Conditioned suppression of motility: possibility for evaluation of learning and memory in mice

Mice showed a marked suppression of motility when placed in the same environment where they had been given electric shocks (ES) 24 h before. This conditioned suppression of motility (CS) was attenuated by the administration of cycloheximide (CXM, 25-150 mg/kg) immediately after ES treatment in a dose-dependent manner. CXM (50 mg/kg) administered 1 h after ES failed to attenuate the CS. These effects seem to be caused by retrograde amnesia. Furthermore, the amnesic action of CXM was antagonized by naloxone (10 mg/kg), which did not affect CS. Physostigmine (0.2 mg/kg), propranolol (1 mg/kg) and cyproheptadine (2 mg/kg) did not antagonize CXM-induced amnesia significantly. In the same way, the amnesia-inducing actions of phencyclidine and scopolamine were detected. The CS method seems to be useful to examine learning and memory performances in animals and has the advantage that evaluation is extremely easy.