Effects of D-amphetamine sulfate and reserpine on an avoidance response

Abstract

Twenty-eight naive male albino rats, 120 days of ago, of the Sprague-Dawley strain were trained to a criterion of 25 per cent avoidance responding. As the Ss reached criterion they wore randomly assigned to one of seven treatment orders. The treatment conditions were as follows: 1.0 and 3.0 mg/kg reserpine; 0.5 mg/kg saline; no injection; 0.8, 1.4, and 3.0 mg/kg d-amphetamine sulfate. All injections were intraperitoneal with a 48-hour delay between treatments. The Ss were placed in the experimental apparatus for a 30-minute period on alternate days. Avoidance response measures wares (1) Total avoidance responses; (2) Avoidance responses during dark periods of session; and (3) Avoidance responses to warning stimulus. It was found that reserpine, at the two dosage levels employed, significantly reduced avoidance responding below the saline and no injection conditions. Avoidance responses in the saline and no injection conditions were not significantly different. The effects of the three dosage levels of d-amphetamine sulfate resulted in a significant increase in avoidance responding when compared with the reserpine, saline and no injection conditions. However, a 3.0 mg/kg injection of d-amphetamine sulfate resulted in a significant decrease in avoidance responding when compared with the 1.4 mg/kg d-amphetamine condition. Though the 3.0 mg/kg injection resulted in a decrease in avoidance responding, it was significantly above the 0.8 mg/kg level. It was evident that treatment conditions did not result in significant differences in total responding, i.e., only the avoidance response appeared to be influenced by the treatments. The results were interpreted by postulating that d-amphetamine sulfate, in extreme doses (3.0 mg/kg), results in an activation of the reticular formation which is detrimental to the adequate performance of the avoidance response. This interpretation supports the contention of Berlyne (1960) that extreme increases in arousal result in decreased performance. The effects of reserpine were interpreted according to Carlton (1963), who assumes that the catecholamines are normally involved in maintaining activation and that reserpine tends to reduce the stores of these substances in the brain.