Post-training reversible inactivation of hippocampus reveals interference between memory systems

A post‐training reversible lesion technique was used to examine the effects of neural inactivation of the dorsal hippocampus on place and response learning. Male Long‐Evans rats trained in one of two versions of a water plus‐maze task received post‐training intra‐hippocampal infusions of the local anesthetic drug bupivacaine (0.75% solution, 0.5 μl), or saline. Post‐training intra‐hippocampal infusions of bupivacaine attenuated acquisition of the place task and enhanced acquisition of the response task. Delayed (2‐h) post‐training infusions of bupivacaine did not affect retention in either task. The findings demonstrate (1) enhanced learning after reversible hippocampal lesions that is independent of treatment influences on non‐mnemonic factors, and (2) inactivation of the dorsal hippocampus during the post‐training memory consolidation period is sufficient to enhance response learning. Hippocampus 2002;12:280–284. © 2002 Wiley‐Liss, Inc.