The role of hippocampal (CA1) NMDA receptor on learning and memory in presence and absence of zinc chloride in adult male rats

Introduction: Zinc is an essential trace element that plays an important role in the synaptic plasticity and modulation of the CNS activity and is also involved in learning and memory. Synaptic vesicle zinc in the hippocampus area exerts modulatory effects on NMDA glutamate receptors. Methods: In this study, the effects of intra hippocampal administration of NMDA agonist and antagonist in the presence and absence of ZnCl2 was investigated on passive avoidance learning and memory by using step down task in adult male rats. Animals were divided into 10 groups (n = 8 each group). Control group, second group received NMDA 0.1 μg/rat in 1 μl saline for 4 days. Sham group received saline with the same volume. Fourth group received MK-801 1 μg/rat in 1 μl saline 10 min before training for 4 days. Sham group received saline in the same volume. Groups 6-10 received 30 mg/kg/day Zncl2 in drinking water for 2 weeks. Sixth group received only ZnCl2, but groups 7, 8, 9, and 10 received drug and saline in the same conditions as groups 2, 3, 4 and 5 in addition to ZnCl2 in their drinking water. Results: Our experiments showed that consumption of 30 mg/kg/day ZnCl2 impaired learning and memory in adult male rats (P < 0.05). Administration of NMDA improved the impairments caused by ZnCl2 consumption (P < 0.05), while the administration of MK-801 increased the impairments. Conclusion: It seems that zinc impairs passive avoidance learning and memory by modulating the subunits of NMDA receptors in hippocampus.