Abstract
The predominant effects of the sympathetic innervation of the lower urinary tract in man are mediation of contraction of the bladder base and the urethra and inhibition of the parasympathetic pathways at spinal and ganglion levels. Sympathetic tone also mediates the contractility of smooth muscle fibres in the prostatic stroma, and it has an important role in maintaining the penis in a flaccid state and in ejaculation. In the detrusor muscle of most species, β-adrenoceptors (β-ARs) mediating relaxation normally dominate over α-ARs mediating contraction, and the effect of noradrenaline (NA) is relaxation. The human detrusor is able to express β1-, β2- and β3-ARs and stimulation of β3-ARs causes relaxation. Low, but reproducible expression of α1-ARs (α1a and α1d) has been found in human detrusor muscle, but the α1-AR subtypes mediating contraction have not been established. The sympathetic pathways to the penis may mediate anti-erectile as well as erectile effects. Although α1 and α2-ARs have been demonstrated in human corpus cavernosum tissue, available information supports the view of a functional predominance of α1-ARs. The human vas deferens also has an important adrenergic innervation and α1A-ARs seem to mediate contraction.

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