Abstract

Three male albino rats were trained to lever press for food on a fixed-interval 75-second schedule of reinforcement. Responding in the first and last 15 seconds of the interval, as well as overall response rates, were analyzed. After stabilization of fixed-interval responding, the effects of lysergic acid diethylamide-25 (LSD) (0.005-0.150 mg/kg), d-amphetamine sulfate (0.10-0.96 mg/kg) and mescaline hydrochloride (1-12 mg/kg) on fixed-interval responding were investigated. LSD (0.015 mg/kg) increased responding in all portions of the interval, whereas higher doses tended to decrease responding. d-Amphetamine (0.15 and 0.48 mg/kg) increased rates of responding except at the highest dose (0.96 mg/kg) which decreased responding in the last 15 seconds of the interval. Mescaline (3-12 mg/kg) produced dose-related increases in responding in the initial 15-sedond segment while decreasing responding in the last portion of the interval. In rats tolerant to the effects of mescaline (3 mg/kg), there were indications of cross-tolerance to the effects of 0.15 mg of d-amphetamine per kg, but no cross-tolerance was observed when the order of drug presentation was reversed. A two-way, partial cross-tolerance was observed between the effects of 0.045 mg of LSD pen kg and 3 mg of mescaline per kg and rats tolerant to tue effects of 0.015 mg of LSD per kg did not show cross-tolerance to the effects of 0.15 mg of d-amphetamine per kg regardless of the order of drug presentation. These data suggest mescaline shares common mechanisms or components of behavioral action with both LSD and d-amphetamine in the rat.