Effects of naloxone on schedule-controlled behavior in monkeys

Abstract

The many unanswered questions about the influence of the endorphins on behavior have enhanced interest in the behavioral pharmacology of the narcotic antagonists. Because narcotic antagonists can effectively block opiate receptors, which mediate the actions of the endorphins, the behavioral effects of appropriate doses of narcotic antagonists might reveal functional characteristics of the endorphin system. Studies in several species have indicated that naloxone, an effective narcotic antagonist, has no remarkable effects on behavior at doses that are known to block opiate receptors (Byrd, 1976; Downs and Woods, 1976; El-Sobky et al. 1976; Goldberg et al. 1976; Goldstein et al. 1976). Theseresults have led some investigators to suggest that the endorphin system, like some other neurohumoral or hormonal systems, is dormant until activated by certain types of events. Because the opiates are known to be effective analgesics, it has been assumed that naloxone would be most likely to affect behavior controlled by painful or noxious stimuli.