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| Paper IPM / Cognitive / 12180 |
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| Abstract: | |||||||
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The aim of the present study was to investigate the existence of possible functional correlation between GABA-A and dopamine (DA) receptors of the dorsal hippocampus
and the ventral tegmental area (VTA) in passive avoidance learning. Two guide cannulas were stereotaxically implanted in the CA1 region of the dorsal hippocampus and the
VTA of male Wistar rats. In order to measure memory retrieval, the animals were trained in a step-through type passive avoidance task and tested 24 h after training. Post-training intra-CA1 administration of a GABA-A receptor agonist, muscimol (0.01?0.02 μg/rat) dose-dependently impaired memory retrieval. Post-training intra- VTA administration of SCH23390 (a dopamine D1 receptor antagonist; 0.1?0.8 μg/rat) or sulpiride (a D2
receptor antagonist; 0.5?1.5 μg/rat) decreased the inhibitory effect of muscimol (0.02 ıμg/rat, intra-CA1) on memory retrieval. Intra-VTA administration of the same doses of SCH23390, but not sulpiride, decreased the step-through latencies. On the other hand, posttraining administration of muscimol (0.02 μg/rat) into the VTA inhibited memory
retrieval. The administration of SCH23390 (0.01?0.2 ıμg/rat) or sulpiride (0.1?1 ıμg/rat) into the CA1 region, immediately after training, had no effect on memory
retrieval. Furthermore, the amnesic effect of intra-VTA administration of muscimol was significantly decreased by intra-CA1 administration of sulpiride (0.5 and 1 ıμg/rat, intra- CA1), but not SCH23390. The practical conclusion is that the relationship between the hippocampus and the VTA may regulate memory formation in passive avoidance learning. Also, the correlation between the hippocampus and VTA by a dopaminergic system may be involved in mediating muscimol-induced amnesia.
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