Corelease of vasoactive intestinal polypeptide and peptide histidine isoleucine in relation to atropine-resistant vasodilation in cat submandibular salivary gland.

Parasympathetic nerve stimulation of the submandibular salivary gland in the cat caused salivary secretion, vasodilation and a corelease of vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI) immunoreactivities (IR) into the venous effluent, as indicated by an increase in output. The ratio between the released VIP-IR and PHI-IR was close to 1:1. Gel-permeation chromatography of plasma from the submandibular venous effluent indicated that the released VIP-IR and PHI-IR were very similar to porcine VIP and PHI, respectively. Atropine pretreatment enhanced output of both VIP-IR and PHI-IR during the parasympathetic nerve stimulation to a similar extent (about 5-fold) compared to control stimulations. This increase could be due to an inhibitory presynaptic muscarinic receptor regulation of VIP and PHI release. Since VIP and PHI are present in the same postganglionic parasympathetic nerves in the gland and both peptides have vasodilator activity, the present data suggest that both VIP and PHI may contribute to the atropine-resistant vasodilation seen upon stimulation of the chorda-lingual nerve. The parasympathetic control of salivary gland function may thus involve, a multimessenger system with the classical transmitter acetylcholine and the peptides VIP and PHI.