كليدواژه :
اسكوپولامين , هيپوكامپ پشتي , حافظه اجتنابي مهاري , يادگيري وابسته به وضعيت
چكيده لاتين :
Introduction: Similarities in the memory impairment between Alzheimer patients and scopolamine treated animals have been reported. In the present study, the possible role of a-adrenergic receptors of the dorsal hippocampus on scopolamine state-dependent memory in adult male Wistar rats was evaluated.
Methods: The animals were bilaterally implanted with chronic cannulae in the CA1 regions of the dorsal hippocampus, trained in a step-through type inhibitory avoidance task, and tested 24 h after training to measure step- through latency.
Results: Post-training intra-CAl administration of scopolamine (0.5 and 2|ig/rat) dose-dependently reduced the step-through latency, showing an amnestic response. Amnesia produced by post-training scopolamine (2 fig/rat) was reversed by pre-test administration of the scopolamine (0.5 and 2 fig/rat) that is due to a state-dependent effect. Pre-test intra-CAl injection of a 1-adrenoceptor agonist, phenylephrine (0.25, 0.5 jig/rat) in the dose range that we used, could not affect memory impairment induced by post-training injection of scopolamine (2 fig/rat). However intra-CAl pretest injection of a2-adrenoceptor agonist, clonidine (0.5 jig/rat) improved post-training scopolamine (2 fig/rat) intra- CAl injection induced retrieval impairment. Furthermore, pre-test intra-CAl microinjection of phenylephrine (0.25 and 0.5 |ig/rat) or clonidine (0.25 and 0.5 |ig/rat) with an ineffective dose of scopolamine (0.25 fig/rat), synergistically improved memory performance impaired by post-training scopolamine (2 |ig/rat). Our results also showed that, pre-test injection of a 1-receptor antagonist prazosin (1, 2 fig/rat) or a2-receptors antagonist yohimbine (1, 2 jig/rat) before effective dose of scopolamine (2 fig/rat) prevented the improvement of memory by pre-test scopolamine.
Conclusion: These results suggest that al- and a2-adrenergic receptors of the dorsal hippocampal CA1 region may play an important role in scopolamine-induced amnesia and scopolamine state-dependent memory.
