COMPARATIVE STUDY OF EFFECTS OF SUBSTANCE-P ON BLOOD PRESSURE, SALIVATORY FUNCTIONS AND INTESTINAL MOTILITY

1. The effects of substance P and other tachykinins, on parotid and submaxillary secretion, submaxillary and intestinal blood flow, jejunal and ileal motility and blood pressure were measured in anaesthesized dogs. 2. Vasodilatation (recorded in the submaxillary gland and in the intestine) and a fall of blood pressure were the predominant effects of substance P, physalaemin and a physalaemin-like octapeptide. In higher doses, this was followed by parotid and later also submaxillary secretion. No increase, but merely an occasional decrease, of jejunal tension was observed after high doses of substance P. High doses of physalaemin mainly increased the jejunal tension for 1-2 min. 3. Atropine inhibited the submaxillary secretion elicited by chorda stimulation, but did not alter the concomitant vasodilatation or the vascular and secretory actions of substance P on the salivary gland. 4. Chorda stimulation neither potentiated nor antagonized the salivatory effect of substance P, and substance P failed to affect responses to chorda stimulation. Moreover, there was no development of cross tachyphylaxis to chorda stimulation and substance P. Therefore it is unlikely that chorda stimulation releases endogenous substance P. © 1969 Springer-Verlag.