A study of vasoactive intestinal peptide and acetylcholine as possible mediators of vasodilatation in the cat submandibular gland.

Vasoactive intestinal polypeptide (VIP) is a powerful vasodilator agent in the submandibular gland of the cat, and its effect can be reduced by avian pancreatic polypeptide (APP), or by desensitization of the gland's blood vessels to VIP. However, the vasodilatation caused by parasympathetic nerve stimulation is not reduced by either of these means. We conclude, therefore, that VIP is unlikely to be a major mediator of this atropine-resistant vasodilatation. Experiments with a potentiator of acetylcholine, eserine, and with a depleter, suggest that acetylcholine plays some role in this vasodilatation, but it too does not appear to be the major physiological mechanism. Substance P and ATP were neither potent nor consistent vasodilators and are unlikely mediators.