[Autonomic nervous system and prostatic physiology. Specific features of the alpha-adrenergic system]

A better understanding of the rich autonomic innervation of the prostate allows more effective treatment of voiding disorders secondary to benign prostatic hyperplasia. The glandular contingent possesses mainly cholinergic innervation (M2 muscarinic receptors). Smooth muscle cells are richly supplied with alpha and beta catecholaminergic receptors, involved in muscle contraction and muscle relaxation, respectively, but they may also be involved in growth. These alpha receptors, divided into 2 families (alpha 1 and alpha 2), belong to the family of G protein-coupled seven membrane-spanning helix receptors. The genes, followed by the recombinant proteins of 3 subtypes of alpha 1 receptors have been described: alpha 1-a, -b, -d. In the prostate, these receptors are predominantly located in the stroma, mainly in the centroprostatic region. The mRNA present mainly code for the alpha 1a subtype. The use of specific agonists and antagonists shows that these receptors control smooth muscle contraction according to a mechanism initially considered to be of the alpha 1a type. However, their low affinity for prazosin and the development of new alpha 1 blocking agents is in favour of the involvement of a different functional subtype: alpha 1L. This difference could be explained by a different conformation of the receptor or by different coupling mechanisms. The subtype involved in prostatic smooth muscle contraction has yet to be characterized.