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Jablonski MR, King N, Wang Y, Winner JG, Watterson LR, Gunselman S, Dechairo BM. Analytical validation of a psychiatric pharmacogenomic test. Per Med 2018; 15:189-197. [DOI: 10.2217/pme-2017-0094] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Aim: The aim of this study was to validate the analytical performance of a combinatorial pharmacogenomics test designed to aid in the appropriate medication selection for neuropsychiatric conditions. Materials & methods: Genomic DNA was isolated from buccal swabs. Twelve genes (65 variants/alleles) associated with psychotropic medication metabolism, side effects, and mechanisms of actions were evaluated by bead array, MALDI-TOF mass spectrometry, and/or capillary electrophoresis methods (GeneSight Psychotropic, Assurex Health, Inc.). Results: The combinatorial pharmacogenomics test has a dynamic range of 2.5–20 ng/μl of input genomic DNA, with comparable performance for all assays included in the test. Both the precision and accuracy of the test were >99.9%, with individual gene components between 99.4 and 100%. Conclusion: This study demonstrates that the combinatorial pharmacogenomics test is robust and reproducible, making it suitable for clinical use.
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Affiliation(s)
| | - Nina King
- Assurex Health, Inc., Mason, OH, USA
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Simmons SJ, Gregg RA, Tran FH, Mo L, von Weltin E, Barker DJ, Gentile TA, Watterson LR, Rawls SM, Muschamp JW. Comparing rewarding and reinforcing properties between 'bath salt' 3,4-methylenedioxypyrovalerone (MDPV) and cocaine using ultrasonic vocalizations in rats. Addict Biol 2018; 23:102-110. [PMID: 27910188 DOI: 10.1111/adb.12479] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 10/20/2016] [Accepted: 11/01/2016] [Indexed: 12/21/2022]
Abstract
Abuse of synthetic psychostimulants like synthetic cathinones has risen in recent years. 3,4-Methylenedioxypyrovalerone (MDPV) is one such synthetic cathinone that demonstrates a mechanism of action similar to cocaine. Compared to cocaine, MDPV is more potent at blocking dopamine and norepinephrine reuptake and is readily self-administered by rodents. The present study compared the rewarding and reinforcing properties of MDPV and cocaine using systemic injection dose-response and self-administration models. Fifty kilohertz ultrasonic vocalizations (USVs) were recorded as an index of positive affect throughout experiments. In Experiment 1, MDPV and cocaine dose-dependently elicited 50-kHz USVs upon systemic injection, but MDPV increased USVs at greater rates and with greater persistence relative to cocaine. In Experiment 2, latency to begin MDPV self-administration was shorter than latency to begin cocaine self-administration, and self-administered MDPV elicited greater and more persistent rates of 50-kHz USVs versus cocaine. MDPV-elicited 50-kHz USVs were sustained over the course of drug load-up whereas cocaine-elicited USVs waned following initial infusions. Notably, we observed a robust presence of context-elicited 50-kHz USVs from both MDPV and cocaine self-administering rats. Collectively, these data suggest that MDPV has powerfully rewarding and reinforcing effects relative to cocaine at one-tenth doses. Consistent with prior work, we additionally interpret these data in supporting that MDPV has significant abuse risk based on its potency and subjectively positive effects. Future studies will be needed to better refine therapeutic strategies targeted at reducing the rewarding effects of cathinone analogs in efforts to ultimately reduce abuse liability.
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Affiliation(s)
- Steven J. Simmons
- Center for Substance Abuse Research; Lewis Katz School of Medicine at Temple University; USA
| | - Ryan A. Gregg
- Center for Substance Abuse Research; Lewis Katz School of Medicine at Temple University; USA
| | - Fionya H. Tran
- Center for Substance Abuse Research; Lewis Katz School of Medicine at Temple University; USA
| | - Lili Mo
- Center for Substance Abuse Research; Lewis Katz School of Medicine at Temple University; USA
| | - Eva von Weltin
- Center for Substance Abuse Research; Lewis Katz School of Medicine at Temple University; USA
| | - David J. Barker
- National Institute on Drug Abuse, Neuronal Networks Section; National Institutes of Health; USA
| | - Taylor A. Gentile
- Center for Substance Abuse Research; Lewis Katz School of Medicine at Temple University; USA
| | - Lucas R. Watterson
- Center for Substance Abuse Research; Lewis Katz School of Medicine at Temple University; USA
| | - Scott M. Rawls
- Center for Substance Abuse Research; Lewis Katz School of Medicine at Temple University; USA
| | - John W. Muschamp
- Center for Substance Abuse Research; Lewis Katz School of Medicine at Temple University; USA
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Abstract
Since the mid- to late 2000s, there has been a dramatic rise in the use and abuse of synthetic derivatives of cathinone, a stimulant alkaloid found in the African shrub Catha edulis. Cathinone novel psychoactive substances (NPS), also referred to as synthetic cathinones or "bath salt"-type drugs, have gained popularity among drug users due to their potency, low cost, ease of procurement, and diverse array of evolving chemical structures. While the ability of cathinone NPS to produce psychotomimetic effects, multiple organ system toxicity, and death in humans is well documented, there has been limited scientific investigation into the reinforcing effects and abuse liability of these drugs. In this chapter, we will summarize the existing literature on the reinforcing effects of cathinone NPS in rodents using the intravenous self-administration (IVSA) paradigm. We will also compare the ability of cathinone NPS to serve as reinforcers to that of classical psychostimulants such as cocaine, methamphetamine, and methylenedioxymethamphetamine (MDMA). The chapter will conclude with a summary and indications for future avenues of research on cathinone NPS.
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Affiliation(s)
- Lucas R Watterson
- Department of Psychology, Arizona State University, 871104, Tempe, AZ, 85287, USA
| | - M Foster Olive
- Department of Psychology, Arizona State University, 871104, Tempe, AZ, 85287, USA.
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Watterson E, Spitzer A, Watterson LR, Brackney RJ, Zavala AR, Olive MF, Sanabria F. Nicotine-induced behavioral sensitization in an adult rat model of attention deficit/hyperactivity disorder (ADHD). Behav Brain Res 2016; 312:333-40. [PMID: 27363925 DOI: 10.1016/j.bbr.2016.06.050] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2016] [Revised: 06/23/2016] [Accepted: 06/26/2016] [Indexed: 12/23/2022]
Abstract
Attention deficit hyperactivity disorder (ADHD) is associated with increased risk of tobacco dependence. Nicotine, the main psychoactive component of tobacco, appears to be implicated in ADHD-related tobacco dependence. However, the behavioral responsiveness to nicotine of the prevalent animal model of ADHD, the spontaneously hypertensive rat (SHR), is currently underinvestigated. The present study examined the activational effects of acute and chronic nicotine on the behavior of adult male SHRs, relative to Wistar Kyoto (WKY) controls. Experiment 1 verified baseline strain differences in open-field locomotor activity. Experiment 2 tested for baseline strain differences in rotational behavior using a Rotorat apparatus. Adult SHR and WKY rats were then exposed to a 7-day regimen of 0.6mg/kg/d s.c. nicotine, or saline, prior to each assessment. A separate group of SHRs underwent similar training, but was pre-treated with mecamylamine, a cholinergic antagonist. Nicotine sensitization, context conditioning, and mecamylamine effects were then tested. Baseline strain differences were observed in open-field performance and in the number of full rotations in the Rotorat apparatus, but not in the number of 90° rotations or direction changes. In these latter measures, SHRs displayed weaker nicotine-induced rotational suppression than WKYs. Both strains expressed nicotine-induced sensitization of rotational activity, but evidence for strain differences in sensitization was ambiguous; context conditioning was not observed. Mecamylamine reversed the effects of nicotine on SHR performance. These findings are consistent with the hypothesis that a reduced aversion to nicotine (expressed in rats as robust locomotion) may facilitate smoking among adults with ADHD.
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Affiliation(s)
- Elizabeth Watterson
- Arizona State University, Department of Psychology, P.O. Box 871104, Tempe, AZ 85287, United States
| | - Alexander Spitzer
- Arizona State University, Department of Psychology, P.O. Box 871104, Tempe, AZ 85287, United States
| | - Lucas R Watterson
- Arizona State University, Department of Psychology, P.O. Box 871104, Tempe, AZ 85287, United States; Center for Substance Abuse Research Temple University School of Medicine, 3500N. Broad St., Medical Education and Research Bldg., 8th Floor, Philadelphia, PA 19140, United States
| | - Ryan J Brackney
- Arizona State University, Department of Psychology, P.O. Box 871104, Tempe, AZ 85287, United States
| | - Arturo R Zavala
- California State University, Long Beach, CA 90840, United States
| | - M Foster Olive
- Arizona State University, Department of Psychology, P.O. Box 871104, Tempe, AZ 85287, United States
| | - Federico Sanabria
- Arizona State University, Department of Psychology, P.O. Box 871104, Tempe, AZ 85287, United States.
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Taylor SB, Watterson LR, Kufahl PR, Nemirovsky NE, Tomek SE, Conrad CD, Olive MF. Chronic variable stress and intravenous methamphetamine self-administration - Role of individual differences in behavioral and physiological reactivity to novelty. Neuropharmacology 2016; 108:353-63. [PMID: 27163191 DOI: 10.1016/j.neuropharm.2016.05.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 04/30/2016] [Accepted: 05/05/2016] [Indexed: 11/16/2022]
Abstract
Stress is a contributing factor to the development and maintenance of addiction in humans. However, few studies have shown that stress potentiates the rewarding and/or reinforcing effects of methamphetamine in rodent models of addiction. The present study assessed the effects of exposure to 14 days of chronic variable stress (CVS), or no stress as a control (CON), on the rewarding and reinforcing effects of methamphetamine in adult rats using the conditioned place preference (Experiment 1) and intravenous self-administration (Experiment 2) paradigms. In Experiment 2, we also assessed individual differences in open field locomotor activity, anxiety-like behavior in the elevated plus maze (EPM), and physiological responses to a novel environment as possible predictors of methamphetamine intake patterns. Exposure to CVS for 14 days did not affect overall measures of methamphetamine conditioned reward or reinforcement. However, analyses of individual differences and direct vs. indirect effects revealed that rats exhibiting high physiological reactivity and locomotor activity in the EPM and open field tests self-administered more methamphetamine and reached higher breakpoints for drug reinforcement than rats exhibiting low reactivity. In addition, CVS exposure significantly increased the proportion of rats that exhibited high reactivity, and high reactivity was significantly correlated with increased levels of methamphetamine intake. These findings suggest that individual differences in physiological and locomotor reactivity to novel environments, as well as their interactions with stress history, predict patterns of drug intake in rodent models of methamphetamine addiction. Such predictors may eventually inform future strategies for implementing individualized treatment strategies for amphetamine use disorders.
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Affiliation(s)
- S B Taylor
- Department of Psychology, Arizona State University, Tempe, AZ, USA.
| | - L R Watterson
- Department of Psychology, Arizona State University, Tempe, AZ, USA
| | - P R Kufahl
- Department of Psychology, Arizona State University, Tempe, AZ, USA
| | - N E Nemirovsky
- Department of Psychology, Arizona State University, Tempe, AZ, USA
| | - S E Tomek
- Department of Psychology, Arizona State University, Tempe, AZ, USA
| | - C D Conrad
- Department of Psychology, Arizona State University, Tempe, AZ, USA; Interdisciplinary Graduate Program in Neuroscience, Arizona State University, Tempe, AZ, USA
| | - M F Olive
- Department of Psychology, Arizona State University, Tempe, AZ, USA; Interdisciplinary Graduate Program in Neuroscience, Arizona State University, Tempe, AZ, USA.
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Watterson LR, Kufahl PR, Taylor SB, Nemirovsky NE, Olive MF. Sensitization to the motor stimulant effects of 3,4-methylenedioxypyrovalerone (MDPV) and cross-sensitization to methamphetamine in rats. ACTA ACUST UNITED AC 2016; 5. [PMID: 27284493 DOI: 10.4303/jdar/235967] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND In recent years, there has been a dramatic increase in abuse of the synthetic cathinone 3,4-methylenedioxypyrovalerone (MDPV), often in combination with other illicit stimulants. PURPOSE We sought to determine if repeated exposure to MDPV would produce sensitization to the motor stimulant effects of the drug, and whether cross-sensitization would develop with the stimulant effects of methamphetamine (METH). STUDY DESIGN Male Sprague-Dawley rats were administered MDPV (1 or 5 mg/kg) or saline once daily for 5 days at 24 hour intervals, or were administered MDPV (1 mg/kg) or saline once daily for 5 days at 48 hour intervals. For cross-sensitization experiments, rats were administered METH (1 mg/kg) or MDPV (1 or 5 mg/kg) once daily for 5 days at 48 hour intervals, and following a 5 day incubation period, were given an acute challenge injection of either MDPV (0.5 mg/kg) or METH (0.5 mg/kg), respectively. RESULTS Rats repeatedly administered MDPV (1 mg/kg) every 48 hours, but not every 24 hours, demonstrated increased motor activity when given either a subsequent challenge of MDPV (0.5 mg/kg i.p.) or METH (0.5 mg/kg), indicating the development of behavioral sensitization and cross-sensitization, respectively. Moreover, rats repeatedly administered METH (1 mg/kg) every 48 hours did not exhibit cross-sensitization to the motor stimulating effects of a subsequent challenge with MDPV (0.5 mg/kg). CONCLUSION These results suggest that specific patterns of MDPV administration may lead to lasting changes in behavioral responses to subsequent METH exposure.
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Affiliation(s)
| | - Peter R Kufahl
- Arizona State University, Department of Psychology, Tempe, AZ, USA
| | - Sara B Taylor
- Arizona State University, Department of Psychology, Tempe, AZ, USA.,Hendrix College, Department of Psychology, Conway, AR, USA
| | | | - M Foster Olive
- Arizona State University, Department of Psychology, Tempe, AZ, USA.,Arizona State University, Interdisciplinary Graduate Program in Neuroscience, Tempe, AZ, USA
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Burrows BT, Watterson LR, Johnson MA, Olive MF. Effects of modafinil and R-modafinil on brain stimulation reward thresholds: implications for their use in the treatment of psychostimulant dependence. ACTA ACUST UNITED AC 2015; 4. [PMID: 27284492 DOI: 10.4303/jdar/235958] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND Modafinil and its enantiomer R-modafinil are approved for the treatment of various sleep disorders, and may also be efficacious in the treatment of psychostimulant abuse. However, the ability of modafinil and R-modafinil to alter brain reward function has not yet been assessed. PURPOSE This study assessed the effects of modafinil and R-modafinil on brain reward function using the intracranial self-stimulation (ICSS) paradigm. STUDY DESIGN Male Sprague-Dawley rats were trained to respond for ICSS using current-intensity threshold determination procedures. Changes in ICSS thresholds were then assessed following administration of modafinil and R-modafinil (50, 100, and 150 mg/kg), or cocaine (2.5 - 20 mg/kg) as a positive control. RESULTS ICSS thresholds were reduced by modafinil at the 150 mg/kg dose, as well as by cocaine at the 10 and 20 mg/kg doses. R-modafinil only produced non-significant trends towards reducing ICSS thresholds. CONCLUSION Modafinil and R-modafinil have limited effects on brain reward function in otherwise drug-naïve subjects. Additional assessments of these effects in the context of psychostimulant dependence are needed.
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Affiliation(s)
- Brian T Burrows
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, AZ, USA
| | - Lucas R Watterson
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, AZ, USA
| | - Meagan A Johnson
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, AZ, USA
| | - M Foster Olive
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, AZ, USA; Arizona State University, Interdisciplinary Graduate Program in Neuroscience, Tempe, AZ, USA
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Watterson E, Daniels CW, Watterson LR, Mazur GJ, Brackney RJ, Olive MF, Sanabria F. Nicotine-induced place conditioning and locomotor activity in an adolescent animal model of attention deficit/hyperactivity disorder (ADHD). Behav Brain Res 2015; 291:184-188. [PMID: 26008156 DOI: 10.1016/j.bbr.2015.05.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 05/09/2015] [Accepted: 05/16/2015] [Indexed: 11/28/2022]
Abstract
Attention deficit/hyperactivity disorder (ADHD) is a risk factor for tobacco use and dependence. This study examines the responsiveness to nicotine of an adolescent model of ADHD, the spontaneously hypertensive rat (SHR). The conditioned place preference (CPP) procedure was used to assess nicotine-induced locomotion and conditioned reward in SHR and the Wistar Kyoto (WKY) control strain over a range of nicotine doses (0.0, 0.1, 0.3 and 0.6 mg/kg). Prior to conditioning, SHRs were more active and less biased toward one side of the CPP chamber than WKY rats. Following conditioning, SHRs developed CPP to the highest dose of nicotine (0.6 mg/kg), whereas WKYs did not develop CPP to any nicotine dose tested. During conditioning, SHRs displayed greater locomotor activity in the nicotine-paired compartment than in the saline-paired compartment across conditioning trials. SHRs that received nicotine (0.1, 0.3, 0.6 mg/kg) in the nicotine-paired compartment showed an increase in locomotor activity between conditioning trials. Nicotine did not significantly affect WKY locomotor activity. These findings suggest that the SHR strain is a suitable model for studying ADHD-related nicotine use and dependence, but highlights potential limitations of the WKY control strain and the CPP procedure for modeling ADHD-related nicotine reward.
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Affiliation(s)
| | | | - Lucas R Watterson
- Arizona State University, United States; Center for Substance Abuse Research, Temple University School of Medicine, United States
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Watterson LR, Burrows BT, Hernandez RD, Moore KN, Grabenauer M, Marusich JA, Olive MF. Effects of α-pyrrolidinopentiophenone and 4-methyl-N-ethylcathinone, two synthetic cathinones commonly found in second-generation "bath salts," on intracranial self-stimulation thresholds in rats. Int J Neuropsychopharmacol 2014; 18:pyu014. [PMID: 25522379 PMCID: PMC4368864 DOI: 10.1093/ijnp/pyu014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Use of synthetic cathinones, which are designer stimulants found in "bath salts," has increased dramatically in recent years. Following governmental bans of methylenedioxypyrovalerone, mephedrone, and methylone, a second generation of synthetic cathinones with unknown abuse liability has emerged as replacements. METHODS Using a discrete trials current intensity threshold intracranial self-stimulation procedure, the present study assessed the effects of 2 common second-generation synthetic cathinones, α-pyrrolidinopentiophenone (0.1-5 mg/kg) and 4-methyl-N-ethcathinone (1-100 mg/kg) on brain reward function. Methamphetamine (0.1-3 mg/kg) was also tested for comparison purposes. RESULTS Results revealed both α-pyrrolidinopentiophenone and 4-methyl-N-ethcathinone produced significant intracranial self-stimulation threshold reductions similar to that of methamphetamine. α-Pyrrolidinopentiophenone (1 mg/kg) produced a significant maximal reduction in intracranial self-stimulation thresholds (~19%) most similar to maximal reductions produced by methamphetamine (1 mg/kg, ~20%). Maximal reductions in intracranial self-stimulation thresholds produced by 4-methyl-N-ethcathinone were observed at 30 mg/kg (~15%) and were comparable with those observed with methamphetamine and α-pyrrolidinopentiophenone tested at the 0.3-mg/kg dose (~14%). Additional analysis of the ED50 values from log-transformed data revealed the rank order potency of these drugs as methamphetamine ≈ α-pyrrolidinopentiophenone>4-methyl-N-ethcathinone. CONCLUSIONS These data suggest that the newer second-generation synthetic cathinones activate the brain reward circuitry and thus may possess a similar degree of abuse potential as prototypical illicit psychostimulants such as methamphetamine as well as the first generation synthetic cathinone methylenedioxypyrovalerone, as previously reported.
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Affiliation(s)
- Lucas R Watterson
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, Arizona (Dr Watterson, Mr Burrows, Mr Hernandez, and Dr Olive); Arizona State University Interdisciplinary Graduate Program in Neuroscience, Tempe, Arizona (Dr Olive); Discovery and Analytical Science, Research Triangle Institute International, Research Triangle Park, North Carolina (Drs Moore, Grabenauer, and Marusich).
| | - Brian T Burrows
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, Arizona (Dr Watterson, Mr Burrows, Mr Hernandez, and Dr Olive); Arizona State University Interdisciplinary Graduate Program in Neuroscience, Tempe, Arizona (Dr Olive); Discovery and Analytical Science, Research Triangle Institute International, Research Triangle Park, North Carolina (Drs Moore, Grabenauer, and Marusich)
| | - Raymundo D Hernandez
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, Arizona (Dr Watterson, Mr Burrows, Mr Hernandez, and Dr Olive); Arizona State University Interdisciplinary Graduate Program in Neuroscience, Tempe, Arizona (Dr Olive); Discovery and Analytical Science, Research Triangle Institute International, Research Triangle Park, North Carolina (Drs Moore, Grabenauer, and Marusich)
| | - Katherine N Moore
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, Arizona (Dr Watterson, Mr Burrows, Mr Hernandez, and Dr Olive); Arizona State University Interdisciplinary Graduate Program in Neuroscience, Tempe, Arizona (Dr Olive); Discovery and Analytical Science, Research Triangle Institute International, Research Triangle Park, North Carolina (Drs Moore, Grabenauer, and Marusich)
| | - Megan Grabenauer
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, Arizona (Dr Watterson, Mr Burrows, Mr Hernandez, and Dr Olive); Arizona State University Interdisciplinary Graduate Program in Neuroscience, Tempe, Arizona (Dr Olive); Discovery and Analytical Science, Research Triangle Institute International, Research Triangle Park, North Carolina (Drs Moore, Grabenauer, and Marusich)
| | - Julie A Marusich
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, Arizona (Dr Watterson, Mr Burrows, Mr Hernandez, and Dr Olive); Arizona State University Interdisciplinary Graduate Program in Neuroscience, Tempe, Arizona (Dr Olive); Discovery and Analytical Science, Research Triangle Institute International, Research Triangle Park, North Carolina (Drs Moore, Grabenauer, and Marusich)
| | - M Foster Olive
- Arizona State University, Department of Psychology, Behavioral Neuroscience Area, Tempe, Arizona (Dr Watterson, Mr Burrows, Mr Hernandez, and Dr Olive); Arizona State University Interdisciplinary Graduate Program in Neuroscience, Tempe, Arizona (Dr Olive); Discovery and Analytical Science, Research Triangle Institute International, Research Triangle Park, North Carolina (Drs Moore, Grabenauer, and Marusich)
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Abstract
INTRODUCTION Globally, alcohol abuse and dependence are significant contributors to chronic disease and injury and are responsible for nearly 4% of all deaths annually. Acamprosate (Campral), one of only three pharmacological treatments approved for the treatment of alcohol dependence, has shown mixed efficacy in clinical trials in maintaining abstinence of detoxified alcoholics since studies began in the 1980s. Yielding inconsistent results, these studies have prompted skepticism. AREAS COVERED Herein, the authors review the preclinical studies which have assessed the efficacy of acamprosate in various animal models of alcohol dependence and discuss the disparate findings from the major clinical trials. Moreover, the authors discuss the major limitations of these preclinical and clinical studies and offer explanations for the often-contradictory findings. The article also looks at the importance of the calcium moiety that accompanies the salt form of acamprosate and its relevance to its activity. EXPERT OPINION The recent discovery that large doses of calcium largely duplicate the effects of acamprosate in animal models has introduced a serious challenge to the widely held functional association between this drug and the glutamate neurotransmission system. Future research on acamprosate or newer pharmacotherapeutics should consider assessing plasma and/or brain levels of calcium as a correlate or mediating factor in anti-relapse efficacy. Further, preclinical research on acamprosate has thus far lacked animal models of chemical dependence on alcohol, and the testing of rodents with histories of alcohol intoxication and withdrawal is suggested.
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Affiliation(s)
- Peter R Kufahl
- Arizona State University, Behavioral Neuroscience Area, Department of Psychology , Tempe, AZ 85287 , USA
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11
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Abstract
Synthetic cathinones, colloquially referred to as "bath salts", are derivatives of the psychoactive alkaloid cathinone found in Catha edulis (Khat). Since the mid-to-late 2000's, these amphetamine-like psychostimulants have gained popularity amongst drug users due to their potency, low cost, ease of procurement, and constantly evolving chemical structures. Concomitant with their increased use is the emergence of a growing collection of case reports of bizarre and dangerous behaviors, toxicity to numerous organ systems, and death. However, scientific information regarding the abuse liability of these drugs has been relatively slower to materialize. Recently we have published several studies demonstrating that laboratory rodents will readily self-administer the "first generation" synthetic cathinones methylenedioxypyrovalerone (MDPV) and methylone via the intravenous route, in patterns similar to those of methamphetamine. Under progressive ratio schedules of reinforcement, the rank order of reinforcing efficacy of these compounds are MDPV ≥ methamphetamine > methylone. MDPV and methylone, as well as the "second generation" synthetic cathinones α-pyrrolidinovalerophenone (α-PVP) and 4-methylethcathinone (4-MEC), also dose-dependently increase brain reward function. Collectively, these findings indicate that synthetic cathinones have a high abuse and addiction potential and underscore the need for future assessment of the extent and duration of neurotoxicity induced by these emerging drugs of abuse.
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Affiliation(s)
| | - M. Foster Olive
- Department of Psychology Arizona State University Tempe, Arizona USA
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12
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Watterson LR, Kufahl PR, Nemirovsky NE, Sewalia K, Grabenauer M, Thomas BF, Marusich JA, Wegner S, Olive MF. Potent rewarding and reinforcing effects of the synthetic cathinone 3,4-methylenedioxypyrovalerone (MDPV). Addict Biol 2014; 19:165-74. [PMID: 22784198 PMCID: PMC3473160 DOI: 10.1111/j.1369-1600.2012.00474.x] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reports of abuse and toxic effects of synthetic cathinones, frequently sold as 'bath salts' or 'legal highs', have increased dramatically in recent years. One of the most widely used synthetic cathinones is 3,4-methylenedioxypyrovalerone (MDPV). The current study evaluated the abuse potential of MDPV by assessing its ability to support intravenous self-administration and to lower thresholds for intracranial self-stimulation (ICSS) in rats. In the first experiment, the rats were trained to intravenously self-administer MDPV in daily 2-hour sessions for 10 days at doses of 0.05, 0.1 or 0.2 mg/kg per infusion. The rats were then allowed to self-administer MDPV under a progressive ratio (PR) schedule of reinforcement. Next, the rats self-administered MDPV for an additional 10 days under short access (ShA; 2 hours/day) or long access (LgA; 6 hours/day) conditions to assess escalation of intake. A separate group of rats underwent the same procedures, with the exception of self-administering methamphetamine (0.05 mg/kg per infusion) instead of MDPV. In the second experiment, the effects of MDPV on ICSS thresholds following acute administration (0.1, 0.5, 1 and 2 mg/kg, i.p.) were assessed. MDPV maintained self-administration across all doses tested. A positive relationship between MDPV dose and breakpoints for reinforcement under PR conditions was observed. LgA conditions led to escalation of drug intake at 0.1 and 0.2 mg/kg doses, and rats self-administering methamphetamine showed similar patterns of escalation. Finally, MDPV significantly lowered ICSS thresholds at all doses tested. Together, these findings indicate that MDPV has reinforcing properties and activates brain reward circuitry, suggesting a potential for abuse and addiction in humans.
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Watterson LR, Olive MF. Are AMPA receptor positive allosteric modulators potential pharmacotherapeutics for addiction? Pharmaceuticals (Basel) 2013; 7:29-45. [PMID: 24380895 PMCID: PMC3915193 DOI: 10.3390/ph7010029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 12/13/2013] [Accepted: 12/24/2013] [Indexed: 01/01/2023] Open
Abstract
Positive allosteric modulators (PAMs) of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are a diverse class of compounds that increase fast excitatory transmission in the brain. AMPA PAMs have been shown to facilitate long-term potentiation, strengthen communication between various cortical and subcortical regions, and some of these compounds increase the production and release of brain-derived neurotrophic factor (BDNF) in an activity-dependent manner. Through these mechanisms, AMPA PAMs have shown promise as broad spectrum pharmacotherapeutics in preclinical and clinical studies for various neurodegenerative and psychiatric disorders. In recent years, a small collection of preclinical animal studies has also shown that AMPA PAMs may have potential as pharmacotherapeutic adjuncts to extinction-based or cue-exposure therapies for the treatment of drug addiction. The present paper will review this preclinical literature, discuss novel data collected in our laboratory, and recommend future research directions for the possible development of AMPA PAMs as anti-addiction medications.
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Affiliation(s)
- Lucas R Watterson
- Department of Psychology, Behavioral Neuroscience Area, Arizona State University, Tempe, AZ 85287, USA.
| | - M Foster Olive
- Department of Psychology, Behavioral Neuroscience Area, Arizona State University, Tempe, AZ 85287, USA
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Kufahl PR, Nemirovsky NE, Watterson LR, Zautra N, Olive MF. Positive or negative allosteric modulation of metabotropic glutamate receptor 5 (mGluR5) does not alter expression of behavioral sensitization to methamphetamine. F1000Res 2013; 2:84. [PMID: 24358885 PMCID: PMC3814922 DOI: 10.12688/f1000research.2-84.v1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/01/2013] [Indexed: 01/29/2023] Open
Abstract
We investigated the role of metabotropic glutamate receptor type 5 (mGluR5) in methamphetamine-induced behavioral sensitization. The mGluR5 positive allosteric modulator (3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl) benzamide (CDPPB) and negative allosteric modulator fenobam were tested in separate experiments. Sprague-Dawley rats were repeatedly injected with 1 mg/kg methamphetamine or saline, and then given a locomotor challenge test using a dose of 0.5 mg/kg methamphetamine. Prior to the challenge test session, rats were injected with CDPPB, fenobam, or a vehicle. Doses from previous studies showed reduced drug-conditioned behavior; however in this study neither CDPPB nor fenobam pretreatment resulted in an altered expression of behavioral sensitization, indicating a lack of mGluR5 involvement in sensitized methamphetamine-induced locomotion. Additionally, the high dose (30 mg/kg) of fenobam resulted in decreased methamphetamine-induced locomotion in rats regardless of drug exposure history, which suggests evidence of nonspecific behavioral inhibition.
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Affiliation(s)
- Peter R Kufahl
- Department of Psychology, Arizona State University, Tempe, AZ, 85287-1104, USA
| | - Natali E Nemirovsky
- Department of Psychology, Arizona State University, Tempe, AZ, 85287-1104, USA
| | - Lucas R Watterson
- Department of Psychology, Arizona State University, Tempe, AZ, 85287-1104, USA
| | - Nicholas Zautra
- Department of Psychology, Arizona State University, Tempe, AZ, 85287-1104, USA
| | - M Foster Olive
- Department of Psychology, Arizona State University, Tempe, AZ, 85287-1104, USA
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Abstract
Acamprosate (calcium acetylhomotaurine) is an amino acid modulator that has displayed efficacy in some clinical trials in reducing craving and promoting abstinence in alcohol dependent patients following detoxification. While acamprosate is safe and generally well-tolerated, not all studies have demonstrated clinical efficacy that is superior to placebo. In addition, the precise neurochemical mechanisms of action of acamprosate have still not yet been identified. In this review, we summarize current clinical data on the safety, efficacy, and pharmacokinetic properties of acamprosate, as well theories on its potential mechanism of action. We also discuss tolerability and patient preference issues and conclude with a discussion of the place of acamprosate in addiction medicine and therapy.
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Affiliation(s)
- Stephanie L. Yahn
- Department of Psychology, Program in Behavioral Neuroscience, Arizona State University, Tempe, AZ, USA
| | - Lucas R. Watterson
- Department of Psychology, Program in Behavioral Neuroscience, Arizona State University, Tempe, AZ, USA
| | - M. Foster Olive
- Department of Psychology, Program in Behavioral Neuroscience, Arizona State University, Tempe, AZ, USA
- Interdisciplinary Graduate Program in Neuroscience, Arizona State University, Tempe, AZ, USA
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Watterson LR, Hood L, Sewalia K, Tomek SE, Yahn S, Johnson CT, Wegner S, Blough BE, Marusich JA, Olive MF. The Reinforcing and Rewarding Effects of Methylone, a Synthetic Cathinone Commonly Found in "Bath Salts". ACTA ACUST UNITED AC 2013; Suppl 9. [PMID: 24244886 DOI: 10.4172/2155-6105.s9-002] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Methylone is a member of the designer drug class known as synthetic cathinones which have become increasingly popular drugs of abuse in recent years. Commonly referred to as "bath salts", these amphetamine-like compounds are sold as "legal" alternatives to illicit drugs such as cocaine, methamphetamine, and 3,4-methylenedioxymethamphetamine (MDMA, ecstasy). Following their dramatic rise in popularity along with numerous reports of toxicity and death, several of these drugs were classified as Schedule I drugs in the United States in 2012. Despite these bans, these drugs and other new structurally similar analogues continue to be abused. Currently, however, it is unknown whether these compounds possess the potential for compulsive use and addiction. The present study sought to determine the relative abuse liability of methylone by employing intravenous self-administration (IVSA) and intracranial self-stimulation (ICSS) paradigms in rats. We demonstrate that methylone (0.05, 0.1, 0.2, and 0.5 mg/kg/infusion) dose-dependently functions as a reinforcer, and that there is a significant positive relationship between methylone dose and reinforcer efficacy. Furthermore, responding during short access sessions (ShA, 2 hr/day) appeared more robust than previous IVSA studies with MDMA. However, unlike previous findings with abused stimulants such as cocaine or methamphetamine, long access sessions (LgA, 6 hr/day) did not lead to escalated drug intake or increased reinforcer efficacy. Finally, methylone produced a dose-dependent, but statistically non-significant, trend towards reductions in ICSS thresholds. Together these results reveal that methylone may possess an addiction potential similar to or greater than MDMA, yet patterns of self-administration and effects on brain reward function suggest that this drug may have a lower potential for abuse and compulsive use than prototypical psychostimulants.
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Affiliation(s)
- Lucas R Watterson
- Department of Psychology (LRW, LEH, KS, SET, SY, CTJ, SW, MFO) and Interdisciplinary Graduate Program in Neuroscience (MFO), Arizona State University, Tempe, Arizona, USA ; Discovery and Analytical Sciences, Research Triangle Institute, International Research Triangle Park, North Carolina, USA
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Watterson LR, Kufahl PR, Nemirovsky NE, Sewalia K, Hood LE, Olive MF. Attenuation of reinstatement of methamphetamine-, sucrose-, and food-seeking behavior in rats by fenobam, a metabotropic glutamate receptor 5 negative allosteric modulator. Psychopharmacology (Berl) 2013; 225:151-9. [PMID: 22820868 PMCID: PMC3742304 DOI: 10.1007/s00213-012-2804-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Accepted: 07/04/2012] [Indexed: 12/22/2022]
Abstract
RATIONALE Methamphetamine (METH) is a highly potent and addictive psychostimulant with severe detrimental effects to the health of users. Currently, METH addiction is treated with a combination of cognitive and behavioral therapies, but these traditional approaches suffer from high relapse rates. Furthermore, there are currently no pharmacological treatment interventions approved by the FDA specifically for the treatment of METH addiction. OBJECTIVES Metabotropic glutamate receptor 5 (mGluR5) negative allosteric modulators (NAMs) have shown promise in significantly attenuating drug self-administration and drug-seeking in reinstatement paradigms. However, studies assessing the potential efficacy of mGluR5 NAMs that have been tested in human subjects are lacking. The current study sought to assess the effect of the mGluR5 NAM fenobam on METH-seeking behavior. METHODS Rats were trained to self-administer METH (0.05 mg/kg i.v.), and following extinction, tested for effects of fenobam (5, 10, or 15 mg/kg intraperitoneal) on cue- and drug-induced reinstatement of METH-seeking. To determine if fenobam also alters reinstatement of seeking of natural reinforcers, separate groups of rats were trained to self-administer sucrose or food pellets and were tested for the effects of fenobam on cue-induced reinstatement of sucrose- and food-seeking. RESULTS Fenobam attenuated drug- and cue-induced reinstatement of METH-seeking behavior at doses of 10 and 15 mg/kg. Fenobam also attenuated cue-induced reinstatement of sucrose- and food-seeking at all doses tested. CONCLUSIONS The mGluR5 NAM fenobam attenuates the reinstatement of METH-seeking behavior, but these effects may be due to nonspecific suppression of general appetitive behaviors.
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Kufahl PR, Hood LE, Nemirovsky NE, Barabas P, Halstengard C, Villa A, Moore E, Watterson LR, Olive MF. Positive Allosteric Modulation of mGluR5 Accelerates Extinction Learning but Not Relearning Following Methamphetamine Self-Administration. Front Pharmacol 2012. [PMID: 23189054 PMCID: PMC3506114 DOI: 10.3389/fphar.2012.00194] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Recent studies have implicated glutamate neurotransmission as an important substrate for the extinction of conditioned behaviors, including responding for drug reinforcement. Positive allosteric modulation of the type-5 metabotropic glutamate receptor (mGluR5) in particular has emerged as a treatment strategy for the enhancement of extinction of drug-motivated behaviors. Here, we investigated the effects of the mGluR5 positive allosteric modulator CDPPB, a compound known for its cognitive enhancing effects in rodents, on extinction learning in rats with different histories of methamphetamine (METH) training. Rats were trained to self-administer METH under two conditions: 16 daily sessions of short access (90 min/day, ShA), or eight daily sessions of short access followed by eight sessions of long access (6 h/day, LgA). Control rats self-administered sucrose pellets in daily 30 min sessions. Next, rats were administered vehicle or 30 mg/kg CDPPB prior to seven consecutive daily extinction sessions, subjected to additional extinction sessions to re-establish a post-treatment baseline, and then tested for reinstatement of behavior in the presence of METH- or sucrose-paired cues. Rats were then subjected to a second series of extinction sessions, preceded by vehicle or 30 mg/kg CDPPB, and an additional test for cue-triggered reinstatement. CDPPB treatment resulted in a more rapid extinction of responding on the active lever, especially in the early sessions of the first extinction sequence. However, treatment effects were minimal during subsequent cue reinstatement tests and non-existent during the second series of extinction sessions. Rats with histories of ShA, LgA, and sucrose training expressed similar behavioral sensitivities to CDPPB, with LgA rats demonstrating a modestly higher treatment effect. Positive allosteric modulation of mGluR5 may therefore have some beneficial effects on efforts to facilitate extinction learning and reduce methamphetamine seeking.
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Affiliation(s)
- Peter R Kufahl
- Department of Psychology, Arizona State University Tempe, AZ, USA
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Watterson LR, Kufahl PR, Nemirovsky NE, Sewalia K, Grabenauer M, Thomas BF, Marusich JA, Wegner S, Olive MF. Potent rewarding and reinforcing effects of the synthetic cathinone 3,4-methylenedioxypyrovalerone (MDPV). Addict Biol 2012. [PMID: 22784198 DOI: 10.1111/j.1369–1600.2012.00474.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Reports of abuse and toxic effects of synthetic cathinones, frequently sold as 'bath salts' or 'legal highs', have increased dramatically in recent years. One of the most widely used synthetic cathinones is 3,4-methylenedioxypyrovalerone (MDPV). The current study evaluated the abuse potential of MDPV by assessing its ability to support intravenous self-administration and to lower thresholds for intracranial self-stimulation (ICSS) in rats. In the first experiment, the rats were trained to intravenously self-administer MDPV in daily 2-hour sessions for 10 days at doses of 0.05, 0.1 or 0.2 mg/kg per infusion. The rats were then allowed to self-administer MDPV under a progressive ratio (PR) schedule of reinforcement. Next, the rats self-administered MDPV for an additional 10 days under short access (ShA; 2 hours/day) or long access (LgA; 6 hours/day) conditions to assess escalation of intake. A separate group of rats underwent the same procedures, with the exception of self-administering methamphetamine (0.05 mg/kg per infusion) instead of MDPV. In the second experiment, the effects of MDPV on ICSS thresholds following acute administration (0.1, 0.5, 1 and 2 mg/kg, i.p.) were assessed. MDPV maintained self-administration across all doses tested. A positive relationship between MDPV dose and breakpoints for reinforcement under PR conditions was observed. LgA conditions led to escalation of drug intake at 0.1 and 0.2 mg/kg doses, and rats self-administering methamphetamine showed similar patterns of escalation. Finally, MDPV significantly lowered ICSS thresholds at all doses tested. Together, these findings indicate that MDPV has reinforcing properties and activates brain reward circuitry, suggesting a potential for abuse and addiction in humans.
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Kufahl PR, Watterson LR, Nemirovsky NE, Hood LE, Villa A, Halstengard C, Zautra N, Olive MF. Attenuation of methamphetamine seeking by the mGluR2/3 agonist LY379268 in rats with histories of restricted and escalated self-administration. Neuropharmacology 2012; 66:290-301. [PMID: 22659409 DOI: 10.1016/j.neuropharm.2012.05.037] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Revised: 05/16/2012] [Accepted: 05/18/2012] [Indexed: 11/30/2022]
Abstract
Recent findings implicate group II metabotropic glutamate receptors (mGluR(2/3)) in the reinforcing effects of psychostimulants and have identified these receptors as potential treatment targets for drug addiction. Here, we investigated the effects of mGluR(2/3) stimulation on cue- and drug-primed reinstatement in rats with different histories of methamphetamine (METH) self-administration training, under two conditions: 16 daily sessions of short access (90 min/day, ShA), or 8 daily sessions of short access followed by 8 sessions of long access (6 h/day, LgA). Following self-administration and subsequent extinction training, rats were pretreated with the selective mGluR(2/3) agonist LY379268 (variable dose, 0-3 mg/kg), exposed to METH-paired cues or a priming injection of METH (1 mg/kg), and tested for reinstatement of METH-seeking behavior. LgA rats self-administered greater amounts of METH during the second half of training, but when pretreated with vehicle, ShA and LgA rats showed cue- and drug-primed reinstatement at equivalent response rates. However, LgA rats demonstrated greater sensitivity to mGluR(2/3) stimulation with attenuated responding during cue-induced reinstatement after 0.3 mg/kg and higher doses of LY379268, whereas ShA rats decreased cue-induced reinstatement behavior following 1.0 mg/kg and 3.0 mg/kg LY379268. Additionally, both LgA and ShA rats exhibited decreased METH-primed reinstatement behavior following 0.3 mg/kg and higher doses of LY379268. A separate group of control rats was trained to self-administer sucrose pellets, and demonstrated attenuated cue-induced sucrose-seeking behavior following 1.0 and 3.0 mg/kg LY379268. Together, the results indicate that LY379268 has differential attenuating effects on cue-induced reinstatement behavior in rats with different histories of METH intake. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.
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Affiliation(s)
- Peter R Kufahl
- Department of Psychology, Arizona State University, PO Box 871104, Tempe, AZ 85287-1104, USA.
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Cleva RM, Watterson LR, Johnson MA, Olive MF. Differential Modulation of Thresholds for Intracranial Self-Stimulation by mGlu5 Positive and Negative Allosteric Modulators: Implications for Effects on Drug Self-Administration. Front Pharmacol 2012; 2:93. [PMID: 22232603 PMCID: PMC3252814 DOI: 10.3389/fphar.2011.00093] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2011] [Accepted: 12/21/2011] [Indexed: 12/20/2022] Open
Abstract
Pharmacological manipulation of the type 5 metabotropic glutamate (mGlu5) receptor alters various addiction related behaviors such as drug self-administration and the extinction and reinstatement of drug-seeking behavior. However, the effects of pharmacological modulation of mGlu5 receptors on brain reward function have not been widely investigated. We examined the effects of acute administration of positive and negative allosteric modulators (PAMs and NAMs, respectively) on brain reward function by assessing thresholds for intracranial self-stimulation (ICSS). In addition, when acute effects were observed, we examined changes in ICSS thresholds following repeated administration. Male Sprague-Dawley rats were implanted with bipolar electrodes into the medial forebrain bundle and trained to respond for ICSS, followed by assessment of effects of mGlu5 ligands on ICSS thresholds using a discrete trials current–intensity threshold determination procedure. Acute administration of the selective mGlu5 NAMs MTEP (0, 0.3, 1, or 3 mg/kg) and fenobam (0, 3, 10, or 30 mg/kg) dose-dependently increased ICSS thresholds (∼70% at the highest dose tested), suggesting a deficit in brain reward function. Acute administration of the mGlu5 PAMs CDPPB (0, 10, 30, and 60 mg/kg) or ADX47273 (0, 10, 30, and 60 mg/kg) was without effect at any dose tested. When administered once daily for five consecutive days, the development of tolerance to the ability of threshold-elevating doses of MTEP and fenobam to increase ICSS thresholds was observed. We conclude that mGlu5 PAMs and NAMs differentially affect brain reward function, and that tolerance to the ability of mGlu5 NAMs to reduce brain reward function develops with repeated administration. These brain reward deficits should be taken into consideration when interpreting acute effects of mGlu5 NAMs on drug self-administration, and repeated administration of these ligands may be an effective method to reduce these deficits.
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Affiliation(s)
- Richard M Cleva
- Interdisciplinary Graduate Program in Neuroscience, Arizona State University Tempe, AZ, USA
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