Yohimbine exacerbates and clonidine attenuates acute morphine withdrawal in rats.
The involvement of alpha 2-noradrenergic receptors in the expression of opiate withdrawal was studied using an operant behavioral model of acute morphine dependence. Clonidine, an alpha 2-agonist, attenuated and yohimbine, an alpha 2-antagonist, exacerbated the naloxone-induced suppression of fixed ratio 15 responding in rats pretreated several hours earlier with a single, moderate dose of morphine. These data indicate that the alpha 2-agonist action of clonidine is responsible for its amelioration of withdrawal symptoms. It also validates the acute dependence model for studying the pharmacology of opiates and associated adaptive processes.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology*; D004347:Drug Interactions; D006801:Humans; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012055:Reinforcement Schedule; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*; D015016:Yohimbine / Q000494:pharmacology*
D015016:Yohimbine; D009270:Naloxone; D009020:Morphine; D003000:Clonidine