KETAMINE SELF-ADMINISTRATION BY RHESUS-MONKEY

Abstract

I.v. administered ketamine, a nonbarbiturate anesthetic, served as a reinforcer of self-administration behavior in rhesus monkeys during daily 2 h sessions. When the ketamine dose was varied over a wide range at fixed-ratio [FR] schedules of reinforcement of 1, 8 and 64, the response rate was an inverted U-shaped function of the dose. Maximal response rates occurred at progressively higher doses as the FR size was increased; drug intake per session was positively related to the dose. When the ketamine dose was held constant and the FR was increased in a geometric series, the response rate increased as the FR was increased to FR 128 or FR 256; additional increases in FR size produced abrupt decreases in respnoses rates. Since the response rate increased linearly as the FR was increased geometrically, drug intake was a decreasing function of the response requirement. With respect to magnitude of reinforcement and FR response requirement, ketamine maintained self-administration behavior in a manner similar to that of a number of other drugs of abuse and conventional reinforcers.