ABSTRACT
PURPOSE: Pituitary adenylate cyclase-activating polypeptide (PACAP) showed the relaxant effect and distribution patterns in the penile corpus cavernosum. We investigated the presence, distribution, and effects of PACAP-(1-27) in the clitoral cavernosum (CC). MATERIALS AND METHODS: The isometric tension was measured in the strip of rabbit CC. Immunohistochemistry was used to localize PACAP-(1-27) immunoreactivity in nerve fibers in CC. Possible co-localization of the PACAP-(1-27) immunoreactive nerve fiber with other nerve fiber was investigated by application of double immunofluorescent labeling technique using antibody to protein gene product 9.5 (PGP 9.5). Western blotting was used to identify the expression of PACAP-(1-27) protein. RESULTS: The pre-contracted CC smooth muscle strip with phenylephrine was relaxed dose-dependently with PACAP-(1-27). PACAP-(6-27), PACAP-(1-27) receptor antagonist did not affect the PACAP-(1-27) induced relaxant responses. Pre-treatment with Nw- nitro-L-arginine methyl ester (NO synthase inhibitor) did not affect the relaxation induced by PACAP-(1-27). CC was not stained by anti-human PACAP-(1-27) guinea pig polyclonal antibody and the immunoreactivity for anti-human PGP 9.5 mouse monoclonal antibody was observed throught the CC. Western blotting demonstrated the presence of immunoreactive protein band corresponding to 35 KDa PACAP-(1-27). CONCLUSIONS: The present study shows that PACAP-(1-27) has a possible role in the modulation of smooth muscle tone of the CC resulting in erection.