The effects of chlorpromazine on one-trial passive avoidance learning in mice: further examination of pre- and post-learning administration.

Abstract

Chlorpromazine in doses of 0.5 mg/kg was administered to mice 0.5, 2, or 10 min after a one-trial passive avoidance learning experience. The drug produced effects on the magnitude and rate of extinction of the learned response dependent upon the injection, time, confirming results contained in an earlier report. In a second experiment with doses of 2.0 mg/kg, the effects of further injecion times were investigated. The drug had no effect when given 240 min before learning, but produced maximal blocking of response acquisition when given 120 and 8 min before learning. Drug injections 6 and 3 min before learning were suggested as having actions on post-learning memory traces. A distinction was noted between the effects of drug injections 1 and 1.5 min after learning and this was related to an effect on a rapidly decaying short-term memory trace. Chlorpromazine had no effect when given 20 min after learning.