Interaction between dopamine D2 and NMDA receptors in the dorsal hippocampus of rats in the elevated plus-maze test of anxiety

Different studies have indicated that glutamate and dopamine are involved in producing anxiety. Furthermore, interaction between NMDA and dopamine receptors has been demonstrated in the modulation of some behaviors. In the present study, the role of dopaminergic D2 receptor in producing anxiety-like behavior induced by inhibition of NMDA receptors was investigated in male wistar rats. Rats were anesthetized with intra-peritoneal injection of ketamine hydrochloride, plus xylazine and then placed in a stereotaxic apparatus. Two stainless-steel cannuale were placed in the CA1 region of hippocampus. All animals were allowed to recover for one week before beginning behavioral test. The elevated plus maze test was used to test anxiety-like behaviors. The results of this study showed that intra-CA1 injection of MK801 (2 µg/rat) induced anxiolytic effects. Intra-CA1 injection sulpiride (0.25, 0.5 and 0.75 µg/rat) by itself had no effect on anxiety-like behaviors, but administration of the same doses of sulpiride 5 mins before injection of the effective dose of MK801 (2 µg/rat, intra-CA1) inhibited anxiolytic effects of MK801. The results indicated that CA1 region of hippocampus have an important role in anxiolytic effects of MK801 and anxiolytic effect of NMDA receptors antagonist is at least partly mediated via D2 receptors of the dorsal hippocampus.