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Jiang Y, Ray A, Junaid MSA, Bhattaccharjee SA, Kelley K, Banga AK, Blough BE, Murnane KS. The pharmacokinetics of 3-fluoroamphetamine following delivery using clinically relevant routes of administration. Drug Deliv Transl Res 2020; 10:271-281. [PMID: 31642004 PMCID: PMC6982562 DOI: 10.1007/s13346-019-00685-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
3-Fluoroamphetamine (also called PAL-353) is a synthetic amphetamine analog that has been investigated for cocaine use disorder (CUD), yet no studies have characterized its pharmacokinetics (PK). In the present study, we determined the PK of PAL-353 in male Sprague Dawley rats following intravenous bolus injection (5 mg/kg). Plasma samples were analyzed using a novel bioanalytical method that coupled liquid-liquid extraction and LC-MS/MS. The primary PK parameters determined by WinNonlin were a C0 (ng/mL) of 1412.09 ± 196.12 and a plasma half-life of 2.27 ± 0.67 h. As transdermal delivery may be an optimal approach to delivering PAL-353 for CUD, we assessed its PK profile following application of 50 mg of transdermal gel (10% w/w drug over 5 cm2). The 10% w/w gel resulted in a short lag time, sustained delivery, and a rapid clearance in plasma immediately after removal. The rodent PK data were verified by examining in vitro permeation through human epidermis mounted on Franz diffusion cells. An in vitro-in vivo correlation (IVIVC) analysis was performed using the Phoenix IVIVC toolkit to assess the predictive relationship between rodent and human skin absorption/permeation. The in vitro permeation study revealed a dose-proportional cumulative and steady-state flux with ~ 70% of drug permeated. The fraction absorbed in vivo and fraction permeated in vitro showed a linear relationship. In conclusion, we have characterized the PK profile of PAL-353, demonstrated that it has favorable PK properties for transdermal administration for CUD, and provided preliminary evidence of the capacity of rodent data to predict human skin flux.
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Affiliation(s)
- Ying Jiang
- Department of Pharmaceutical Sciences, Mercer University College of Pharmacy, Mercer University Health Sciences Center, 3001 Mercer University Dr., Atlanta, GA, 30341, USA
| | - Azizi Ray
- Department of Pharmaceutical Sciences, Mercer University College of Pharmacy, Mercer University Health Sciences Center, 3001 Mercer University Dr., Atlanta, GA, 30341, USA
| | - Mohammad Shajid Ashraf Junaid
- Department of Pharmaceutical Sciences, Mercer University College of Pharmacy, Mercer University Health Sciences Center, 3001 Mercer University Dr., Atlanta, GA, 30341, USA
| | - Sonalika Arup Bhattaccharjee
- Department of Pharmaceutical Sciences, Mercer University College of Pharmacy, Mercer University Health Sciences Center, 3001 Mercer University Dr., Atlanta, GA, 30341, USA
| | - Kayla Kelley
- Department of Pharmaceutical Sciences, Mercer University College of Pharmacy, Mercer University Health Sciences Center, 3001 Mercer University Dr., Atlanta, GA, 30341, USA
| | - Ajay K Banga
- Department of Pharmaceutical Sciences, Mercer University College of Pharmacy, Mercer University Health Sciences Center, 3001 Mercer University Dr., Atlanta, GA, 30341, USA
| | - Bruce E Blough
- Center for Drug Discovery, Research Triangle Institute, Research Triangle Park, Durham, NC, 27709, USA
| | - Kevin S Murnane
- Department of Pharmaceutical Sciences, Mercer University College of Pharmacy, Mercer University Health Sciences Center, 3001 Mercer University Dr., Atlanta, GA, 30341, USA.
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Microdialysis and its use in behavioural studies: Focus on acetylcholine. J Neurosci Methods 2018; 300:206-215. [DOI: 10.1016/j.jneumeth.2017.08.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 08/01/2017] [Accepted: 08/11/2017] [Indexed: 12/28/2022]
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Smith DA, Negus SS, Poklis JL, Blough BE, Banks ML. Cocaine-like discriminative stimulus effects of alpha-pyrrolidinovalerophenone, methcathinone and their 3,4-methylenedioxy or 4-methyl analogs in rhesus monkeys. Addict Biol 2017; 22:1169-1178. [PMID: 27060605 DOI: 10.1111/adb.12399] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 02/25/2016] [Accepted: 03/01/2016] [Indexed: 01/20/2023]
Abstract
Synthetic cathinones are beta-ketone amphetamine analogs that have emerged as a heterogeneous class of abused compounds that function as either monoamine transporter substrates or inhibitors. Pre-clinical drug discrimination procedures are useful for interrogating structure-activity relationships of abuse-related drug effects; however, in vivo structure-activity relationship comparisons between synthetic cathinones with different mechanisms of action are lacking. The aim of the present study was to determine whether the cocaine-like discriminative stimulus effects of the monoamine transporter inhibitor alpha-pyrrolidinovalerophenone (alpha-PVP) and the monoamine transporter substrate methcathinone were differentially sensitive to 3,4-methylenedioxy and 4-methyl substitutions. Male rhesus monkeys (n = 4) were trained to discriminate intramuscular cocaine (0.32 mg/kg) from saline in a two-key food-reinforced discrimination procedure. Potency and timecourse of cocaine-like discriminative stimulus effects were determined for (±)-alpha-PVP, (±)-methcathinone and their 3,4-methylenedioxy or 4-methyl analogs. Alpha-PVP and methcathinone produced dose- and time-dependent cocaine-like effects. A 3,4-methylenedioxy addition to either alpha-PVP or methcathinone (methylone) did not alter the potency or efficacy to produce cocaine-like effects, but did prolong the time course. A 4-methyl addition to alpha-PVP (pyrovalerone) did not alter the potency or efficacy to produce cocaine-like effects, but did prolong the time course. In contrast, addition of a 4-methyl moiety to methcathinone (4MMC; mephedrone) significantly attenuated efficacy to produce cocaine-like effects. Overall, these results suggest different structural requirements for cocaine-like discriminative stimulus effects of monoamine transporter inhibitor and substrate synthetic cathinone analogs. Given that 4MMC is more hydrophobic than MDMC, these results suggest that hydrophobicity may be an important determinant for limiting monoamine transporter substrate abuse-related behavioral effects.
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Affiliation(s)
- Douglas A. Smith
- Department of Pharmacology and Toxicology; Virginia Commonwealth University; Richmond VA USA 23298
| | - S. Stevens Negus
- Department of Pharmacology and Toxicology; Virginia Commonwealth University; Richmond VA USA 23298
- Institute for Drug and Alcohol Studies; Virginia Commonwealth University; Richmond VA USA 23298
| | - Justin L. Poklis
- Department of Pharmacology and Toxicology; Virginia Commonwealth University; Richmond VA USA 23298
| | - Bruce E. Blough
- Center for Drug Discovery; Research Triangle Institute; Research Triangle Park NC USA 27709
| | - Matthew L. Banks
- Department of Pharmacology and Toxicology; Virginia Commonwealth University; Richmond VA USA 23298
- Institute for Drug and Alcohol Studies; Virginia Commonwealth University; Richmond VA USA 23298
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New Psychoactive Substances: Chemistry, Pharmacology, Metabolism, and Detectability of Amphetamine Derivatives With Modified Ring Systems. Ther Drug Monit 2016; 38:4-11. [PMID: 26327309 DOI: 10.1097/ftd.0000000000000240] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In recent years, new amphetamine derivatives with modified ring systems were sold and consumed as new drugs of abuse. They belong together with other new drugs of abuse classes to the so-called new psychoactive substances (NPS). The chemistry, pharmacology, toxicology, metabolism, and toxicokinetics are shortly discussed of camfetamine, 3 methylphenyl-amphetamines (2-MA, 3-MA, and 4-MA), 2-methiopropamine (2-MPA), and 5-(2-aminopropyl)benzofuran (5-APB), 6-(2-aminopropyl)benzofuran (6-APB, so-called "benzofury") and their N-methyl derivatives 5-MAPB and 6-MAPB. Only a rough assessment of the pharmacology and toxicology NPS can be performed in most cases using published data of analogs, trip reports, and described clinical cases. Accordingly, they all act more or less as central nervous stimulants mainly by increasing the concentration of the neurotransmitters noradrenaline, dopamine, and serotonin (5-HT) by inducing their release and reuptake inhibition. Thus, the acute toxicity is associated with the sympathomimetic effects, such as mydriasis, hyperthermia, hypertension, tachycardia, insomnia, and anxiety. With the exception of 5- and 6-APB, these NPS were extensively metabolized by N-demethylation and/or aromatic hydroxylation catalyzed by various cytochrome P450 isoenzymes followed by partial glucuronidation and/or sulfation. For urinalysis, the unchanged drugs and/or the nor-metabolites are the main targets.
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Howell LL, Cunningham KA. Serotonin 5-HT2 receptor interactions with dopamine function: implications for therapeutics in cocaine use disorder. Pharmacol Rev 2015; 67:176-97. [PMID: 25505168 DOI: 10.1124/pr.114.009514] [Citation(s) in RCA: 167] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Cocaine exhibits prominent abuse liability, and chronic abuse can result in cocaine use disorder with significant morbidity. Major advances have been made in delineating neurobiological mechanisms of cocaine abuse; however, effective medications to treat cocaine use disorder remain to be discovered. The present review will focus on the role of serotonin (5-HT; 5-hydroxytryptamine) neurotransmission in the neuropharmacology of cocaine and related abused stimulants. Extensive research suggests that the primary contribution of 5-HT to cocaine addiction is a consequence of interactions with dopamine (DA) neurotransmission. The literature on the neurobiological and behavioral effects of cocaine is well developed, so the focus of the review will be on cocaine with inferences made about other monoamine uptake inhibitors and releasers based on mechanistic considerations. 5-HT receptors are widely expressed throughout the brain, and several different 5-HT receptor subtypes have been implicated in mediating the effects of endogenous 5-HT on DA. However, the 5-HT2A and 5-HT2C receptors in particular have been implicated as likely candidates for mediating the influence of 5-HT in cocaine abuse as well as to traits (e.g., impulsivity) that contribute to the development of cocaine use disorder and relapse in humans. Lastly, new approaches are proposed to guide targeted development of serotonergic ligands for the treatment of cocaine use disorder.
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Affiliation(s)
- Leonard L Howell
- Yerkes National Primate Research Center, Emory University, Atlanta, Georgia (L.L.H.); and Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas (K.A.C.)
| | - Kathryn A Cunningham
- Yerkes National Primate Research Center, Emory University, Atlanta, Georgia (L.L.H.); and Center for Addiction Research and Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston, Texas (K.A.C.)
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Chavant F, Boucher A, Le Boisselier R, Deheul S, Debruyne D. New synthetic drugs in addictovigilance. Therapie 2015; 70:167-89. [PMID: 25858573 DOI: 10.2515/therapie/2015001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 10/21/2014] [Indexed: 01/23/2023]
Abstract
New substances, also known as "designer drugs" or "legal highs" are increasingly available to drug users. Two hundred and fifteen hitherto unlisted substances have been notified by European Union member states since 2005. These synthetic drugs, which have been developed to side-step the legislation on drugs, are analogues or derivatives of existing drugs and medications. The availability of these "legal highs", sold on Internet under various denominations such as bath salt, plant fertilizer, chemical not intended for human use, or spice, is unlimited. The effects felt by users vary, and the substances may be stimulant, entactogenic, hallucinogenic, psychedelic or dissociative. The pharmacological targets also vary, and may be either the increase of extracellular levels of neurotransmitters via different mechanisms (reuptake inhibition, stimulation of intracellular release) or else fixation on specific receptors. Several chemical classes, themselves divided into sub-classes, are involved: phenethylamines, tryptamines, piperazines, cathinones, cannabinoids etc. The toxicity of the main members of these categories is increasingly well known, the most deleterious being behavioural effects, physical manifestations, and cardiovascular consequences. However, small variations in their chemical structure can generate effects that are quantitatively different, thus enhancing their toxicity or addictive potential, and much remains to be achieved in terms of knowledge about these new drugs. These substances are indeed present on the French territory, as shown by data provided by the Observatoire Français des Drogues et Toxicomanies, and notifications by the French Addictovigilance network. Screening in clinical toxicology laboratories is not widespread, since these molecules are not detected by the standard screening tests, so that there is probably an under-estimation of the use of these new drugs. The legislation on these substances changes regularly, with more and more countries classifying them as "narcotics" or illegal psychotropic drugs so as to restrict their use, applying a generic classification when possible.
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Affiliation(s)
| | | | | | - Sylvie Deheul
- Centre d'Addictovigilance de Lille, Faculté de médecine, Lille, France
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Chavant F, Boucher A, Le Boisselier R, Deheul S, Debruyne D. Nouvelles drogues de synthèse en addictovigilance. Therapie 2015. [DOI: 10.2515/therapie/2014235] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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8
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Studies on the metabolism and the detectability of 4-methyl-amphetamine and its isomers 2-methyl-amphetamine and 3-methyl-amphetamine in rat urine using GC-MS and LC-(high-resolution)-MS n. Anal Bioanal Chem 2014; 406:1957-74. [DOI: 10.1007/s00216-013-7595-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 12/12/2013] [Accepted: 12/19/2013] [Indexed: 10/25/2022]
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Serotonin 2A receptors differentially contribute to abuse-related effects of cocaine and cocaine-induced nigrostriatal and mesolimbic dopamine overflow in nonhuman primates. J Neurosci 2013; 33:13367-74. [PMID: 23946394 DOI: 10.1523/jneurosci.1437-13.2013] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Two of the most commonly used procedures to study the abuse-related effects of drugs in laboratory animals are intravenous drug self-administration and reinstatement of extinguished behavior previously maintained by drug delivery. Intravenous self-administration is widely accepted to model ongoing drug-taking behavior, whereas reinstatement procedures are accepted to model relapse to drug taking following abstinence. Previous studies indicate that 5-HT2A receptor antagonists attenuate the reinstatement of cocaine-maintained behavior but not cocaine self-administration in rodents. Although the abuse-related effects of cocaine have been closely linked to brain dopamine systems, no previous study has determined whether this dissociation is related to differential regulation of dopamine neurotransmission. To elucidate the neuropharmacological and neuroanatomical mechanisms underlying this phenomenon, we evaluated the effects of the selective 5-HT2A receptor antagonist M100907 on intravenous cocaine self-administration and drug- and cue-primed reinstatement in rhesus macaques (Macaca mulatta). In separate subjects, we evaluated the role of 5-HT2A receptors in cocaine-induced dopamine overflow in the nucleus accumbens (n = 4) and the caudate nucleus (n = 5) using in vivo microdialysis. Consistent with previous studies, M100907 (0.3 mg/kg, i.m.) significantly attenuated drug- and cue-induced reinstatement but had no significant effects on cocaine self-administration across a range of maintenance doses. Importantly, M100907 (0.3 mg/kg, i.m.) attenuated cocaine-induced (1.0 mg/kg, i.v.) dopamine overflow in the caudate nucleus but not in the nucleus accumbens. These data suggest that important abuse-related effects of cocaine are mediated by distinct striatal dopamine projection pathways.
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Blanckaert P, van Amsterdam J, Brunt T, van den Berg J, Van Durme F, Maudens K, van Bussel J. 4-Methyl-amphetamine: a health threat for recreational amphetamine users. J Psychopharmacol 2013; 27:817-22. [PMID: 23784740 DOI: 10.1177/0269881113487950] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
4-Methylamphetamine (4-MA) was originally developed as an appetite suppressant, but development was halted due to side effects. It has recently resurfaced as a new psychoactive substance in Europe, and is mostly found together with amphetamine. Around 11.5% of tested Dutch speed samples were positive for 4-MA. In Belgium, 4-MA was also found in speed samples. In 2011 and 2012, several fatal incidents after amphetamine use were observed in Belgium, the United Kingdom and The Netherlands. In all victims, toxicological analysis confirmed the presence of 4-MA, in addition to amphetamine. The observed blood amphetamine levels were too low to be fatal. Contrary to amphetamine, which displays noradrenergic and dopaminergic activity, 4-MA also shows serotonergic activity, which may contribute to the observed toxicity. Other mechanisms of toxicity are put forward in this paper as well. To conclude, the observed toxicity is most likely the result of the combined dopaminergic activity of amphetamine and the serotonergic activity of 4-MA. In addition, the presence of 4-MA may have dampened the psychoactive effects of amphetamine by attenuation of the amphetamine-induced dopamine release, potentially inclining users to ingest higher doses of contaminated speed. Also, slower metabolism of 4-MA and its MAO-inhibiting properties can also contribute to the unusual high toxicity of 4-MA.
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Affiliation(s)
- P Blanckaert
- Belgian Early Warning System on Drugs, Scientific Institute of Public Health, Brussels, Belgium.
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Manvich DF, Kimmel HL, Cooper DA, Howell LL. The serotonin 2C receptor antagonist SB 242084 exhibits abuse-related effects typical of stimulants in squirrel monkeys. J Pharmacol Exp Ther 2012; 342:761-9. [PMID: 22685342 DOI: 10.1124/jpet.112.195156] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Antagonists of the serotonin (5-hydroxytryptamine; 5-HT) type 2C receptor (5-HT(2C)R) are being considered as potential pharmacotherapeutics for various affective disorders, but evidence suggests that these compounds enhance the effects of cocaine and related psychostimulants in rodents. However, the effects of selective 5-HT(2C)R antagonists have not been evaluated in nonhuman primates. The present studies used operant-behavioral and in vivo microdialysis techniques to assess the impact of 5-HT(2C)R antagonism on the behavioral and neurochemical effects of cocaine in squirrel monkeys. In subjects trained to lever-press on a fixed-interval schedule of stimulus termination, pretreatment with the highly selective 5-HT(2C)R antagonist 6-chloro-2,3-dihydro-5-methyl-N-[6-[(2-methyl-3-pyridinyl)oxy]-3-pyridinyl]-1H-indole-1-carboxyamide dihydrochloride (SB 242084) (vehicle, 0.01-0.1 mg/kg) produced behavioral-stimulant effects alone and interacted with cocaine in an apparently additive manner. In monkeys trained to self-administer intravenous cocaine according to a second-order schedule of drug delivery, SB 242084 (vehicle, 0.03-0.1 mg/kg) modulated cocaine-induced reinstatement of previously extinguished responding and maintained self-administration behavior when substituted for cocaine availability. These studies are the first to assess the direct reinforcing effects of a 5-HT(2C)R-selective antagonist in any species. Finally, in vivo microdialysis studies revealed that pretreatment with SB 242084 (0.1 mg/kg) modulated cocaine-induced dopamine increases within the nucleus accumbens, but not the caudate nucleus, of awake subjects. Taken together, the results suggest that SB 242084 exhibits a behavioral profile that is qualitatively similar to other psychostimulants, although its efficacy is modest compared with cocaine. The observed interactions with cocaine and the substitution for cocaine self-administration may be indicative of some degree of abuse potential in humans.
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Affiliation(s)
- Daniel F Manvich
- Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
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Manvich DF, Kimmel HL, Howell LL. Effects of serotonin 2C receptor agonists on the behavioral and neurochemical effects of cocaine in squirrel monkeys. J Pharmacol Exp Ther 2012; 341:424-34. [PMID: 22328576 DOI: 10.1124/jpet.111.186981] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Accumulating evidence indicates that the serotonin system modulates the behavioral and neurochemical effects of cocaine, but the receptor subtypes mediating these effects remain unknown. Recent studies have demonstrated that pharmacological activation of the serotonin 2C receptor (5-HT(2C)R) attenuates the behavioral and neurochemical effects of cocaine in rodents, but such compounds have not been systematically evaluated in nonhuman primates. The present experiments sought to determine the impact of pretreatment with the preferential 5-HT(2C)R agonist m-chlorophenylpiperazine (mCPP) and the selective 5-HT(2C)R agonist Ro 60-0175 [(α-S)-6-chloro-5-fluoro-α-methyl-1H-indole-1-ethanamine fumarate] on the behavioral and neurochemical effects of cocaine in squirrel monkeys. In subjects trained to lever-press according to a 300-s fixed-interval schedule of stimulus termination, pretreatment with either 5-HT(2C)R agonist dose-dependently and insurmountably attenuated the behavioral stimulant effects of cocaine. In subjects trained to self-administer cocaine, both compounds dose-dependently and insurmountably attenuated cocaine-induced reinstatement of previously extinguished responding in an antagonist-reversible manner, and the selective agonist Ro 60-0175 also attenuated the reinforcing effects of cocaine during ongoing cocaine self-administration. It is noteworthy that the selective agonist Ro 60-0175 exhibited behavioral specificity because it did not significantly alter nondrug-maintained responding. Finally, in vivo microdialysis studies revealed that pretreatment with Ro 60-0175 caused a reduction of cocaine-induced dopamine increases within the nucleus accumbens, but not the caudate nucleus. These results suggest that 5-HT(2C)R agonists functionally antagonize the behavioral effects of cocaine in nonhuman primates, possibly via a selective modulation of cocaine-induced dopamine increases within the mesolimbic dopamine system and may therefore represent a novel class of pharmacotherapeutics for the treatment of cocaine abuse.
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Affiliation(s)
- Daniel F Manvich
- Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
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Schenk S, Colussi-Mas J, Do J, Bird J. Profile of MDMA Self-Administration from a Large Cohort of Rats: MDMA Develops a Profile of Dependence with Extended Testing. ACTA ACUST UNITED AC 2012. [DOI: 10.4303/jdar/235602] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Baumann MH, Clark RD, Woolverton WL, Wee S, Blough BE, Rothman RB. In vivo effects of amphetamine analogs reveal evidence for serotonergic inhibition of mesolimbic dopamine transmission in the rat. J Pharmacol Exp Ther 2011; 337:218-25. [PMID: 21228061 DOI: 10.1124/jpet.110.176271] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Evidence suggests that elevations in extracellular serotonin (5-HT) in the brain can diminish stimulant effects of dopamine (DA). To assess this proposal, we evaluated the pharmacology of amphetamine analogs (m-fluoroamphetamine, p-fluoroamphetamine, m-methylamphetamine, p-methylamphetamine), which display similar in vitro potency as DA releasers (EC(50) = 24-52 nM) but differ in potency as 5-HT releasers (EC(50) = 53-1937 nM). In vivo microdialysis was used to assess the effects of drugs on extracellular DA and 5-HT in rat nucleus accumbens, while simultaneously measuring ambulation (i.e., forward locomotion) and stereotypy (i.e., repetitive movements). Rats received two intravenous injections of drug, 1 mg/kg at time 0 followed by 3 mg/kg 60 min later. All analogs produced dose-related increases in dialysate DA and 5-HT, but the effects on DA did not agree with in vitro predictions. Maximal elevation of dialysate DA ranged from 5- to 14-fold above baseline and varied inversely with 5-HT response, which ranged from 6- to 24-fold above baseline. All analogs increased ambulation and stereotypy, but drugs causing greater 5-HT release (e.g., p-methylamphetamine) were associated with significantly less forward locomotion. The magnitude of ambulation was positively correlated with extracellular DA (p < 0.001) and less so with the ratio of DA release to 5-HT release (i.e., percentage DA increase divided by percentage 5-HT increase) (p < 0.029). Collectively, our findings are consistent with the hypothesis that 5-HT release dampens stimulant effects of amphetamine-type drugs, but further studies are required to address the precise mechanisms underlying this phenomenon.
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Affiliation(s)
- Michael H Baumann
- Translational Pharmacology Section, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, USA
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Schenk S. MDMA ("ecstasy") abuse as an example of dopamine neuroplasticity. Neurosci Biobehav Rev 2010; 35:1203-18. [PMID: 21184779 DOI: 10.1016/j.neubiorev.2010.12.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 12/12/2010] [Accepted: 12/15/2010] [Indexed: 01/12/2023]
Abstract
A number of reviews have focused on the short- and long-term effects of MDMA and, in particular, on the persistent deficits in serotonin neurotransmission that accompany some exposure regimens. The mechanisms underlying the serotonin deficits and their relevance to various behavioral and cognitive consequences of MDMA use are still being debated. It has become clear, however, that some individuals develop compulsive and uncontrolled drug-taking that is consistent with abuse. For other drugs of abuse, this transition has been attributed to neuroadaptations in central dopamine mechanisms that occur as a function of repeated drug exposure. A question remains as to whether similar neuroadaptations occur as a function of exposure to MDMA and the impact of serotonin neurotoxicity in the transition from use to abuse. This review focuses specifically on this issue by first providing an overview of human studies and then reviewing the animal literature with specific emphasis on paradigms that measure subjective effects of drugs and self-administration as indices of abuse liability. It is suggested that serotonin deficits resulting from repeated exposure to MDMA self-administration lead to a sensitized dopaminergic response to the drug and that this sensitized response renders MDMA comparable to other drugs of abuse.
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Affiliation(s)
- Susan Schenk
- Victoria University of Wellington, School of Psychology, Kelburn Pde, Easterfield Bldg Rm 702, Wellington, New Zealand.
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