The effects of capsaicin applied topically to inferior alveolar nerve on antidromic vasodilatation in cat gingiva.

Electrical stimulation of the cut inferior alveolar nerve caused 3 different patterns of vasoresponses in the cat gingiva: vasodilatation, vasoconstriction, and biphasic response consisting of vasoconstriction and vasodilatation. Topical capsaicin application onto the inferior alveolar nerve produced a vasodilatation in all of cats tested. After the repeated application of capsaicin, the vasodilator response was no more elicited by electrical stimulation of the inferior alveolar nerve, while the vasoconstrictor response was observed in every preparation. The vasoconstrictor response caused by electrical stimulation of the inferior alveolar nerve was not affected by the capsaicin application, but was completely inhibited by phentolamine, sympathetic alpha-adrenergic receptor antagonist. The present results suggest that vasodilatation induced by electrical stimulation of the inferior alveolar nerve occurs via the sensory nerve, and vasoconstriction via the sympathetic nerve.