Differences in the duration of reserpine action in the rat depending on the measure employed

Abstract

The effects of reserpine were determined on eleven measures of drug action at 2, 26, and 50 hr following an acute injection. All measures were almost equally affected at 2 hr after injection and estimates of ED-50 from the log dose-effect curves ranged from 1·20 to 2·12 mg/kg. There were large differences, however, between the various indices in the time required for recovery from reserpine action. Five separate patterns of recovery would be distinguished. (1) Complete recovery within 26 hr; tremor and conditioned escape. (2) Partial recovery at 26 hr and complete recovery by 50 hr; muscle tone and hunched posture. (3) Little or no recovery at 26 hr but complete recovery by 50 hr; ptosis, exploratory behavior and lever pressing on variable interval schedules. (4) No recovery at 26 hr and only partial recovery by 50 hr; spontaneous locomotor activity and lever pressing on a continuous reinforcement schedule. (5) No recovery at 26 or 50 hr; the conditioned avoidance response. These differences in the duration of reserpine action are discussed with respect to differences in duration of neurochemical effects of the drug on monoamine in the brain.