Vasoactive intestinal polypeptide (VIP) is not an androgen-dependent neuromediator of penile erection

The effects of castration on vasoactive intestinal polypeptide (VIP) immunostaining in human corpus cavernosum ( CC) and the relationship between VIP immunostaining and erectile function were studied in patients with localised prostate cancer who had ( Group 1 = castrated) or had not ( Group 2 = control) undergone 3-month neoadjuvant chemical castration before radical prostatectomy. Evaluation of erectile function included medical and sexual history, physical examination, and measurement of total serum testosterone. CC biopsies were taken at the end of radical prostatectomy and samples immunostained with anti-human VIP antibody. Specific staining was quantified by image analysis and expressed in arbitrary units (AU). Chemical castration induced erectile function deterioration in 70% of patients due to loss of sexual interest and confidence in the ability of having an erection rather than reduced ability of obtaining sexually induced erections. Average VIP content was 34.5 AU in Group 1 and 39 AU in Group 2 and this difference was not statistically significant. Chemical castration does not influence VIP immunostaining of human CC, suggesting that VIP is not an androgen-dependent neuromediator of penile erection and that it can be responsible for sexually induced erections in castrated patients.