High-frequency stimulation of the facial nerve results in local cortical release of vasoactive intestinal polypeptide in the anesthetised cat.

Local cortical release of vasoactive intestinal polypeptide (VIP) was measured using a sensitive radioimmunoassay following direct electrical stimulation of the facial nerve in the anaesthetised cat. During activation of the facial nerve dilator pathway VIP was released at the cortex and collected into a physiological superfusate, its concentration increasing from 4.2 +/- 1.2 to 15.5 +/- 2.4 pmol/l. Administration of the nicotinic ganglion blocking agent hexamethonium (10 mg/kg i.v.) eliminated this response demonstrating that the release is mediated via an autonomic ganglion. Given previous experiments that have demonstrated that stimulation of the facial nerve leads to a neurogenically mediated dilatation of the cerebral vasculature, these data further implicate VIP as the transmitter in this pathway.