EFFECTS OF d-AMPHETAMINE ON SCHEDULE-CONTROLLED KEY PRESSING AND DRINKING IN THE CHIMPANZEE

¹ Laboratory of Psychobiology, Department of Psychiatry, Harvard Medical School, at the New England Regional Primate Research Center, Southborough, Massachusetts

Effects of d-amphetamine on schedule-controlled key pressing and on water intake were studied in the chimpanzee. Key pressing during daily sessions was maintained under a multiple schedule comprising a 10-minute fixed-interval schedule and a 100-response fixed-ratio schedule of food delivery. Water intake during the two-hour session totaled 1.5 to 2.0 liters in one chimpanzee and was greatest during the 10-minute fixed-interval schedule. Effects of d-amphetamine on key pressing and drinking during the session, and on drinking in the living area following the session, were dose related. Mean rates of key pressing under the fixed-interval schedule were enhanced by 0.3 to 1.0 mg/kg, and mean rates uimder the fixed-ratio schedule were enhanced by 0.03 to 0.3 mg/kg. Effects of d-amphetamine on key pressing during Successive quarters of the fixed-interval schedule were a function of control rates of responding. Drinking during the session and drinking in the living area during the first 12 hours following the session were decreased by doses (0.03-0.3 mg/kg) that had either little effect or an enhancing effect on key pressing. Drinking was nearly completely eliminated by 1.0 to 3.0 mg/kg of d-amphetamine. At none of the doses studied did d-amphetamine enhance drinking.