Effect of periurethral denervation on smooth muscles of the lower urinary tract

Objective This study was undertaken to determine the effect of periurethral denervation on contractile function of the smooth muscle of the lower urinary tract of the female rat. Study design Periurethral nerve transection or sham operation was performed in 35 young female rats. Contractile function of the bladder dome and base was determined as a function of time after surgery. Statistical analysis was conducted by Student t test. Results Periurethral denervation resulted in impaired contractile responses to electrical field stimulation in the bladder base (nerve-transected 45 ± 11 g/cm2; sham 84 ± 10 g/cm2, P< .05) and dome (nerve-transected 179 ± 16 g/cm2; sham 334 ± 29 g/cm2, P< .05) 2 weeks after nerve transection. The ability to respond to potassium chloride and the muscarinic agonist, carbachol, and the rates of contraction and relaxation, however, remained intact. Baseline phasic contractile activity was increased significantly in bladders from nerve-transected animals. Maximal field-stimulated contractions of the longitudinal urethra smooth muscle were not altered by periurethral denervation (sham 21 ± 6 g/cm2, nerve-transected 19 ± 5 g/cm2, P = .4). Compromised nerve-mediated contractions of the bladder dome and base improved significantly by 21 days. Conclusion Periurethral nerve transection results in transient impairment of neurogenic contractile responses in the bladder base and dome, though the intrinsic ability of the bladder to contract remains intact. This compromised response of the dome, in conjunction with previous results demonstrating impaired urethral smooth muscle relaxation, suggests that transection of periurethral neurons may have complex effects on the entire lower urinary tract.