The timing of an injection procedure affects pharmacological actions on memory.

In a series of experiments examining the effects of the protein synthesis inhibitor anisomycin on memory for a novel active avoidance task in mice, we found that the timing of administering the drug (pretraining or posttraining) affected its amnestic potency. Anisomycin injected after training was more effective than when injected before training. Adding a saline injection, such that all groups received both pre- and posttraining injections, resulted in greater amnesia with anisomycin given before rather than after training. These results indicate that the procedure of drug administration alters the effectiveness of amnestic agents.