Behavioral impairments caused by injections of the protein synthesis inhibitor anisomycin after contextual retrieval reverse with time.

Recent accounts of memory suggest that retrieval of a learning experience transforms that memory into a labile state that requires a period of protein synthesis to be reconsolidated into a fixed state. In this article, we show that the impairments in behavior caused by the protein synthesis inhibitor anisomycin given after retrieval are temporary and are thus not likely to reflect disruptions in a protein synthesis-dependent reconsolidation process. Mice received injections of anisomycin after either initial acquisition or retrieval of contextual fear conditioning. When anisomycin injections followed acquisition, freezing was impaired during memory tests the next day and 21 days later. When anisomycin injections followed normal retrieval of contextual fear conditioning, freezing was impaired the next day but recovered to levels of control mice when testing occurred 21 days later. This recovery effect occurred after short or long durations of exposure during the retrieval period and was specific to the conditioning context. These results suggest that anisomycin injections after retrieval do not retroactively affect the memory from conditioning.