Muscarinic and NMDA receptors interaction in the dorsal hippocampus of rats in the elevated plus-maze anxiety test

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Abstract

Background and Objective: Excitatory transmission through glutamate receptors is critical for cognition such as learning and anxiety. In the present study, the involvement of dorsal hippocampal muscarinic cholinergic receptor on anxiety-like behavior induced by inhibition of NMDA receptors was investigated. Materials and Methods: In this experimental study, 105 adult male rats weighing 200–250 g were used. The animals were anaesthetized and cannulae implanted bilaterally in the CA1 regions of the dorsal hippocampus using stereotaxic device. Seven days after recovery from surgery, the behavioral testing was started in elevated plus maze task. The data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey test.  Results: Our finding indicated that intra-CA1 administration of MK801 (2 µg/rat) and scopolamine (4 µg/rat) by itself increased percentage of open arm time and open arm entries but did not alter locomotion. On the other hand, intra-CA1 co-administration of ineffective doses of scopolamine with ineffective dose of MK801 (1 µg/rat) did not alter locomotion activity but increased percentage of open arm time and open arm entries.  Conclusion: These results show that both NMDA receptors and muscarinic cholinergic receptors not only play a part in the modulation of anxiety in the dorsal hippocampus of rats but also demonstrate a complex interaction as well.

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