase in [Ca(2+)](i) and for the enhanced effects of METH on [Ca(2+)](i) elevation. Calmodulin-dependent protein kinase II and protein kinase C inhibitors alone or in combination also blocked AMPH- or METH-induced Ca(2+) responses. Finally, in the rat nucleus accumbens, in vivo voltammetry showed that systemic application of METH inhibited DAT-mediated DA clearance more efficiently than AMPH, resulting in excess external DA. Together these data demonstrate that METH has a stronger effect on DAT-mediated cell physiology than AMPH, which may contribute to the euphoric and addictive properties of METH compared with AMPH.
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Affiliation(s)
- J Shawn Goodwin
- Department of Cancer Biology, Meharry Medical College, Nashville, Tennessee 37208
| | - Gaynor A Larson
- Department of Pharmacology, University of Colorado Denver, Aurora, Colorado 80045
| | - Jarod Swant
- Departments of Neurobiology and Neurotoxicology, Meharry Medical College, Nashville, Tennessee 37208
| | - Namita Sen
- Departments of Psychiatry and Pharmacology, Center for Molecular Recognition, Columbia University, New York, New York 10027-6902
| | - Jonathan A Javitch
- Departments of Psychiatry and Pharmacology, Center for Molecular Recognition, Columbia University, New York, New York 10027-6902
| | - Nancy R Zahniser
- Department of Pharmacology, University of Colorado Denver, Aurora, Colorado 80045
| | - Louis J De Felice
- Center for Molecular Neuroscience, Vanderbilt University, Nashville, Tennessee 37232; Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232
| | - Habibeh Khoshbouei
- Departments of Neurobiology and Neurotoxicology, Meharry Medical College, Nashville, Tennessee 37208
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95
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Wellman P. Effects of acute administration of phentermine, alone or in combination with dexfenfluramine, on pain reactivity in the adult rat. Pharmacol Biochem Behav 2008; 90:339-43. [DOI: 10.1016/j.pbb.2008.03.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2007] [Revised: 02/19/2008] [Accepted: 03/14/2008] [Indexed: 11/26/2022]
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96
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Lee MJ, Swann AC, Dafny N. Methylphenidate sensitization is prevented by prefrontal cortex lesion. Brain Res Bull 2008; 76:131-40. [DOI: 10.1016/j.brainresbull.2007.12.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 12/04/2007] [Accepted: 12/07/2007] [Indexed: 02/05/2023]
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