The pharmacological perspective: role for the sympathetic nervous system in micturition and sexual function

The predominant effects of the sympathetic innervation of the lower urinary tract in man are mediation of contraction of the bladder base and the uret hra and inhibition of the parasympathetic pathways at spinal and ganglion l evels. Sympathetic tone also mediates the contractility of smooth muscle fi bres in the prostatic stroma, and it has an important role in maintaining t he penis in a flaccid state and in ejaculation. In the detrusor muscle of m ost species, P-adrenoceptors (beta-ARs) mediating relaxation normally domin ate over alpha-ARs mediating contraction, and the effect of noradrenaline ( NA) is relaxation. The human detrusor is able to express beta 1-, beta 2- a nd beta 3-ARs and stimulation of beta 3-ARs causes relaxation. Low, but rep roducible expression of alpha(1)-ARs (alpha(1a) and alpha(1d)) has been fou nd in human detrusor muscle, but the alpha(1)-AR subtypes mediating contrac tion have not been established. The sympathetic pathways to the penis may m ediate anti-erectile as well as erectile effects. Although alpha(1) and alp ha(2)-ARs have been demonstrated in human corpus cavernosum tissue, availab le information supports the view of a functional predominance of alpha(1)-A RS. The human vas deferens also has an important adrenergic innervation and alpha(1A)-ARs seem to mediate contraction.