Memory formation as related to genotypic or experimental variations of hippocampal cholinergic activity in mice.

Two successive experiments were designed to compare learning and retention and the post-training effect of hippocampal electrical stimulation on retention of a lever-press conditioning among several groups of mice. In parallel experiments, we studied the enzymes involved in acetylcholine metabolism in the dorsal hippocampus. Results showed that either a genotypic or an experimentally induced decrease of choline acetyltransferase activity weakened both long-term retention and the facilitatory effect of post-trial stimulation but improved short-term retention. The role of hippocampal cholinergic synapses in response execution and memory consolidation is discussed.