Effect of somatostatin on intragastric pressure and smooth muscle contractility of the rainbow trout, Oncorhynchus mykiss Walbaum

These studies investigated the effects of somatostatin on gastric motility in the rainbow trout. Two experimental models were used, the isolated vascularly‐perfused stomach and isolated strips of gastrointestinal smooth muscle. Both models demonstrated that somatostatin can inhibit gastrointestinal motility and may therefore modulate gastric emptying in fish. In the vascularly‐perfused stomach, somatostatin (10–1000 nm) decreased maximum and baseline intragastric pressure by 10–20% in the presence of stimulatory doses of carbachol or 5‐hydroxytryptamine. In addition, somatostatin (1 μm) inhibited by 50% the magnitude of spontaneous contractions generated by distension. Somatostatin had little effect on the pressure gradient or contractile frequency. These results suggest that somatostatin may negatively modulate gastric emptying in the rainbow trout. In isolated gastric smooth muscle strips, somatostatin (100 pmol) inhibited tension stimulated by carbachol (circular orientation of muscle) or 5‐hydroxytryptamine (longitudinal orientation). These results correlated with those observed in the vascularly perfused stomach preparation. Somatostatin also decreased tension stimulated by carbachol and 5‐hydroxytryptamine in intestinal smooth muscle strips, suggesting that under some conditions somatostatin could increase gastric emptying rate by relaxing intestinal musculature.