The involvement of the hippocampal CA1 cholinergic receptors in the effects of ghrelin on morphine-induced amnesia in adult male rats

The ghrelin hormone that is secreted from the stomach has an effect on memory and learning. Administration of morphine after training reduces the inhibitory avoidance memory and causes amnesia. In this study, the involvement of cholinergic receptors of the CA1 region of the hippocampus in the effects of ghrelin on morphine amnesia was studied. In all groups, cannulation was performed in the CA1 region of the hippocampus and the memory of the rats was assessed by the inhibitory avoidance test. Morphine subcutaneous injection after training dose-dependently (0.5, 2.5, 5, 7.5 mg/kg) reduced memory and caused amnesia (P <0.001). Subcutaneous injection of nicotine (0.2, 0.3, 0.4 mg/kg) after training, 5 minutes before injection of morphine (7.5 mg/kg) improved morphine amnesia (P <0.001). Intra CA1 injection of ghrelin dose-dependently (0.03, 0.3, 3 nmol/μl) 5 minutes before the injection of an effective dose of morphine (7.5 mg/kg) improved the morphineinduced amnesia (P<0.001). Intra CA1 injection of an ineffective dose of ghrelin (0.03 nmol/μl) with subcutaneous injection of an ineffective dose of nicotine (0.2 mg/kg), 5 minutes before injection of morphine (7.5 mg/kg) significantly improved the morphine-induced amnesia (P <0.001). The results indicate that memory and learning can be affected by ghrelin. It seems that stimulation of cholinergic receptors in the CA1 region by synergistic effects with ghrelin lead to increase memory and improve morphine-induced amnesia.