Intra-VTA injection of ghrelin improved morphine amnesia in male Wistar rats

Morphine is the major agonist of opioid receptors that causes memory impairment. Ghrelin is secreted by the stomach and released into the circulation. Studies have shown that ghrelin increases memory. The ventral tegmental area is a part of the rewarding neural pathway that involves synaptic plasticity. In this study, the role of the ventral tegmental area in ghrelin effects on morphineinduced amnesia was studied. The experimental groups consist of the control group, morphine groups, groups treated with ghrelin-saline and ghrelin- morphine. All groups were cannulated bilaterally in the ventral tegmental area. To investigating memory, an avoidance test was used. Animals received, post-training subcutaneous administration of saline (1 ml/kg) or morphine (0.25 - 0.5 -5 - 7.5 mg/kg) and in other groups, received intra-VTA administration of ghrelin (0.3 -1.5 -3 nmol/μl) 5 minutes before the saline (1ml/kg) or morphine (7.5 mg/kg) injection. Morphine dose-dependently reduced the learning and induced amnesia compared with saline group (P<0.0001). Intra-VTA injection of ghrelin (0.3 -1.5 -3nmol/μl) 5 minutes before the effective dose of morphine (7.5 mg/kg) dose-dependently restored the memory retrieval (P<0.0001). Injection of ghrelin with saline did not have any significant effect on memory retention (p<0.05). The results showed that memory and learning can be affected by ghrelin. Intra-VTA injection of ghrelin after training improved morphine-induced memory impairment.

کلیدواژه ها:

Ghrelin ، Memory ، Morphine ، Ventral tegmental area