Post-training intra-CA1 administration of a GABAA receptor agonist, muscimol (0.05 and 0.1 渭g/mouse) dose dependently induced impairment of memory retention. Pre-test injection of muscimol (0.05 and 0.1 渭g/mouse) induced state-dependent retrieval of the memory acquired under post-training muscimol (0.1 渭g/mouse, intra-CA1) influence.
Pre-test injection of a NO precursor, l-arginine (1 and 2 渭g/mouse, intra-CA1) improved memory retention, although the low dose of the drug (0.5 渭g/mouse) did not affect memory retention.
Pre-test injection of an inhibitor of NO-synthase, l-NAME (0.5 and 1 渭g/mouse, intra-CA1) impaired memory retention, although the low dose of the drug (0.25 渭g/mouse) did not affect memory retention.
In other series of experiments, pre-test intra-CA1 injection of l-arginine (0.25 and 0.5 渭g/mouse) 5 min before the administration of muscimol (0.1 渭g/mouse, intra-CA1) dose dependently inhibited muscimol state-dependent memory. Pre-test intra-CA1 administration of l-arginine (0.125, 0.25 and 0.5 渭g/mouse) by itself cannot affect memory retention.
Pre-test intra-CA1 injection of l-NAME (0.25 渭g/mouse, intra-CA1) reversed the memory impairment induced by post-training administration of muscimol (0.1 渭g/mouse, intra-CA1). Moreover, pre-test administration of l-NAME (0.125 and 0.25 渭g/mouse, intra-CA1) with an ineffective dose of muscimol (0.025 渭g/mouse, intra-CA1) significantly restored the retrieval and induced muscimol state-dependent memory. Pre-test intra-CA1 administration of l-NAME (0.0625, 0.125 and 0.25 渭g/mouse) by itself cannot affect memory retention.
It may be suggested that the nitric oxide in the dorsal hippocampal area play an important role in muscimol state-dependent memory.