Abstract
Monkeys were trained to press a level under variable-interval or fixed-ratio schedules of food presentation. In each session, nonpunishment periods in which only the schedule of food presentation was in effect alternated with punishment periods in which the schedule of food presentation was in effect and each response produced the delivery of a brief electric shock to the tail. Punishment periods were designated by a red stimulus light. Morphine, 0.5 to 4.0 mg/kg. depressed unpunished and punished behavior equally. Tolerance developed to this effect. Physical dependence was produced by chronic morphine treatment with s.c. injection every six hours at two dose levels: 4.0 and 8.0 mg/kg/day. Withdrawal from either level of morphine maintenance produced marked decreases in unpunished behavior. Under one-minute variable-interval and 120-response fixed-ratio schedules, the decreases in unpunished responding produced by withdrawal were very consistent within and between monkeys. Under fixed-ratio schedules of 15, 30 or 60 the the effects of morphine withdrawal on behavior were highly variable. Punished responding emitted at high base-line rates also was decreased by morphine withdrawal. However, punished responding emitted at low baseline rates was increased by withdrawal. Drugs producing physical dependence of the morphine type, hut not other classes of drugs, restored both unpunished and punished behavior disrupted by morphine withdrawal.
Footnotes
- Received September 29, 1971.
- Accepted October 29, 1972.
- © 1973 by The Williams & Wilkins Co.