ABSTRACT
Penile erection is caused by relaxation o f the b lood vessels and trabecular m esh w ork o f sm ooth muscle that constitutes the co rpora cavernosa.1,2 A lthough p ara sy m p a th e tic in n e rv a tio n is invo lved in erectile function, a nonadrenergic, noncholinergic (NANC) m echanism m ay also play a ro le in pen ile e rec tio n .1,2 H aving been found localized in nerve fibers around cav ernous sm ooth muscle and b lood vessels, vasoactive intestinal peptide has been pos tu la ted to be a n e u ro tran sm itte r an d /o r n e u ro m o d u la to r fo r e rec tile fu n c t io n .1 Similarly, calcitonin gene-related pep tide (CGRP), a po ten t vasodilator and sm ooth m usc le re lax an t, has been show n to be localized in high concentrations in the gen itofem oral nerve and penile tissue o f the ra t.3 CGRP has recently been reported to induce penile erections in prim ates and m ay serve to m odulate penile erection.4
