Role of orexinergic receptors in the dentate gyrus of the hippocampus in the acquisition and expression of morphine-induced conditioned place preference in rats

Background and Aim : Orexinergic projections derived from the lateral hypothalamus (LH) play a crucial role in the acquisition and expression of morphine-conditioned place preference (CPP). The dentate gyrus (DG) region of the hippocampus, which receives projections of LH orexinergic neurons, have demonstrated that orexinergic receptors are expressed in there. This study examined the effects of intra-DG orexin-1 (OX1) and orexin-2 (OX2) receptor antagonists on the acquisition and expression of CPP induced by morphine.Methods : Two separate cannulas were inserted bilaterally into the DG, and a CPP paradigm was performed. The CPP scores and locomotor activities were recorded using EthoVision software.Results : The results show that an intra-DG microinjection of SB334867 (a selective OX1R antagonist) (0.5, 2.5, 12.5 nM/0.5 μl DMSO) and TCSOX229 (a selective OX2R antagonist) (0.5, 2.5, 12.5 nM/0.5 μl DMSO) before a morphine subcutaneous injection (5 mg/kg) during a three-day conditioning phase dose-dependently represses the acquisition of morphine-induced CPP in rats. Furthermore, these antagonists reduced the CPP score in the expression phase.Conclusion : Consequently, it was established that orexinergic receptors in the DG are involved in the acquisition and expression of morphine-induced CPP.

کلیدواژه ها:

Reward ، Orexinergic receptors ، Dentate gyrus ، Morphine ، Conditioned place preference ، Rat