[Modern concept of peripheral erectile mechanisms]

The article describes the peripheral mechanisms of erection and control over them. This knowledge has been acquired as a result of the recent development of pharmacological research designed to study the regulation of erectile smooth muscle tone. Smooth muscle fibres of the corpora cavernosa and arteries supplying the penis relax in response to a reduction of intracellular calcium. This relaxation allows both an increase of the blood flow to the penis and opening of sinusoid spaces. Cyclic nucleotides, cGMP and cAMP, are intracellular messengers of the mediators acting on smooth muscle fibres and regulating these intracellular calcium movements. Nitric oxide (NO) increases the intracellular cGMP concentration that triggers relaxation. Other proerectile mediators, such as vasoactive intestinal polypeptide, prostaglandin E1, are of the secondary importance. In contrast, neurotransmitters of the sympathetic nervous system (norepinephrine), neuropeptide Y, and endothelin induce contraction of cavernous smooth muscle fibres, thereby opposing erection. Oxygenation of the cavernous tissue is also an important factor in the regulation of local mechanisms of erection. Regulation of calcium sensitivity as well as functioning of intracellulare contact--gap junction are of certain interest. A better understanding of the peripheral pharmacology of erection opens the way to new pathophysiological and therapeutic prospects in the broad context of erectile dysfunction.