JPET #121806 Noradrenergic Mechanisms in Cocaine-Induced
Total Page：16
File Type：pdf, Size：1020Kb
JPET Fast Forward. Published on May 15, 2007 as DOI: 10.1124/jpet.107.121806 JPETThis Fast article Forward. has not been Published copyedited andon formatted. May 15, The 2007 final asversion DOI:10.1124/jpet.107.121806 may differ from this version. JPET #121806 Noradrenergic Mechanisms in Cocaine-Induced Reinstatement of Drug Seeking in Squirrel Monkeys Donna M. Platt, James K. Rowlett and Roger D. Spealman Downloaded from Harvard Medical School, New England Primate Research Center, Southborough, MA, USA jpet.aspetjournals.org (DMP, JKR, RDS) at ASPET Journals on October 1, 2021 1 Copyright 2007 by the American Society for Pharmacology and Experimental Therapeutics. JPET Fast Forward. Published on May 15, 2007 as DOI: 10.1124/jpet.107.121806 This article has not been copyedited and formatted. The final version may differ from this version. JPET #121806 Running title: Norepinephrine and reinstatement Corresponding author: Donna M. Platt, Ph.D. Harvard Medical School New England Primate Research Center One Pine Hill Drive, Box 9102 Southborough, MA 01772-9102 Phone: (508) 624-8090 Fax: (508) 624-8172 Downloaded from Email: [email protected] Number of text pages: 19 (Introduction through Discussion) jpet.aspetjournals.org Number of tables: 2 Number of figures: 5 Number of references: 46 at ASPET Journals on October 1, 2021 Words in Abstract: 241 Words in Introduction: 589 Words in Discussion: 1598 Abbreviations: DA, dopamine; NE, norepinephrine; BNST, bed nucleus of the stria terminalis; FI, fixed-interval; FR, fixed-ratio Section assignment: Behavioral Pharmacology 2 JPET Fast Forward. Published on May 15, 2007 as DOI: 10.1124/jpet.107.121806 This article has not been copyedited and formatted. The final version may differ from this version. JPET #121806 Abstract Norepinephrine (NE) uptake and NE receptor mechanisms play important modulating roles in the discriminative stimulus and stimulant effects of cocaine. The present study investigated the role of NE mechanisms in cocaine priming-induced reinstatement of extinguished drug seeking. Squirrel monkeys were trained to stability under a second-order fixed-interval, fixed-ratio schedule of drug self-administration in which operant responding was maintained jointly by i.v. cocaine injections and presentations of a cocaine-paired stimulus. Drug seeking was then extinguished by replacing cocaine with vehicle and eliminating the cocaine-paired stimulus. In Downloaded from test sessions during which the cocaine-paired stimulus was reintroduced but only vehicle was available for self-administration, priming with cocaine, the dopamine transport inhibitor GBR jpet.aspetjournals.org 12909, and the NE transport inhibitors nisoxetine and talsupram induced dose-dependent reinstatement of drug seeking. The maximum effect of the NE transport inhibitors was less than half that of cocaine. Both nisoxetine and talsupram augmented the priming effects of a low but at ASPET Journals on October 1, 2021 not a high dose of cocaine. The priming effects of nisoxetine were blocked by the α1- adrenoceptor antagonist prazosin, the α2-adrenoceptor agonist clonidine, and the β- adrenoceptor antagonist propranolol, but not by the dopamine receptor antagonist flupenthixol. The priming effects of cocaine were antagonized by clonidine and flupenthixol. Neither nisoxetine nor cocaine increased physiological (salivary cortisol) or behavioral (self-directed behaviors) markers of stress. These findings suggest that NE transporter inhibition and α2- adrenoceptor mechanisms play a significant role in cocaine-induced reinstatement of drug- seeking that is not secondary to activation of brain stress pathways. 3 JPET Fast Forward. Published on May 15, 2007 as DOI: 10.1124/jpet.107.121806 This article has not been copyedited and formatted. The final version may differ from this version. JPET #121806 Introduction Cocaine is a relatively nonselective inhibitor of monoamine uptake (Koe, 1976; Heikkila et al., 1979; Reith and Salmeci, 1992), and long-term exposure to cocaine results in neuroadaptations of the dopamine (DA) transporter and DA receptors (e.g., Letchworth et al., 2001, Nader et al., 2002). Recent evidence suggests that extended cocaine exposure also can induce changes in the noradrenergic system. In monkeys self-administering cocaine under chronic conditions, the norepinephrine (NE) transporter is upregulated in the bed nucleus of the stria terminalis (BNST) and other brain regions implicated in drug reinforcement and relapse, Downloaded from including portions of the extended amygdala and the hippocampus (Macey et al., 2003; Beveridge et al., 2005). jpet.aspetjournals.org Although inhibition of DA uptake and subsequent stimulation of DA receptors are established mechanisms mediating the abuse-related effects of cocaine, there is evidence that NE uptake and NE receptor mechanisms can serve important modulating roles in cocaine’s at ASPET Journals on October 1, 2021 behavioral effects in laboratory animals. In pigeons, rats and monkeys trained to discriminate relatively low doses of cocaine from vehicle, NE transport inhibitors partially mimic the discriminative stimulus effects of cocaine (Cunningham and Callahan, 1991; Baker et al., 1993; Johanson and Barrett, 1993; Terry et al., 1994; Spealman, 1995), and when combined with cocaine or the selective DA transport inhibitor GBR 12909, NE transport inhibitors have been shown to enhance their discriminative stimulus effects (Cunningham and Callahan, 1991; Spealman, 1995; Kleven and Koek,1998). Additionally, the discriminative stimulus effects of cocaine and the cocaine-like effects of the NE transport inhibitors talsupram and tomoxetine can be attenuated by the α1-adrenoceptor antagonist prazosin (Johanson and Barrett, 1993; Spealman, 1995). Clinical evidence points to incidental re-exposure to cocaine (priming), environmental stimuli associated with previous cocaine use, and stress as triggers of relapse in people. These same triggers have been found to induce reinstatement of cocaine-seeking behavior in 4 JPET Fast Forward. Published on May 15, 2007 as DOI: 10.1124/jpet.107.121806 This article has not been copyedited and formatted. The final version may differ from this version. JPET #121806 laboratory animals, providing potentially useful models for investigating the biological basis of relapse (Spealman et al., 2004; Bossert et al., 2005). The strongest evidence for a role for the noradrenergic system in cocaine relapse comes from studies of stress-induced reinstatement of drug-seeking. For example, the α2-adrenoceptor antagonists yohimbine and RS-79948 can reinstate cocaine-seeking behavior in monkeys at doses that induce physiological and behavioral indicators of stress (Lee et al., 2004). Moreover, the priming effects of yohimbine can be reversed with the α2-adrenoceptor agonist clonidine (Lee et al., 2004). Clonidine and Downloaded from other α2-agonists also have been shown to inhibit footshock-induced reinstatement of cocaine seeking in rats (Erb et al., 2000). Beta adrenergic mechanisms also may play a role in stress- induced reinstatement as central administration of β1- and β2-adrenoceptor antagonists block jpet.aspetjournals.org footshock-induced reinstatement of cocaine-seeking (Leri et al., 2002). The purpose of the present study was to investigate the role of NE mechanisms in cocaine priming-induced reinstatement in monkeys by evaluating the ability of the selective NE at ASPET Journals on October 1, 2021 transport inhibitors talsupram and nisoxetine to mimic or modulate the relapse-inducing effects of cocaine and the cocaine-like priming effects of GBR 12909, a selective DA transport inhibitor. Additional studies were conducted to assess the role of specific subtypes of adrenergic receptors in cocaine priming-induced reinstatement by investigating the degree to which selective α1- and β-adrenoceptor antagonists (prazosin and propranolol, respectively) and a selective α2-adrenoceptor agonist (clonidine) attenuated reinstatement of drug seeking induced by nisoxetine, GBR 12909 and cocaine priming. Finally, the ability of nisoxetine and cocaine to engender physiological and behavioral indices of stress was evaluated in an additional group of monkeys. Understanding the neurobiological mechanisms mediating reinstatement of cocaine seeking in animals may aid development of pharmacotherapies to combat relapse to cocaine use in people. 5 JPET Fast Forward. Published on May 15, 2007 as DOI: 10.1124/jpet.107.121806 This article has not been copyedited and formatted. The final version may differ from this version. JPET #121806 Materials and Methods Subjects and surgical procedure. Twelve adult squirrel monkeys (Saimiri sciureus), weighing 650 to 1000 g, were studied in daily experimental sessions (Monday to Friday). Eight monkeys served as subjects in the reinstatement studies, and four monkeys served as subjects in the observation/salivary cortisol studies. Between sessions, monkeys lived in individual home cages where they had unrestricted access to food (Teklad Monkey Diet, supplemented with fresh fruit) and water. All animals were maintained in accordance with the guidelines of the Committee on Animals of the Harvard Medical School and the “Guide for Care and Use of Downloaded from Laboratory Animals” of the Institute of Laboratory Animal Resources, National Research Council, Department of Health, Education and Welfare Publication No. (NIH) 85-23, revised jpet.aspetjournals.org 1996. Research protocols were approved by the Harvard Medical