Influence of apomorphine in dorsal hippocampus (CA1) on scopolamine induced state-dependent memory

Cholinergic and dopaminergic systems of the brain play an important role in learning and memory.Previously shown that morphine, histamine and lithium induce state-dependent learning. In the present study, the effects of the dopaminergic receptor agonist apomorphine on scopolamine state-dependent learning were examined in rats. In this experimental study 200 adult male Wistar rats were used. Rats were anesthetized and then placed in a stereotaxic apparatus. Two stainless-steel cannuale were placed 1 mm above CA1 region of dorsal hippocamus. One week later animals trained in a step-through type inhibitory avoidance task. The drugs injected 5 min before training or testing. One-way analyses of variance (ANOVAs) followed by Tukey test, were used for analysis of the data. Pre-training intra-CA1 administration of scopolamine impaired memory retrieval on the test day. The memory impairment induced by pre-training injection of scopolamine was reversed by pre-test administration of scopolamine and/or apomorphine, suggesting scopolamine induced state-dependent learning and apomorphine influence this type of learninig. These results suggest that dopaminergic receptors of the dorsal hippocampal CA1 regions may play an important role in scopolamine-induced amnesia and scopolamine state-dependent memory.