Substance P: a powerful intestinal vasodilator in the pig

In anaesthetized young pigs the influence of intra-arterial infusions of Substance P (SP) on mesenteric vascular resistance is studied, both before and after serotoninergic and nervous conductivity blockade by dihydroergotamine (DHE) and tetrodotoxin (TTX). SP has a strong dilator effect on pig mesenterial vessels, which is not significantly modified by DHE or TTX; presumably SP acts directly on the vascular smooth muscle. By comparing the threshold level of SP with that of other intestinal vasdodilators, it may be concluded that SP is the most powerful intestinal vasodilator so far extperimented in the pig.