The adrenergic component in the proximal urethra.

Two experimental systems are described in which simultaneous radiological and perfusion pressure monitoring of proximal urethral function can be carried out. In one series of experiments, hypogastric nerve stimulation and noradrenaline administration caused urethral constriction while isoprenaline caused dilatation. Using a model similar to a stress cystogram, hypogastric nerve section resulted in opening of the urethra earlier under the same stress, and wider when a steady flow was established. This effect was greater than the influence of parasympathetic or somatic nerve supplies to the urethra. It was concluded that sympathetically innervated smooth muscle has a significant influence on urinary continence and urethral wall tension.