The Role of Middle Septal Ghrelin Receptors in theEffects of Morphine on Memory Consolidationin Passive Avoidance Learning

Evidence indicates that morphine impairs memory process. Ghrelin hormone has been linked to learning and memory processes and modulates reward properties of addictive drugs. In this study we examined the role of middle septal ghrelin receptors in the effects of morphine on memory consolidation in passive avoidance learning.

In this experimental study, 91 male Wistar rats were randomly divided into 13 (n=7) groups: saline (1ml/kg), morphine (0.5- 7.5 mg/kg), ghrelin (0- 1 nmol/μl) plus morphine (7.5 mg/kg) or saline (1ml/kg). In ghrelin treated groups animals received intra- medial Septum injection of ghrelin immediately after training and 5 min later saline or morphine was injected subcutaneously. Testing phase was done 24 h after training. Data were analyzed using ANOVA analysis followed by Tukey multiple comparison test. Ethics code: IR.ARAKMU.REC.1397.215

Post-training administration of morphine reduced step-through latency and increased Total dark chamber compared with saline group (p< 0.001). Intra- medial Septum injection of ghrelin inhibited morphine-induced amnesia (p< 0.001). Administration of ghrelin alone had no significant effect on memory retrieval (P > 0.05).

Ghrelin is able to prevent the deleterious effects of morphine on memory and learning in the inhibitory avoidance model and the medial septal region may be involved in this effect.