Immunoblockade of response to capsaicin in the rat vas deferens: evidence for the involvement of endogenous calcitonin gene-related peptide.

In the rat isolated vas deferens, capsaicin induced a transitory inhibition of the nerve-mediated contractions. This effect was not observed in preparations excised from capsaicin-pretreated rats nor following a first exposure to a high concentration of capsaicin in vitro. Exogenous calcitonin gene-related peptide (CGRP) induced a concentration-related inhibition of the nerve-mediated contractions. A highly avid and specific anti-CGRP serum raised in rabbits against conjugated synthetic rat CGRP inhibited selectively the capsaicin effect. These findings are consistent with the hypothesis that, in this preparation, the specific visceromotor response to capsaicin is brought about by the release of endogenous CGRP from sensory nerves.