The ghrelin hormone secreted from the stomach has an effect on the hippocampus, which improves memory and learning. Administration of morphine after training improves the avoidance of inhibitory 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 induced 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 inhibitory avoidance test.Morphine subcutaneous injection after training (0.5, 2.5, 5, 7.5 mg/kg) dose dependently caused memory loss and 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) resulted in improvement of morphine-induced amnesia (P <0.001).Intra CA1 injection of ineffective dose of ghrelin (0.03 nmol/μl) with subcutaneous injection of ineffective dose of nicotine (0.2 mg/kg), 5 minutes before injection of morphine (7.5 mg/kg) significantly improved the morphine-induced memory loss (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 nicotine as synergistic with ghrelin leads to increased memory andImprovement of morphine induced amnesia.
