Effect of substance P on somatostatin release from the isolated perfused rat stomach.

The effect of substance P (SP) on the release of gastric somatostatinlike immunoreactivity (SLI) was studied. Substance P inhibited both basal SLI release and SLI release stimulated by gastric inhibitory polypeptide or 1-isoproterenol. This inhibitory action of SP was not blocked by atropine or hexamethonium, suggesting that a cholinergic mechanism was not involved. The SP-suppressed SLI release was also not reversed by the administration of naloxone, which indicated that enkephalinergic involvement was absent. However, the SP antagonist [D-Pro2, D-Trp7,9]-SP abolished the inhibition of SLI release by SP. It is concluded that SP might be involved in the control of gastric SLI release and that the inhibitory action of SP was probably mediated directly or indirectly on the gastric D cells through SP receptors.