(231) Endogenous Vasoactive Peptides in the Control of Human Penile Erectile Tissue: Is There a Significance of the Neuropeptide Y (NPY)?

Abstract

Abstract Introduction Aside from the neurotransmitters of the sympathetic adrenergic system, vasoconstrictor peptides may also play a role in mediating the constant tone of the erectile tissue during penile flaccidity and in returning the erect penis to the flaccid state. Neuropeptide Y (NPY) is present in high concentrations in the male genital tract. The peptide has been shown to induce contraction of isolated human penile tissue (corpus cavernosum, penile arteries) and potentiate its response to noradrenaline. Objective The purpose of our study was to measure in the cavernous and systemic blood of healthy male volunteers the course of NPY through different stages of sexual arousal. Methods Whole blood was drawn from the corpus cavernosum and the cubital vein of 15 healthy male volunteers during penile flaccidity (Fl), tumescence (Tu), rigidity (Ri) and detumescence (Det). Penile tumescence and erection were induced by applying audiovisual and tactile stimulation. Plasma levels of NPY (given in pmol/L) were determined by means of an enzyme-linked immunoassay (ELISA, IBL GmbH, Hamburg, Germany). Results NPY significantly decreased in the cavernous blood with the beginning of sexual arousal, when the flaccid penis became tumescent and finally rigid (Fl: 88.8 ± 35.8, Tu: 62.4 ± 22.7, Ri: 62.3 ± 19.7). In the phase of detumescence, only a slight increase was noted (64.8 ± 23). In the systemic circulation, no pronounced alterations in the concentration of NPY were registered through the different penile stages (Fl: 64.4 ± 27, Tu: 65.8 ± 19, Ri: 59.6-25, Det: 67.6 ± 29.3). Conclusions Our findings are in favor of the hypothesis that NPY could contribute to the maintenance of the resting state of cavernous smooth muscle. It remains to be elucidated whether the peptide may play a role in the pathophysiology of erectile dysfunction. Disclosure No