1
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Dabbs J, Ericson MN, Wilde JH, Lombardo RF, Ashcraft EC, Dickie DA, Harman WD. The Tungsten-Promoted Synthesis of Piperidyl-Modified erythro-Methylphenidate Derivatives. ACS CENTRAL SCIENCE 2023; 9:1775-1783. [PMID: 37780360 PMCID: PMC10540299 DOI: 10.1021/acscentsci.3c00556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Indexed: 10/03/2023]
Abstract
Due to its efficacy as a dopamine receptor agonist, methylphenidate (MPH) is of interest as a potential therapeutic for cocaine addiction. While numerous derivatives of MPH have been investigated for their potential medicinal value, functionalization of the piperidine ring has not been explored. The pyridine borane ligand in WTp(NO)(PMe3)(η2-pyBH3) is dearomatized by the metal and can be elaborated to the analogous η2-mesylpyridinium complex. Installing a methyl phenylacetate moiety at the C2' position via a Reformatsky reaction followed by a tandem protonation/nucleophilic addition sequence results in a library of erythro MPH analogues functionalized at the piperidyl C5' position. The functional group is added chemoselectively to C5', cis to the methyl phenylacetate. Repeating this procedure with an enantioenriched source of the tungsten reagent results in enantioenriched MPH derivatives. All identities of the newly reported compounds are supported by comprehensive 2D NMR and HRMS data or crystallographic data.
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Affiliation(s)
| | | | - Justin H. Wilde
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Rachel F. Lombardo
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Earl C. Ashcraft
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Diane A. Dickie
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - W. Dean Harman
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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2
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Nepal B, Das S, Reith ME, Kortagere S. Overview of the structure and function of the dopamine transporter and its protein interactions. Front Physiol 2023; 14:1150355. [PMID: 36935752 PMCID: PMC10020207 DOI: 10.3389/fphys.2023.1150355] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 02/21/2023] [Indexed: 03/06/2023] Open
Abstract
The dopamine transporter (DAT) plays an integral role in dopamine neurotransmission through the clearance of dopamine from the extracellular space. Dysregulation of DAT is central to the pathophysiology of numerous neuropsychiatric disorders and as such is an attractive therapeutic target. DAT belongs to the solute carrier family 6 (SLC6) class of Na+/Cl- dependent transporters that move various cargo into neurons against their concentration gradient. This review focuses on DAT (SCL6A3 protein) while extending the narrative to the closely related transporters for serotonin and norepinephrine where needed for comparison or functional relevance. Cloning and site-directed mutagenesis experiments provided early structural knowledge of DAT but our contemporary understanding was achieved through a combination of crystallization of the related bacterial transporter LeuT, homology modeling, and subsequently the crystallization of drosophila DAT. These seminal findings enabled a better understanding of the conformational states involved in the transport of substrate, subsequently aiding state-specific drug design. Post-translational modifications to DAT such as phosphorylation, palmitoylation, ubiquitination also influence the plasma membrane localization and kinetics. Substrates and drugs can interact with multiple sites within DAT including the primary S1 and S2 sites involved in dopamine binding and novel allosteric sites. Major research has centered around the question what determines the substrate and inhibitor selectivity of DAT in comparison to serotonin and norepinephrine transporters. DAT has been implicated in many neurological disorders and may play a role in the pathology of HIV and Parkinson's disease via direct physical interaction with HIV-1 Tat and α-synuclein proteins respectively.
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Affiliation(s)
- Binod Nepal
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Sanjay Das
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - Maarten E. Reith
- Department of Psychiatry, New York University School of Medicine, New York City, NY, United States
| | - Sandhya Kortagere
- Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, PA, United States
- *Correspondence: Sandhya Kortagere,
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3
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Ragu Varman D, Subler MA, Windle JJ, Jayanthi LD, Ramamoorthy S. Novelty-induced hyperactivity and suppressed cocaine induced locomotor activation in mice lacking threonine 53 phosphorylation of dopamine transporter. Behav Brain Res 2021; 408:113267. [PMID: 33794225 DOI: 10.1016/j.bbr.2021.113267] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 03/03/2021] [Accepted: 03/24/2021] [Indexed: 12/26/2022]
Abstract
Dopamine (DA) transporter (DAT) is dynamically regulated by several protein kinases and the Thr53 phosphorylation of DAT (pT53-DAT) is documented in heterologous cell models and in rat brain. However, the role of endogenous pT53-DAT in living animals has never been addressed. Here we generated and studied the pT53-lacking DAT mouse model (DAT-Ala53) by CRISPR/Cas9 technology. DAT-Ala53 mice showed normal growth, body weight, body temperature, grip strength, and sucrose preference while pT53-DAT was completely absent. However, DAT-Ala53 mice showed hyperlocomotion, pronounced vertical exploratory behavior, and stereotypy in a novel environment compared to wild-type littermates (WT). DAT-Ala53 mice displayed unaltered levels of monoamines, glutamate, and GABA in the striatum compared to WT. There were also no significant differences between DAT-Ala53 mice and WT in tyrosine hydroxylase (TH) and phospho-TH levels, or in total and surface DAT levels, or in DA-transport kinetic parameters Vmax and Km. Immunohistochemical and colocalization analyses of TH and DAT in caudate-putamen and nucleus accumbens revealed no significant differences between DAT-Ala53 and WT mice. Interestingly, cocaine's potency to inhibit striatal DA transport and cocaine-induced locomotor activation were significantly reduced in the DAT-Ala53 mice. Also, ERK1/2 inhibitors completely failed to inhibit striatal DA uptake in DAT-Ala53 mice. Collectively, our findings reveal that the mice lacking pT53-DAT display novelty-induced hyperactive phenotype despite having normal transporter protein expression, DA-transport kinetics and DA-linked markers. The results also reveal that the lack of endogenous pT53-DAT renders DAT resistant to ERK1/2 inhibition and also less susceptible to cocaine inhibition and cocaine-evoked locomotor stimulation.
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Affiliation(s)
- Durairaj Ragu Varman
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Mark A Subler
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Jolene J Windle
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Lankupalle D Jayanthi
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Sammanda Ramamoorthy
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, 23298, USA.
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4
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Davies SG, Fletcher AM, Peters ME, Roberts PM, Thomson JE. The asymmetric synthesis of (S,S)-methylphenidate hydrochloride via ring-opening of an enantiopure aziridinium intermediate with phenylmagnesium bromide. Tetrahedron 2019. [DOI: 10.1016/j.tet.2019.130713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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5
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Zsilla G, Hegyi DE, Baranyi M, Vizi ES. 3,4-Methylenedioxymethamphetamine, mephedrone, and β-phenylethylamine release dopamine from the cytoplasm by means of transporters and keep the concentration high and constant by blocking reuptake. Eur J Pharmacol 2018; 837:72-80. [DOI: 10.1016/j.ejphar.2018.08.037] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 08/24/2018] [Accepted: 08/29/2018] [Indexed: 02/02/2023]
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6
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Davidson C, Raby CAR, Barrese V, Ramsey J. In Vitro Neurochemical Assessment of Methylphenidate and Its "Legal High" Analogs 3,4-CTMP and Ethylphenidate in Rat Nucleus Accumbens and Bed Nucleus of the Stria Terminalis. Front Psychiatry 2018; 9:149. [PMID: 29892233 PMCID: PMC5985416 DOI: 10.3389/fpsyt.2018.00149] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 04/03/2018] [Indexed: 12/31/2022] Open
Abstract
3,4-dichloromethylphenidate (3,4-CTMP) and ethylphenidate are new psychoactive substances and analogs of the attention deficit medication methylphenidate. Both drugs have been reported on online user fora to induce effects similar to cocaine. In the UK, 3,4-CTMP appeared on the drug market in 2013 and ethylphenidate has been sold since 2010. We aimed to explore the neurochemical effects of these drugs on brain dopamine and noradrenaline efflux. 3,4-CTMP and ethylphenidate, purchased from online vendors, were analyzed using gas chromatography and mass spectroscopy to confirm their identity. Drugs were then tested in adolescent male rat brain slices of the nucleus accumbens and stria terminalis for effects on dopamine and noradrenaline efflux respectively. Fast cyclic voltammetry was used to measure transmitter release. Methylphenidate (10 μM) increased evoked dopamine and noradrenaline efflux by 4- and 2-fold, respectively. 3,4-CTMP (0.1 and 1 μM) increased evoked dopamine and noradrenaline efflux by ~6-fold and 2-fold, respectively. Ethylphenidate (1 μM) doubled evoked dopamine and noradrenaline efflux in both cases. 3,4-CTMP's effect on dopamine efflux was greater than that of methylphenidate, but ethylphenidate appears to be a weaker dopamine transporter inhibitor. Experiments using the dopamine D2 antagonist haloperidol, the noradrenaline α2 receptor antagonist yohimbine, the dopamine transporter inhibitor GBR12909 and the noradrenaline transporter inhibitor desipramine confirmed that we were measuring dopamine in the accumbens and noradrenaline in the ventral BNST. All three psychostimulant drugs, through their effects on dopamine efflux, may have addictive liability although the effect of 3,4-CTMP on dopamine suggests that it might be most addictive and ethylphenidate least addictive.
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Affiliation(s)
- Colin Davidson
- Basic Medical Science, St George's University of London, London, United Kingdom.,Pharmacy & Biomedical Sciences, University of Central Lancashire, Preston, United Kingdom
| | | | - Vincenzo Barrese
- Basic Medical Science, St George's University of London, London, United Kingdom
| | - John Ramsey
- TICTAC Communications Ltd, St George's University of London, London, United Kingdom
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7
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Tamilselvan T, Siddique SA, Vishnupriya M, Sindhu G, Balamurugan E. Behavioral and neurochemical evaluation of ethanol on olanzapine treated methylphenidate induced manic like behaviors in swiss albino mice. BENI-SUEF UNIVERSITY JOURNAL OF BASIC AND APPLIED SCIENCES 2017. [DOI: 10.1016/j.bjbas.2017.01.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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8
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Calipari ES, Ferris MJ, Siciliano CA, Jones SR. Differential influence of dopamine transport rate on the potencies of cocaine, amphetamine, and methylphenidate. ACS Chem Neurosci 2015; 6:155-62. [PMID: 25474655 PMCID: PMC4304485 DOI: 10.1021/cn500262x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
![]()
Dopamine
transporter (DAT) levels vary across brain regions and
individuals, and are altered by drug history and disease states; however,
the impact of altered DAT expression on psychostimulant effects in
brain has not been systematically explored. Using fast scan cyclic
voltammetry, we measured the effects of elevated DAT levels on presynaptic
dopamine parameters as well as the uptake inhibition potency of the
blockers cocaine and methylphenidate (MPH) and the releaser amphetamine
(AMPH) in the nucleus accumbens core. Here we found that increases
in DAT levels, resulting from either genetic overexpression or MPH
self-administration, caused markedly increased maximal rates of uptake
(Vmax) that were positively correlated
with the uptake inhibition potency of AMPH and MPH, but not cocaine.
AMPH and MPH were particularly sensitive to DAT changes, with a 100%
increase in Vmax resulting in a 200% increase
in potency. The relationship between Vmax and MPH potency was the same as that for AMPH, but was different
from that for cocaine, indicating that MPH more closely resembles
a releaser with regard to uptake inhibition. Conversely, the effects
of MPH on stimulated dopamine release were similar to those of cocaine,
with inverted U-shaped increases in release over a concentration–response
curve. This was strikingly different from the release profile of AMPH,
which showed only reductions at high concentrations, indicating that
MPH is not a pure releaser. These data indicate that although MPH
is a DAT blocker, its uptake-inhibitory actions are affected by DAT
changes in a similar manner to releasers. Together, these data show
that fluctuations in DAT levels alter the potency of releasers and
MPH but not blockers and suggest an integral role of the DAT in the
addictive potential of AMPH and related compounds.
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Affiliation(s)
- Erin S. Calipari
- Department
of Physiology
and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Mark J. Ferris
- Department
of Physiology
and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina 27157, United States
| | - Cody A. Siciliano
- 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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9
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Calipari ES, Jones SR. Sensitized nucleus accumbens dopamine terminal responses to methylphenidate and dopamine transporter releasers after intermittent-access self-administration. Neuropharmacology 2014; 82:1-10. [PMID: 24632529 DOI: 10.1016/j.neuropharm.2014.02.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Revised: 01/30/2014] [Accepted: 02/11/2014] [Indexed: 12/11/2022]
Abstract
Long-access methylphenidate (MPH) self-administration has been shown to produce enhanced amphetamine potency at the dopamine transporter and concomitant changes in reinforcing efficacy, suggesting that MPH abuse may change the dopamine system in a way that promotes future drug abuse. While long-access self-administration paradigms have translational validity for cocaine, it may not be as relevant a model of MPH abuse, as it has been suggested that people often take MPH intermittently. Although previous work outlined the neurochemical and behavioral consequences of long-access MPH self-administration, it was not clear whether intermittent access (6 h session; 5 min access/30 min) would result in similar changes. For cocaine, long-access self-administration resulted in tolerance to cocaine's effects on dopamine and behavior while intermittent-access resulted in sensitization. Here we assessed the neurochemical consequences of intermittent-access MPH self-administration on dopamine terminal function. We found increased maximal rates of uptake, increased stimulated release, and subsensitive D2-like autoreceptors. Consistent with previous work using extended-access MPH paradigms, the potencies of amphetamine and MPH, but not cocaine, were increased, demonstrating that unlike cocaine, MPH effects were not altered by the pattern of intake. Although the potency results suggest that MPH may share properties with releasers, dopamine release was increased following acute application of MPH, similar to cocaine, and in contrast to the release decreasing effects of amphetamine. Taken together, these data demonstrate that MPH exhibits properties of both blockers and releasers, and that the compensatory changes produced by MPH self-administration may increase the abuse liability of amphetamines, independent of the pattern of administration.
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Affiliation(s)
- Erin S Calipari
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157, USA
| | - Sara R Jones
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Blvd., Winston-Salem, NC 27157, USA.
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10
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Calipari ES, Ferris MJ, Melchior JR, Bermejo K, Salahpour A, Roberts DCS, Jones SR. Methylphenidate and cocaine self-administration produce distinct dopamine terminal alterations. Addict Biol 2014; 19:145-55. [PMID: 22458761 DOI: 10.1111/j.1369-1600.2012.00456.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Methylphenidate (MPH) is a commonly abused psychostimulant prescribed for the treatment of attention deficit hyperactivity disorder. MPH has a mechanism of action similar to cocaine (COC) and is commonly characterized as a dopamine transporter (DAT) blocker. While there has been extensive work aimed at understanding dopamine (DA) nerve terminal changes following COC self-administration, very little is known about the effects of MPH self-administration on the DA system. We used fast scan cyclic voltammetry in nucleus accumbens core slices from animals with a 5-day self-administration history of 40 injections/day of either MPH (0.56 mg/kg) or COC (1.5 mg/kg) to explore alterations in baseline DA release and uptake kinetics as well as alterations in the interaction of each compound with the DAT. Although MPH and COC have similar behavioral effects, the consequences of self-administration on DA system parameters were found to be divergent. We show that COC self-administration reduced DAT levels and maximal rates of DA uptake, as well as reducing electrically stimulated release, suggesting decreased DA terminal function. In contrast, MPH self-administration increased DAT levels, DA uptake rates and DA release, suggesting enhanced terminal function, which was supported by findings of increased metabolite/DA tissue content ratios. Tyrosine hydroxylase messenger RNA, protein and phosphorylation levels were also assessed in both groups. Additionally, COC self-administration reduced COC-induced DAT inhibition, while MPH self-administration increased MPH-induced DAT inhibition, suggesting opposite pharmacodynamic effects of these two drugs. These findings suggest that the factors governing DA system adaptations are more complicated than simple DA uptake blockade.
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Affiliation(s)
- Erin S Calipari
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston Salem, NC, USA Department of Pharmacology, University of Toronto, Toronto, Canada
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11
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Calipari ES, Ferris MJ, Siciliano CA, Zimmer BA, Jones SR. Intermittent cocaine self-administration produces sensitization of stimulant effects at the dopamine transporter. J Pharmacol Exp Ther 2014; 349:192-8. [PMID: 24566123 DOI: 10.1124/jpet.114.212993] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous literature investigating neurobiological adaptations following cocaine self-administration has shown that high, continuous levels of cocaine intake (long access; LgA) results in reduced potency of cocaine at the dopamine transporter (DAT), whereas an intermittent pattern of cocaine administration (intermittent access; IntA) results in sensitization of cocaine potency at the DAT. Here, we aimed to determine whether these changes are specific to cocaine or translate to other psychostimulants. Psychostimulant potency was assessed by fast-scan cyclic voltammetry in brain slices containing the nucleus accumbens following IntA, short access, and LgA cocaine self-administration, as well as in brain slices from naive animals. We assessed the potency of amphetamine (a releaser), and methylphenidate (a DAT blocker, MPH). MPH was selected because it is functionally similar to cocaine and structurally related to amphetamine. We found that MPH and amphetamine potencies were increased following IntA, whereas neither was changed following LgA or short access cocaine self-administration. Therefore, whereas LgA-induced tolerance at the DAT is specific to cocaine as shown in previous work, the sensitizing effects of IntA apply to cocaine, MPH, and amphetamine. This demonstrates that the pattern with which cocaine is administered is important in determining the neurochemical consequences of not only cocaine effects but potential cross-sensitization/cross-tolerance effects of other psychostimulants as well.
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Affiliation(s)
- Erin S Calipari
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, North Carolina
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12
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Crowley NA, Cody PA, Davis MI, Lovinger DM, Mateo Y. Chronic methylphenidate exposure during adolescence reduces striatal synaptic responses to ethanol. Eur J Neurosci 2014; 39:548-56. [PMID: 24236977 PMCID: PMC4163970 DOI: 10.1111/ejn.12426] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Revised: 10/11/2013] [Accepted: 10/17/2013] [Indexed: 12/01/2022]
Abstract
Dopamine (DA) plays an important role in integrative functions contributing to adaptive behaviors. In support of this essential function, DA modulates synaptic plasticity in different brain areas, including the striatum. Many drugs used for cognitive enhancement are psychostimulants, such as methylphenidate (MPH), which enhance DA levels. MPH treatment is of interest during adolescence, a period of enhanced neurodevelopment during which the DA system is in a state of flux. Recent epidemiological studies report the co-abuse of MPH and ethanol in adolescents and young adults. Although repeated MPH treatment produces enduring changes that affect subsequent behavioral responses to other psychostimulants, few studies have investigated the interactions between MPH and ethanol. Here we addressed whether chronic therapeutic exposure to MPH during adolescence predisposed mice to an altered response to ethanol and whether this was accompanied by altered DA release and striatal plasticity. C57BL/6J mice were administered MPH (3-6 mg/kg/day) via the drinking water between post-natal days 30 and 60. Voltammetry experiments showed that sufficient brain MPH concentrations were achieved during adolescence in mice to increase the DA clearance in adulthood. The treatment also increased long-term depression and reduced the effects of ethanol on striatal synaptic responses. Although the injection of 0.4 or 2 g/kg ethanol dose-dependently decreased locomotion in control mice, only the higher dose decreased locomotion in MPH-treated mice. These results suggested that the administration of MPH during development promoted long-term effects on synaptic plasticity in forebrain regions targeted by DA. These changes in plasticity might, in turn, underlie alterations in behaviors controlled by these brain regions into adulthood.
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Affiliation(s)
- Nicole A Crowley
- Laboratory for Integrative Neuroscience, Section on Synaptic Pharmacology, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, 5625 Fishers Lane, Rockville, MD, 20852, USA
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13
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Calipari ES, Ferris MJ, Salahpour A, Caron MG, Jones SR. Methylphenidate amplifies the potency and reinforcing effects of amphetamines by increasing dopamine transporter expression. Nat Commun 2013; 4:2720. [PMID: 24193139 PMCID: PMC4017736 DOI: 10.1038/ncomms3720] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 10/07/2013] [Indexed: 01/04/2023] Open
Abstract
Methylphenidate (MPH) is commonly diverted for recreational use, but the neurobiological consequences of exposure to MPH at high, abused doses are not well defined. Here we show that MPH self-administration in rats increases dopamine transporter (DAT) levels and enhances the potency of MPH and amphetamine on dopamine responses and drug-seeking behaviours, without altering cocaine effects. Genetic overexpression of the DAT in mice mimics these effects, confirming that MPH self-administration-induced increases in DAT levels are sufficient to induce the changes. Further, this work outlines a basic mechanism by which increases in DAT levels, regardless of how they occur, are capable of increasing the rewarding and reinforcing effects of select psychostimulant drugs, and suggests that individuals with elevated DAT levels, such as ADHD sufferers, may be more susceptible to the addictive effects of amphetamine-like drugs.
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Affiliation(s)
- Erin S. Calipari
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Mark J Ferris
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Ali Salahpour
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
| | - Marc G. Caron
- Department of Cell Biology, Medicine and Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Sara R. Jones
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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14
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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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15
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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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Volz TJ. Neuropharmacological mechanisms underlying the neuroprotective effects of methylphenidate. Curr Neuropharmacol 2010; 6:379-85. [PMID: 19587858 PMCID: PMC2701286 DOI: 10.2174/157015908787386041] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 08/06/2008] [Accepted: 08/25/2008] [Indexed: 11/24/2022] Open
Abstract
Methylphenidate is a psychostimulant that inhibits the neuronal dopamine transporter. In addition, methylphenidate has the intriguing ability to provide neuroprotection from the neurotoxic effects of methamphetamine and perhaps also Parkinson’s disease; both of which may likely involve the abnormal accumulation of cytoplasmic dopamine inside dopaminergic neurons and the resulting formation of dopamine-associated reactive oxygen species. As delineated in this review, the neuroprotective effects of methylphenidate are due, at least in part, to its ability to attenuate or prevent this abnormal cytoplasmic dopamine accumulation through several possible neuropharmacological mechanisms. These may include 1) direct interactions between methylphenidate and the neuronal dopamine transporter which may attenuate or prevent the entry of methamphetamine into dopaminergic neurons and may also decrease the synthesis of cytoplasmic dopamine through a D2 receptor-mediated signal cascade process, and 2) indirect effects upon the functioning of the vesicular monoamine transporter-2 which may increase vesicular dopamine sequestration through both vesicle trafficking and the kinetic upregulation of the vesicular monoamine transporter-2 protein. Understanding these neuropharmacological mechanisms of methylphenidate neuroprotection may provide important insights into the physiologic regulation of dopaminergic systems as well as the pathophysiology of a variety of disorders involving abnormal dopamine disposition ranging from substance abuse to neurodegenerative diseases such as Parkinson’s disease.
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Affiliation(s)
- T J Volz
- Department of Pharmacology and Toxicology, University of Utah, 30 South 2000 East, Room 201, Salt Lake City, UT 84112, USA.
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17
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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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Volz TJ, Farnsworth SJ, Hanson GR, Fleckenstein AE. Methylphenidate-induced alterations in synaptic vesicle trafficking and activity. Ann N Y Acad Sci 2008; 1139:285-90. [PMID: 18991873 DOI: 10.1196/annals.1432.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The psychostimulant, methylphenidate (MPD), is commonly prescribed to treat attention-deficit hyperactivity disorder. MPD binds to the neuronal dopamine (DA) transporter, where it blocks the inward transport of DA. The present study expands upon these findings by examining the effects of in vivo MPD administration on the vesicular monoamine transporter-2 (VMAT-2) in membrane-associated vesicle and cytoplasmic vesicle subcellular fractions (i.e., those vesicles that do and do not co-fractionate with synaptosomal membranes after osmotic lysis, respectively) isolated from lysates of rat striatal synaptosomes. The results indicate that a single MPD administration redistributes VMAT-2 and associated vesicles within nerve terminals away from the synaptosomal membranes and into the cytoplasm, as assessed 1 hour after treatment. DA transport is also increased by MPD in both vesicle fractions (on account of vesicle trafficking in the cytoplasmic vesicles and to kinetic upregulation of the VMAT-2 in the membrane-associated vesicles). This, in turn, leads to an increase in the DA content of both vesicle fractions as well as an increase in the velocity and magnitude of K(+)-stimulated DA release from striatal suspensions. Taken together, these data show that the trafficking, DA sequestration function, DA content, and exocytotic DA release function of synaptic vesicles can all be pharmacologically manipulated by in vivo MPD treatment. These findings may provide important insights useful for understanding and treating disorders involving abnormal DA transmission including drug abuse, Parkinson's disease, and attention-deficit hyperactivity disorder.
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Affiliation(s)
- Trent J Volz
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah, USA
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Farnsworth SJ, Volz TJ, Hanson GR, Fleckenstein AE. Cocaine alters vesicular dopamine sequestration and potassium-stimulated dopamine release: the role of D2 receptor activation. J Pharmacol Exp Ther 2008; 328:807-12. [PMID: 19038779 DOI: 10.1124/jpet.108.146159] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Cocaine is a psychostimulant that inhibits the inward transport of dopamine (DA) via the neuronal DA transporter, thereby increasing DA concentrations in the synaptic cleft. Cocaine administration also causes a redistribution of striatal vesicular monoamine transporter (VMAT)-2-containing vesicles that co-fractionate with synaptosomal membranes after osmotic lysis (referred to herein as membrane-associated vesicles) to a nonmembrane-associated, cytoplasmic subcellular fraction. Although previous studies from our laboratory have focused on the impact of cocaine on cytoplasmic vesicles, the present report describes the pharmacological effects of cocaine on the membrane-associated vesicle population. Results revealed that the redistribution of VMAT-2 and associated vesicles away from synaptosomal membranes is associated with a decrease in total DA transport and DA content in the membrane-associated VMAT-2-containing subcellular fraction. Cocaine also decreases the velocity and magnitude of K+-stimulated exocytotic DA release from whole striatal suspensions. The cocaine-induced VMAT-2 redistribution, decrease in DA release, and decrease in total DA transport are mediated by D2 receptors as these events were prevented by pretreatment with the D2 receptor antagonist, eticlopride [S-(-)-3-chloro-5-ethyl-N-[(1-ethyl-2-pyrrolidinyl)methyl]-6-hydroxy-2-methoxybenzamide hydrochloride]. These data suggest that after cocaine administration, D2 receptors are activated because of increased synaptic DA, resulting in a redistribution of DA-containing vesicles away from synaptosomal membranes, thus leading to less DA released after a depolarizing stimulus. These findings provide insight into not only the mechanism of action of cocaine but also mechanisms underlying the regulation of dopaminergic neurons.
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Affiliation(s)
- Sarah J Farnsworth
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT 84112, USA
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Volz TJ, Farnsworth SJ, Hanson GR, Fleckenstein AE. Method development and validation of an in vitro model of the effects of methylphenidate on membrane-associated synaptic vesicles. J Neurosci Methods 2008; 177:177-82. [PMID: 18992277 DOI: 10.1016/j.jneumeth.2008.10.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Revised: 10/03/2008] [Accepted: 10/07/2008] [Indexed: 11/18/2022]
Abstract
In vivo methylphenidate (MPD) administration decreases vesicular monoamine transporter-2 (VMAT-2) immunoreactivity in membrane-associated vesicles isolated from the striata of treated rats while concurrently kinetically upregulating VMAT-2-mediated vesicular dopamine (DA) sequestration. The functional consequences of these MPD-induced effects include an increase in both vesicular DA content and exocytotic DA release. This report describes experiments designed to develop and validate an in vitro MPD model to further elucidate the molecular mechanism(s) underlying the effects of MPD on the VMAT-2 in membrane-associated vesicles. Method development experiments revealed that in vitro MPD incubation of striatal homogenates, but not striatal synaptosomes, increased DA transport velocities and decreased VMAT-2 immunoreactivity in membrane-associated vesicles. An incubation time of 30min with a MPD concentration of 10mM was optimal. Method validation experiments indicated that in vitro MPD incubation kinetically upregulated VMAT-2 in membrane-associated vesicles, increased vesicular DA content, and increased exocytotic DA release. These results reveal that the in vitro MPD incubation model successfully reproduced the salient features of in vivo MPD administration. This in vitro MPD incubation model may provide novel insights into the receptor-mediated mechanism(s) of action of in vivo MPD in the striatum as well as the physiological regulation of vesicular DA sequestration and synaptic transmission. Accordingly, this in vitro model may help to advance the treatment of disorders involving abnormal DA disposition including Parkinson's disease, attention-deficit hyperactivity disorder, and substance abuse.
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Affiliation(s)
- Trent J Volz
- Department of Pharmacology and Toxicology, University of Utah, 30 South 2000 East, Room 201, Salt Lake City, UT 84112, USA
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Bjorklund NL, Sorg BA, Schenk JO. Neuronal dopamine transporter activity, density and methamphetamine inhibition are differentially altered in the nucleus accumbens and striatum with no changes in glycosylation in rats behaviorally sensitized to methamphetamine. Synapse 2008; 62:736-45. [DOI: 10.1002/syn.20528] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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22
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Volz TJ, Farnsworth SJ, Rowley SD, Hanson GR, Fleckenstein AE. Methylphenidate-induced increases in vesicular dopamine sequestration and dopamine release in the striatum: the role of muscarinic and dopamine D2 receptors. J Pharmacol Exp Ther 2008; 327:161-7. [PMID: 18591219 DOI: 10.1124/jpet.108.139386] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Methylphenidate (MPD) administration alters the subcellular distribution of vesicular monoamine transporter-2 (VMAT-2)-containing vesicles in rat striatum. This report reveals previously undescribed pharmacological features of MPD by elucidating its receptor-mediated effects on VMAT-2-containing vesicles that cofractionate with synaptosomal membranes after osmotic lysis (referred to herein as membrane-associated vesicles) and on striatal dopamine (DA) release. MPD administration increased DA transport into, and decreased the VMAT-2 immunoreactivity of, the membrane-associated vesicle subcellular fraction. These effects were mimicked by the D2 receptor agonist quinpirole and blocked by the D2 receptor antagonist eticlopride. Both MPD and quinpirole increased vesicular DA content. However, MPD increased, whereas quinpirole decreased, K(+)-stimulated DA release from striatal suspensions. Like MPD, the muscarinic receptor agonist, oxotremorine, increased K(+)-stimulated DA release. Both eticlopride and the muscarinic receptor antagonist scopolamine blocked MPD-induced increases in K(+)-stimulated DA release, whereas the N-methyl-d-aspartate receptor antagonist (-)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) was without effect. This suggests that D2 receptors mediate both the MPD-induced redistribution of vesicles away from synaptosomal membranes and the MPD-induced up-regulation of vesicles remaining at the membrane. This results in a redistribution of DA within the striatum from the cytoplasm into vesicles, leading to increased DA release. However, D2 receptor activation alone is not sufficient to mediate the MPD-induced increases in striatal DA release because muscarinic receptor activation is also required. These novel findings provide insight into the mechanism of action of MPD, regulation of DA sequestration/release, and treatment of disorders affecting DA disposition, including attention-deficit hyperactivity disorder, substance abuse, and Parkinson's disease.
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Affiliation(s)
- Trent J Volz
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, UT 84112, USA
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23
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Performance enhancing, non-prescription use of Ritalin: a comparison with amphetamines and cocaine. J Addict Dis 2008; 26:1-6. [PMID: 18032226 DOI: 10.1300/j069v26n04_01] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ritalin, known under chemical name methylphenidate (MPH), is a psychostimulant prescribed to treat attention-deficit/hyperactivity disorder (ADHD) and other conditions. Psychotropic effects and pharmacological pathways evoked by MPH are similar, but not identical to those produced by amphetamines and cocaine. Although not completely understood in detail, MPH psychostimulation is mediated by the increase of central dopamine (DA) and possibly norepinephrine (NE) and serotonin (ST) due to decrease of their re-uptake via binding to and inhibition of DA, NE, and ST transporters. Despite similarity in psychopharmacological effects, the rewarding/ reinforcing ability of MPH appears to be significantly lower than amphetamines and especially cocaine. MPH and similar medications have been widely used on College campuses and by students preparing for exams. Nicknamed 'steroids for SATs,' MPH and related medications are purchased without prescription and their use may even be encouraged by parents and tutors. However, while widely and safely used and administered for over forty years, Ritalin generated significant controversy including MPH abuse and addiction, and adverse reactions. It is now clear that treatment of ADD/ADHD with psychostimulants prevents drug abuse and addictions. Use by those without any medical or psychiatric diagnosis is increasing. In this mini-review, we discuss psychopharmacological and behavioral aspects, and outline neurochemical mechanisms that may provoke Ritalin abuse, addiction and adverse effects compared to amphetamines and cocaine.
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Volz TJ, Farnsworth SJ, King JL, Riddle EL, Hanson GR, Fleckenstein AE. Methylphenidate administration alters vesicular monoamine transporter-2 function in cytoplasmic and membrane-associated vesicles. J Pharmacol Exp Ther 2007; 323:738-45. [PMID: 17693585 DOI: 10.1124/jpet.107.126888] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
In vivo methylphenidate (MPD) administration increases vesicular monoamine transporter-2 (VMAT-2) immunoreactivity, VMAT-2-mediated dopamine (DA) transport, and DA content in a nonmembrane-associated (referred to herein as cytoplasmic) vesicular subcellular fraction purified from rat striatum: a phenomenon attributed to a redistribution of VMAT-2-associated vesicles within nerve terminals. In contrast, the present study elucidated the nature of, and the impact of MPD on, VMAT-2-associated vesicles that cofractionate with synaptosomal membranes after osmotic lysis (referred to herein as membrane-associated vesicles). Results revealed that, in striking contrast to the cytoplasmic vesicles, DA transport velocity versus substrate concentration curves in the membrane-associated vesicles were sigmoidal, suggesting positive cooperativity with respect to DA transport. Additionally, DA transport into membrane-associated vesicles was greater in total capacity in the presence of high DA concentrations than transport into cytoplasmic vesicles. Of potential therapeutic relevance, MPD increased DA transport into the membrane-associated vesicles despite rapidly decreasing (presumably by redistributing) VMAT-2 immunoreactivity in this fraction. Functional relevance was suggested by findings that MPD treatment increased both the DA content of the membrane-associated vesicle fraction and K(+)-stimulated DA release from striatal suspensions. In summary, the present data demonstrate the existence of a previously uncharacterized pool of membrane-associated VMAT-2-containing vesicles that displays novel transport kinetics, has a large sequestration capacity, and responds to in vivo pharmacological manipulation. These findings provide insight into both the regulation of vesicular DA sequestration and the mechanism of action of MPD, and they may have implications regarding treatment of disorders involving abnormal DA disposition, including Parkinson's disease and substance abuse.
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Affiliation(s)
- Trent J Volz
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah 84112, USA
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25
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Bjorklund NL, Volz TJ, Schenk JO. Differential effects of Zn2+ on the kinetics and cocaine inhibition of dopamine transport by the human and rat dopamine transporters. Eur J Pharmacol 2007; 565:17-25. [PMID: 17408612 DOI: 10.1016/j.ejphar.2007.02.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Revised: 02/08/2007] [Accepted: 02/09/2007] [Indexed: 11/17/2022]
Abstract
Zn2+ may play a major role in the modulation of neurotransmission because it modulates membrane receptors and channels. Recent literature has shown Zn2+ inhibits dopamine transport by the dopamine transporter (DAT), the main target of cocaine and some other drugs of abuse. Cocaine inhibits DAT and modulation of the DAT by Zn2+ may alter effects of cocaine on dopamine neurotransmission. This study investigates how Zn2+ changes DAT kinetics and its inhibition by cocaine. Steady-state and pre-steady-state kinetics of DAT activity were investigated using rotating disk electrode voltammetry. Values of KM and Vmax in hDAT and effects of cocaine match those in the literature. Zn2+ allosterically inhibited transport in the human DAT (hDAT) with a KI=7.9+/-0.42 microM. Removal of endogenous Zn2+ with penicillamine in hDAT increased transport values. In contrast, Zn2+ did not alter transport by rat DAT (rDAT), with KM and Vmax values of 1.2+/-0.49 microM and 15.7+/-2.57 pmol/(sx10(6) cells), respectively, and removal of Zn2+ did not increase dopamine transport values. Zn2+ allosterically reduced the inhibition by cocaine in hDAT. Results of pre-steady-state studies demonstrated that Zn2+ increases the second order binding rate constant for dopamine to hDAT (3.5 fold to 19.2x10(6) M-1 s-1 for hDAT). In rat striatal homogenates Zn2+ increased initial dopamine transport velocity and decreased cocaine inhibition providing evidence for differences in sensitivity to Zn2+ between the three different preparations. Modulation of the DAT by Zn2+ needs to be assessed further in development of cocaine antagonists.
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Affiliation(s)
- Nicole L Bjorklund
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
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26
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Riddle EL, Fleckenstein AE, Hanson GR. Role of monoamine transporters in mediating psychostimulant effects. AAPS JOURNAL 2005; 7:E847-51. [PMID: 16594636 PMCID: PMC2750953 DOI: 10.1208/aapsj070481] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Monoamine transporters such as the dopamine (DA) transporter (DAT) and the vesicular monoamine transporter-2 (VMAT-2) are critical regulators of DA disposition within the brain. Alterations in DA disposition can lead to conditions such as drug addiction, Parkinson's disease, and schizophrenia, a fact that underscores the importance of understanding DAergic signaling. Psychostimulants alter DAergic signaling by influencing both DAT and VMAT-2, and although the effects of these drugs result in increased levels of synaptic DA, the mechanisms by which this occurs and the effects that these drugs exert on DAT and VMAT-2 vary. Many psychostimulants can be classified as releasers (ie, amphetamine analogs) or uptake blockers (ie, cocaine-like drugs) based on the mechanism of their acute effects on neurotransmitter flux through the DAT. Releasers and uptake blockers differentially modulate the activity and subcellular distribution of monoamine transporters, a phenomenon likely related to the neurotoxic potential of these drugs to DAergic neurons. This article will review some of the recent findings whereby releasers and uptake blockers alter DAT and VMAT-2 activity and how these alterations may be involved in neurotoxicity, thus providing insight on the neurodegeneration observed in Parkinson's disease.
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Affiliation(s)
- Evan L. Riddle
- Department of Pharmacology and Toxicology, University of Utah, 30 South 2000 East, Room 201, 84112 Salt Lake City, Utah
| | - Annette E. Fleckenstein
- Department of Pharmacology and Toxicology, University of Utah, 30 South 2000 East, Room 201, 84112 Salt Lake City, Utah
| | - Glen R. Hanson
- Department of Pharmacology and Toxicology, University of Utah, 30 South 2000 East, Room 201, 84112 Salt Lake City, Utah
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Chen R, Han DD, Gu HH. A triple mutation in the second transmembrane domain of mouse dopamine transporter markedly decreases sensitivity to cocaine and methylphenidate. J Neurochem 2005; 94:352-9. [PMID: 15998286 DOI: 10.1111/j.1471-4159.2005.03199.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Previously, we reported that Phe105 in transmembrane domain 2 of the mouse dopamine transporter (DAT) is crucial for high-affinity cocaine binding. In the current study, we investigated whether other residues surrounding Phe105 also affect the potency of cocaine inhibition. After three rounds of sequential random mutagenesis at these residues, we found a triple mutant (L104V, F105C and A109V) of mouse DAT that retained over 50% uptake activity and was 69-fold less sensitive to cocaine inhibition when compared with the wild-type mouse DAT. The triple mutation also resulted in a 47-fold decrease in sensitivity to methylphenidate inhibition, suggesting that the binding sites for cocaine and methylphenidate may overlap. In contrast, the inhibition of dopamine uptake by amphetamine or methamphetamine was not significantly changed by the mutations, suggesting that the binding sites for the amphetamines differ from those for cocaine and methylphenidate. Such functional but cocaine-insensitive DAT mutants can be used to generate a knock-in mouse line to study the role of DAT in cocaine addiction.
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Affiliation(s)
- Rong Chen
- Department of Pharmacology, The Ohio State University College of Medicine, Columbus, Ohio, USA
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28
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Dar DE, Mayo C, Uhl GR. The interaction of methylphenidate and benztropine with the dopamine transporter is different than other substrates and ligands. Biochem Pharmacol 2005; 70:461-9. [PMID: 15950948 DOI: 10.1016/j.bcp.2005.04.032] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Revised: 04/04/2005] [Accepted: 04/05/2005] [Indexed: 10/25/2022]
Abstract
A substantial body of evidence suggests that the dopamine transporter (DAT) is the principal site for cocaine-induced reward and euphoria. Interactions between the DAT and its substrates and ligands may therefore be of clinical relevance. The pharmacological characteristics of DAT compounds were compared in wild type (WT) and mutant DATs. The DAT mutants chosen for study were those with reduced binding and uptake activities (aspartic acid 79 mutated to alanine, termed D79A), reduced binding but normal uptake (tyrosine 251 mutated to alanine, termed Y251A; tyrosine 273 mutated to alanine, termed, Y273A), and normal binding but reduced uptake (a double mutation: serines 356 and 359 mutated to alanine, termed S356,359A). The WT and mutant DATs were transfected into COS-7 cells, and their pharmacological activities were examined 3 days later. Different patterns of pharmacological activity emerged. GBR 12909, cocaine, and mazindol each showed reduced affinity for the Y251A and the Y273A mutants, but their affinity for the S356,359A mutant was similar to that of the WT DAT. d-Amphetamine, MPP+, and dopamine each showed reduced affinity for the S356,359A mutant. Benztropine and methylphenidate had a different effect. Relative to the WT DAT, they both showed reduced affinity for the S356,359A mutant when displacing radioactive carboxyfluorotropane (CFT) binding, but similar affinity when inhibiting radioactive dopamine uptake. These results indicate that methylphenidate and benztropine may interact with the DAT in a different fashion then other substrates and ligands.
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Affiliation(s)
- Dalit E Dar
- National Institute on Drug Abuse, Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA.
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29
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Schenk JO, Wright C, Bjorklund N. Unraveling neuronal dopamine transporter mechanisms with rotating disk electrode voltammetry. J Neurosci Methods 2005; 143:41-7. [PMID: 15763135 DOI: 10.1016/j.jneumeth.2004.09.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Herein we describe how the rotating disk electrode voltammetric technique can be used to examine the mechanism(s) of the inward transport of dopamine by the neuronal transporter for dopamine (DAT). The usefulness of making measurements kinetically resolving dopamine transport, interpretations of changes in Km and Vmax, approaches to defining pre-steady-state binding of dopamine to DAT, interactions between competing inhibitors, chemical modification of functional groups within DAT, and a presentation of a hypothetical multi-state model of dopamine transport are presented and discussed.
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Affiliation(s)
- James O Schenk
- Department of Chemistry, Washington State University, Pullman, WA 99164-4630, USA.
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30
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Gilbert KM, Skawinski WJ, Misra M, Paris KA, Naik NH, Buono RA, Deutsch HM, Venanzi CA. Conformational analysis of methylphenidate: comparison of molecular orbital and molecular mechanics methods. J Comput Aided Mol Des 2005; 18:719-38. [PMID: 15865064 DOI: 10.1007/s10822-004-7610-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methylphenidate (MP) binds to the cocaine binding site on the dopamine transporter and inhibits reuptake of dopamine, but does not appear to have the same abuse potential as cocaine. This study, part of a comprehensive effort to identify a drug treatment for cocaine abuse, investigates the effect of choice of calculation technique and of solvent model on the conformational potential energy surface (PES) of MP and a rigid methylphenidate (RMP) analogue which exhibits the same dopamine transporter binding affinity as MP. Conformational analysis was carried out by the AM1 and AM1/SM5.4 semiempirical molecular orbital methods, a molecular mechanics method (Tripos force field with the dielectric set equal to that of vacuum or water) and the HF/6-31G* molecular orbital method in vacuum phase. Although all three methods differ somewhat in the local details of the PES, the general trends are the same for neutral and protonated MP. In vacuum phase, protonation has a distinctive effect in decreasing the regions of space available to the local conformational minima. Solvent has little effect on the PES of the neutral molecule and tends to stabilize the protonated species. The random search (RS) conformational analysis technique using the Tripos force field was found to be capable of locating the minima found by the molecular orbital methods using systematic grid search. This suggests that the RS/Tripos force field/vacuum phase protocol is a reasonable choice for locating the local minima of MP. However, the Tripos force field gave significantly larger phenyl ring rotational barriers than the molecular orbital methods for MP and RMP. For both the neutral and protonated cases, all three methods found the phenyl ring rotational barriers for the RMP conformers/invertamers (denoted as cte, tte, and cta) to be: cte, tte > MP > cta. Solvation has negligible effect on the phenyl ring rotational barrier of RMP. The B3LYP/6-31G* density functional method was used to calculate the phenyl ring rotational barrier for neutral MP and gave results very similar to those of the HF/6-31G* method.
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Affiliation(s)
- Kathleen M Gilbert
- Department of Chemistry and Environmental Science, New Jersey Institute of Technology, 323 King Blvd., Newark, NJ 07102, USA
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Federici M, Geracitano R, Bernardi G, Mercuri NB. Actions of methylphenidate on dopaminergic neurons of the ventral midbrain. Biol Psychiatry 2005; 57:361-5. [PMID: 15705351 DOI: 10.1016/j.biopsych.2004.11.030] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Revised: 10/04/2004] [Accepted: 11/18/2004] [Indexed: 11/24/2022]
Abstract
BACKGROUND Methylphenidate has been suggested to exert its therapeutic effect mainly by blocking the dopamine transporter. In spite of the importance of this interaction, no detailed information is available yet on its actions on single dopaminergic neurons. METHODS We examined the effects of methylphenidate on dopaminergic neurons using electrophysiological recordings from rat midbrain slices. RESULTS Methylphenidate inhibited spontaneous firing and caused a membrane hyperpolarization in current clamp or an outward current in voltage clamp. These effects were antagonized by the D(2) receptor antagonist sulpiride. An acute dopamine-depleting treatment of the slices with the dopa-decarboxylase inhibitor carbidopa significantly reduced the effects of methylphenidate. This drug potentiated, in a concentration-dependent manner, cellular responses to exogenous dopamine application. CONCLUSIONS Our electrophysiological data are consistent with the hypothesis that methylphenidate inhibits dopamine transporter and suggest that the depression of firing is mediated by the release of newly synthesized dopamine which accumulates extracellularly due to inhibition of its reuptake.
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Affiliation(s)
- Mauro Federici
- Laboratory of Experimental Neurology, IRCCS-Fondazione Santa Lucia, Rome, Italy
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Volz TJ, Bjorklund NL, Schenk JO. Methylphenidate analogs with behavioral differences interact differently with arginine residues on the dopamine transporter in rat striatum. Synapse 2005; 57:175-8. [PMID: 15945061 DOI: 10.1002/syn.20161] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The methylphenidate analogs N-methyl-4-methyl-methylphenidate and N-benzylmethylphenidate are believed to interact differently with the dopamine transporter (DAT) in vitro and in vivo. Herein, we report that methylphenidate and N-methyl-4-methyl-methylphenidate, but not N-benzylmethylphenidate, protect the rat striatal DAT from the arginine-selective chemical modifying agent, phenylglyoxal. This suggests that methylphenidate and N-methyl-4-methyl-methylphenidate, but not N-benzylmethylphenidate, interact with the guanidine groups of arginine residues in the DAT of rat striatum. This differential interaction may, at least in part, explain the in vitro and in vivo differences between N-methyl-4-methyl-methylphenidate and N-benzylmethylphenidate.
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Affiliation(s)
- Trent J Volz
- Department of Chemistry, Washington State University, Pullman, Washington 99164-4630, USA
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Davies HML, Hopper DW, Hansen T, Liu Q, Childers SR. Synthesis of methylphenidate analogues and their binding affinities at dopamine and serotonin transport sites. Bioorg Med Chem Lett 2004; 14:1799-802. [PMID: 15026075 DOI: 10.1016/j.bmcl.2003.12.097] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2003] [Accepted: 12/23/2003] [Indexed: 10/26/2022]
Abstract
The rhodium(II)-catalyzed intermolecular C-H insertion of methyl aryldiazoacetates with either N-Boc-piperidine or N-Boc-pyrrolidine followed by deprotection with trifluoroacetic acid is a very direct method for the synthesis of methylphenidate analogues. By using either dirhodium tetraacetate or dirhodium tetraprolinate derivatives as catalyst, either the racemic or enantioenriched methylphenidate analogues can be prepared. The binding affinities of the methylphenidate analogues to both the dopamine and the serotonin transporters are described. The most notable compounds are the erythro-(2-naphthyl) analogues which display high binding affinity and selectivity for the serotonin transporter.
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Affiliation(s)
- Huw M L Davies
- Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260-3000, USA.
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Schenk JO. The functioning neuronal transporter for dopamine: kinetic mechanisms and effects of amphetamines, cocaine and methylphenidate. PROGRESS IN DRUG RESEARCH. FORTSCHRITTE DER ARZNEIMITTELFORSCHUNG. PROGRES DES RECHERCHES PHARMACEUTIQUES 2003; 59:111-31. [PMID: 12458965 DOI: 10.1007/978-3-0348-8171-5_4] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The dopamine transporter (DAT) is a transmembrane spanning protein that catalyzes the transport of dopamine across the neuronal membrane to concentrate the neurotransmitter inside the cell. Although the uptake of dopamine has been studied since the 1960s, more recent advances in knowledge of the protein itself and in making kinetically resolved measurements of its action have led to more insights into its mechanism and pharmacology. The literature of the kinetics of transporters and kinetic measurements of DAT activity is reviewed to provide an overview of the multisubstrate mechanism of DAT activity, its pharmacology with regard to amphetamine, cocaine and methylphenidate, and correlations of DAT activity with some behavioral outputs.
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Affiliation(s)
- James O Schenk
- Department of Chemistry, School of Molecular Biosciences, and Program in Pharmacology/Toxicology, Washington State University, Pullman, WA 99164-4630, USA.
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