Functional and molecular characterisation of the bilateral pelvic nerve crush injury rat model for neurogenic detrusor underactivity.

Abstract

To create a rat model for neurogenic detrusor underactivity (DU) by bilateral pelvic nerve crush injury (BPNI) and to study temporal changes in detrusor contractility and morphology. Male Sprague-Dawley rats were subjected to BPNI or sham surgery and evaluated at 1, 3 and 9weeks after surgery. Bladder function was determined invivo by awake cystometry, micturition pattern analysis, and 24-h urine collection. Bladders were harvested for invitro pharmacological investigation by isometric tension recording. Bladders and major pelvic ganglia were investigated by quantitative reverse transcription-polymerasechain reaction and histochemistry. Overflow incontinence was observed at 1week after BPNI. At 3 and 9weeks after BPNI, rats showed a bladder phenotype characteristic for DU with increased post-void residual urine volumes, reduced voiding efficiencies, and lower maximum pressures. In isolated bladder strips, contractile responses to KCl, carbachol, and α,β-methylene adenosine 5'-triphosphate (α,β-mATP) were preserved. On the other hand, neural-induced contractility was reduced after BPNI, in line with reduced expression of protein gene product 9.5 and choline acetyltransferase in the major pelvic ganglion at 1week after BPNI. The bladder-to-body weight ratio and detrusor thickness increased after BPNI, indicating detrusor hypertrophy to compensate for the reduced neural input. BPNI induces a rat model for neurogenic DU. In this model, the detrusor maintains its contractility but denervation of the detrusor was observed.