The alpha1 adrenergic receptor antagonist prazosin reduces heroin self-administration in rats with extended access to heroin administration.
Previous studies have reported that noradrenergic antagonists alleviate some of the symptoms of opiate withdrawal and dependence. Clinical studies also have shown that modification of the noradrenergic system may help protect patients from relapse. The present study tested the hypothesis that a dysregulated noradrenergic system has motivational significance in heroin self-administration of dependent rats. Prazosin, an alpha1-adrenergic antagonist (0.5, 1.0, 1.5 and 2.0 mg/kg, i.p.), was administered to adult male Wistar rats with a history of limited (1 h/day; short access) or extended (12 h/day; long access) access to intravenous heroin self-administration. Prazosin dose-dependently reduced heroin self-administration in long-access rats but not short-access rats, with 2 mg/kg of systemic prazosin significantly decreasing 1 h and 2 h heroin intake. Prazosin also reversed some changes in meal pattern associated with extended heroin access, including the taking of smaller and briefer meals (at 3 h), while also increasing total food intake and slowing the eating rate within meals (both 3 h and 12 h). Thus, prazosin appears to stimulate food intake in extended access rats by restoring meals to the normal size and duration. The data suggest that the alpha1 adrenergic system may contribute to mechanisms that promote dependence in rats with extended access.
Greenwell
Thomas N
TN
Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 North Torrey Pines Road, SP30-2400, La Jolla, CA 92037, United States. greenwellt@mail.nih.gov
Walker
Brendan M
BM
Cottone
Pietro
P
Zorrilla
Eric P
EP
Koob
George F
GF
D058646:Adrenergic alpha-1 Receptor Agonists; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D003932:Heroin / Q000008:administration & dosage; D006556:Heroin Dependence / Q000188:drug therapy* / Q000523:psychology*; D008297:Male; D009294:Narcotics / Q000008:administration & dosage; D011224:Prazosin / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012055:Reinforcement Schedule; D012646:Self Administration; D015819:Substance Abuse, Intravenous
D058646:Adrenergic alpha-1 Receptor Agonists; D000317:Adrenergic alpha-Antagonists; D009294:Narcotics; D003932:Heroin; D011224:Prazosin