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Algallal HE, Jacquemet V, Samaha AN. Intermittent nicotine access is as effective as continuous access in promoting nicotine seeking and taking in rats. Psychopharmacology (Berl) 2024; 241:1135-1149. [PMID: 38326505 DOI: 10.1007/s00213-024-06546-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 01/20/2024] [Indexed: 02/09/2024]
Abstract
RATIONALE Nicotine is a principal psychoactive agent in tobacco, contributing to tobacco's addictive potential. Preclinical studies on the effects of voluntary nicotine intake typically use self-administration procedures that provide continuous nicotine access during each self-administration session. However, many smokers consume cigarettes intermittently rather than continuously throughout each day. For drugs including cocaine and opioids, research in laboratory rats shows that intermittent intake can be more effective than continuous intake in producing patterns of drug use relevant to addiction. OBJECTIVE We determined how intermittent versus continuous nicotine self-administration influences nicotine seeking and taking behaviours. METHODS Female and male rats had continuous (i.e., Long Access; LgA, 6 h/day) or intermittent (IntA; 12 min ON, 60 min OFF, for 6 h/day) access to intravenous nicotine (15 µg/kg/infusion), for 12 daily sessions. We then assessed intake, responding for nicotine under a progressive ratio schedule of drug reinforcement and cue- and nicotine-induced reinstatement of drug seeking. We also estimated nicotine pharmacokinetic parameters during LgA and IntA self-administration. RESULTS Overall, LgA rats took twice more nicotine than did IntA rats, yielding more sustained increases in estimated brain concentrations of the drug. However, the two groups showed similar motivation to seek and take nicotine, as measured using reinstatement and progressive ratio procedures, respectively. CONCLUSIONS Intermittent nicotine use is just as effective as continuous use in producing addiction-relevant behaviours, despite significantly less nicotine exposure. This has implications for modeling nicotine self-administration patterns in human smokers and resulting effects on brain and behaviour.
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Affiliation(s)
- Hajer E Algallal
- Biomedical Sciences, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
| | - Vincent Jacquemet
- Institute of Biomedical Engineering, Faculty of Medicine, Université de Montréal, Montreal, QC, Canada
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montreal, QC, H3C 3J7, Canada
| | - Anne-Noël Samaha
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montreal, QC, H3C 3J7, Canada.
- Neural Signaling and Circuitry Research Group (SNC), Faculty of Medicine, Université de Montréal, Montreal, QC, Canada.
- Center for Interdisciplinary Research On the Brain and Learning (CIRCA), Université de Montréal, Montreal, QC, Canada.
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Khoo SYS, Samaha AN. Metabotropic glutamate group II receptor activation in the ventrolateral dorsal striatum suppresses incentive motivation for cocaine in rats. Psychopharmacology (Berl) 2023; 240:1247-1260. [PMID: 37060471 DOI: 10.1007/s00213-023-06363-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 04/03/2023] [Indexed: 04/16/2023]
Abstract
RATIONALE After a history of intermittent cocaine intake, rats develop patterns of drug use characteristic of substance use disorder. The dorsal striatum is involved in the increased pursuit of cocaine after intermittent drug self-administration experience. Within the dorsal striatum, chronic cocaine use changes metabotropic glutamate type II receptor (mGlu2/3) density and function. OBJECTIVES We examined the extent to which activity at Glu2/3 receptors mediates responding for cocaine after intermittent cocaine use. METHODS Male (n = 11) and female (n = 10) Wistar rats self-administered 0.25 mg/kg/infusion cocaine during 10 daily intermittent access (IntA) sessions (5 min ON/25 min OFF, for 5 h/session). We then examined the effects of microinjections of the mGlu2/3 receptor agonist LY379268 (0, 1, and 3 µg/hemisphere) into the ventrolateral part of the dorsal striatum on cocaine self-administration under a progressive ratio schedule of reinforcement. RESULTS Across 10 IntA sessions, the sexes showed similar levels of cocaine intake. In females only, locomotion significantly increased over sessions, suggesting that female rats developed psychomotor sensitization to self-administered cocaine. After 10 IntA sessions, intra-dorsal striatum LY379268 significantly reduced breakpoints achieved for cocaine, active lever presses, and cocaine infusions earned under progressive ratio. LY379268 had no effects on locomotion or inactive lever presses, indicating no motor effects. CONCLUSIONS These results suggest that mGlu2/3 receptor activation in the ventrolateral dorsal striatum suppresses incentive motivation for cocaine, and this holds promise for new treatments to manage substance use disorder.
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Affiliation(s)
- Shaun Yon-Seng Khoo
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, H3T 1J4, Canada
- Conduct and Integrity Office, Division of Planning and Assurance, UNSW Sydney, Sydney, NSW, 2052, Australia
| | - Anne-Noël Samaha
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Montréal, QC, H3T 1J4, Canada.
- Research Group on Neural Signaling and Circuits, Faculty of Medicine, Université de Montréal, Montréal, QC, H3T 1J4, Canada.
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3
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Saraswat AA, Longyear LG, Kawa AB, Ferrario CR. Cocaine-induced plasticity, motivation, and cue responsivity do not differ in obesity-prone vs obesity-resistant rats; implications for food addiction. Psychopharmacology (Berl) 2023; 240:853-870. [PMID: 36806961 PMCID: PMC10006066 DOI: 10.1007/s00213-023-06327-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 01/25/2023] [Indexed: 02/20/2023]
Abstract
RATIONALE Compared to obesity-resistant rats, obesity-prone rats consume more food, work harder to obtain food, show greater motivational responses to food-cues, and show greater striatal plasticity in response to eating sugary/fatty foods. Therefore, it is possible that obesity-prone rats may also be more sensitive to the motivational properties of cocaine and cocaine-paired cues, and to plasticity induced by cocaine. OBJECTIVE To examine baseline differences in motivation for cocaine and effects of intermittent access (IntA) cocaine self-administration on cocaine motivation, neurobehavioral responsivity to cocaine-paired cues, and locomotor sensitization in male obesity-prone vs obesity-resistant rats. METHODS Intravenous cocaine self-administration was used to examine drug-taking and drug-seeking in males. Motivation for cocaine was measured using a within session threshold procedure. Cue-induced c-Fos expression in mesocorticolimbic regions was measured. RESULTS Drug-taking and drug-seeking, cue-induced c-Fos, locomotor sensitization, and preferred level of cocaine consumption (Q0) were similar between obesity-prone and obesity-resistant groups. Maximal responding during demand testing (Rmax) was lower in obesity-prone rats. IntA experience enhanced motivation for cocaine (Pmax) in obesity-prone rats. CONCLUSIONS The results do not support robust inherent differences in motivation for cocaine, cue-induced cocaine seeking, or neurobehavioral plasticity induced by IntA in obesity-prone vs obesity-resistant rats. This contrasts with previously established differences seen for food and food cues in these populations and shows that inherent enhancements in motivation for food and food-paired cues do not necessarily transfer to drugs and drug-paired cues.
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Affiliation(s)
- Anish A Saraswat
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, 48109, USA
- Psychology Department (Biopsychology), University of Michigan, Ann Arbor, MI, 48109, USA
| | - Lauren G Longyear
- Psychology Department (Biopsychology), University of Michigan, Ann Arbor, MI, 48109, USA
| | - Alex B Kawa
- Psychology Department (Biopsychology), University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Carrie R Ferrario
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, 48109, USA.
- Psychology Department (Biopsychology), University of Michigan, Ann Arbor, MI, 48109, USA.
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Slivicki RA, Earnest T, Chang YH, Pareta R, Casey E, Li JN, Tooley J, Abiraman K, Vachez YM, Wolf DK, Sackey JT, Kumar Pitchai D, Moore T, Gereau RW, Copits BA, Kravitz AV, Creed MC. Oral oxycodone self-administration leads to features of opioid misuse in male and female mice. Addict Biol 2023; 28:e13253. [PMID: 36577735 DOI: 10.1111/adb.13253] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 10/19/2022] [Accepted: 10/21/2022] [Indexed: 11/18/2022]
Abstract
Use of prescription opioids, particularly oxycodone, is an initiating factor driving the current opioid epidemic. There are several challenges with modelling oxycodone abuse. First, prescription opioids including oxycodone are orally self-administered and have different pharmacokinetics and dynamics than morphine or fentanyl, which have been more commonly used in rodent research. This oral route of administration determines the pharmacokinetic profile, which then influences the establishment of drug-reinforcement associations in animals. Moreover, the pattern of intake and the environment in which addictive drugs are self-administered are critical determinants of the levels of drug intake, of behavioural sensitization and of propensity to relapse behaviour. These are all important considerations when modelling prescription opioid use, which is characterized by continuous drug access in familiar environments. Thus, to model features of prescription opioid use and the transition to abuse, we designed an oral, homecage-based oxycodone self-administration paradigm. Mice voluntarily self-administer oxycodone in this paradigm without any taste modification such as sweeteners, and the majority exhibit preference for oxycodone, escalation of intake, physical signs of dependence and reinstatement of seeking after withdrawal. In addition, a subset of animals demonstrate drug taking that is resistant to aversive consequences. This model is therefore translationally relevant and useful for studying the neurobiological substrates of prescription opioid abuse.
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Affiliation(s)
- Richard A Slivicki
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Tom Earnest
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Yu-Hsuan Chang
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Rajesh Pareta
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Eric Casey
- Department of Psychiatry, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Jun-Nan Li
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Jessica Tooley
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Kavitha Abiraman
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Yvan M Vachez
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Drew K Wolf
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Jason T Sackey
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA
| | | | | | - Robert W Gereau
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Neuroscience, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Bryan A Copits
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Neuroscience, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Alexxai V Kravitz
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Psychiatry, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Neuroscience, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Meaghan C Creed
- Washington University Pain Center, Department of Anesthesiology, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Psychiatry, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Neuroscience, Washington University in St. Louis, St. Louis, Missouri, USA.,Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
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5
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D-amphetamine maintenance therapy reduces cocaine use in female rats. Psychopharmacology (Berl) 2022; 239:3755-3770. [PMID: 36357743 DOI: 10.1007/s00213-022-06271-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 10/19/2022] [Indexed: 11/12/2022]
Abstract
RATIONALE D-amphetamine maintenance therapy is a promising strategy to reduce drug use in cocaine use disorder (addiction). In both male rats and human cocaine users, d-amphetamine treatment reduces cocaine-taking and -seeking. However, this has not been examined systematically in female animals, even though cocaine addiction afflicts both sexes, and the sexes can differ in their response to cocaine. OBJECTIVES We determined how d-amphetamine maintenance therapy during cocaine self-administration influences cocaine use in female rats. METHODS In experiment 1, two groups of female rats received 14 intermittent access (IntA) cocaine self-administration sessions. One group received concomitant d-amphetamine maintenance treatment (COC + A rats; 5 mg/kg/day, via minipump), the other group did not (COC rats). After discontinuing d-amphetamine treatment, we measured responding for cocaine under a progressive ratio schedule, responding under extinction, and cocaine-primed reinstatement of drug-seeking. In experiment 2, we assessed the effects of d-amphetamine maintenance on these measures in already IntA cocaine-experienced rats. Thus, rats first received 14 IntA cocaine self-administration sessions without d-amphetamine. They then received 14 more IntA sessions, now either with (COC/COC + A rats) or without (COC/COC rats) concomitant d-amphetamine treatment. RESULTS In both experiments, d-amphetamine treatment did not significantly influence ongoing cocaine self-administration behaviour. After d-amphetamine treatment cessation, cocaine-primed reinstatement of cocaine-seeking was also unchanged. However, after d-amphetamine treatment cessation, rats responded less for cocaine both under progressive ratio and extinction conditions. CONCLUSIONS D-amphetamine treatment can both prevent and reverse increases in the motivation to take and seek cocaine in female animals.
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Everett AC, Graul BE, Ronström JW, Robinson JK, Watts DB, España RA, Siciliano CA, Yorgason JT. Effectiveness and Relationship between Biased and Unbiased Measures of Dopamine Release and Clearance. ACS Chem Neurosci 2022; 13:1534-1548. [PMID: 35482592 PMCID: PMC10763521 DOI: 10.1021/acschemneuro.2c00033] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Fast-scan cyclic voltammetry (FSCV) is an effective tool for measuring dopamine release and clearance throughout the brain, especially the striatum where dopamine terminals are abundant and signals are heavily regulated by release machinery and the dopamine transporter (DAT). Peak height measurement is perhaps the most common method for measuring dopamine release, but it is influenced by changes in clearance. Michaelis-Menten-based modeling has been a standard in measuring dopamine clearance, but it is problematic in that it requires experimenter fitted modeling subject to experimenter bias. This study presents the use of the first derivative (velocity) of evoked dopamine signals as an alternative approach for measuring and distinguishing dopamine release from clearance. Maximal upward velocity predicts reductions in dopamine peak height due to D2 and GABAB receptor stimulation and by alterations in calcium concentrations. The Michaelis-Menten maximal velocity (Vmax) measure, an approximation for DAT levels, predicts maximal downward velocity in slices and in vivo. Dopamine peak height and upward velocity were similar between wild-type and DAT knock-out (DATKO) mice. In contrast, downward velocity was lower and exponential decay (tau) was higher in DATKO mice, supporting the use of both measures for extreme changes in DAT activity. In slices, the competitive DAT inhibitors cocaine, PTT, and WF23 increased peak height and upward velocity differentially across increasing concentrations, with PTT and cocaine reducing these measures at high concentrations. Downward velocity and tau values decreased and increased respectively across concentrations, with greater potency and efficacy observed with WF23 and PTT. In vivo recordings demonstrated similar effects of WF23, PTT, and cocaine on measures of release and clearance. Tau was a more sensitive measure at low concentrations, supporting its use as a surrogate for the Michaelis-Menten measure of apparent affinity (Km). Together, these results inform on the use of these various measures for dopamine release and clearance.
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Affiliation(s)
- Anna C. Everett
- Brigham Young University, Department of Cellular Biology and Physiology, Provo, UT 84602, USA
| | - Ben E. Graul
- Brigham Young University, Department of Cellular Biology and Physiology, Provo, UT 84602, USA
| | - Joakim W. Ronström
- Brigham Young University, Department of Cellular Biology and Physiology, Provo, UT 84602, USA
| | - J. Kayden Robinson
- Brigham Young University, Department of Cellular Biology and Physiology, Provo, UT 84602, USA
| | - Daniel B. Watts
- Brigham Young University, Department of Cellular Biology and Physiology, Provo, UT 84602, USA
| | - Rodrigo A. España
- Drexel University, Department of Neurobiology & Anatomy, Philadelphia, PA 28619, USA
| | - Cody A. Siciliano
- Vanderbilt University, Center for Addiction Research, Nashville, TN 37203, USA
| | - Jordan T. Yorgason
- Brigham Young University, Department of Cellular Biology and Physiology, Provo, UT 84602, USA
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Brown RM, Dayas CV, James MH, Smith RJ. New directions in modelling dysregulated reward seeking for food and drugs. Neurosci Biobehav Rev 2022; 132:1037-1048. [PMID: 34736883 PMCID: PMC8816817 DOI: 10.1016/j.neubiorev.2021.10.043] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 10/08/2021] [Accepted: 10/19/2021] [Indexed: 01/03/2023]
Abstract
Behavioral models are central to behavioral neuroscience. To study the neural mechanisms of maladaptive behaviors (including binge eating and drug addiction), it is essential to develop and utilize appropriate animal models that specifically focus on dysregulated reward seeking. Both food and cocaine are typically consumed in a regulated manner by rodents, motivated by reward and homeostatic mechanisms. However, both food and cocaine seeking can become dysregulated, resulting in binge-like consumption and compulsive patterns of intake. The speakers in this symposium for the 2021 International Behavioral Neuroscience Meeting utilize behavioral models of dysregulated reward-seeking to investigate the neural mechanisms of binge-like consumption, enhanced cue-driven reward seeking, excessive motivation, and continued use despite negative consequences. In this review, we outline examples of maladaptive patterns of intake and explore recent animal models that drive behavior to become dysregulated, including stress exposure and intermittent access to rewards. Lastly, we explore select behavioral and neural mechanisms underlying dysregulated reward-seeking for both food and drugs.
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Affiliation(s)
- Robyn M Brown
- Department of Biochemistry and Pharmacology, University of Melbourne, Parkville, VIC, 3052, Australia; Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, VIC, 3052, Australia.
| | - Christopher V Dayas
- School of Biomedical Sciences & Pharmacy, Faculty of Health, University of Newcastle, Callaghan, NSW, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW, Australia
| | - Morgan H James
- Department of Psychiatry, Robert Wood Johnson Medical School, Rutgers University, Piscataway, NJ, 08854, USA; Brain Health Institute, Rutgers University, Piscataway, NJ, 08854, USA.
| | - Rachel J Smith
- Department of Psychological & Brain Sciences, Institute for Neuroscience, Texas A&M University, College Station, TX, 77843, USA
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8
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Dopamine 'ups and downs' in addiction revisited. Trends Neurosci 2021; 44:516-526. [PMID: 33892963 DOI: 10.1016/j.tins.2021.03.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 01/14/2021] [Accepted: 03/16/2021] [Indexed: 12/11/2022]
Abstract
Repeated drug use can change dopamine (DA) function in ways that promote the development and persistence of addiction, but in what direction? By one view, drug use blunts DA neurotransmission, producing a hypodopaminergic state that fosters further drug use to overcome a DA deficiency. Another view is that drug use enhances DA neurotransmission, producing a sensitized, hyperdopaminergic reaction to drugs and drug cues. According to this second view, continued drug use is motivated by sensitization of drug 'wanting'. Here we discuss recent evidence supporting the latter view, both from preclinical studies using intermittent cocaine self-administration procedures that mimic human patterns of use and from related human neuroimaging studies. These studies have implications for the modeling of addiction in the laboratory and for treatment.
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Bakhti-Suroosh A, Towers EB, Lynch WJ. A buprenorphine-validated rat model of opioid use disorder optimized to study sex differences in vulnerability to relapse. Psychopharmacology (Berl) 2021; 238:1029-1046. [PMID: 33404740 PMCID: PMC7786148 DOI: 10.1007/s00213-020-05750-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 12/08/2020] [Indexed: 12/13/2022]
Abstract
RATIONALE Opioid use disorder (OUD) is a major epidemic in the USA. Despite evidence indicating that OUD may be particularly severe for women, preclinical models have yet to establish sex as a major factor in OUD. OBJECTIVES Here, we examined sex differences in vulnerability to relapse following intermittent access fentanyl self-administration and protracted abstinence and used buprenorphine, the FDA-approved treatment for OUD, to test the validity of our model. METHODS Following acquisition of fentanyl self-administration under one of two training conditions, male and female rats were given extended, 24-h/day access to fentanyl (0.25 μg/kg/infusion, 10 days) using an intermittent access procedure. Vulnerability to relapse was assessed using an extinction/cue-induced reinstatement procedure following 14 days of abstinence; buprenorphine (0 or 3 mg/kg/day) was administered throughout abstinence. RESULTS Levels of drug-seeking were high following extended-access fentanyl self-administration and abstinence; buprenorphine markedly decreased drug-seeking supporting the validity of our relapse model. Females self-administered more fentanyl and responded at higher levels during subsequent extinction testing. Buprenorphine was effective in both sexes and eliminated sex and estrous phase differences in drug-seeking. Interestingly, the inclusion of a time-out during training had a major impact on later fentanyl self-administration in females, but not males, indicating that the initial exposure conditions can persistently impact vulnerability in females. CONCLUSIONS These findings demonstrate the utility of this rat model for determining sex and hormonal influences on the development and treatment of OUD.
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Affiliation(s)
- Anousheh Bakhti-Suroosh
- Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, P.O. Box 801402, Charlottesville, VA, 22904, USA
| | - Eleanor Blair Towers
- Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, P.O. Box 801402, Charlottesville, VA, 22904, USA
| | - Wendy J Lynch
- Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, P.O. Box 801402, Charlottesville, VA, 22904, USA.
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Intermittent access cocaine self-administration produces psychomotor sensitization: effects of withdrawal, sex and cross-sensitization. Psychopharmacology (Berl) 2020; 237:1795-1812. [PMID: 32206828 PMCID: PMC7244391 DOI: 10.1007/s00213-020-05500-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 02/28/2020] [Indexed: 02/05/2023]
Abstract
RATIONALE With repeated administration, the psychomotor activating effects of drugs such as cocaine or amphetamine can change in very different ways-showing sensitization or tolerance-depending on whether they are administered more or less intermittently. This behavioral plasticity is thought to reflect, at least in part, changes in dopamine (DA) neurotransmission, and therefore, may provide insights into the development of substance use disorders. Indeed, the most widely used preclinical model of cocaine addiction, which involves Long Access (LgA) self-administration procedures, is reported to produce tolerance to cocaine's psychomotor activating effects and effects on DA activity. In contrast, Intermittent Access (IntA) cocaine self-administration is more effective than LgA in producing addiction-like behavior, but sensitizes DA neurotransmission. There is, however, very little information concerning the effects of IntA experience on the psychomotor activating effects of cocaine. OBJECTIVE The objective of this study was to determine whether IntA experience produces psychomotor sensitization with similar characteristics to that produced by the intermittent, noncontingent administration of cocaine. RESULTS IntA to cocaine did indeed produce psychomotor sensitization that (1) was greater after a long (30 days) vs. short (1 day) period of withdrawal, (2) was greater in females than males, and (3) resulted in cross-sensitization to another psychomotor stimulant drug, amphetamine. CONCLUSION The tolerance sometimes associated with LgA cocaine self-administration has been cited in support of the idea that, in addiction, drug-seeking and drug-taking is motivated to overcome a DA deficiency and associated anhedonia. In contrast, the neurobehavioral sensitization associated with IntA cocaine self-administration favors an incentive-sensitization view.
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Phasic Dopamine Release Magnitude Tracks Individual Differences in Sensitization of Locomotor Response following a History of Nicotine Exposure. Sci Rep 2020; 10:173. [PMID: 31932634 PMCID: PMC6957501 DOI: 10.1038/s41598-019-56884-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 12/06/2019] [Indexed: 02/04/2023] Open
Abstract
Smoking remains the primary cause of preventable death in the United States and smoking related illness costs more than $300 billion annually. Nicotine (the primary reinforcer in cigarettes) causes changes in behavior and neurochemistry that lead to increased probability of relapse. Given the role of mesolimbic dopamine projections in motivation, substance use disorder, and drug relapse, we examined the effect of repeated nicotine on rapid dopamine signals in the nucleus accumbens (NAc) of rats. Adult, male Sprague-Dawley rats were exposed to nicotine (0.2 or 0.4 mg/kg, subcutaneous) once daily for 7 days. On day 8, dopamine release and uptake dynamics, and their modulation by nicotinic receptor agonists and antagonists, were assessed using fast scan cyclic voltammetry in the NAc core. Nicotine exposure decreased electrically-stimulated dopamine release across a range of stimulation frequencies and decreased α6β2-containing nicotinic receptor control over dopamine release. Additionally, nicotine locomotor sensitization correlated with accumbal dopamine modulation by nicotine and mecamylamine. Taken together, our study suggests that repeated exposure to nicotine blunts dopamine release in the NAc core through changes in α6β2 modulation of dopamine release and individual differences in the sensitivity to this outcome may predict variation in behavioral models of vulnerability to substance use disorder.
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12
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Kuhn BN, Kalivas PW, Bobadilla AC. Understanding Addiction Using Animal Models. Front Behav Neurosci 2019; 13:262. [PMID: 31849622 PMCID: PMC6895146 DOI: 10.3389/fnbeh.2019.00262] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 11/15/2019] [Indexed: 12/13/2022] Open
Abstract
Drug addiction is a neuropsychiatric disorder with grave personal consequences that has an extraordinary global economic impact. Despite decades of research, the options available to treat addiction are often ineffective because our rudimentary understanding of drug-induced pathology in brain circuits and synaptic physiology inhibits the rational design of successful therapies. This understanding will arise first from animal models of addiction where experimentation at the level of circuits and molecular biology is possible. We will review the most common preclinical models of addictive behavior and discuss the advantages and disadvantages of each. This includes non-contingent models in which animals are passively exposed to rewarding substances, as well as widely used contingent models such as drug self-administration and relapse. For the latter, we elaborate on the different ways of mimicking craving and relapse, which include using acute stress, drug administration or exposure to cues and contexts previously paired with drug self-administration. We further describe paradigms where drug-taking is challenged by alternative rewards, such as appetitive foods or social interaction. In an attempt to better model the individual vulnerability to drug abuse that characterizes human addiction, the field has also established preclinical paradigms in which drug-induced behaviors are ranked by various criteria of drug use in the presence of negative consequences. Separation of more vulnerable animals according to these criteria, along with other innate predispositions including goal- or sign-tracking, sensation-seeking behavior or impulsivity, has established individual genetic susceptibilities to developing drug addiction and relapse vulnerability. We further examine current models of behavioral addictions such as gambling, a disorder included in the DSM-5, and exercise, mentioned in the DSM-5 but not included yet due to insufficient peer-reviewed evidence. Finally, after reviewing the face validity of the aforementioned models, we consider the most common standardized tests used by pharmaceutical companies to assess the addictive potential of a drug during clinical trials.
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Affiliation(s)
| | - Peter W. Kalivas
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, United States
| | - Ana-Clara Bobadilla
- Department of Neuroscience, Medical University of South Carolina, Charleston, SC, United States
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Marie N, Canestrelli C, Noble F. Role of pharmacokinetic and pharmacodynamic parameters in neuroadaptations induced by drugs of abuse, with a focus on opioids and psychostimulants. Neurosci Biobehav Rev 2019; 106:217-226. [DOI: 10.1016/j.neubiorev.2018.06.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 05/29/2018] [Accepted: 06/06/2018] [Indexed: 01/16/2023]
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Minogianis EA, Servonnet A, Filion MP, Samaha AN. Role of the orbitofrontal cortex and the dorsal striatum in incentive motivation for cocaine. Behav Brain Res 2019; 372:112026. [PMID: 31195036 DOI: 10.1016/j.bbr.2019.112026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 05/30/2019] [Accepted: 06/08/2019] [Indexed: 12/11/2022]
Abstract
Drug addiction involves increased incentive motivation for drug. Intermittent access to cocaine (IntA; 5-6 minutes ON, 25-26 minutes OFF, for 5-6 hours/session) enhances motivation to take the drug. The orbitofrontal cortex (OFC) and the dorsal striatum (DS) are part of a corticolimbic circuit that encodes incentive value and regulates reward-directed behaviour. We predicted that inactivation of the OFC, DS or both suppresses incentive motivation for cocaine after IntA experience. Male Wistar rats had IntA to cocaine (0.25 mg/kg/infusion) for 10 sessions. The rats developed a 'loading' pattern of intake, taking most of their cocaine in the first minute of each drug-available period. They also developed psychomotor sensitization to self-administered cocaine. We then measured incentive motivation for cocaine using a progressive ratio schedule of reinforcement (PR). Before some PR sessions, rats received microinfusions of a baclofen/muscimol cocktail (0.3 and 0.03 nmol/hemisphere, respectively, or saline) to temporarily inactivate the OFC or DS, or to disconnect the two regions. None of these treatments changed spontaneous locomotion in cocaine-naïve rats. However, both baclofen/muscimol and saline infusions influenced cocaine self-administration behaviour. Infusing baclofen/muscimol or saline into the OFC or into the OFC and contralateral DS decreased responding for cocaine under PR, with baclofen/muscimol and saline having similar effects, except that only OFC-DS disconnection with baclofen/muscimol slowed the pace of cocaine intake. Baclofen/muscimol or saline into the DS also reduced responding for cocaine under PR, but baclofen/muscimol was more effective. We conclude that neuronal activity in the OFC and DS might regulate incentive motivation for cocaine.
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Affiliation(s)
- Ellie-Anna Minogianis
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Canada
| | - Alice Servonnet
- Department of Neuroscience, Faculty of Medicine, Université de Montréal, Canada
| | - Marie-Pier Filion
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Canada
| | - Anne-Noël Samaha
- Department of Pharmacology and Physiology, Faculty of Medicine, Université de Montréal, Canada; Central Nervous System Research Group (GRSNC), Faculty of Medicine, Université de Montréal, Canada.
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Allain F, Samaha A. Revisiting long-access versus short-access cocaine self-administration in rats: intermittent intake promotes addiction symptoms independent of session length. Addict Biol 2019; 24:641-651. [PMID: 29920865 DOI: 10.1111/adb.12629] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 04/06/2018] [Accepted: 04/11/2018] [Indexed: 12/19/2022]
Abstract
In rats, continuous cocaine access during long self-administration sessions (6 versus 1-2 hours) promotes the development of behavioral symptoms of addiction. This has led to the assumption that taking large amounts of drug during extended daily bouts is necessary to develop an addiction phenotype. Recent work shows that within-session intermittent access (IntA) to cocaine produces much less drug intake than continuous-access procedures (i.e. long-access sessions) but evokes addiction symptoms more effectively. IntA-sessions are also long, typically lasting 6 hours. It is not known whether IntA-sessions must be extended to promote addiction-relevant changes in drug use over time. Here, we determined the influence of IntA-session length on patterns of cocaine use relevant to addiction. Two groups of male Wistar rats self-administered cocaine (0.25 mg/kg/injection, injected over 5 seconds) during 18 daily IntA-sessions. One group had long 6-hour sessions (Long-IntA), the other group had shorter, 2-hour sessions (Short-IntA). Only Long-IntA rats escalated their cocaine intake over sessions, but both groups developed a burst-like pattern of drug use over time and similar levels of psychomotor sensitization. The two groups also showed robust and similar levels of both responding for cocaine under a progressive ratio schedule of reinforcement and cocaine-induced reinstatement of extinguished drug-seeking behavior. In summary, long IntA-sessions lead to greater cocaine intake than shorter IntA-sessions, but the two conditions are equally effective in evoking the patterns of drug-taking and drug-seeking that define addiction. This suggests that chronic intermittent cocaine use, even during short daily bouts, is sufficient to promote addiction symptoms.
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Affiliation(s)
- Florence Allain
- Department of Pharmacology and Physiology, Faculty of MedicineUniversité de Montréal Canada
| | - Anne‐Noël Samaha
- Department of Pharmacology and Physiology, Faculty of MedicineUniversité de Montréal Canada
- CNS Research Group, Faculty of MedicineUniversité de Montréal Canada
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Incubation of Cocaine Craving After Intermittent-Access Self-administration: Sex Differences and Estrous Cycle. Biol Psychiatry 2019; 85:915-924. [PMID: 30846301 PMCID: PMC6534474 DOI: 10.1016/j.biopsych.2019.01.015] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 01/17/2019] [Accepted: 01/17/2019] [Indexed: 11/20/2022]
Abstract
BACKGROUND Studies using continuous-access drug self-administration showed that cocaine seeking increases during abstinence (incubation of cocaine craving). Recently, studies using intermittent-access self-administration showed increased motivation to self-administer and seek cocaine. We examined whether intermittent cocaine self-administration would potentiate incubation of craving in male and female rats and examined the estrous cycle's role in this incubation. METHODS In experiment 1, male and female rats self-administered cocaine either continuously (8 hours/day) or intermittently (5 minutes ON, 25 minutes OFF × 16) for 12 days, followed by relapse tests after 2 or 29 days. In experiments 2 and 3, female rats self-administered cocaine intermittently for six, 12, or 18 sessions. In experiment 4, female rats self-administered cocaine continuously followed by relapse tests after 2 or 29 days. In experiments 3 and 4, the estrous cycle was measured using a vaginal smear test. RESULTS Incubation of cocaine craving was observed in both sexes after either intermittent or continuous drug self-administration. Independent of access condition and abstinence day, cocaine seeking was higher in female rats than in male rats. In both sexes, cocaine seeking on both abstinence days was higher after intermittent drug access than after continuous drug access. In female rats, incubation of craving after either intermittent or continuous drug access was significantly higher during estrus than during non-estrus; for intermittent drug access, this effect was independent of the training duration. CONCLUSIONS In both sexes, intermittent cocaine access caused time-independent increases in drug seeking during abstinence. In female rats, the time-dependent increase in drug seeking (incubation) is critically dependent on the estrous cycle phase.
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The transition to cocaine addiction: the importance of pharmacokinetics for preclinical models. Psychopharmacology (Berl) 2019; 236:1145-1157. [PMID: 30820634 PMCID: PMC6592776 DOI: 10.1007/s00213-019-5164-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 01/03/2019] [Indexed: 01/10/2023]
Abstract
A key question in addiction research concerns how, in some individuals, initial recreational or casual patterns of drug use may change brain and psychological function in ways that promote a transition to the problematic patterns of use that define substance use disorders (addiction). In preclinical studies, this is modeled using self-administration procedures. However, most cocaine self-administration procedures produce continuously high brain concentrations of drug, whereas in people, bouts of use are thought to be more intermittent. Here, we ask whether such temporal pharmacokinetic factors matter, by comparing and contrasting the neuropsychological consequences of intermittent vs. long access cocaine self-administration experience. It turns out, the temporal pattern of cocaine use has profound effects on a number of outcomes. First, despite much less total drug consumption, intermittent access to cocaine is more effective in producing addiction-like behavior. Second, intermittent and long access cocaine self-administration change the brain in very different ways to influence motivated behavior. We argue that intermittent access self-administration procedures might be better suited than traditional self-administration procedures for isolating drug-induced changes in neuropsychological function that contribute to the transition to cocaine addiction.
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López AJ, Siciliano CA, Calipari ES. Activity-Dependent Epigenetic Remodeling in Cocaine Use Disorder. Handb Exp Pharmacol 2019; 258:231-263. [PMID: 31628597 DOI: 10.1007/164_2019_257] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Substance use disorder (SUD) is a behavioral disorder characterized by cycles of abstinence, drug seeking, and relapse. SUD is characterized by aberrant learning processes which develop after repeated exposure to drugs of abuse. At the core of this phenotype is the persistence of symptoms, such as craving and relapse to drug seeking, long after the cessation of drug use. The neural basis of these behavioral changes has been linked to dysfunction in neural circuits across the brain; however, the molecular drivers that allow for these changes to persist beyond the lifespan of any individual protein remain opaque. Epigenetic adaptations - where DNA is modified to increase or decrease the probability of gene expression at key genes - have been identified as a mechanism underlying the long-lasting nature of drug-seeking behavior. Thus, to understand SUD, it is critical to define the interplay between neuronal activation and longer-term changes in transcription and epigenetic remodeling and define their role in addictive behaviors. In this review, we discuss the current understanding of drug-induced changes to circuit function, recent discoveries in epigenetic mechanisms that mediate these changes, and, ultimately, how these adaptations drive the persistent nature of relapse, with emphasis on adaptations in models of cocaine use disorder. Understanding the complex interplay between epigenetic gene regulation and circuit activity will be critical in elucidating the neural mechanisms underlying SUD. This, with the advent of novel genetic-based techniques, will allow for the generation of novel therapeutic avenues to improve treatment outcomes in SUD.
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Affiliation(s)
- Alberto J López
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA.,Vanderbilt Center for Addiction Research, Vanderbilt University School of Medicine, Nashville, TN, USA.,Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Cody A Siciliano
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA.,Vanderbilt Center for Addiction Research, Vanderbilt University School of Medicine, Nashville, TN, USA.,Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Erin S Calipari
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA. .,Vanderbilt Center for Addiction Research, Vanderbilt University School of Medicine, Nashville, TN, USA. .,Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, TN, USA. .,Department of Molecular Physiology and Biophysics, Vanderbilt Institute for Infection, Immunology, and Infection, Vanderbilt University School of Medicine, Nashville, TN, USA. .,Department of Psychiatry and Behavioral Sciences, Vanderbilt Institute for Infection, Immunology, and Infection, Vanderbilt University School of Medicine, Nashville, TN, USA.
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High and escalating levels of cocaine intake are dissociable from subsequent incentive motivation for the drug in rats. Psychopharmacology (Berl) 2018; 235:317-328. [PMID: 29085961 DOI: 10.1007/s00213-017-4773-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 10/20/2017] [Indexed: 12/20/2022]
Abstract
RATIONALE Taking high and increasing amounts of cocaine is thought to be necessary for the development of addiction. Consequently, a widely used animal model of drug self-administration involves giving animals continuous drug access during long sessions (LgA), as this produces high and escalating levels of intake. However, human cocaine addicts likely use the drug with an intermittent rather than continuous pattern, producing spiking brain cocaine levels. OBJECTIVES Using an intermittent-access (IntA) cocaine self-administration procedure in rats, we studied the relationship between escalation of cocaine intake and later incentive motivation for the drug, as measured by responding under a progressive ratio schedule of cocaine reinforcement. RESULTS First, under IntA, rats escalated their cocaine use both within and between sessions. However, escalation did not predict later incentive motivation for the drug. Second, incentive motivation for cocaine was similar in IntA-rats limited to low- and non-escalating levels of drug intake (IntA-Lim) and in IntA-rats that took high and escalating levels of drug. Finally, IntA-Lim rats took much less cocaine than rats given continuous drug access during each self-administration session (LgA-rats). However, IntA-Lim rats later responded more for cocaine under a progressive ratio schedule of reinforcement. CONCLUSIONS Taking large and escalating quantities of cocaine does not appear necessary to increase incentive motivation for the drug. Taking cocaine in an intermittent pattern-even in small amounts-is more effective in producing this addiction-relevant change. Thus, beyond the amount of drug taken, the temporal kinetics of drug use predict change in drug use over time.
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20
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De Nobrega AK, Lyons LC. Drosophila: An Emergent Model for Delineating Interactions between the Circadian Clock and Drugs of Abuse. Neural Plast 2017; 2017:4723836. [PMID: 29391952 PMCID: PMC5748135 DOI: 10.1155/2017/4723836] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 08/13/2017] [Indexed: 01/12/2023] Open
Abstract
Endogenous circadian oscillators orchestrate rhythms at the cellular, physiological, and behavioral levels across species to coordinate activity, for example, sleep/wake cycles, metabolism, and learning and memory, with predictable environmental cycles. The 21st century has seen a dramatic rise in the incidence of circadian and sleep disorders with globalization, technological advances, and the use of personal electronics. The circadian clock modulates alcohol- and drug-induced behaviors with circadian misalignment contributing to increased substance use and abuse. Invertebrate models, such as Drosophila melanogaster, have proven invaluable for the identification of genetic and molecular mechanisms underlying highly conserved processes including the circadian clock, drug tolerance, and reward systems. In this review, we highlight the contributions of Drosophila as a model system for understanding the bidirectional interactions between the circadian system and the drugs of abuse, alcohol and cocaine, and illustrate the highly conserved nature of these interactions between Drosophila and mammalian systems. Research in Drosophila provides mechanistic insights into the corresponding behaviors in higher organisms and can be used as a guide for targeted inquiries in mammals.
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Affiliation(s)
- Aliza K. De Nobrega
- Department of Biological Science, Program in Neuroscience, Florida State University, Tallahassee, FL 32306, USA
| | - Lisa C. Lyons
- Department of Biological Science, Program in Neuroscience, Florida State University, Tallahassee, FL 32306, USA
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Engmann O, Labonte B, Mitchell A, Bashtrykov P, Calipari ES, Rosenbluh C, Loh YHE, Walker DM, Burek D, Hamilton PJ, Issler O, Neve RL, Turecki G, Hurd Y, Chess A, Shen L, Mansuy I, Jeltsch A, Akbarian S, Nestler EJ. Cocaine-Induced Chromatin Modifications Associate With Increased Expression and Three-Dimensional Looping of Auts2. Biol Psychiatry 2017; 82:794-805. [PMID: 28577753 PMCID: PMC5671915 DOI: 10.1016/j.biopsych.2017.04.013] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 04/03/2017] [Accepted: 04/04/2017] [Indexed: 12/29/2022]
Abstract
BACKGROUND Exposure to drugs of abuse alters the epigenetic landscape of the brain's reward regions, such as the nucleus accumbens. We investigated how combinations of chromatin modifications affect genes that regulate responses to cocaine. We focused on Auts2, a gene linked to human evolution and cognitive disorders, which displays strong clustering of cocaine-induced chromatin modifications in this brain region. METHODS We combined chromosome conformation capture, circularized chromosome conformation capture, and related approaches with behavioral paradigms relevant to cocaine phenotypes. Cell type-specific functions were assessed by fluorescence-activated cell sorting and viral-mediated overexpression in Cre-dependent mouse lines. RESULTS We observed that Auts2 gene expression is increased by repeated cocaine administration specifically in D2-type medium spiny neurons in the nucleus accumbens, an effect seen in male but not female mice. Auts2 messenger RNA expression was also upregulated postmortem in the nucleus accumbens of male human cocaine addicts. We obtained evidence that chromosomal looping, bypassing 1524 kb of linear genome, connects Auts2 to the Caln1 gene locus under baseline conditions. This looping was disrupted after repeated cocaine exposure, resulting in increased expression of both genes in D2-type medium spiny neurons. Cocaine exposure reduces binding of CCCTC-binding factor, a chromosomal scaffolding protein, and increases histone and DNA methylation at the Auts-Caln1 loop base in the nucleus accumbens. Cell type-specific overexpression of Auts2 or Caln1 in D2-type medium spiny neurons demonstrated that both genes promote cocaine reward. CONCLUSIONS These findings suggest that cocaine-induced alterations of neuronal three-dimensional genome organization destabilize higher order chromatin at specific loci that regulate responses to the drug.
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Affiliation(s)
- Olivia Engmann
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Benoit Labonte
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Amanda Mitchell
- Departments of Psychiatry and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Pavel Bashtrykov
- Institute of Biochemistry, Stuttgart University, Stuttgart, Germany
| | - Erin S. Calipari
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Chaggai Rosenbluh
- Departments of Developmental and Regenerative Biology and of Genetics and Genomic Sciences and Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Yong-Hwee E. Loh
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Deena M. Walker
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Dominika Burek
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Peter J. Hamilton
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Orna Issler
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Rachael L. Neve
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Gustavo Turecki
- Douglas Mental Health University Institute, Montreal, Canada
| | - Yasmin Hurd
- Departments of Psychiatry and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Andrew Chess
- Departments of Developmental and Regenerative Biology and of Genetics and Genomic Sciences and Icahn Institute for Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Li Shen
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
| | - Isabelle Mansuy
- University of Zurich / ETH Zurich, Brain Research Institute, Zurich, Switzerland
| | - Albert Jeltsch
- Institute of Biochemistry, Stuttgart University, Stuttgart, Germany
| | - Schahram Akbarian
- Departments of Psychiatry and Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Eric J. Nestler
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY USA
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Are Cocaine-Seeking "Habits" Necessary for the Development of Addiction-Like Behavior in Rats? J Neurosci 2017; 38:60-73. [PMID: 29158359 DOI: 10.1523/jneurosci.2458-17.2017] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 10/10/2017] [Accepted: 10/31/2017] [Indexed: 12/21/2022] Open
Abstract
Drug self-administration models of addiction typically require animals to make the same response (e.g., a lever-press or nose-poke) over and over to procure and take drugs. By their design, such procedures often produce behavior controlled by stimulus-response (S-R) habits. This has supported the notion of addiction as a "drug habit," and has led to considerable advances in our understanding of the neurobiological basis of such behavior. However, to procure such drugs as cocaine, addicts often require considerable ingenuity and flexibility in seeking behavior, which, by definition, precludes the development of habits. To better model drug-seeking behavior in addicts, we first developed a novel cocaine self-administration procedure [puzzle self-administration procedure (PSAP)] that required rats to solve a new puzzle every day to gain access to cocaine, which they then self-administered on an intermittent access (IntA) schedule. Such daily problem-solving precluded the development of S-R seeking habits. We then asked whether prolonged PSAP/IntA experience would nevertheless produce "symptoms of addiction." It did, including escalation of intake, sensitized motivation for drug, continued drug use in the face of adverse consequences, and very robust cue-induced reinstatement of drug seeking, especially in a subset of "addiction-prone" rats. Furthermore, drug-seeking behavior continued to require dopamine neurotransmission in the core of the nucleus accumbens (but not the dorsolateral striatum). We conclude that the development of S-R seeking habits is not necessary for the development of cocaine addiction-like behavior in rats.SIGNIFICANCE STATEMENT Substance-use disorders are often characterized as "habitual" behaviors aimed at obtaining and administering drugs. Although the actions involved in consuming drugs may involve a rigid repertoire of habitual behaviors, evidence suggests that addicts must be very creative and flexible when trying to procure drugs, and thus drug seeking cannot be governed by habit alone. We modeled flexible drug-seeking behavior in rats by requiring animals to solve daily puzzles to gain access to cocaine. We find that habitual drug-seeking isn't necessary for the development of addiction-like behavior, and that our procedure doesn't result in transfer of dopaminergic control from the ventral to dorsal striatum. This approach may prove useful in studying changes in neuropsychological function that promote the transition to addiction.
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Cocaine Potency at the Dopamine Transporter Tracks Discrete Motivational States During Cocaine Self-Administration. Neuropsychopharmacology 2017; 42:1893-1904. [PMID: 28139678 PMCID: PMC5520781 DOI: 10.1038/npp.2017.24] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 12/23/2016] [Accepted: 01/12/2017] [Indexed: 02/07/2023]
Abstract
Although the dopamine transporter (DAT) is the primary site of action for cocaine, and the dopamine system is known to mediate the reinforcing effects of cocaine, the dopaminergic variations underlying individual differences in cocaine self-administration behaviors are not fully understood. Recent advances in the application of economic principles to operant tasks in rodents have allowed for the within-subject, within-session determination of both consummatory and appetitive responding for reinforcers. Here we combined a behavioral economics approach with cocaine self-administration and ex vivo voltammetric recording of dopamine signaling in the core of the nucleus accumbens of rats to determine the relationship between dopamine signaling and discrete aspects of cocaine taking and seeking. We found neither dopamine release or uptake tracked individual differences in cocaine consumption or the reinforcing efficacy of cocaine. Cocaine potency at the DAT was correlated with reinforcing efficacy, but was not related to cocaine consumption. Further, we introduce a novel analysis that determines perseverative responding within the same procedure, and find that cocaine potency at the DAT also tracks differences in perseverative responding. Together, we demonstrate that cocaine effects at the DAT determine the reinforcing efficacy of cocaine, and perseverative responding for sub-threshold doses of cocaine that do not maintain responding when presented in isolation. Surprisingly, we find that variations in cocaine potency do not account for differences in cocaine consumption, suggesting that satiation for cocaine is determined by other targets or mechanisms. Finally, we outline a novel approach for relating drug-target interactions and potency to discrete motivational states during a single self-administration session.
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Abstract
An increasing emphasis has been placed on the development and use of animal models of addiction that capture defining features of human drug addiction, including escalation/binge drug use, enhanced motivation for the drug, preference for the drug over other reward options, use despite negative consequences, and enhanced drug-seeking/relapse vulnerability. The need to examine behavior in both males and females has also become apparent given evidence demonstrating that the addiction process occurs differently in males and females. This review discusses the procedures that are used to model features of addiction in animals, as well as factors that influence their development. Individual differences are also discussed, with a particular focus on sex differences. While no one procedure consistently produces all characteristics, different models have been developed to focus on certain characteristics. A history of escalating/binge patterns of use appears to be critical for producing other features characteristic of addiction, including an enhanced motivation for the drug, enhanced drug seeking, and use despite negative consequences. These characteristics tend to emerge over abstinence, and appear to increase rather than decrease in magnitude over time. In females, these characteristics develop sooner during abstinence and/or following less drug exposure as compared to males, and for psychostimulant addiction, may require estradiol. Although preference for the drug over other reward options has been demonstrated in non-human primates, it has been more difficult to establish in rats. Future research is needed to define the parameters that optimally induce each of these features of addiction in the majority of animals. Such models are essential for advancing our understanding of human drug addiction and its treatment in men and women.
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Affiliation(s)
- Wendy J Lynch
- Department of Psychiatry and Neurobehavioral Sciences, University of Virginia, Charlottesville, VA 22904, USA.
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Fordahl SC, Jones SR. High-Fat-Diet-Induced Deficits in Dopamine Terminal Function Are Reversed by Restoring Insulin Signaling. ACS Chem Neurosci 2017; 8:290-299. [PMID: 27966885 DOI: 10.1021/acschemneuro.6b00308] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Systemically released insulin crosses the blood-brain barrier and binds to insulin receptors on several neural cell types, including dopaminergic neurons. Insulin has been shown to decrease dopamine neuron firing in the ventral tegmental area (VTA), but potentiate release and reuptake at dopamine terminals in the nucleus accumbens (NAc). Here we show that prolonged consumption of a high fat diet blocks insulin's effects in the NAc, but insulin's effects are restored by inhibiting protein tyrosine phosphatase 1B, which supports insulin receptor signaling. Mice fed a high fat diet (60% kcals from fat) displayed significantly higher fasting blood glucose 160 mg/dL, compared to 101 mg/dL for control-diet-fed mice, and high-fat-diet-fed mice showed reduced blood glucose clearance after an intraperitoneal glucose tolerance test. Using fast scan cyclic voltammetry to measure electrically evoked dopamine in brain slices containing the NAc core, high-fat-diet-fed mice exhibited slower dopamine reuptake compared to control-diet-fed mice (2.2 ± 0.1 and 2.67 ± 0.15 μM/s, respectively). Moreover, glucose clearance rate was negatively correlated with Vmax. Insulin (10 nM to 1 μM) dose dependently increased reuptake rates in control-diet-fed mice compared with in the high-fat-diet group; however, the small molecule insulin receptor sensitizing agent, TCS 401 (300 nM), restored reuptake in high-fat-diet-fed mice to control-diet levels, and a small molecule inhibitor of the insulin receptor, BMS 536924 (300 nM), attenuated reuptake, similar to high-fat-diet-fed mice. These data show that a high-fat diet impairs dopamine reuptake by attenuating insulin signaling at dopamine terminals.
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Affiliation(s)
- Steve C. Fordahl
- 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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Pitchers KK, Wood TR, Skrzynski CJ, Robinson TE, Sarter M. The ability for cocaine and cocaine-associated cues to compete for attention. Behav Brain Res 2016; 320:302-315. [PMID: 27890441 DOI: 10.1016/j.bbr.2016.11.024] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 11/06/2016] [Accepted: 11/11/2016] [Indexed: 12/18/2022]
Abstract
In humans, reward cues, including drug cues in individuals experiencing addiction, are especially effective in biasing attention towards them, so much so they can disrupt ongoing task performance. It is not known, however, whether this happens in rats. To address this question, we developed a behavioral paradigm to assess the capacity of an auditory drug (cocaine) cue to evoke cocaine-seeking behavior, thus distracting thirsty rats from performing a well-learned sustained attention task (SAT) to obtain a water reward. First, it was determined that an auditory cocaine cue (tone-CS) reinstated drug-seeking equally in sign-trackers (STs) and goal-trackers (GTs), which otherwise vary in the propensity to attribute incentive salience to a localizable drug cue. Next, we tested the ability of an auditory cocaine cue to disrupt performance on the SAT in STs and GTs. Rats were trained to self-administer cocaine intravenously using an Intermittent Access self-administration procedure known to produce a progressive increase in motivation for cocaine, escalation of intake, and strong discriminative stimulus control over drug-seeking behavior. When presented alone, the auditory discriminative stimulus elicited cocaine-seeking behavior while rats were performing the SAT, but it was not sufficiently disruptive to impair SAT performance. In contrast, if cocaine was available in the presence of the cue, or when administered non-contingently, SAT performance was severely disrupted. We suggest that performance on a relatively automatic, stimulus-driven task, such as the basic version of the SAT used here, may be difficult to disrupt with a drug cue alone. A task that requires more top-down cognitive control may be needed.
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Affiliation(s)
- Kyle K Pitchers
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA.
| | - Taylor R Wood
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA
| | - Cari J Skrzynski
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA
| | - Terry E Robinson
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA
| | - Martin Sarter
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA
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Mash DC. Excited Delirium and Sudden Death: A Syndromal Disorder at the Extreme End of the Neuropsychiatric Continuum. Front Physiol 2016; 7:435. [PMID: 27790150 PMCID: PMC5061757 DOI: 10.3389/fphys.2016.00435] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 09/13/2016] [Indexed: 01/15/2023] Open
Abstract
Over the past decade, the excited delirium syndrome (ExDS) has raised continued controversy regarding the cause and manner of death of some highly agitated persons held in police custody, restrained or incapacitated by electrical devices. At autopsy, medical examiners have difficulty in identifying an anatomic cause of death, but frequently cite psychostimulant intoxication as a contributing factor. The characteristic symptoms of ExDS include bizarre and aggressive behavior, shouting, paranoia, panic, violence toward others, unexpected physical strength, and hyperthermia. Throughout the United States and Canada, these cases are most frequently associated with cocaine, methamphetamine, and designer cathinone abuse. Acute exhaustive mania and sudden death presents with behavioral symptoms that are identical to what is described for ExDS in psychostimulant abusers. Bell's mania or acute exhaustive mania was first described in the 1850's by American psychiatrist Luther Bell in institutionalized psychiatric patients. This rare disorder of violent mania, elevated body temperature and autonomic collapse continued to be described by others in the psychiatric literature, but with different names until the first cases of ExDS were seen at the beginning of the cocaine epidemic by medical examiners. The neurochemical pathology examination of brain tissues after death revealed a loss of dopamine transporter regulation together with increases in heat shock protein 70 (hsp70) expression as a biomarker of hyperthermia. The similarity in the behavioral symptoms between extremely agitated psychostimulant abusers and unmedicated psychiatric patients suggests that a genetic disorder that leads to dysregulated central dopamine transporter function could be a precipitating cause of the acute delirium and sudden death. While the precise cause and mechanism of lethality remains controversial, the likely whys and wherefores of sudden death of ExDS victims are seen to be "biological," since excessive dopamine in the brain triggers the manic excitement and delirium, which unabated, culminates in a loss of autonomic function that progresses to cardiorespiratory collapse.
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Affiliation(s)
- Deborah C Mash
- Department of Neurology and Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine Miami, FL, USA
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Kawa AB, Bentzley BS, Robinson TE. Less is more: prolonged intermittent access cocaine self-administration produces incentive-sensitization and addiction-like behavior. Psychopharmacology (Berl) 2016; 233:3587-602. [PMID: 27481050 PMCID: PMC5023484 DOI: 10.1007/s00213-016-4393-8] [Citation(s) in RCA: 111] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 07/19/2016] [Indexed: 01/09/2023]
Abstract
RATIONALE Contemporary animal models of cocaine addiction focus on increasing the amount of drug consumption to produce addiction-like behavior. However, another critical factor is the temporal pattern of consumption, which in humans is characterized by intermittency, both within and between bouts of use. OBJECTIVE To model this, we combined prolonged access to cocaine (∼70 days in total) with an intermittent access (IntA) self-administration procedure and used behavioral economic indicators to quantify changes in motivation for cocaine. RESULTS IntA produced escalation of intake, a progressive increase in cocaine demand (incentive-sensitization), and robust drug- and cue-induced reinstatement of drug-seeking behavior. We also asked whether rats that vary in their propensity to attribute incentive salience to reward cues (sign-trackers [STs] vs. goal-trackers [GTs]) vary in the development of addiction-like behavior. Although STs were more motivated to take cocaine after limited drug experience, after IntA, STs and GTs no longer differed on any measure of addiction-like behavior. CONCLUSIONS Exposure to large quantities of cocaine is not necessary for escalation of intake, incentive-sensitization, or other addiction-like behaviors (IntA results in far less total cocaine consumption than 'long access' procedures). Also, the ST phenotype may increase susceptibility to addiction, not because STs are inherently susceptible to incentive-sensitization (perhaps all individuals are at risk), but because this phenotype promotes continued drug use, subjecting them to incentive-sensitization. Thus, the pharmacokinetics associated with the IntA procedure are especially effective in producing a number of addiction-like behaviors and may be valuable for studying associated neuroadaptations and for assessing individual variation in vulnerability.
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Affiliation(s)
- Alex B Kawa
- Department of Psychology (Biopsychology Program), University of Michigan, 530 Church Street, East Hall, Ann Arbor, MI, 48109, USA
| | - Brandon S Bentzley
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA
| | - Terry E Robinson
- Department of Psychology (Biopsychology Program), University of Michigan, 530 Church Street, East Hall, Ann Arbor, MI, 48109, USA.
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High fat diet augments amphetamine sensitization in mice: Role of feeding pattern, obesity, and dopamine terminal changes. Neuropharmacology 2016; 109:170-182. [PMID: 27267686 DOI: 10.1016/j.neuropharm.2016.06.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 05/21/2016] [Accepted: 06/03/2016] [Indexed: 11/20/2022]
Abstract
High fat (HF) diet-induced obesity has been shown to augment behavioral responses to psychostimulants that target the dopamine system. The purpose of this study was to characterize dopamine terminal changes induced by a HF diet that correspond with enhanced locomotor sensitization to amphetamine. C57BL/6J mice had limited (2hr 3 d/week) or extended (24 h 7 d/week) access to a HF diet or standard chow for six weeks. Mice were then repeatedly exposed to amphetamine (AMPH), and their locomotor responses to an amphetamine challenge were measured. Fast scan cyclic voltammetry was used to identify changes in dopamine terminal function after AMPH exposure. Exposure to a HF diet reduced dopamine uptake and increased locomotor responses to acute, high-dose AMPH administration compared to chow fed mice. Microdialysis showed elevated extracellular dopamine in the nucleus accumbens (NAc) coincided with enhanced locomotion after acute AMPH in HF-fed mice. All mice exhibited locomotor sensitization to amphetamine, but both extended and limited access to a HF diet augmented this response. Neither HF-fed group showed the robust amphetamine sensitization-induced increases in dopamine release, reuptake, and amphetamine potency observed in chow fed animals. However, the potency of amphetamine as an uptake inhibitor was significantly elevated after sensitization in mice with extended (but not limited) access to HF. Conversely, after amphetamine sensitization, mice with limited (but not extended) access to HF displayed reduced autoreceptor sensitivity to the D2/D3 agonist quinpirole. Additionally, we observed reduced membrane dopamine transporter (DAT) levels after HF, and a shift in DAT localization to the cytosol was detected with limited access to HF. This study showed that different patterns of HF exposure produced distinct dopamine terminal adaptations to repeated AMPH, which differed from chow fed mice, and enhanced sensitization to AMPH. Locomotor sensitization in chow fed mice coincided with elevated DAT function and increased AMPH potency; however, the enhanced behavioral response to AMPH after HF exposure was unique in that it coincided with reduced DAT function and diet pattern-specific adaptations.
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Allain F, Minogianis EA, Roberts DC, Samaha AN. How fast and how often: The pharmacokinetics of drug use are decisive in addiction. Neurosci Biobehav Rev 2015; 56:166-79. [DOI: 10.1016/j.neubiorev.2015.06.012] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 05/28/2015] [Accepted: 06/12/2015] [Indexed: 12/18/2022]
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Calipari ES, Siciliano CA, Zimmer BA, Jones SR. Brief intermittent cocaine self-administration and abstinence sensitizes cocaine effects on the dopamine transporter and increases drug seeking. Neuropsychopharmacology 2015; 40:728-35. [PMID: 25212486 PMCID: PMC4289961 DOI: 10.1038/npp.2014.238] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 01/27/2023]
Abstract
Although traditional sensitization paradigms, which result in an augmentation of cocaine-induced locomotor behavior and dopamine (DA) overflow following repeated experimenter-delivered cocaine injections, are often used as a model to study drug addiction, similar effects have been difficult to demonstrate following cocaine self-administration. We have recently shown that intermittent access (IntA) to cocaine can result in increased cocaine potency at the DA transporter (DAT); however, traditional sensitization paradigms often show enhanced effects following withdrawal/abstinence periods. Therefore, we determined a time course of IntA-induced sensitization by examining the effects of 1 or 3 days of IntA, as well as a 7-day abstinence period on DA function, cocaine potency, and reinforcement. Here we show that cocaine potency is increased following as little as 3 days of IntA and further augmented following an abstinence period. In addition, IntA plus abstinence produced greater evoked DA release in the presence of cocaine as compared with all other groups, demonstrating that following abstinence, both cocaine's ability to increase DA release and inhibit uptake at the DAT, two separate mechanisms for increasing DA levels, are enhanced. Finally, we found that IntA-induced sensitization of the DA system resulted in an increased reinforcing efficacy of cocaine, an effect that was augmented after the 7-day abstinence period. These results suggest that sensitization of the DA system may have an important role in the early stages of drug abuse and may drive the increased drug seeking and taking that characterize the transition to uncontrolled drug use. Human data suggest that intermittency, sensitization, and periods of abstinence have an integral role in the process of addiction, highlighting the importance of utilizing pre-clinical models that integrate these phenomena, and suggesting that IntA paradigms may serve as novel models of human addiction.
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Affiliation(s)
- Erin S Calipari
- Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, USA,Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Cody A Siciliano
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Benjamin A Zimmer
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA,Department of Neuroscience, The Medical University of South Carolina, Charleston, SC, USA
| | - Sara R Jones
- Department of Physiology and Pharmacology, Wake Forest School of Medicine, Winston-Salem, NC, USA,Department of Physiology and Pharmacology, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA, Tel: 336 716 8533, Fax: 336 716 8501, E-mail:
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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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