Mechanical stimulation and capsaicin evoked vasodilation by parasympathetic reflex mechanisms in the pig nasal mucosa.

Abstract

A model was developed using pentobarbital anesthetized pigs to study bilateral blood flow changes in the nasal mucosa by flow-probes on both sphenopalatine arteries. Unilateral mechanical stimulation of the nasal mucosa for 10s as well as close intra-arterial capsaicin infusion induced bilateral vasodilation. The magnitude of the vasodilator responses were similar on both sides, although the capsaicin effect (maximal increase in arterial blood flow by about 100 ml/min) was larger than that of the mechanical stimulation. Pretreatment with atropine (0.5 mg x kg-1) had no effect on the vascular responses to capsaicin or mechanical stimulation. However, when the pigs were pretreated with the ganglionic nicotinic receptor blocking agent, chlorisondamine (3 mg x kg-1), the vasodilatory responses to mechanical stimulation were abolished and the responses to capsaicin infusion markedly reduced (90-95%). These data indicate that unilateral mechanical stimulation as well as capsaicin infusion evoke bilateral nasal vasodilation which is probably mediated via a central reflex arch with a parasympathetic non-cholinergic final step.