Effects of antidromic trigeminal nerve stimulation in relation to parasympathetic vasodilation in cat nasal mucosa

Abstract

High threshold stimulation of the trigeminal nerve in sympathectomized cats caused an atropine and hexamethonium resistant vasodilation in the nasal mucosa. Stimulation of efferent parasympathetic neurons to the nose caused a partially atropine sensitive vasodilation which was abolished by hexamethonium. Combined trigeminal and parasympathetic nerve stimulation did not reveal any obvious functional interactions between these 2 systems. Local intra-arterial infusions of substance P, VIP [vasoactive intestinal peptide] and acetylcholine caused a dose dependent vasodilation in the nasal mucosa. The relative vasodilatory potencies were substance P .mchgt. VIP > acetylcholine. Local infusions of capsaicin, known to release substance P from nerve endings, caused a marked longlasting biphasic vasodilation which was atropine and hexamethonium resistant. There are 2 vasodilator mechanisms of different nervous origin in the nasal mucosa. The trigeminal response is probably mediated via release of substance P, while the parasympathetic effect seems to be caused by acetylcholine and VIP.