Urethral compensatory mechanisms to maintain urinary continence after pudendal nerve injury in female rats

Introduction and hypothesis This study was conducted to investigate the urethral compensatory mechanisms to maintain urinary continence after pudendal nerve injury. Methods In naive, acute pudendal nerve transection (PNT) and 4 weeks after PNT (PNT-4w) female rats, leak point pressures (LPPs) during bladder compression were measured before and after the application of hexamethonium (C6), propranolol, and N-omega-nitro-L-arginine-methyl ester (L-NAME), or terazosin and atropine. Responses to carbachol and phenylephrine of proximal and middle urethral muscle strips from naive and PNT-4w rats were also examined. Results LPPs were significantly decreased in PNT rats but not in PNT-4w rats. LPPs in PNT rats were significantly increased by C6 or L-NAME while LPPs in PNT-4w rats were significantly decreased by C6, or terazosin and atropine. Excitatory responses to carbachol and phenylephrine in the proximal urethral muscle were significantly larger in PNT-4w rats. Conclusions These results suggest that alpha(1)-adrenoceptor and muscarinic receptor-mediated contractility is upregulated in the proximal urethra 4 weeks after PNT.