Capsaicin-sensitive nerves are involved in bile-oleate-induced intestinal hyperemia.

The purpose of the present study is to assess the role of capsaicin-sensitive afferent nerves of the gut in bile-oleate-induced intestinal hyperemia. In anesthetized rats, intestinal blood flow (BF) was determined with a pulsed Doppler flowmeter. Systemic arterial blood pressure and heart rate were also measured. Test solutions containing either 40 or 80 mM oleic acid, combined with 10% natural bile, were introduced into the jejunum and produced abrupt increases in BF (64 +/- 12 and 118 +/- 14% of control, respectively). The vasodilator response was abolished by pretreatment with systemic capsaicin in neonatal life and by topical application of either capsaicin or lidocaine to the mucosa in adult animals. The response was inhibited 69 +/- 6% by an antiserum to vasoactive intestinal peptide. We found no significant inhibition of the vasodilator response by pretreating animals with antisera to cholecystokinin octapeptide or substance P, nor with hexamethonium, atropine, or reserpine. It appears that bile-oleate-induced intestinal vasodilation involves primary afferent nerve fibers of gut that release vasoactive intestinal peptide.