Ghrelin inhibited serotonin release from hippocampal slices.

Ghrelin (Ghr) is a peptide produced peripherally and centrally. It participates in the modulation of different biological processes. In our laboratory we have shown that (a) Ghr administration, either intracerebroventricular or directly into the hippocampus enhanced memory consolidation in a step down test in rats (b) the effect of Ghr upon memory decreases in animals pretreated with a serotonin (5-HT) reuptake inhibitor, Fluoxetine, suggesting that Ghr effects in the hippocampus could be related to the availability of 5-HT. It has been demonstrated that Ghr inhibits 5-HT release from rat hypothalamic synaptosomes. Taking in mint these evidences, we studied the release of radioactive 5-HT to the superfusion medium from hippocampal slices treated with two doses of Ghr (0.3 and 3 nm/μl). Ghr inhibited significantly the 5-HT release in relation to those superfused with artificial cerebrospinal fluid (ACSF) (H = 9.48, df = 2, p ≤ 0.05). In another set of experiments, Ghr was infused into the CA1 area of hippocampus of the rats immediately after training in the step down test and the 5-HT release from slices was studied 24h after Ghr injection showing that in this condition also the 5-HT release was inhibited (H = 11.72, df = 1, p ≤ 0.05). In conclusion, results provide additional evidence about the neurobiological bases of Ghr action in hippocampus.