An analysis of some perceptual effects of morphine, chlorpromazine, and LSD.

Male albino rats were trained to detect either a pure tone or a weak footshock embedded in white noise by utilizing a discrete-trial two-choice, successive discrimination procedure. The effects of morphine, chlorpromazine (CPZ), and lysergic acid diethylamide (LSD) were then analyzed on several measures of performance. Morphine (2.5--10 mg/kg) produced a nonspecific decrease in accuracy of discrimination on trials when the stimulus was presented as well as on trials when no stimulus occurred. Morphine was also followed by dose-dependent decreased in speed to initiate trials and by increases in intersubject variability. CPZ (1.0--4.0 mg/kg) caused a decrease in accuracy only on no-stimulus trials and, like morphine decreased speed to initiate trials. LSD (0.04--0.16 mg/kg/ decreased overall accuracy in a nonspecific manner (i.e., when shock and tone discriminations were considered together) and decreased speed by producing periods of nonresponding.