Cycloheximide induced amnesia and recovery as a function of training parameters

Mice were given 2 or 3 training trials in a passive avoidance task following an injection of cycloheximide or saline. They were tested 1, 1.5, 3, 24, or 72 hr after training and tested again 72 hr after the first test trial. All the cycloheximide groups except the 1 hr groups were inferior to saline controls on the first test trial, and there was no suggestion of spontaneous recovery over the intervals tested. Test 2 performance was generally inferior to Test 1 performance for all groups, but the cycloheximide groups showed the greatest drop in performance. A second experiment extended train/test intervals to 144, 146, 148, and 192 hr. Spontaneous or test induced recovery again did not occur. The discussion attempts to reconcile these results with prior reports of recovery in terms of differential conditioning of different components of passive avoidance memory by the different training procedures. This results in partial sparing of some components of passive avoidance memory by cycloheximide, which has the appearance of recovery under certain test conditions.