Self-administration of psychoactive substances by the monkey

A method has been developed which permits monkeys to self-administer drug solutions, at will, through indwelling intravenous catheters. Psychological dependence on the effects of a drug occurs when a naive monkey voluntarily initiates and maintains self-administration of the drug. If, in addition to psychological dependence, the drug also produces psychotoxicity, either directly or upon abrupt withdrawal, it has a potential abuse liability. In the present study monkeys developed psychological dependence on morphine, codeine, cocaine, d-amphetamine, pentobarbital, ethanol, and caffeine. All of these drugs except caffeine produced psychotoxicity. Monkeys did not develop psychological dependence on nalorphine, morphine-nalorphine mixtures, chlorpromazine, mescaline or physiological saline.