COMPARISON OF RESPONSES TO ADRENOMEDULLIN AND CALCITONIN-GENE-RELATEDPEPTIDE IN THE FELINE ERECTION MODEL

The purpose of the present study was to investigate the effects of int racavernosal injections of adrenomedullin (ADM) and calcitonin gene-re lated peptide (CGRP), two structurally similar peptides, on penile ere ction in the anesthetized cat. Erectile responses to ADM and CGRP were compared with responses to a standard drug combination (1.65 mg papav erine, 25 mu g phentolamine, and 0.5 mu g prostaglandin E-1 [PGE(1)]). Intracavernosal injections of ADM (0.1-3 nmol) and CGRP (0.01-0.3 nmo l) induced erection in a dose-dependent manner. The maximal increase i n intracavernosal pressure in response to ADM was a 75% increase, whil e the maximal response to CGRP was comparable to that induced by the r eference combination, and the maximal increase in penile length was co mparable with ADM, CGRP, and the standard drug combination. The durati on of the maximal pressure increase and the total duration of the resp onse to ADM and CGRP were more abbreviated than with the control combi nation, and systemic blood pressure was reduced significantly after ad ministration of CGRP, the control combination, and the higher doses of ADM. The nitric oxide synthase inhibitor, L-NAME, and the K-ATP(+)-ch annel antagonist, glybenclamide, had no effect on the erectile respons e to CGRP or ADM. The CGRP receptor antagonist CGRP(8-37) attenuated t he erectile response to CGRP but not to ADM. These data suggest that t he erectile responses to ADM and CGRP are not mediated by nitric oxide release or the opening of K-ATP(+) channels, two mechanisms reported to be involved in penile erection, and that CGRP and ADM induce penile erection by activating different receptors.