Effect of bilateral sacral decentralization on detrusor contractility and passive properties in dog

Abstract

AbstractA series of five dogs underwent complete parasympathetic decentralization through a lumbosacral laminectomy. A full‐thickness biopsy was taken from the anterior wall of the bladder before and 12 weeks after surgery. Both mucosa and adventitia were dissected out and muscle layer was cut into several consecutive longitudinal strips. Each strip was mounted in a muscle chamber and frequencyresponse curves were obtained at different pulse duration. Activelpassive force‐length relationships were then obtained under condi tions of maximal electrical stimulation (100 V, 2 msec, 40 cps), by stretching the strips in successive increments until length of maximal active force development was reached. Curves were normalized per unit cross‐sectional area of muscle. The maximum active stress of the specimens was taken as a measure of bladder contractility, and the rate of exponential increase in passive stress with strain (ratio of deformed to undeformed length) as a measure of detrusor stiffness.Twelve weeks after detrusor decentralization the following changes were found: (1) The frequency that yielded maximum contraction was 10 cps at 2‐ and 5‐;msec pulse duration as compared to 40 cps in controls at every pulse duration. (2) The maximum active stress was 123.9 ± 13.8 vs 244.7 ± 24.7 gm/cm2 in controls (p<.001). (3) The level of strain corresponding to the maximal active stress was significantly reduced. (4) The stiffness of the bladder wall was markedly increased; the rate of exponential increase was 4.47 ± 0.63 vs 2.19 ± 0.42 in controls (p<.001). (5) Thickness of the bladder wall was significantly increased (7 ± 1 vs 4 ± 1 mm; p<.001). (6) Histology sections of the specimens demonstrated collagen infiltration in all layers as well as smooth muscle hyperplasia.In summary, the effects of parasympathetic decentralization of the bladder wall are collagen infiltration, increased thickness, increased stiffness, and decreased contractility.