Cycloheximide impairs and enhances memory depending on dose and footshock intensity

Abstract

This experiment examined the effects on memory of interactions of cycloheximide dose and training foot shock intensity. Mice received injections of cycloheximide (120mg/kg, s.c.) or saline 30min prior to inhibitory avoidance training with shock intensities of 100, 150, 250 or 300μA (1s duration). Memory was tested 48h later. The saline control mice showed increasing memory latencies as a function of shock intensity. The ability of cycloheximide to impair memory increased as the training shock intensity increased. In a second experiment, mice were trained with a 200μA (1s duration) shock and received injections of saline or cycloheximide at one of several doses (30, 60 or 120mg/kg). Under these training conditions, cycloheximide enhanced memory in an inverted-U dose–response manner. These findings are consistent with prior findings suggesting that protein synthesis inhibitors act on memory by altering modulators of memory formation as a secondary consequence of the inhibition of protein synthesis rather than by interfering with training-initiated synthesis of proteins required for memory formation.