The Effect of Dorsal Hippocampal α2-Adrenegic Receptors on WIN55,212-2 State-Dependent Memory of Passive Avoidance

Cannabinoids are a class of psychoactive compounds that produce a wide array of effects in a large number of species. In the present study, the effects of bilateral intra-CA1 injections of an α2-adrenergic receptor agents, on WIN55,212-2 state-dependent learning were examined in adult male Wistar rats. The animals were bilaterally implanted with chronic cannulae in the CA1 regions of the dorsal hippocampus, trained in a step-down type inhibitory avoidance task, and tested 24h after training to measure step-down latency. Post-training intra-CA1 injection of WIN55,212-2 (0.25 and 0.5µg/rat) induced impairment of memory retention. Amnesia produced by post-training WIN55,212-2 (0.5µg/rat) was reversed by pre-test administration of the same dose of WIN55,212-2 that is due to a state-dependent effect. Pre-test intra-CA1 injection of clonidine (0.5 and 0.75µg/rat, intra-CA1) improved post-training WIN55,212-2 (0.5µg/rat, intra-CA1)-induced retrieval impairment, while pre-test intra-CA1 injection of yohimbine (1µg/rat, intra-CA1) 2min before the administration of WIN55,212-2 (0.5µg/rat, intra-CA1) inhibited WIN55,212-2 state-dependent memory. These results suggest that α2-adrenergic receptors of the dorsal hippocampal CA1 regions may play an important role in Win55,212-2-induced amnesia and WIN55,212-2 state-dependent memory.