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Martínez M, Espinoza VE, Garcia V, Uribe KP, Negishi K, Estevao IL, Carcoba LM, O'Dell LE, Khan AM, Mendez IA. Withdrawal from repeated nicotine vapor exposure increases somatic signs of physical dependence, anxiety-like behavior, and brain reward thresholds in adult male rats. Neuropharmacology 2023; 240:109681. [PMID: 37611823 PMCID: PMC11253717 DOI: 10.1016/j.neuropharm.2023.109681] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 07/31/2023] [Accepted: 08/01/2023] [Indexed: 08/25/2023]
Abstract
Nicotine vapor consumption via electronic nicotine delivery systems has increased over the last decade. While prior work has shed light on the health effects of nicotine vapor inhalation, its unique effects on the brain and behavior have not been thoroughly explored. In this study we assessed markers of withdrawal following 14 days of nicotine vapor exposure. For Experiment 1, 21 adult male rats were exposed to ambient air or 6, 12, or 24 mg/mL nicotine vapor for 14 consecutive days. Following exposure on day 14, rats were injected with the nicotinic receptor antagonist mecamylamine (3.0 mg/mL) and assessed for somatic withdrawal signs and anxiety-like behavior in the elevated plus maze. For Experiment 2, 12 adult male rats were tested for intracranial self-stimulation (ICSS) immediately following exposure to vehicle vapor (50%/50%, vegetable glycerin/propylene glycol) or 24 mg/mL nicotine vapor, for 14 consecutive days. ICSS behavior was assessed for an additional 14 days, following cessation of repeated vapor exposure. Results reveal that rats with repeated nicotine vapor exposure display an increase in behavioral indicators of withdrawal following injection of mecamylamine (precipitated withdrawal). Additionally, increases in ICSS stimulation thresholds, indicative of reduced brain reward sensitivity, persist following cessation of repeated nicotine vapor exposure (spontaneous withdrawal). These data suggest that repeated e-cigarette use leads to nicotine dependence and withdrawal that affects behavior and brain reward function. Further characterization of the health effects of nicotine vapor is necessary to improve treatment strategies for nicotine use disorder and public health policies related to novel nicotine delivery systems.
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Affiliation(s)
- Michelle Martínez
- Department of Psychology, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Veronika E Espinoza
- Department of Psychology, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Valeria Garcia
- Department of Psychology, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Kevin P Uribe
- Department of Psychology, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Kenichiro Negishi
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Igor L Estevao
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Luis M Carcoba
- Department of Psychology, The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Laura E O'Dell
- Department of Psychology, The University of Texas at El Paso, El Paso, TX, 79968, USA; Interdisciplinary Group for Neuroscience Investigation, Training and Education (IGNITE), The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Arshad M Khan
- Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, 79968, USA; Interdisciplinary Group for Neuroscience Investigation, Training and Education (IGNITE), The University of Texas at El Paso, El Paso, TX, 79968, USA
| | - Ian A Mendez
- School of Pharmacy, Department of Pharmaceutical Sciences, The University of Texas at El Paso, El Paso, TX, 79968, USA; Interdisciplinary Group for Neuroscience Investigation, Training and Education (IGNITE), The University of Texas at El Paso, El Paso, TX, 79968, USA.
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2
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Harris AC, Muelken P, Alcheva A, Stepanov I, LeSage MG. Cigarette Smoke Extract, but Not Electronic Cigarette Aerosol Extract, Inhibits Monoamine Oxidase in vitro and Produces Greater Acute Aversive/Anhedonic Effects Than Nicotine Alone on Intracranial Self-Stimulation in Rats. Front Neurosci 2022; 16:868088. [PMID: 35712461 PMCID: PMC9196039 DOI: 10.3389/fnins.2022.868088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 04/25/2022] [Indexed: 12/14/2022] Open
Abstract
Conventional tobacco cigarettes appear to have greater abuse liability than non-combusted products such as electronic cigarettes (ECs) and nicotine replacement therapy (NRT). This may be due to the higher levels of behaviorally active non-nicotine constituents [e.g., monoamine oxidase (MAO) inhibitors such as β-carbolines] in cigarette smoke (CS) compared to non-combusted products. To evaluate this hypothesis, the current studies compared the relative abuse liability of CS and EC aerosol extracts containing nicotine and a range of non-nicotine constituents to that of nicotine alone (NRT analog) using intracranial self-stimulation (ICSS) in rats. Effects of formulations on brain MAO activity in vitro and ex vivo were also studied to evaluate the potential role of MAO inhibition in the ICSS study. CS extract contained higher levels of several behaviorally active non-nicotine constituents (e.g., the β-carbolines norharmane and harmane) than EC extract. Nicotine alone reduced ICSS thresholds at a moderate nicotine dose, suggesting a reinforcement-enhancing effect that may promote abuse liability, and elevated ICSS thresholds at a high nicotine dose, suggesting an aversive/anhedonic effect that may limit abuse liability. CS extract elevated ICSS thresholds to a greater degree than nicotine alone at high nicotine doses. Effects of EC extract on ICSS did not differ from those of nicotine alone. Finally, CS extract significantly inhibited MAO-A and MAO-B activity in vitro, whereas EC extract and nicotine alone did not. None of the formulations inhibited MAO measured ex vivo. These findings indicate greater acute aversive/anhedonic effects for CS extract compared to nicotine alone, suggesting lower abuse liability. Although confirmation of our findings using other dosing regimens, preclinical addiction models, and tobacco product extracts is needed, these findings suggest that the centrally-mediated effects of MAO inhibitors and other non-nicotine constituents may not account for the greater abuse liability of cigarettes compared to non-combusted products. Nonetheless, identifying the specific constituent(s) mediating the effects of CS extracts in this study could help clarify mechanisms mediating tobacco addiction and inform FDA product standards.
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Affiliation(s)
- Andrew C. Harris
- Hennepin Healthcare Research Institute, Minneapolis, MN, United States,Department of Medicine, University of Minnesota, Minneapolis, MN, United States,Department of Psychology, University of Minnesota, Minneapolis, MN, United States,*Correspondence: Andrew C. Harris,
| | - Peter Muelken
- Hennepin Healthcare Research Institute, Minneapolis, MN, United States
| | - Aleksandra Alcheva
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, United States
| | - Irina Stepanov
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, United States
| | - Mark G. LeSage
- Hennepin Healthcare Research Institute, Minneapolis, MN, United States,Department of Medicine, University of Minnesota, Minneapolis, MN, United States,Department of Psychology, University of Minnesota, Minneapolis, MN, United States
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Harris AC. Further pharmacological characterization of a preclinical model of the early development of nicotine withdrawal. Drug Alcohol Depend 2021; 226:108870. [PMID: 34216863 DOI: 10.1016/j.drugalcdep.2021.108870] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/24/2021] [Accepted: 06/10/2021] [Indexed: 10/21/2022]
Abstract
BACKGROUND Establishing preclinical models of the development of nicotine withdrawal following acute nicotine exposure could inform tobacco addiction-related research, treatment, and policy. To this end, this lab has previously reported that rats exhibit withdrawal-like elevations in intracranial self-stimulation (ICSS) thresholds (anhedonia-like behavior) following acute nicotine exposure. The goal of this study was to provide further pharmacological characterization of ICSS as a measure of spontaneous and antagonist-precipitated withdrawal from acute nicotine. METHODS AND RESULTS Rats exhibited a small increase in ICSS thresholds over time following a single nicotine injection (1.0 mg/kg, s.c.), suggesting a modest spontaneous withdrawal effect (Experiment 1). In Experiment 2, the antidepressant bupropion (5.0 mg/kg, i.p.), which is used to treat tobacco addiction and attenuates nicotine withdrawal in both humans and rodents, blocked elevations in ICSS thresholds induced by a single injection of nicotine (0.5 mg/kg, s.c.) followed ≈ 2 h later by the non-selective, non-competitive nicotinic acetylcholine receptor (nAChR) antagonist mecamylamine (3.0 mg/kg, s.c.). In Experiment 3a, s.c. administration of the competitive, relatively selective α4ß2 nAChR antagonist dihydro-beta-erythroidine (DHßE) (5.6 mg/kg, but not 3.0 mg/kg) following each of 5 daily injections of nicotine (0.5 mg/kg, s.c.) elevated ICSS thresholds. Mecamylamine (3.0 mg/kg, s.c.) also elevated ICSS thresholds when administered following all 5 daily nicotine injections (0.5 mg/kg, s.c., Experiment 3b). CONCLUSIONS These findings provide further characterization of elevations in ICSS thresholds as a measure of withdrawal from acute nicotine exposure. Further use of these models may be useful for understanding the early development of nicotine withdrawal.
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Affiliation(s)
- Andrew C Harris
- Hennepin Healthcare Research Institute, 701 Park Avenue, Minneapolis, MN 55415, United States; Departments of Medicine and Psychology, University of Minnesota Minneapolis, MN, United States.
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4
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Chellian R, Wilks I, Levin B, Xue S, Behnood-Rod A, Wilson R, McCarthy M, Ravula A, Chandasana H, Derendorf H, Bruijnzeel AW. Tobacco smoke exposure enhances reward sensitivity in male and female rats. Psychopharmacology (Berl) 2021; 238:845-855. [PMID: 33410984 PMCID: PMC7914215 DOI: 10.1007/s00213-020-05736-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 11/25/2020] [Indexed: 12/14/2022]
Abstract
RATIONALE Systemic administration of the tobacco smoke constituent nicotine stimulates brain reward function in rats. However, it is unknown if the inhalation of tobacco smoke affects brain reward function. OBJECTIVES These experiments investigated if exposure to smoke from high-nicotine SPECTRUM research cigarettes increases reward function and affects the rewarding effects of nicotine in adult male and female Wistar rats. METHODS Reward function after smoke or nicotine exposure was investigated using the intracranial self-stimulation (ICSS) procedure. A decrease in reward thresholds reflects an increase in reward function. In the first experiment, the rats were exposed to tobacco smoke for 40 min/day for 9 days, and the rewarding effects of nicotine (0.03-0.6 mg/kg) were investigated 3 weeks later. In the second experiment, the dose effects of tobacco smoke exposure (40-min sessions, 1-4 cigarettes burnt simultaneously) on reward function were investigated. RESULTS Tobacco smoke exposure did not affect the nicotine-induced decrease in reward thresholds or response latencies in male and female rats. Smoke exposure lowered the brain reward thresholds to a similar degree in males and females and caused a greater decrease in latencies in females. There was a positive relationship between plasma nicotine and cotinine levels and the nicotine content of the SPECTRUM research cigarettes. Similar smoke exposure conditions led to higher plasma nicotine and cotinine levels in female than male rats. CONCLUSION These findings indicate that tobacco smoke exposure enhances brain reward function but does not potentiate the rewarding effects of nicotine in male and female rats.
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Affiliation(s)
- Ranjithkumar Chellian
- Department of Psychiatry, University of Florida, 1149 Newell Dr., Gainesville, FL, 32611, USA
| | - Isaac Wilks
- Department of Psychiatry, University of Florida, 1149 Newell Dr., Gainesville, FL, 32611, USA
| | - Brandon Levin
- Department of Psychiatry, University of Florida, 1149 Newell Dr., Gainesville, FL, 32611, USA
| | - Song Xue
- Department of Psychiatry, University of Florida, 1149 Newell Dr., Gainesville, FL, 32611, USA
| | - Azin Behnood-Rod
- Department of Psychiatry, University of Florida, 1149 Newell Dr., Gainesville, FL, 32611, USA
| | - Ryann Wilson
- Department of Psychiatry, University of Florida, 1149 Newell Dr., Gainesville, FL, 32611, USA
| | - Megan McCarthy
- Department of Psychiatry, University of Florida, 1149 Newell Dr., Gainesville, FL, 32611, USA
| | - Abhigyan Ravula
- Department of Pharmaceutics, University of Florida, Gainesville, USA
| | - Hardik Chandasana
- Department of Pharmaceutics, University of Florida, Gainesville, USA
| | - Hartmut Derendorf
- Department of Pharmaceutics, University of Florida, Gainesville, USA
| | - Adriaan W Bruijnzeel
- Department of Psychiatry, University of Florida, 1149 Newell Dr., Gainesville, FL, 32611, USA.
- Department of Neuroscience, University of Florida, Gainesville, FL, USA.
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5
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Koob GF. Drug Addiction: Hyperkatifeia/Negative Reinforcement as a Framework for Medications Development. Pharmacol Rev 2021; 73:163-201. [PMID: 33318153 PMCID: PMC7770492 DOI: 10.1124/pharmrev.120.000083] [Citation(s) in RCA: 154] [Impact Index Per Article: 51.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Compulsive drug seeking that is associated with addiction is hypothesized to follow a heuristic framework that involves three stages (binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation) and three domains of dysfunction (incentive salience/pathologic habits, negative emotional states, and executive function, respectively) via changes in the basal ganglia, extended amygdala/habenula, and frontal cortex, respectively. This review focuses on neurochemical/neurocircuitry dysregulations that contribute to hyperkatifeia, defined as a greater intensity of negative emotional/motivational signs and symptoms during withdrawal from drugs of abuse in the withdrawal/negative affect stage of the addiction cycle. Hyperkatifeia provides an additional source of motivation for compulsive drug seeking via negative reinforcement. Negative reinforcement reflects an increase in the probability of a response to remove an aversive stimulus or drug seeking to remove hyperkatifeia that is augmented by genetic/epigenetic vulnerability, environmental trauma, and psychiatric comorbidity. Neurobiological targets for hyperkatifeia in addiction involve neurocircuitry of the extended amygdala and its connections via within-system neuroadaptations in dopamine, enkephalin/endorphin opioid peptide, and γ-aminobutyric acid/glutamate systems and between-system neuroadaptations in prostress corticotropin-releasing factor, norepinephrine, glucocorticoid, dynorphin, hypocretin, and neuroimmune systems and antistress neuropeptide Y, nociceptin, endocannabinoid, and oxytocin systems. Such neurochemical/neurocircuitry dysregulations are hypothesized to mediate a negative hedonic set point that gradually gains allostatic load and shifts from a homeostatic hedonic state to an allostatic hedonic state. Based on preclinical studies and translational studies to date, medications and behavioral therapies that reset brain stress, antistress, and emotional pain systems and return them to homeostasis would be promising new targets for medication development. SIGNIFICANCE STATEMENT: The focus of this review is on neurochemical/neurocircuitry dysregulations that contribute to hyperkatifeia, defined as a greater intensity of negative emotional/motivational signs and symptoms during withdrawal from drugs of abuse in the withdrawal/negative affect stage of the drug addiction cycle and a driving force for negative reinforcement in addiction. Medications and behavioral therapies that reverse hyperkatifeia by resetting brain stress, antistress, and emotional pain systems and returning them to homeostasis would be promising new targets for medication development.
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Affiliation(s)
- George F Koob
- National Institute on Alcohol Abuse and Alcoholism and National Institute on Drug Abuse, National Institutes of Health, Bethesda, Maryland
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Harris AC, Muelken P, LeSage MG. β-Carbolines found in cigarette smoke elevate intracranial self-stimulation thresholds in rats. Pharmacol Biochem Behav 2020; 198:173041. [PMID: 32926882 PMCID: PMC7554228 DOI: 10.1016/j.pbb.2020.173041] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 09/04/2020] [Accepted: 09/07/2020] [Indexed: 12/25/2022]
Abstract
Identifying novel constituents that contribute to tobacco addiction is essential for developing more effective treatments and informing FDA regulation of tobacco products. While preclinical data indicate that monoamine oxidase (MAO) inhibitors can have abuse liability or potentiate the addiction-related effects of nicotine, most of these studies have used clinical MAO inhibitors (e.g., tranylcypromine) that are not present in cigarette smoke. The primary goal of this study was to evaluate the abuse potential of the β-carbolines harmane, norharmane, and harmine - MAO inhibitors that are found in cigarette smoke - in an intracranial self-simulation (ICSS) model in rats. A secondary goal was to evaluate the ability of norharmane to influence nicotine's acute effects on ICSS. None of the β-carbolines lowered ICSS thresholds at any dose studied when administered alone, suggesting a lack of abuse liability. Rather, all three β-carbolines produced dose-dependent elevations in ICSS thresholds, indicating aversive/anhedonic effects. Harmane and harmine also elevated ICSS response latencies, suggesting a disruption of motor function, albeit with reduced potency compared to their ICSS threshold-elevating effects. Norharmane (2.5 mg/kg) modestly attenuated the effects of nicotine on ICSS thresholds. Our findings indicate that these β-carbolines produced only aversive/anhedonic effects in an ICSS model when administered alone, and that norharmane unexpectedly attenuated nicotines acute effects on ICSS. Future work evaluating the addiction-related effects of nicotine combined with these and other MAO inhibitors present in smoke may be useful for understanding the role of MAO inhibition in tobacco addiction and informing FDA tobacco regulation.
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Affiliation(s)
- Andrew C Harris
- Hennepin Healthcare Research Institute, Minneapolis, MN, United States of America; Department of Medicine, University of Minnesota Medical School, Minneapolis, MN, United States of America; Department of Psychology, University of Minnesota, Minneapolis, MN, United States of America.
| | - Peter Muelken
- Hennepin Healthcare Research Institute, Minneapolis, MN, United States of America
| | - Mark G LeSage
- Hennepin Healthcare Research Institute, Minneapolis, MN, United States of America; Department of Medicine, University of Minnesota Medical School, Minneapolis, MN, United States of America; Department of Psychology, University of Minnesota, Minneapolis, MN, United States of America
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Geste JR, Levin B, Wilks I, Pompilus M, Zhang X, Esser KA, Febo M, O'Dell L, Bruijnzeel AW. Relationship Between Nicotine Intake and Reward Function in Rats With Intermittent Short Versus Long Access to Nicotine. Nicotine Tob Res 2020; 22:213-223. [PMID: 30958557 DOI: 10.1093/ntr/ntz052] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Accepted: 04/01/2019] [Indexed: 11/12/2022]
Abstract
INTRODUCTION Tobacco use improves mood states and smoking cessation leads to anhedonia, which contributes to relapse. Animal studies have shown that noncontingent nicotine administration enhances brain reward function and leads to dependence. However, little is known about the effects of nicotine self-administration on the state of the reward system. METHODS To investigate the relationship between nicotine self-administration and reward function, rats were prepared with intracranial self-stimulation electrodes and intravenous catheters. The rats were trained on the intracranial self-stimulation procedure and allowed to self-administer 0.03 mg/kg/infusion of nicotine. All rats self-administered nicotine daily for 10 days (1 hour/day) and were then switched to an intermittent short access (ShA, 1 hour/day) or long access (LgA, 23 hour/day) schedule (2 days/week, 5 weeks). RESULTS During the first 10 daily, 1-hour sessions, nicotine self-administration decreased the reward thresholds, which indicates that nicotine potentiates reward function. After switching to the intermittent LgA or ShA schedule, nicotine intake was lower in the ShA rats than the LgA rats. The LgA rats increased their nicotine intake over time and they gradually consumed a higher percentage of their nicotine during the light phase. The nicotinic acetylcholine receptor (nAChR) antagonist mecamylamine induced a larger increase in reward thresholds (ie, anhedonia) in the LgA rats than the ShA rats. In the LgA rats, nAChR blockade with mecamylamine decreased nicotine intake for 2 hours and this was followed by a rebound increase in nicotine intake. CONCLUSIONS A brief period of nicotine self-administration enhances reward function and a high level of nicotine intake leads to dependence. IMPLICATIONS These animal studies indicate that there is a strong relationship between the level of nicotine intake and brain reward function. A high level of nicotine intake was more rewarding than a low level of nicotine intake and nicotine dependence was observed after long, but not short, access to nicotine. This powerful combination of nicotine reward and withdrawal makes it difficult to quit smoking. Blockade of nAChRs temporarily decreased nicotine intake, but this was followed by a large rebound increase in nicotine intake. Therefore, nAChR blockade might not decrease the use of combustible cigarettes or electronic cigarettes.
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Affiliation(s)
- Jean R Geste
- Department of Psychiatry, University of Florida, Gainesville, FL
| | - Brandon Levin
- Department of Psychiatry, University of Florida, Gainesville, FL
| | - Isaac Wilks
- Department of Psychiatry, University of Florida, Gainesville, FL
| | - Marjory Pompilus
- Department of Psychiatry, University of Florida, Gainesville, FL
| | - Xiping Zhang
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL
| | - Karyn A Esser
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL
| | - Marcelo Febo
- Department of Psychiatry, University of Florida, Gainesville, FL.,Department of Neuroscience, University of Florida, Gainesville, FL
| | - Laura O'Dell
- Department of Psychology, University of Texas at El Paso, El Paso, TX
| | - Adriaan W Bruijnzeel
- Department of Psychiatry, University of Florida, Gainesville, FL.,Department of Neuroscience, University of Florida, Gainesville, FL
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Swain Y, Muelken P, Skansberg A, Lanzdorf D, Haave Z, LeSage MG, Gewirtz JC, Harris AC. Higher anhedonia during withdrawal from initial opioid exposure is protective against subsequent opioid self-administration in rats. Psychopharmacology (Berl) 2020; 237:2279-2291. [PMID: 32388620 PMCID: PMC7354901 DOI: 10.1007/s00213-020-05532-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 04/17/2020] [Indexed: 12/15/2022]
Abstract
RATIONALE Understanding factors contributing to individual differences in vulnerability to opioid addiction is essential for developing more effective preventions and treatments, yet few reliable behavioral predictors of subsequent opioid self-administration have been identified in rodents. Sensitivity to the acute effects of initial drug exposure predicts later addiction vulnerability in both humans and animals, but the relationship between sensitivity to withdrawal from initial drug exposure and later drug use vulnerability is unclear. OBJECTIVE The goal of the current study was to evaluate whether the degree of anhedonia experienced during withdrawal from early opioid exposure predicts subsequent vulnerability to opioid self-administration. METHODS Rats were first tested for withdrawal sensitivity following acute injections of morphine (i.e., "acute dependence"), measured as elevations in intracranial self-stimulation (ICSS) thresholds (anhedonia-like behavior) during naloxone-precipitated and spontaneous withdrawal. Rats were then tested for addiction-like behavior using various measures of i.v. morphine self-administration (MSA) including acquisition, demand, extinction, and reinstatement induced by morphine, stress, and/or drug-associated cues. RESULTS Greater naloxone-precipitated withdrawal across repeated morphine injections and greater peak spontaneous withdrawal severity following a single morphine injection were associated with lower addiction-like behavior on multiple MSA measures. Withdrawal-induced anhedonia predicted a wider range of MSA measures than did any individual measure of MSA itself. CONCLUSIONS Our data establish WIA as one of the first behavioral measures to predict individual differences in opioid SA in rodents. This model promises to be useful for furthering our understanding of behavioral and neurobiological mechanisms underlying vulnerability to opioid addiction.
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Affiliation(s)
- Yayi Swain
- Hennepin Healthcare Research Institute,,University of Minnesota Department of Psychology
| | | | - Annika Skansberg
- Hennepin Healthcare Research Institute,,University of Minnesota Department of Psychology
| | - Danielle Lanzdorf
- Hennepin Healthcare Research Institute,,University of Minnesota Department of Psychology
| | - Zachary Haave
- Hennepin Healthcare Research Institute,,University of Minnesota Department of Neuroscience
| | - Mark G. LeSage
- Hennepin Healthcare Research Institute,,University of Minnesota Department of Psychology,,University of Minnesota Department of Medicine
| | - Jonathan C. Gewirtz
- University of Minnesota Department of Psychology,,University of Minnesota Department of Neuroscience
| | - Andrew C. Harris
- Hennepin Healthcare Research Institute,,University of Minnesota Department of Psychology,,University of Minnesota Department of Medicine
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9
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Harris AC, Muelken P, Haave Z, Swain Y, Smethells JR, LeSage MG. Propylene glycol, a major electronic cigarette constituent, attenuates the adverse effects of high-dose nicotine as measured by intracranial self-stimulation in rats. Drug Alcohol Depend 2018; 193:162-168. [PMID: 30384324 PMCID: PMC6278948 DOI: 10.1016/j.drugalcdep.2018.08.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Revised: 07/25/2018] [Accepted: 08/26/2018] [Indexed: 11/19/2022]
Abstract
BACKGROUND Non-nicotine tobacco constituents may contribute to the abuse liability of tobacco products. We previously reported that electronic cigarette (EC) refill liquids containing nicotine and a range of non-nicotine constituents attenuated the anhedonic/aversive effects of nicotine in an intracranial self-stimulation (ICSS) model. The alcohol propylene glycol (PG) is a primary ingredient in these and other EC liquids, yet its abuse potential has not been established. The goal of this study was to evaluate the effects of parenteral administration of PG alone and PG combined with nicotine on ICSS in rats. METHODS AND RESULTS PG alone did not affect ICSS at concentrations up to 100%. PG (25% or 60%) did not affect nicotine's reinforcement-enhancing (ICSS threshold-decreasing) effects at low to moderate nicotine doses, but attenuated nicotine's reinforcement-attenuating/aversive (ICSS threshold-increasing) effects at a high nicotine dose. PG concentrations similar to those in EC liquid doses used in our previous studies (1% or 3%) modestly attenuated the ICSS threshold-elevating effects of a high nicotine dose. CONCLUSIONS PG attenuated elevations in ICSS thresholds induced by high-dose nicotine, which may reflect an attenuation of nicotine's acute aversive/anhedonic and/or toxic effects. PG may have contributed to the attenuated ICSS threshold-elevating effects of EC liquids reported previously. Further examination of PG in models of addiction and toxicity is needed to understand the consequences of EC use and to inform the development of EC product standards by the FDA.
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Affiliation(s)
- Andrew C Harris
- Hennepin Healthcare Research Institute, 701 Park Avenue, Minneapolis, MN USA; Departments of Medicine, University of Minnesota Medical School, Variety Club Research Center (VCRC), 401 East River Parkway, 1(st) Floor - Suite 131, Minneapolis, MN 55455, USA; Departments of Psychology, University of Minnesota Medical School, N218 Elliott Hall, 75 E River Rd, Minneapolis, MN 55455, USA.
| | - Peter Muelken
- Hennepin Healthcare Research Institute, 701 Park Avenue, Minneapolis, MN USA
| | - Zach Haave
- Hennepin Healthcare Research Institute, 701 Park Avenue, Minneapolis, MN USA; Departments of Neuroscience, University of Minnesota Medical School, 6-145 Jackson Hall, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Yayi Swain
- Hennepin Healthcare Research Institute, 701 Park Avenue, Minneapolis, MN USA; Departments of Psychology, University of Minnesota Medical School, N218 Elliott Hall, 75 E River Rd, Minneapolis, MN 55455, USA
| | - John R Smethells
- Hennepin Healthcare Research Institute, 701 Park Avenue, Minneapolis, MN USA; Departments of Psychiatry, University of Minnesota Medical School, Fairview Riverside West Building, 2312 S. 6th St., Floor 2, Suite F-275, Minneapolis, MN 55454, USA
| | - Mark G LeSage
- Hennepin Healthcare Research Institute, 701 Park Avenue, Minneapolis, MN USA; Departments of Medicine, University of Minnesota Medical School, Variety Club Research Center (VCRC), 401 East River Parkway, 1(st) Floor - Suite 131, Minneapolis, MN 55455, USA; Departments of Psychology, University of Minnesota Medical School, N218 Elliott Hall, 75 E River Rd, Minneapolis, MN 55455, USA
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10
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LeSage MG, Smethells JR, Harris AC. Status and Future Directions of Preclinical Behavioral Pharmacology in Tobacco Regulatory Science. ACTA ACUST UNITED AC 2018; 18:252-274. [PMID: 30214916 DOI: 10.1037/bar0000113] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Behavioral pharmacology is a branch of the experimental analysis of behavior that has had great influence in drug addiction research and policy. This paper provides an overview of recent behavioral pharmacology research in the field of tobacco regulatory science, which provides the scientific foundation for the Food and Drug Administration Center for Tobacco Products (FDA CTP) to set tobacco control policies. The rationale and aims of tobacco regulatory science are provided, including the types of preclinical operant behavioral models it deems important for assessing the abuse liability of tobacco products and their constituents. We then review literature relevant to key regulatory actions being considered by the FDA CTP, including regulations over nicotine and menthol content of cigarettes, and conclude with suggesting some directions for future research. The current era of tobacco regulatory science provides great opportunities for behavioral pharmacologists to address the leading cause of preventable death and disease worldwide.
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Affiliation(s)
- Mark G LeSage
- Department of Medicine, Minneapolis Medical Research Foundation
- Departments of Medicine, University of Minnesota
- Department of Psychology, University of Minnesota
| | - John R Smethells
- Department of Medicine, Minneapolis Medical Research Foundation
- Departments of Medicine, University of Minnesota
| | - Andrew C Harris
- Department of Medicine, Minneapolis Medical Research Foundation
- Departments of Medicine, University of Minnesota
- Department of Psychology, University of Minnesota
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11
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Semenova S, Jin X, McClure-Begley TD, Tadman MP, Marks MJ, Markou A. Differential effects of withdrawal from intermittent and continuous nicotine exposure on reward deficit and somatic aspects of nicotine withdrawal and expression of α4β2* nAChRs in Wistar male rats. Pharmacol Biochem Behav 2018; 171:54-65. [PMID: 29908200 DOI: 10.1016/j.pbb.2018.06.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 06/03/2018] [Accepted: 06/12/2018] [Indexed: 10/14/2022]
Abstract
BACKGROUND Chronic nicotine exposure produces neuroadaptations in brain reward systems and α4β2 nicotinic acetylcholine receptors (nAChRs) in the corticolimbic brain areas. We previously demonstrated opposite effects of nicotine exposure delivered by self-administration or pumps on brain reward thresholds that can be attributed to the different temporal pattern and contingency of nicotine exposure. We investigated the effects of these two factors on reward thresholds and somatic signs during nicotine withdrawal, and on nAChRs binding in corticolimbic brain areas. METHODS The intracranial self-stimulation procedure was used to assess reward thresholds in rats prepared with pumps delivering various doses of nicotine continuously or intermittently. Separate group of rats were randomly exposed to nicotine via pumps (non-contingent) or nicotine self-administration (contingent) to determine [125I]-epibatidine binding at α4β2* nAChRs. RESULTS Withdrawal from continuous non-contingent nicotine exposure led to significant elevations in thresholds and increases in somatic signs in rats, while there was no significant effect of withdrawal from intermittent non-contingent nicotine exposure at the same doses. nAChRs were upregulated during withdrawal from continuous non-contingent nicotine exposure. α4β2* nAChRs were upregulated in the ventral tegmental area and prelimbic cortex during withdrawal from non-contingent intermittent exposure and in the nucleus accumbens during withdrawal from contingent intermittent nicotine exposure to the same dose. CONCLUSIONS During non-contingent nicotine exposure, the temporal pattern of nicotine delivery differentially affected thresholds and somatic signs of withdrawal. Upregulation of α4β2* nAChRs was brain site-specific and depended on both temporal pattern and contingency of nicotine exposure.
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Affiliation(s)
- Svetlana Semenova
- Department of Psychiatry, School of Medicine, University California San Diego, 9500 Gilman Drive, M/C 0603, La Jolla, CA 92093, USA.
| | - Xinchun Jin
- Department of Psychiatry, School of Medicine, University California San Diego, 9500 Gilman Drive, M/C 0603, La Jolla, CA 92093, USA
| | | | | | - Michael J Marks
- Institute for Behavioral Genetics, University of Colorado, Boulder, CO 80309, USA; Department of Psychology and Neuroscience, University of Colorado, Boulder, CO 80309, USA
| | - Athina Markou
- Department of Psychiatry, School of Medicine, University California San Diego, 9500 Gilman Drive, M/C 0603, La Jolla, CA 92093, USA
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12
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Harris AC, Muelken P, Smethells JR, Yershova K, Stepanov I, Olson TT, Kellar KJ, LeSage MG. Effects of nicotine-containing and "nicotine-free" e-cigarette refill liquids on intracranial self-stimulation in rats. Drug Alcohol Depend 2018; 185:1-9. [PMID: 29413432 PMCID: PMC5889751 DOI: 10.1016/j.drugalcdep.2017.11.032] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 11/10/2017] [Accepted: 11/30/2017] [Indexed: 11/26/2022]
Abstract
BACKGROUND Animal models are needed to inform FDA regulation of electronic cigarettes (ECs) because they avoid limitations associated with human studies. We previously reported that an EC refill liquid produced less aversive/anhedonic effects at a high nicotine dose than nicotine alone as measured by elevations in intracranial self-stimulation (ICSS) thresholds, which may reflect the presence of behaviorally active non-nicotine constituents (e.g., propylene glycol) in the EC liquids. The primary objective of this study was to assess the generality of our prior ICSS findings to two additional EC liquids. We also compared effects of "nicotine-free" varieties of these EC liquids on ICSS, as well as binding affinity and/or functional activity of nicotine alone, nicotine-containing EC liquids, and "nicotine-free" EC liquids at nicotinic acetylcholine receptors (nAChRs). METHODS AND RESULTS Nicotine alone and nicotine dose-equivalent concentrations of both nicotine-containing EC liquids produced similar lowering of ICSS thresholds at low to moderate nicotine doses, indicating similar reinforcement-enhancing effects. At high nicotine doses, nicotine alone elevated ICSS thresholds (a measure of anhedonia-like behavior) while the EC liquids did not. Nicotine-containing EC liquids did not differ from nicotine alone in terms of binding affinity or functional activity at nAChRs. "Nicotine-free" EC liquids did not affect ICSS, but bound with low affinity at some (e.g., α4ß2) nAChRs. CONCLUSIONS These findings suggest that non-nicotine constituents in these EC liquids do not contribute to their reinforcement-enhancing effects. However, they may attenuate nicotine's acute aversive/anhedonic and/or toxic effects, which may moderate the abuse liability and/or toxicity of ECs.
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Affiliation(s)
- Andrew C. Harris
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN, USA,Department of Medicine, University of Minnesota, Minneapolis, MN, USA,Department of Psychology, University of Minnesota, Minneapolis, MN, USA
| | - Peter Muelken
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN, USA
| | - John R. Smethells
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN, USA,Department of Psychiatry, University of Minnesota, Minneapolis, MN, USA
| | - Katrina Yershova
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Irina Stepanov
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Thao Tran Olson
- Department of Pharmacology and Physiology, Georgetown University School of Medicine, Washington, DC, USA
| | - Kenneth J. Kellar
- Department of Pharmacology and Physiology, Georgetown University School of Medicine, Washington, DC, USA
| | - Mark G. LeSage
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN, USA,Department of Medicine, University of Minnesota, Minneapolis, MN, USA,Department of Psychology, University of Minnesota, Minneapolis, MN, USA
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13
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Harris AC, Muelken P, Smethells JR, Krueger M, LeSage MG. Similar precipitated withdrawal effects on intracranial self-stimulation during chronic infusion of an e-cigarette liquid or nicotine alone. Pharmacol Biochem Behav 2017; 161:1-5. [PMID: 28867606 DOI: 10.1016/j.pbb.2017.08.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 08/28/2017] [Accepted: 08/30/2017] [Indexed: 11/19/2022]
Abstract
The FDA recently extended their regulatory authority to electronic cigarettes (ECs). Because the abuse liability of ECs is a leading concern of the FDA, animal models are urgently needed to identify factors that influence the relative abuse liability of these products. The ability of tobacco products to induce nicotine dependence, defined by the emergence of anhedonia and other symptoms of nicotine withdrawal following cessation of their use, contributes to tobacco abuse liability. The present study compared the severity of precipitated withdrawal during chronic infusion of nicotine alone or nicotine-dose equivalent concentrations of three different EC refill liquids in rats, as indicated by elevations in intracranial self-stimulation (ICSS) thresholds (anhedonia-like behavior). Because these EC liquids contain constituents that may enhance their abuse liability (e.g., minor alkaloids), we hypothesized that they would be associated with greater withdrawal effects than nicotine alone. Results indicated that the nicotinic acetylcholine receptor antagonist mecamylamine precipitated elevations in ICSS thresholds in rats receiving a chronic infusion of nicotine alone or EC liquids (3.2mg/kg/day, via osmotic pump). Magnitude of this effect did not differ between formulations. Our findings indicate that nicotine alone is the primary CNS determinant of the ability of ECs to engender dependence. Combined with our previous findings that nicotine alone and these EC liquids do not differ in other preclinical addiction models, these data suggest that product standards set by the FDA to reduce EC abuse liability should primarily target nicotine, other constituents with peripheral sensory effects (e.g. flavorants), and factors that influence product appeal (e.g., marketing).
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Affiliation(s)
- A C Harris
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN, USA; Department of Medicine, University of Minnesota, Minneapolis, MN, USA; Department of Psychology, University of Minnesota, Minneapolis, MN, USA.
| | - P Muelken
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN, USA
| | - J R Smethells
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN, USA; Department of Psychiatry, University of Minnesota, Minneapolis, MN, USA
| | - M Krueger
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN, USA; Department of Psychology, University of Minnesota, Minneapolis, MN, USA
| | - M G LeSage
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN, USA; Department of Medicine, University of Minnesota, Minneapolis, MN, USA; Department of Psychology, University of Minnesota, Minneapolis, MN, USA
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14
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LeSage MG, Staley M, Muelken P, Smethells JR, Stepanov I, Vogel RI, Pentel PR, Harris AC. Abuse liability assessment of an e-cigarette refill liquid using intracranial self-stimulation and self-administration models in rats. Drug Alcohol Depend 2016; 168:76-88. [PMID: 27627814 PMCID: PMC5257285 DOI: 10.1016/j.drugalcdep.2016.08.628] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 07/14/2016] [Accepted: 08/22/2016] [Indexed: 01/19/2023]
Abstract
BACKGROUND The popularity of electronic cigarettes (ECs) has increased dramatically despite their unknown health consequences. Because the abuse liability of ECs is one of the leading concerns of the Food and Drug Administration (FDA), models to assess it are urgently needed to inform FDA regulatory decisions regarding these products. The purpose of this study was to assess the relative abuse liability of an EC liquid compared to nicotine alone in rats. Because this EC liquid contains non-nicotine constituents that may enhance its abuse liability, we hypothesized that it would have greater abuse liability than nicotine alone. METHODS Nicotine alone and nicotine dose-equivalent concentrations of EC liquid were compared in terms of their acute effects on intracranial self-stimulation (ICSS) thresholds, acquisition of self-administration, reinforcing efficacy (i.e., elasticity of demand), blockade of these behavioral effects by mecamylamine, nicotine pharmacokinetics and nicotinic acetylcholine receptor binding and activation. RESULTS There were no significant differences between formulations on any measure, except that EC liquid produced less of an elevation in ICSS thresholds at high nicotine doses. CONCLUSIONS Collectively, these findings suggest that the relative abuse liability of this EC liquid is similar to that of nicotine alone in terms of its reinforcing and reinforcement-enhancing effects, but that it may have less aversive/anhedonic effects at high doses. The present methods may be useful for assessing the abuse liability of other ECs to inform potential FDA regulation of those products.
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Affiliation(s)
- MG LeSage
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN,Department of Medicine, University of Minnesota, Minneapolis, MN,Department of Psychology, University of Minnesota, Minneapolis, MN, 55455
| | - M Staley
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN
| | - P Muelken
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN
| | - JR Smethells
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN,Department of Psychiatry, University of Minnesota, Minneapolis, MN, 55455
| | - I Stepanov
- Masonic Cancer, Center University of Minnesota, Minneapolis, MN
| | - RI Vogel
- Masonic Cancer Center Biostatistics and Bioinformatics Core ,University of Minnesota Minneapolis, MN
| | - PR Pentel
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN,Department of Medicine, University of Minnesota, Minneapolis, MN
| | - AC Harris
- Department of Medicine, Minneapolis Medical Research Foundation, Minneapolis, MN,Department of Medicine, University of Minnesota, Minneapolis, MN,Department of Psychology, University of Minnesota, Minneapolis, MN, 55455
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15
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Parikh V, Cole RD, Patel PJ, Poole RL, Gould TJ. Cognitive control deficits during mecamylamine-precipitated withdrawal in mice: Possible links to frontostriatal BDNF imbalance. Neurobiol Learn Mem 2016; 128:110-6. [PMID: 26775017 DOI: 10.1016/j.nlm.2016.01.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 12/02/2015] [Accepted: 01/10/2016] [Indexed: 02/06/2023]
Abstract
Nicotine is a major psychoactive and addictive component of tobacco. Although cessation of tobacco use produces various somatic and affective symptoms, withdrawal-related cognitive deficits are considered to be a critical symptom that predict relapse. Therefore, delineating the cognitive mechanisms of nicotine withdrawal may likely provide gainful insights into the neurobiology of nicotine addiction. The present study was designed to examine the effects of nicotine withdrawal induced by mecamylamine, a non-specific nicotinic receptor (nAChR) antagonist, on cognitive control processes in mice using an operant strategy switching task. Brain-derived neurotrophic factor (BDNF) modulates synaptic transmission in frontostriatal circuits, and these circuits are critical for executive functions. Thus, we examined the effects of mecamylamine-precipitated nicotine withdrawal on prefrontal and striatal BDNF protein expression. Mice undergoing precipitated nicotine withdrawal required more trials to attain strategy switching criterion as compared to the controls. Error analysis indicated that impaired performance in these animals was mostly related to their inability to execute the new strategy. The striatal/prefrontal BDNF ratios robustly increased following precipitated nicotine withdrawal. Moreover, higher BDNF ratios were associated with longer task acquisition. Collectively, our findings illustrate that mecamylamine-induced nicotine withdrawal disrupts cognitive control processes and that these changes are possibly linked to perturbations in frontostriatal BDNF signaling.
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Affiliation(s)
- Vinay Parikh
- Department of Psychology and Neuroscience Program, Temple University, Philadelphia, PA 19122, United States.
| | - Robert D Cole
- Department of Psychology and Neuroscience Program, Temple University, Philadelphia, PA 19122, United States
| | - Purav J Patel
- Department of Psychology and Neuroscience Program, Temple University, Philadelphia, PA 19122, United States
| | - Rachel L Poole
- Department of Psychology and Neuroscience Program, Temple University, Philadelphia, PA 19122, United States
| | - Thomas J Gould
- Department of Psychology and Neuroscience Program, Temple University, Philadelphia, PA 19122, United States
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16
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A Two-Day Continuous Nicotine Infusion Is Sufficient to Demonstrate Nicotine Withdrawal in Rats as Measured Using Intracranial Self-Stimulation. PLoS One 2015; 10:e0144553. [PMID: 26658557 PMCID: PMC4684239 DOI: 10.1371/journal.pone.0144553] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 11/19/2015] [Indexed: 01/23/2023] Open
Abstract
Avoidance of the negative affective (emotional) symptoms of nicotine withdrawal (e.g., anhedonia, anxiety) contributes to tobacco addiction. Establishing the minimal nicotine exposure conditions required to demonstrate negative affective withdrawal signs in animals, as well as understanding moderators of these conditions, could inform tobacco addiction-related research, treatment, and policy. The goal of this study was to determine the minimal duration of continuous nicotine infusion required to demonstrate nicotine withdrawal in rats as measured by elevations in intracranial self-stimulation (ICSS) thresholds (anhedonia-like behavior). Administration of the nicotinic acetylcholine receptor antagonist mecamylamine (3.0 mg/kg, s.c.) on alternate test days throughout the course of a 2-week continuous nicotine infusion (3.2 mg/kg/day via osmotic minipump) elicited elevations in ICSS thresholds beginning on the second day of infusion. Magnitude of antagonist-precipitated withdrawal did not change with further nicotine exposure and mecamylamine injections, and was similar to that observed in a positive control group receiving mecamylamine following a 14-day nicotine infusion. Expression of a significant withdrawal effect was delayed in nicotine-infused rats receiving mecamylamine on all test days rather than on alternate test days. In a separate study, rats exhibited a transient increase in ICSS thresholds following cessation of a 2-day continuous nicotine infusion (3.2 mg/kg/day). Magnitude of this spontaneous withdrawal effect was similar to that observed in rats receiving a 9-day nicotine infusion. Our findings demonstrate that rats exhibit antagonist-precipitated and spontaneous nicotine withdrawal following a 2-day continuous nicotine infusion, at least under the experimental conditions studied here. Magnitude of these effects were similar to those observed in traditional models involving more prolonged nicotine exposure. Further development of these models, including evaluation of more clinically relevant nicotine dosing regimens and other measures of nicotine withdrawal (e.g., anxiety-like behavior, somatic signs), may be useful for understanding the development of the nicotine withdrawal syndrome.
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17
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Schmidt CE, Manbeck KE, Shelley D, Harris AC. Blockade of cholinergic transmission elicits somatic signs in nicotine-naïve adolescent rats. Front Pharmacol 2015; 6:239. [PMID: 26539119 PMCID: PMC4611158 DOI: 10.3389/fphar.2015.00239] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 10/05/2015] [Indexed: 01/24/2023] Open
Abstract
High doses of the nicotinic acetylcholine receptor (nAChR) antagonist mecamylamine can elicit somatic signs resembling those associated with nicotine withdrawal in nicotine-naïve adult rats. Understanding this phenomenon, and its possible modulation by acute nicotine and age, could inform the use of mecamylamine as both an experimental tool and potential pharmacotherapy for tobacco dependence and other disorders. This study evaluated the ability of high-dose mecamylamine to elicit somatic signs in adolescent rats, and the potential for acute nicotine pretreatment to potentiate this effect as previously reported in adults. Single or repeated injections of mecamylamine (1.5 or 3.0 mg/kg, s.c.) elicited somatic signs in nicotine-naïve adolescents, but this effect was not influenced by 2 h pretreatment with acute nicotine (0.5 mg/kg, s.c.). In an initial evaluation of the effects of age in this model, mecamylamine (2.25 mg/kg, s.c.) elicited somatic signs in nicotine-naïve adolescents and adults. This effect was modestly enhanced following acute nicotine injections in adults but not in adolescents, even when a higher nicotine dose (1.0 rather than 0.5 mg/kg, s.c.) was used in adolescents to account for age differences in nicotine pharmacokinetics. These studies are the first to show that mecamylamine elicits somatic signs in nicotine-naïve adolescent rats, an effect that should be considered when designing and interpreting studies examining effects of high doses of mecamylamine in adolescents. Our findings also provide preliminary evidence that these signs may be differentially modulated by acute nicotine pretreatment in adolescents versus adults.
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Affiliation(s)
- Clare E Schmidt
- Minneapolis Medical Research Foundation , Minneapolis, MN, USA ; Department of Neuroscience, University of Minnesota , Minneapolis, MN, USA
| | - Katherine E Manbeck
- Minneapolis Medical Research Foundation , Minneapolis, MN, USA ; Department of Psychology, University of Minnesota , Minneapolis, MN, USA
| | - David Shelley
- Minneapolis Medical Research Foundation , Minneapolis, MN, USA
| | - Andrew C Harris
- Minneapolis Medical Research Foundation , Minneapolis, MN, USA ; Department of Psychology, University of Minnesota , Minneapolis, MN, USA ; Department of Medicine, University of Minnesota , Minneapolis, MN, USA
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18
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Falco AM, Bevins RA. Individual differences in the behavioral effects of nicotine: A review of the preclinical animal literature. Pharmacol Biochem Behav 2015; 138:80-90. [PMID: 26410616 DOI: 10.1016/j.pbb.2015.09.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 09/17/2015] [Accepted: 09/23/2015] [Indexed: 12/16/2022]
Abstract
Not everyone who tries tobacco or other nicotine-containing products becomes a long-term user. Certain traits or factors that are differentially present in these individuals must be able to help health care providers and researchers determine who is more likely to become chronic users of nicotine-containing products. Some of these factors, particularly sensation-seeking/novelty, impulsivity, and anxiety, lend themselves to the creation of animal models of reactivity to nicotine. These models of reactivity to nicotine can improve the translational aspects of preclinical animal research on nicotine-induced behaviors and treatments in order to help reduce negative outcomes in human populations. The goal of this review is to evaluate the current status of animal models of individual differences that serve to predict the later behavioral effects of nicotine. The limited utility and inconsistency of existing novelty models is considered, as well as the promise of impulsivity and anxiety models in preclinical animal populations. Finally, other models that could be employed to extend the benefit of the current research are examined.
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Affiliation(s)
- Adriana M Falco
- Department of Psychology, Concord University, Athens, WV 24712-1000, United States.
| | - Rick A Bevins
- Department of Psychology, University of Nebraska-Lincoln, Lincoln, NE 68588-0308, United States
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19
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Pomfrey RL, Bostwick TA, Wetzell BB, Riley AL. Adolescent nicotine exposure fails to impact cocaine reward, aversion and self-administration in adult male rats. Pharmacol Biochem Behav 2015; 137:30-7. [PMID: 26255152 DOI: 10.1016/j.pbb.2015.08.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 07/31/2015] [Accepted: 08/03/2015] [Indexed: 01/09/2023]
Abstract
The present experiments examined the effects of adolescent nicotine pre-exposure on the rewarding and aversive effects of cocaine and on cocaine self-administration in adult male rats. In Experiment 1, adolescent Sprague-Dawley rats (postnatal days 28-43) were given once daily injections of nicotine (0.6mg/kg) or vehicle and then tested for the aversive and rewarding effects of cocaine in a combined conditioned taste avoidance (CTA)/conditioned place preference (CPP) procedure in adulthood. In Experiment 2, adolescent Sprague-Dawley rats were pre-exposed to nicotine then tested for cocaine self-administration (0.25 or 0.75mg/kg), progressive ratio (PR) responding, extinction and cue-induced reinstatement in adulthood. In Experiment 1, rats showed significant dose-dependent cocaine-induced taste avoidance with cocaine-injected subjects consuming less saccharin over trials, but no effect of nicotine pre-exposure. For place preferences, cocaine induced significant place preferences with cocaine injected subjects spending significantly more time on the cocaine-paired side, but again there was no effect of nicotine history. All rats in Experiment 2 showed clear, dose-dependent responding during cocaine acquisition, PR testing, extinction and reinstatement with no effect of nicotine pre-exposure. These studies demonstrate that adolescent nicotine pre-exposure does not have an impact on cocaine's affective properties or its self-administration at least with the specific parametric conditions under which these effects were tested.
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Affiliation(s)
- Rebecca L Pomfrey
- Psychopharmacology Laboratory, Department of Psychology, American University, Washington, DC 20016, United States.
| | - Tamaara A Bostwick
- Psychopharmacology Laboratory, Department of Psychology, American University, Washington, DC 20016, United States
| | - B Bradley Wetzell
- Psychopharmacology Laboratory, Department of Psychology, American University, Washington, DC 20016, United States
| | - Anthony L Riley
- Psychopharmacology Laboratory, Department of Psychology, American University, Washington, DC 20016, United States
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20
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Harris AC, Tally L, Muelken P, Banal A, Schmidt CE, Cao Q, LeSage MG. Effects of nicotine and minor tobacco alkaloids on intracranial-self-stimulation in rats. Drug Alcohol Depend 2015; 153:330-4. [PMID: 26094184 PMCID: PMC4509975 DOI: 10.1016/j.drugalcdep.2015.06.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 06/01/2015] [Accepted: 06/02/2015] [Indexed: 12/22/2022]
Abstract
BACKGROUND While nicotine is the primary addictive compound in tobacco, other tobacco constituents including minor alkaloids (e.g., nornicotine, anabasine) may also contribute to tobacco addiction by mimicking or enhancing the effects of nicotine. Further evaluating the behavioral effects of minor alkaloids is essential for understanding their impact on tobacco addiction and informing development of tobacco product standards by the FDA. METHODS This study compared the addiction-related effects of nicotine and the minor alkaloids nornicotine, anabasine, myosmine, anatabine, and cotinine on intracranial self-stimulation (ICSS) thresholds in rats. RESULTS Acute injection of nicotine produced reinforcement-enhancing (ICSS threshold-decreasing) effects at low to moderate doses, and reinforcement-attenuating/aversive (ICSS threshold-increasing) effects at high doses. Nornicotine and anabasine produced similar biphasic effects on ICSS thresholds, although with lower potency compared to nicotine. Myosmine only elevated ICSS thresholds at relatively high doses, while anatabine and cotinine did not influence ICSS thresholds at any dose. None of the alkaloids significantly influenced ICSS response latencies, indicating a lack of nonspecific motoric effects. CONCLUSIONS These findings indicate that some minor tobacco alkaloids can either fully (nornicotine, anabasine) or partially (myosmine) mimic nicotine's addiction-related effects on ICSS, albeit at reduced potency. These findings emphasize the need for further study of the abuse potential of minor alkaloids, including evaluation of their effects when combined with nicotine and other tobacco constituents to better simulate tobacco exposure in humans. Such work is essential for informing FDA regulation of tobacco products and could also lead to the development of novel pharmacotherapies for tobacco addiction.
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Affiliation(s)
- Andrew C. Harris
- Minneapolis Medical Research Foundation, Minneapolis, MN,Department of Medicine, University of Minnesota Medical School, Minneapolis, MN,Department of Psychology, University of Minnesota, Minneapolis, MN
| | - Laura Tally
- Minneapolis Medical Research Foundation, Minneapolis, MN
| | - Peter Muelken
- Minneapolis Medical Research Foundation, Minneapolis, MN,Department of Ecology, Evolution, and Behavior, University of Minnesota, Minneapolis, MN
| | - Andrew Banal
- Minneapolis Medical Research Foundation, Minneapolis, MN,Department of Psychology, University of Minnesota, Minneapolis, MN
| | - Clare E. Schmidt
- Minneapolis Medical Research Foundation, Minneapolis, MN,Department of Neuroscience, University of Minnesota, Minneapolis, MN
| | - Qing Cao
- Masonic Cancer Center Biostatistics and Bioinformatics Core, University of Minnesota, Minneapolis, MN
| | - Mark G. LeSage
- Minneapolis Medical Research Foundation, Minneapolis, MN,Department of Medicine, University of Minnesota Medical School, Minneapolis, MN,Department of Psychology, University of Minnesota, Minneapolis, MN
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21
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Grebenstein PE, Burroughs D, Roiko SA, Pentel PR, LeSage MG. Predictors of the nicotine reinforcement threshold, compensation, and elasticity of demand in a rodent model of nicotine reduction policy. Drug Alcohol Depend 2015; 151:181-93. [PMID: 25891231 PMCID: PMC4447604 DOI: 10.1016/j.drugalcdep.2015.03.030] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 03/17/2015] [Accepted: 03/18/2015] [Indexed: 12/20/2022]
Abstract
BACKGROUND The FDA is considering reducing the nicotine content in tobacco products as a population-based strategy to reduce tobacco addiction. Research is needed to determine the threshold level of nicotine needed to maintain smoking and the extent of compensatory smoking that could occur during nicotine reduction. Sources of variability in these measures across sub-populations also need to be identified so that policies can take into account the risks and benefits of nicotine reduction in vulnerable populations. METHODS The present study examined these issues in a rodent nicotine self-administration model of nicotine reduction policy to characterize individual differences in nicotine reinforcement thresholds, degree of compensation, and elasticity of demand during progressive reduction of the unit nicotine dose. The ability of individual differences in baseline nicotine intake and nicotine pharmacokinetics to predict responses to dose reduction was also examined. RESULTS Considerable variability in the reinforcement threshold, compensation, and elasticity of demand was evident. High baseline nicotine intake was not correlated with the reinforcement threshold, but predicted less compensation and less elastic demand. Higher nicotine clearance predicted low reinforcement thresholds, greater compensation, and less elastic demand. Less elastic demand also predicted lower reinforcement thresholds. CONCLUSIONS These findings suggest that baseline nicotine intake, nicotine clearance, and the essential value of nicotine (i.e. elasticity of demand) moderate the effects of progressive nicotine reduction in rats and warrant further study in humans. They also suggest that smokers with fast nicotine metabolism may be more vulnerable to the risks of nicotine reduction.
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Affiliation(s)
- Patricia E. Grebenstein
- Department of Medicine, Minneapolis Medical Research Foundation, 701 Park Ave., Minneapolis, MN, 55415,Department of Medicine, University of Minnesota School of Medicine, 420 Delaware St. SE Minneapolis, MN, 55455
| | - Danielle Burroughs
- Department of Medicine, Minneapolis Medical Research Foundation, 701 Park Ave., Minneapolis, MN, 55415
| | - Samuel A. Roiko
- Department of Neuroscience, Gillette Children’s Specialty Healthcare, 183 University Ave E Saint Paul, MN 55101
| | - Paul R. Pentel
- Department of Medicine, Minneapolis Medical Research Foundation, 701 Park Ave., Minneapolis, MN, 55415,Department of Medicine, University of Minnesota School of Medicine, 420 Delaware St. SE Minneapolis, MN, 55455,Department of Pharmacology, University of Minnesota School of Medicine, 6-120 Jackson Hall, 321 Church St. SE, Minneapolis, MN, 55455
| | - Mark G. LeSage
- Department of Medicine, Minneapolis Medical Research Foundation, 701 Park Ave., Minneapolis, MN, 55415,Department of Medicine, University of Minnesota School of Medicine, 420 Delaware St. SE Minneapolis, MN, 55455,Department of Psychology, University of Minnesota, N218 Elliot Hall, 75 E River Rd., Minneapolis, MN, 55455
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Koob GF. The dark side of emotion: the addiction perspective. Eur J Pharmacol 2015; 753:73-87. [PMID: 25583178 PMCID: PMC4380644 DOI: 10.1016/j.ejphar.2014.11.044] [Citation(s) in RCA: 232] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 11/06/2014] [Accepted: 11/26/2014] [Indexed: 01/04/2023]
Abstract
Emotions are "feeling" states and classic physiological emotive responses that are interpreted based on the history of the organism and the context. Motivation is a persistent state that leads to organized activity. Both are intervening variables and intimately related and have neural representations in the brain. The present thesis is that drugs of abuse elicit powerful emotions that can be interwoven conceptually into this framework. Such emotions range from pronounced euphoria to a devastating negative emotional state that in the extreme can create a break with homeostasis and thus an allostatic hedonic state that has been considered key to the etiology and maintenance of the pathophysiology of addiction. Drug addiction can be defined as a three-stage cycle-binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation-that involves allostatic changes in the brain reward and stress systems. Two primary sources of reinforcement, positive and negative reinforcement, have been hypothesized to play a role in this allostatic process. The negative emotional state that drives negative reinforcement is hypothesized to derive from dysregulation of key neurochemical elements involved in the brain incentive salience and stress systems. Specific neurochemical elements in these structures include not only decreases in incentive salience system function in the ventral striatum (within-system opponent processes) but also recruitment of the brain stress systems mediated by corticotropin-releasing factor (CRF), dynorphin-κ opioid systems, and norepinephrine, vasopressin, hypocretin, and substance P in the extended amygdala (between-system opponent processes). Neuropeptide Y, a powerful anti-stress neurotransmitter, has a profile of action on compulsive-like responding for drugs similar to a CRF1 receptor antagonist. Other stress buffers include nociceptin and endocannabinoids, which may also work through interactions with the extended amygdala. The thesis argued here is that the brain has specific neurochemical neurocircuitry coded by the hedonic extremes of pleasant and unpleasant emotions that have been identified through the study of opponent processes in the domain of addiction. These neurochemical systems need to be considered in the context of the framework that emotions involve the specific brain regions now identified to differentially interpreting emotive physiological expression.
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Affiliation(s)
- George F Koob
- National Institute on Alcohol Abuse and Alcoholism, Washington, DC, USA.
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The anti-(+)-methamphetamine monoclonal antibody mAb7F9 attenuates acute (+)-methamphetamine effects on intracranial self-stimulation in rats. PLoS One 2015; 10:e0118787. [PMID: 25742165 PMCID: PMC4350938 DOI: 10.1371/journal.pone.0118787] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 01/22/2015] [Indexed: 11/25/2022] Open
Abstract
Passive immunization with monoclonal antibodies (mAbs) against (+)-methamphetamine (METH) is being evaluated for the treatment of METH addiction. A human/mouse chimeric form of the murine anti-METH mAb7F9 has entered clinical trials. This study examined the effects of murine mAb7F9 on certain addiction-related behavioral effects of METH in rats as measured using intracranial self-stimulation (ICSS). Initial studies indicated that acute METH (0.1-0.56 mg/kg, s.c.) lowered the minimal (threshold) stimulation intensity that maintained ICSS. METH (0.3 mg/kg, s.c.) also blocked elevations in ICSS thresholds (anhedonia-like behavior) during spontaneous withdrawal from a chronic METH infusion (10 mg/kg/day x 7 days). In studies examining effects of i.v. pretreatment with mAb7F9 (at 30, 100, or 200 mg/kg), 200 mg/kg blocked the ability of an initial injection of METH (0.3 mg/kg, s.c.) to reduce baseline ICSS thresholds, but was less capable of attenuating the effect of subsequent daily injections of METH. MAb7F9 (200 mg/kg) also produced a small but significant reduction in the ability of METH (0.3 mg/kg, s.c.) to reverse METH withdrawal-induced elevations in ICSS thresholds. These studies demonstrate that mAb7F9 can partially attenuate some addiction-related effects of acute METH in an ICSS model, and provide some support for the therapeutic potential of mAb7F9 for the treatment of METH addiction.
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Harris AC, Tally L, Schmidt CE, Muelken P, Stepanov I, Saha S, Vogel RI, LeSage MG. Animal models to assess the abuse liability of tobacco products: effects of smokeless tobacco extracts on intracranial self-stimulation. Drug Alcohol Depend 2015; 147:60-7. [PMID: 25561387 PMCID: PMC4337227 DOI: 10.1016/j.drugalcdep.2014.12.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 11/12/2014] [Accepted: 12/11/2014] [Indexed: 01/11/2023]
Abstract
BACKGROUND Preclinical models are needed to inform regulation of tobacco products by the Food and Drug Administration (FDA). Typically, animal models of tobacco addiction involve exposure to nicotine alone or nicotine combined with isolated tobacco constituents (e.g. minor alkaloids). The goal of this study was to develop a model using extracts derived from tobacco products that contain a range of tobacco constituents to more closely model product exposure in humans. METHODS This study compared the addiction-related effects of nicotine alone and nicotine dose-equivalent concentrations of aqueous smokeless tobacco extracts on intracranial self-stimulation (ICSS) in rats. Extracts were prepared from Kodiak Wintergreen, a conventional product, or Camel Snus, a potential "modified risk tobacco product". Binding affinities of nicotine alone and extracts at various nicotinic acetylcholine receptor (nAChR) subtypes were also compared. RESULTS Kodiak and Camel Snus extracts contained levels of minor alkaloids within the range of those shown to enhance nicotine's behavioral effects when studied in isolation. Nonetheless, acute injection of both extracts produced reinforcement-enhancing (ICSS threshold-decreasing) effects similar to those of nicotine alone at low to moderate nicotine doses, as well as similar reinforcement-attenuating/aversive (ICSS threshold-increasing) effects at high nicotine doses. Extracts and nicotine alone also had similar binding affinity at all nAChRs studied. CONCLUSIONS Relative nicotine content is the primary pharmacological determinant of the abuse liability of Kodiak and Camel Snus as measured using ICSS. These models may be useful to compare the relative abuse liability of other tobacco products and to model FDA-mandated changes in product performance standards.
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Affiliation(s)
- Andrew C Harris
- Minneapolis Medical Research Foundation, Minneapolis, MN, USA; Department of Medicine, University of Minnesota Medical School, Minneapolis, MN, USA; Department of Psychology, University of Minnesota, Minneapolis, MN, USA.
| | - Laura Tally
- Minneapolis Medical Research Foundation, Minneapolis, MN, USA
| | - Clare E Schmidt
- Minneapolis Medical Research Foundation, Minneapolis, MN, USA; Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA
| | - Peter Muelken
- Minneapolis Medical Research Foundation, Minneapolis, MN, USA; Department of Ecology, Evolution, and Behavior, University of Minnesota, Minneapolis, MN, USA
| | - Irina Stepanov
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Subhrakanti Saha
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN, USA
| | - Rachel Isaksson Vogel
- Masonic Cancer Center, Biostatistics and Bioinformatics Core, University of Minnesota Minneapolis, MN, USA
| | - Mark G LeSage
- Minneapolis Medical Research Foundation, Minneapolis, MN, USA; Department of Medicine, University of Minnesota Medical School, Minneapolis, MN, USA; Department of Psychology, University of Minnesota, Minneapolis, MN, USA
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Cohen A, Treweek J, Edwards S, Leão RM, Schulteis G, Koob GF, George O. Extended access to nicotine leads to a CRF1 receptor dependent increase in anxiety-like behavior and hyperalgesia in rats. Addict Biol 2015; 20:56-68. [PMID: 23869743 DOI: 10.1111/adb.12077] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Tobacco dependence is associated with the emergence of negative emotional states during withdrawal, including anxiety and nociceptive hypersensitivity. However, the current animal models of nicotine dependence have focused on the mechanisms that mediate the acute reinforcing effects of nicotine and failed to link increased anxiety and pain during abstinence with excessive nicotine self-administration. Here, we tested the hypothesis that the activation of corticotropin-releasing factor-1 (CRF1 ) receptors and emergence of the affective and motivational effects of nicotine abstinence only occur in rats with long access (>21 hours/day, LgA) and not short (1 hour/day, ShA) access to nicotine self-administration. ShA and LgA rats were tested for anxiety-like behavior, nociceptive thresholds, somatic signs of withdrawal and nicotine intake after 3 days of abstinence. The role of CRF1 receptors during abstinence was tested using systemic or intracerebral infusion of MPZP (N,N-bis(2-methoxyethyl)-3-(4-methoxy-2-methylphenyl)-2,5-dimethyl-pyrazolo(1,5α)pyrimidin-7-amine), a CRF1 receptor antagonist, in the central nucleus of the amygdala (CeA). LgA but not ShA rats exhibited abstinence-induced increases in anxiety-like behavior and nociceptive hypersensitivity, which both predicted subsequent excessive nicotine intake and were prevented by systemic administration of MPZP. Intra-CeA MPZP infusion prevented abstinence-induced increases in nicotine intake and nociceptive hypersensitivity. These findings demonstrate that the model of short access to nicotine self-administration has limited validity for tobacco dependence, highlight the translational relevance of the model of extended-intermittent access to nicotine self-administration for tobacco dependence and demonstrate that activation of CRF1 receptors is required for the emergence of abstinence-induced anxiety-like behavior, hyperalgesia and excessive nicotine intake.
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Affiliation(s)
- Ami Cohen
- The Scripps Research Institute; La Jolla CA USA
| | | | | | | | - Gery Schulteis
- Research Service; VA San Diego Healthcare System; San Diego CA USA
- Department of Anesthesiology; University of California San Diego School of Medicine; La Jolla CA USA
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Smith TT, Sved AF, Hatsukami DK, Donny EC. Nicotine reduction as an increase in the unit price of cigarettes: a behavioral economics approach. Prev Med 2014; 68:23-8. [PMID: 25025523 PMCID: PMC4446706 DOI: 10.1016/j.ypmed.2014.07.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 06/04/2014] [Accepted: 07/07/2014] [Indexed: 10/25/2022]
Abstract
Urgent action is needed to reduce the harm caused by smoking. Product standards that reduce the addictiveness of cigarettes are now possible both in the U.S. and in countries party to the Framework Convention on Tobacco Control. Specifically, standards that required substantially reduced nicotine content in cigarettes could enable cessation in smokers and prevent future smoking among current non-smokers. Behavioral economics uses principles from the field of microeconomics to characterize how consumption of a reinforcer changes as a function of the unit price of that reinforcer (unit price=cost/reinforcer magnitude). A nicotine reduction policy might be considered an increase in the unit price of nicotine because smokers are paying more per unit of nicotine. This perspective allows principles from behavioral economics to be applied to nicotine reduction research questions, including how nicotine consumption, smoking behavior, use of other tobacco products, and use of other drugs of abuse are likely to be affected. This paper reviews the utility of this approach and evaluates the notion that a reduction in nicotine content is equivalent to a reduction in the reinforcement value of smoking-an assumption made by the unit price approach.
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Affiliation(s)
- Tracy T Smith
- Department of Psychology, University of Pittsburgh, USA.
| | - Alan F Sved
- Department of Psychology, University of Pittsburgh, USA; Department of Neuroscience, University of Pittsburgh, USA
| | | | - Eric C Donny
- Department of Psychology, University of Pittsburgh, USA.
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Koob GF, Buck CL, Cohen A, Edwards S, Park PE, Schlosburg JE, Schmeichel B, Vendruscolo LF, Wade CL, Whitfield TW, George O. Addiction as a stress surfeit disorder. Neuropharmacology 2014; 76 Pt B:370-82. [PMID: 23747571 PMCID: PMC3830720 DOI: 10.1016/j.neuropharm.2013.05.024] [Citation(s) in RCA: 344] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 05/22/2013] [Accepted: 05/28/2013] [Indexed: 12/15/2022]
Abstract
Drug addiction has been conceptualized as a chronically relapsing disorder of compulsive drug seeking and taking that progresses through three stages: binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation. Drug addiction impacts multiple motivational mechanisms and can be conceptualized as a disorder that progresses from positive reinforcement (binge/intoxication stage) to negative reinforcement (withdrawal/negative affect stage). The construct of negative reinforcement is defined as drug taking that alleviates a negative emotional state. Our hypothesis is that the negative emotional state that drives such negative reinforcement is derived from dysregulation of key neurochemical elements involved in the brain stress systems within the frontal cortex, ventral striatum, and extended amygdala. Specific neurochemical elements in these structures include not only recruitment of the classic stress axis mediated by corticotropin-releasing factor (CRF) in the extended amygdala as previously hypothesized but also recruitment of dynorphin-κ opioid aversive systems in the ventral striatum and extended amygdala. Additionally, we hypothesized that these brain stress systems may be engaged in the frontal cortex early in the addiction process. Excessive drug taking engages activation of CRF not only in the extended amygdala, accompanied by anxiety-like states, but also in the medial prefrontal cortex, accompanied by deficits in executive function that may facilitate the transition to compulsive-like responding. Excessive activation of the nucleus accumbens via the release of mesocorticolimbic dopamine or activation of opioid receptors has long been hypothesized to subsequently activate the dynorphin-κ opioid system, which in turn can decrease dopaminergic activity in the mesocorticolimbic dopamine system. Blockade of the κ opioid system can also block anxiety-like and reward deficits associated with withdrawal from drugs of abuse and block the development of compulsive-like responding during extended access to drugs of abuse, suggesting another powerful brain stress/anti-reward system that contributes to compulsive drug seeking. Thus, brain stress response systems are hypothesized to be activated by acute excessive drug intake, to be sensitized during repeated withdrawal, to persist into protracted abstinence, and to contribute to the development and persistence of addiction. The recruitment of anti-reward systems provides a powerful neurochemical basis for the negative emotional states that are responsible for the dark side of addiction. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.
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Affiliation(s)
- George F Koob
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 North Torrey Pines Road, SP30-2400, La Jolla, CA 92037, USA.
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Effects of oxytocin on nicotine withdrawal in rats. Pharmacol Biochem Behav 2014; 116:84-9. [DOI: 10.1016/j.pbb.2013.11.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 10/31/2013] [Accepted: 11/07/2013] [Indexed: 12/16/2022]
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Grebenstein P, Burroughs D, Zhang Y, LeSage MG. Sex differences in nicotine self-administration in rats during progressive unit dose reduction: implications for nicotine regulation policy. Pharmacol Biochem Behav 2013; 114-115:70-81. [PMID: 24201048 PMCID: PMC3903094 DOI: 10.1016/j.pbb.2013.10.020] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Revised: 10/09/2013] [Accepted: 10/23/2013] [Indexed: 11/23/2022]
Abstract
Reducing the nicotine content in tobacco products is being considered by the FDA as a policy to reduce the addictiveness of tobacco products. Understanding individual differences in response to nicotine reduction will be critical to developing safe and effective policy. Animal and human research demonstrating sex differences in the reinforcing effects of nicotine suggests that males and females may respond differently to nicotine-reduction policies. However, no studies have directly examined sex differences in the effects of nicotine unit-dose reduction on nicotine self-administration (NSA) in animals. The purpose of the present study was to examine this issue in a rodent self-administration model. Male and female rats were trained to self-administer nicotine (0.06mg/kg) under an FR 3 schedule during daily 23h sessions. Rats were then exposed to saline extinction and reacquisition of NSA, followed by weekly reductions in the unit dose (0.03 to 0.00025mg/kg) until extinction levels of responding were achieved. Males and females were compared with respect to baseline levels of intake, resistance to extinction, degree of compensatory increases in responding during dose reduction, and the threshold reinforcing unit dose of nicotine. Exponential demand-curve analysis was also conducted to compare the sensitivity of males and females to increases in the unit price (FR/unit dose) of nicotine (i.e., elasticity of demand or reinforcing efficacy). Females exhibited significantly higher baseline intake and less compensation than males. However, there were no sex differences in the reinforcement threshold or elasticity of demand. Dose-response relationships were very well described by the exponential demand function (r(2) values>0.96 for individual subjects). These findings suggest that females may exhibit less compensatory smoking in response to nicotine reduction policies, even though their nicotine reinforcement threshold and elasticity of demand may not differ from males.
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Affiliation(s)
| | - Danielle Burroughs
- Department of Medicine, Minneapolis Medical Research Foundation, United States
| | - Yan Zhang
- Department of Biostatistics, University of Minnesota, United States
| | - Mark G. LeSage
- Department of Medicine, Minneapolis Medical Research Foundation, United States
- Department of Medicine, University of Minnesota, United States
- Department of Psychology, University of Minnesota, United States
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Abstract
Drug addiction can be defined by a three-stage cycle - binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation - that involves allostatic changes in the brain reward and stress systems. Two primary sources of reinforcement, positive and negative reinforcement, have been hypothesized to play a role in this allostatic process. The negative emotional state that drives negative reinforcement is hypothesized to derive from dysregulation of key neurochemical elements involved in the brain reward and stress systems. Specific neurochemical elements in these structures include not only decreases in reward system function (within-system opponent processes) but also recruitment of the brain stress systems mediated by corticotropin-releasing factor (CRF) and dynorphin-κ opioid systems in the ventral striatum, extended amygdala, and frontal cortex (both between-system opponent processes). CRF antagonists block anxiety-like responses associated with withdrawal, block increases in reward thresholds produced by withdrawal from drugs of abuse, and block compulsive-like drug taking during extended access. Excessive drug taking also engages the activation of CRF in the medial prefrontal cortex, paralleled by deficits in executive function that may facilitate the transition to compulsive-like responding. Neuropeptide Y, a powerful anti-stress neurotransmitter, has a profile of action on compulsive-like responding for ethanol similar to a CRF1 antagonist. Blockade of the κ opioid system can also block dysphoric-like effects associated with withdrawal from drugs of abuse and block the development of compulsive-like responding during extended access to drugs of abuse, suggesting another powerful brain stress system that contributes to compulsive drug seeking. The loss of reward function and recruitment of brain systems provide a powerful neurochemical basis that drives the compulsivity of addiction.
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Affiliation(s)
- George F. Koob
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, USA
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31
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Cohen A, George O. Animal models of nicotine exposure: relevance to second-hand smoking, electronic cigarette use, and compulsive smoking. Front Psychiatry 2013; 4:41. [PMID: 23761766 PMCID: PMC3671664 DOI: 10.3389/fpsyt.2013.00041] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 05/13/2013] [Indexed: 12/23/2022] Open
Abstract
Much evidence indicates that individuals use tobacco primarily to experience the psychopharmacological properties of nicotine and that a large proportion of smokers eventually become dependent on nicotine. In humans, nicotine acutely produces positive reinforcing effects, including mild euphoria, whereas a nicotine abstinence syndrome with both somatic and affective components is observed after chronic nicotine exposure. Animal models of nicotine self-administration and chronic exposure to nicotine have been critical in unveiling the neurobiological substrates that mediate the acute reinforcing effects of nicotine and emergence of a withdrawal syndrome during abstinence. However, important aspects of the transition from nicotine abuse to nicotine dependence, such as the emergence of increased motivation and compulsive nicotine intake following repeated exposure to the drug, have only recently begun to be modeled in animals. Thus, the neurobiological mechanisms that are involved in these important aspects of nicotine addiction remain largely unknown. In this review, we describe the different animal models available to date and discuss recent advances in animal models of nicotine exposure and nicotine dependence. This review demonstrates that novel animal models of nicotine vapor exposure and escalation of nicotine intake provide a unique opportunity to investigate the neurobiological effects of second-hand nicotine exposure, electronic cigarette use, and the mechanisms that underlie the transition from nicotine use to compulsive nicotine intake.
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Affiliation(s)
- Ami Cohen
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, USA
| | - Olivier George
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, USA
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Hatsukami DK, Benowitz NL, Donny E, Henningfield J, Zeller M. Nicotine reduction: strategic research plan. Nicotine Tob Res 2013; 15:1003-13. [PMID: 23100460 PMCID: PMC3646645 DOI: 10.1093/ntr/nts214] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 08/20/2012] [Indexed: 01/19/2023]
Abstract
BACKGROUND Reducing nicotine content in cigarettes and other combustible products to levels that are not reinforcing or addictive has the potential to substantially reduce tobacco-related morbidity and mortality. The authority to reduce nicotine levels as a regulatory measure is provided in the U.S. Family Smoking Prevention and Tobacco Control Act and is consistent with the general regulatory powers envisioned under the relevant articles of the World Health Organization's Framework Convention on Tobacco Control. Many experts have considered reducing nicotine in cigarettes to be a feasible national policy approach, but more research is necessary. PURPOSE This article describes proceedings from a conference that had the goals of identifying specific research gaps, describing methods and measures to consider for addressing these gaps, and considering ways to foster collaboration. RESULTS AND CONCLUSION Identified research gaps included determining the dose of nicotine that would be optimal for reducing and extinguishing cigarette use, examining approaches for reducing nicotine levels in the general and special populations of smokers, understanding how constituents other than nicotine may contribute to the reinforcing effects of tobacco, and identifying unintended consequences to determine ways to mitigate them. Methods that can be used ranged from brain imaging to large human clinical trials. The development and availability of valid biomarkers of exposure and effect are important. Infrastructures to facilitate collaboration need to be established.
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Affiliation(s)
- Dorothy K Hatsukami
- Department of Psychiatry, University of Minnesota, Minneapolis, MN 55414, USA.
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Harris AC, Manbeck KE, Schmidt CE, Shelley D. Mecamylamine elicits withdrawal-like signs in rats following a single dose of nicotine. Psychopharmacology (Berl) 2013; 225:291-302. [PMID: 22868410 DOI: 10.1007/s00213-012-2814-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Accepted: 07/16/2012] [Indexed: 10/28/2022]
Abstract
RATIONALE The ability of nicotine to induce dependence (result in a withdrawal syndrome) is typically thought to require long-term, daily smoking. Emerging evidence suggests that symptoms of nicotine withdrawal may occur following only a few cigarettes. Whether acute exposure to nicotine can induce dependence in animals has not been well established. OBJECTIVE The objective of this paper is to examine whether the nicotinic acetylcholine receptor antagonist mecamylamine elicits withdrawal-like signs in rats following acute nicotine exposure. METHODS AND RESULTS Mecamylamine (3.0 mg/kg, s.c.) administered ≈2 h after a single dose of nicotine (0.5 mg/kg, s.c.) elicited increases in intracranial self-stimulation (ICSS) thresholds and somatic signs, two well-established effects of withdrawal from long-term (chronic) nicotine exposure. The magnitude of these effects remained constant across five daily test sessions. A lower dose of mecamylamine (1.5 mg/kg, s.c.) had little or no effect on ICSS thresholds or somatic signs following acute nicotine exposure, but precipitated robust increases in these measures during a chronic nicotine infusion. Finally, rats exhibited a small increase in ICSS thresholds over time following a single nicotine injection (0.5 mg/kg, s.c.), possibly reflecting a modest spontaneous withdrawal-like effect. CONCLUSIONS Mecamylamine elicited withdrawal-like signs in rats following a single dose of nicotine. The different effects of mecamylamine 1.5 mg/kg following acute versus chronic nicotine exposure supports the notion that these models simulate the early and more advanced stages of nicotine dependence, respectively. While further optimization and validation of these models is necessary, they may provide a novel approach for studying the earliest stages of nicotine dependence.
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Affiliation(s)
- Andrew C Harris
- Minneapolis Medical Research Foundation, 914 South 8th St. S-3 Labs, 860, Minneapolis, MN 55404, USA.
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Donny EC, Taylor TG, LeSage MG, Levin M, Buffalari DM, Joel D, Sved AF. Impact of tobacco regulation on animal research: new perspectives and opportunities. Nicotine Tob Res 2012; 14:1319-38. [PMID: 22949581 PMCID: PMC3611983 DOI: 10.1093/ntr/nts162] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 05/29/2012] [Indexed: 12/29/2022]
Abstract
INTRODUCTION The Family Smoking Prevention and Tobacco Control Act in the United States and the World Health Organization Framework Convention on Tobacco or Health ratified by over 170 countries render scientific investigations into the abuse liability, harm, and effects of tobacco more critical than ever. A key area to explore relates to the potential regulation of nicotine content in cigarettes. Determining the nicotine content per cigarette below which smokers reliably reduce their consumption of and dependence on cigarettes, an idea proposed almost 20 years ago (Benowitz & Henningfield, 1994), could be a powerful approach to reduce the abuse liability and consequent harm from cigarettes. However, this approach is laden with potentially complex issues. Many of these complications can be studied using animal models, but they require a particular perspective. METHODS Herein, we review several challenges for animal researchers interested in nicotine reduction as examples of how this perspective dictates new approaches to animal research. These include defining the threshold nicotine dose for maintaining self-administration, evaluating the differential impact of various implementation strategies, assessing the factors that could interact with nicotine to alter the reinforcement threshold, describing the role of cues in maintaining low dose nicotine self-administration, and examining individual differences in response to nicotine reduction. CONCLUSIONS Researchers who study tobacco using animal models have the opportunity to play a central role in the regulatory science of tobacco and conduct studies that directly inform policy decisions that could impact the lives of millions.
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Affiliation(s)
- Eric C Donny
- Department of Psychology, Dietrich School of Arts and Sciences, University of Pittsburgh, Pittsburgh, PA, USA.
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Abstract
Tobacco dependence is an addiction with high rates of relapse, resulting in multiple quit attempts in individuals who are trying to stop smoking. How these multiple cycles of smoking and withdrawal contribute to nicotine dependence, long-term alterations in brain reward systems, and nicotine receptor regulation is unknown. Therefore, to evaluate how multiple exposures of nicotine and withdrawal periods modulate rewarding properties of nicotine, we used intracranial self-stimulation to measure alterations in the threshold of brain stimulation reward. In addition, we employed the conditioned place preference (CPP) paradigm to evaluate positive context conditioning following each withdrawal period and measured levels of neuronal nicotinic receptors in cortex, striatum, and hippocampus. We found that repeated nicotine exposure and withdrawal enhanced brain stimulation reward and reward sensitivity to acute injections of nicotine. This increased reward was reflected by enhanced CPP to nicotine. Chronic nicotine is known to up-regulate nAChRs (nicotinic acetylcholine receptors) and we found that this up-regulation was maintained for up to 8 days of withdrawal in the striatum and in the hippocampus, but not in the cortex, of animals exposed to multiple nicotine exposure and withdrawal periods. These results demonstrate that repeated exposures to nicotine, followed by withdrawal, induce a persistent increase in both brain reward function and sensitivity to the hedonic value of nicotine and long-lasting up-regulation of neuronal nicotinic receptors. Together, these data suggest that a continuing increase in brain reward function and enhanced sensitivity to nicotine reward following repeated withdrawal periods may be one reason why smokers relapse frequently.
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Harris AC, Stepanov I, Pentel PR, LeSage MG. Delivery of nicotine in an extract of a smokeless tobacco product reduces its reinforcement-attenuating and discriminative stimulus effects in rats. Psychopharmacology (Berl) 2012; 220:565-76. [PMID: 21960181 PMCID: PMC3363290 DOI: 10.1007/s00213-011-2514-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2011] [Accepted: 09/12/2011] [Indexed: 12/21/2022]
Abstract
RATIONALE Animal models of tobacco addiction rely on administration of nicotine alone or nicotine combined with isolated constituents. Models using tobacco extracts derived from tobacco products and containing a range of tobacco constituents might more accurately simulate tobacco exposure in humans. OBJECTIVE To compare the effects of nicotine alone and an aqueous smokeless tobacco extract in several addiction-related animal behavioral models. METHODS Nicotine alone and nicotine dose-equivalent concentrations of extract were compared in terms of their acute effects on intracranial self-stimulation (ICSS) thresholds, discriminative stimulus effects, and effects on locomotor activity. RESULTS Similar levels of nicotine and minor alkaloids were achieved using either artificial saliva or saline for extraction, supporting the clinical relevance of the saline extracts used in these studies. Extract produced reinforcement-enhancing (ICSS threshold-decreasing) effects similar to those of nicotine alone at low to moderate nicotine doses, but reduced reinforcement-attenuating (ICSS threshold-increasing) effects at a high nicotine dose. In rats trained to discriminate nicotine alone from saline, intermediate extract doses did not substitute for the training dose as well as nicotine alone. Locomotor stimulant effects and nicotine distribution to brain were similar following administration of extract or nicotine alone. CONCLUSIONS The reinforcement-attenuating and discriminative stimulus effects of nicotine delivered in an extract of a commercial smokeless tobacco product differed from those of nicotine alone. Extracts of tobacco products may be useful for evaluating the abuse liability of those products and understanding the role of non-nicotine constituents in tobacco addiction.
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Affiliation(s)
- Andrew C. Harris
- Minneapolis Medical Research Foundation, Minneapolis, MN, Minneapolis, MN,Department of Medicine, University of Minnesota Medical School
| | | | - Paul R. Pentel
- Minneapolis Medical Research Foundation, Minneapolis, MN, Minneapolis, MN,Department of Medicine, University of Minnesota Medical School,Department of Pharmacology, University of Minnesota
| | - Mark G. LeSage
- Minneapolis Medical Research Foundation, Minneapolis, MN, Minneapolis, MN,Department of Medicine, University of Minnesota Medical School
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Weaver MT, Sweitzer M, Coddington S, Sheppard J, Verdecchia N, Caggiula AR, Sved AF, Donny EC. Precipitated withdrawal from nicotine reduces reinforcing effects of a visual stimulus for rats. Nicotine Tob Res 2012; 14:824-32. [PMID: 22218403 DOI: 10.1093/ntr/ntr293] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
INTRODUCTION Research has identified at least two positive reinforcement-related effects of nicotine: (a) primary reinforcement and (b) enhancement of reinforcement from concurrently available stimuli. Prior examples of the reinforcement-enhancing effects with rats showed that repeated, intermittent nicotine exposure increased responding for non-nicotine reinforcers, and this effect remained robust over several weeks. However, the effects of continuous nicotine exposure on responding for a non-nicotine reinforcer are unknown, as are the effects of abruptly withdrawing continuous nicotine on behavior maintained by the same reinforcer. METHODS Lever pressing for a visual reinforcer under a fixed ratio schedule was assessed while rats were maintained on a chronic, continuous infusion of nicotine (3.16 mg/kg/day; osmotic minipump). The effects of precipitated withdrawal on responding, following 16 days of continuous nicotine exposure, were assessed by pre-session subcutaneous injections of mecamylamine (1.0 mg/kg). RESULTS Continuous nicotine initially increased active responding for the visual reinforcer; however, continued exposure resulted in an attenuation of this effect. Precipitated withdrawal from nicotine resulted in a significant decline in active responding. CONCLUSIONS The initial increase in responding for the visual reinforcer with chronic nicotine exposure is consistent with prior research showing that intermittent exposure to nicotine acts as a reinforcement enhancer. However, the attenuation of this enhancement following prolonged nicotine exposure is in contrast with the persistent effects previously reported. Finally, the decrease in visual reinforcers below control levels (nicotine-naive animals) following nicotine withdrawal highlights a potential for affective withdrawal, which may serve as a motive for continued nicotine use.
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Affiliation(s)
- Matthew T Weaver
- Department of Psychology, School of Arts and Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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Drug withdrawal-induced depression: Serotonergic and plasticity changes in animal models. Neurosci Biobehav Rev 2012; 36:696-726. [DOI: 10.1016/j.neubiorev.2011.10.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 10/06/2011] [Accepted: 10/15/2011] [Indexed: 12/17/2022]
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