Cholinergic influence on intravenous cocaine self-administration by rhesus monkeys.

WILSON, M. C. AND C. R. SCHUSTER. 67rolhlergic influence on intravenous cocaine self-administration by rhesus monkeys. PHARMAC. BIOCHEM. BEIIAV. 1(6) 643-649, 1973.-The effects of intramuscular administration of atropine, methylatropine and physostigmine on intravenous cocaine self-administration in the rhesus monkey were ascertained. Atropine (0.5-2.0 mg/kg) increased cocaine intake, whereas methylatropine, over the same dosage range, produced no change in this behavior. Physostigmine (0.1-0.5 mg/kg) significantly depressed this behavior. The effect of atropine was interpreted as being the result of its central anti-cholinergic action and that of physostigmine, since it was opposite to that of atropine, was attributed to its central cholinergic action. Furthermore it was hypothesized that the effect of these cholinergic interactions on cocaine self-administration resulted from a modulation of the factors which may control self-administration i.e. drug-induced aversiveness or nonspecific behavioral disruption rather than any specific interaction with the neurochemical mechanisms of cocaine mediated reinforcement. The drug effects support the concept of a central cholinergic behavioral inhibitory system which when blocked, e.g., with atropine, results in behavioral activation.