Effects of dopaminergic drugs in the dorsal hippocampus of rats in the MK801-induced anxiolytic-like behavior

Abstract

Introduction

Excitatory transmission through glutamate receptors constitutes the main mode of synaptic signaling in the brain regions that are critical for cognition such as learning and anxiety.

Objectives

The possible involvement of dorsal hippocampal (intra-CA1) dopaminergic receptor mechanism on the anxiolytic-like response induced by NMDA receptor antagonist, MK801 has been investigated in the present study.

Methods

The male wistar rats were used and the elevated plus maze apparatus has been used to test parameters (%OAT, %OAE, locomotor activity, grooming, rereading and defection) of anxiety-like behaviors in the present study.

Results

The data indicated that intra-CA1 administration of MK801 (2 μg/rat, intra-CA1) increased %OAT and %OAE but not other exploratory behaviors, indicating an anxiolytic-like response. Moreover, intra-CA1injection SCH23390 (0.25, 0.5 and 1 μg/rat) and sulpiride (0.25, 0.5 and 0.75 μg/rat) by itselves, 5 min before testing have no effect on exploratory behaviors. On the other hand, co-administration of ineffective dose of SCH23390 (0.5 μg/rat) with ineffective dose of MK801 (1 g/rat) increased %OAT but not other exploratory behaviors, suggestion anxiolytic-like behaviors. Furthermore, intra-CA1 administration of different doses of sulpiride (0.12, 0.5 and 0.75 μg/rat) 5 min before injection of effective dose of MK801 (2 μg/rat) decreased %OAT and %OAE but did not other exploratory behaviors induced by MK801.

Conclusion

The results may indicate modulatory effect dopaminergic system of CA1 in the anxiolytic-like response induced by MK801.