Role of Striated and Smooth Muscle Components in the Urethral Pressure Profile in Traumatic Neurogenic Bladders: A Neuropharmacological and Urodynamic Study. Preliminary Report

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Abstract
Urodynamic investigations with urethral pressure profile, and vesicle, intrarectal and anal pressure recordings were performed in 37 patients with spinal cord lesions. The recordings were done before and after phentolamine injections and/or pudendal nerve blocks to evaluate the respective contribution of sympathetic and somatic innervation to the maximum urethral closure pressure in the mid and distal portions of the membranous urethra. A pressure gradient was demonstrated in the membranous urethra with higher values in the distal than in the mid portion. The interrupted withdrawal technique is superior to the continuous technique in patients with upper motor neuron bladders. Mid urethral striated and smooth muscle components were shown to represent .apprx. 60 and 30% of the maximum urethral closure pressure, respectively. In the distal urethra striated and smooth components are more abundant than in the mid portion and contribute in equal proportion to the maximum urethral closure pressure. The greatest pressure decrease in the mid and distal urethra of patients with lower motor neuron bladders was believed to be an effect of denervation supersensitivity. The results of pudendal blocks showed sphincter dyssynergia to be mediated through pudendal nerves via spinal reflex arcs. Phentolamine effects on bladder activity suggest that blockade of .alpha.-adrenergic receptors inhibits primarily the transmission in vesical and/or pelvic parasympathetic ganglia and acts secondarily through direct depression of the vesical smooth muscle. Neuropharmacological results raise strong doubts as to the existence of a sympathetic innervation of the striated urethral muscle in humans.