The Effect of Intra-ventral Tegmental Area Injection of Ghrelin on Morphine-Induced Amnesia in Male Rats: An Experimental Study

Extensive evidence shows that morphine impairs cognitive functions. On the other hand, ghrelin is a gastrointestinal hormone that affects learning and memory process. The purpose of the current study was to evaluate the effect of intra-ventral tegmental area (VTA) injection of ghrelin on morphine-induced amnesia in male rats. In this experimental study, 104 male Wistar rats (220-250 g) were randomly divided into 13 groups (n=8 for all groups) including: saline, morphine treated groups (0.5-7.5 mg/kg), ghrelin treatd groups (0-3 nmol/μl) plus morphine (7.5 mg/kg) or saline. Memory was measured in a step-through type inhibitory avoidance apparatus. All groups received intra-ventral tegmental area (intra-VTA) injection of saline or ghrelin immediately after training. After 5 mins saline or morphine was injected subcutaneously. Testing phase was done 24 hrs after training. Data were analyzed using one-way and two-way ANOVA analysis followed by Tukey’s multiple comparison test. The results showed that post-training administration of morphine significantly reduced step-through latency compared with the saline group (p<0.001). Intra-VTA injection of ghrelin also reduced morphine-induced amnesia (7.5 mg/kg) (p< 0.001). Ghrelin plus saline administration had no significant effect on memory retrieval (p>0.05). The results indicate that intra-VTA injction of ghrelin prevents the disrupting effects of morphine on avoidance memory.
Key words: Ghrelin, Inhibitory avoidance learning, Male rat, Morphine, Ventral tegmentum area
Funding: This study was funded by University of Arak.                             
Conflict of interest: None declared.
Ethical approval: The Ethics Committee of Arak University of Medical Sciences approved the study. (1397.139).
How to cite this article: Nazari-serenjeh F, Darbandi N, Yadegary A, Momeni HR. The Effect of Intra-ventral Tegmental Area Injection of Ghrelin on Morphine-Induced Amnesia in Male Rats: An Experimental Study. J Rafsanjan Univ Med Sci 2019; 18 (2): 147-60. [Farsi]