Involvement of dorsal hippocampal α1-adrenergic receptors in the effect of WIN55, 212-2 on memory retrieval in inhibitory avoidance task

The present study evaluated the possible role of α1-adrenergic receptors of the dorsal hippocampus on WIN55, 212-2 induced amnesia and WIN55, 212-2 state-dependent memory in adult male Wistar rats. In this study Phenylephrine as agonist and prazosin as antagonist of α1-adrenergic receptor, WI 55, 212-2 as agonist of cannabinoid receptor was used. 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 24 h after training to measure step-down latency. post-training intra-CA1 administration of WIN55, 212-2 (0.25 and 0.5 μg/rat) impaired the memory retrieval. Amnesia produced by post-training WIN55, 212-2 (0.5 μg/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 phenylephrine (0.5 and 0.75 μg/rat) improved post-training WIN55, 212-2 (0.5 μg/rat) induced retrieval impairment. On the other hand, pre-test injection of prazosin prevented the restoration of memory by pre-test WIN55, 212-2. It is important to note that pre-test intra-CA1 administration of the same doses of prazosin or phenylephrine, alone did not affect memory retrieval. These results suggest that α1-adrenergic receptors of the dorsal hippocampal CA1 regions may play an important role in WIN55, 212-2 state-dependent memory.