The Effect of Intra-Medial Septum Co-Injection of Ghrelin and Nicotine on Morphine Induced Memory Impairment

Evidence indicates that medial septum nicotinic receptors regulate cognitive process. Ghrelin is a gut hormone that regulates energy homeostasis. Ghrelin also is produced in brain and known to be involved in cognitive function. The purpose of the study was to evaluate the effects of medial septal injection of ghrelin on morphine-induced memory impairment in rats. Also, the possible relationship between the medial septal ghrelin and acetylcholine nicotinic receptors on morphine-induced memory impairment was evaluated. Male Wistar rats implanted at the medial septum area and microinjected with ghrelin and nicotinic receptor agents. Memory retrieval was measured in a step-through type inhibitory avoidance apparatus. The results indicated the impairment of memory consolidation by posttraining administration of morphine. Posttraining intra-septal injection of either ghrelin or nicotine alone had no significant influence on memory performance, but their co-application with significant dose of morphine (7.5 mg/kg.s.c) improved memory consolidation. Moreover, posttraining co-application of low doses of the two agonists couldn’t affect morphine-induced memory impairment. These results indicated no interaction between medial septal ghrelin and nicotinic receptors on morphine-induced memory impairments in rats.