Effect of galanin on gastrin and somatostatin release from the rat stomach

Galanin has been shown to be present in the gastrointestinal tract, pancreas and CNS. In the rat stomach, immunohistochemical studies have revealed the presence of galanin in the intrinsic nervous system suggesting a function as putative neurotransmitter or neuromodulator which could affect neighbouring exo- or endocrine cells. Therefore this study was performed to determine the effect of galanin on the secretion of gastrin and somatostatin-like immunoreactivity (SLI) from the isolated perfused rat stomach. The stomach was perfused via the celiac artery and the venous effluent was collected from the portal vein. The luminal content was kept at pH 2 or 7 Galanin at a concentration of 10^-10, 10^-9 and 10^-8M inhibited basal gastrin release by 60-70% (40-100 pg/min; p < 0, 05) at luminal pH 7. At luminal pH 2 higher concentrations of galanin (10^-9 and 10^-8M) decreased basal gastrin secretion by 60-70% (60-100 pg/min; p < 0, 05). This inhibitory effect was also present during infusion of neuromedin-C, a mammalian bombesin-like peptide that stimulates gastrin release. SLI secretion remained unchanged during galanin administration. The inhibitory action of galanin on gastrin secretion was also present during the infusion of tetrodotoxin suggesting that this effect is not mediated via neural pathways. The present data demonstrate that galanin is an inhibitor of basal and stimulated gastrin secretion and has to be considered as an inhibitory neurotransmitter which could participate in the regulation of gastric G-cell function.