Effects of Cyprenorphine Hydrochloride on Sensory Reinforcement in the Rat

Abstract

IN a previous study¹ of the morphine antagonist cyprenorphine hydrochloride (M 285), we examined the possible hallucinogenic effects of this analgesic compound on the light-reinforced behaviour of rats. Control animals receiving saline injections showed typically increased response rates during test sessions in which response–contingent light (RCL) was available, whereas M 285 (0.3 mg/kg) depressed this light reinforcement (LR) effect. The drug had no effect on operant or non-reinforced responding, and so we postulated that it had its principal effect in relation to the relative significance of the stimulation to the animal. More specifically, this drug (in common with other hallucinogenic agents) may raise the arousal level of an animal that is relatively deprived visually, so that it needs very little further stimulation.