Neuromodulation reduces urinary frequency in rats with hydrochloric acid-induced cystitis

Abstract

Objective: To evaluate the effect of sacral neuromodulation on interstitial cystitis (IC) and determine the underlying mechanism of neuromodulation in the treatment of IC. Materials and methods: Twenty Sprague-Dawley rats (body weight 220-250 g) were randomly divided into four equal groups; normal controls, a sham treatment (IC induced by 0.4 mol/L HCl, + saline), a second sham treatment (HCl-induced IC + acetic acid) and a stimulated group (HCl-induced IC + acetic acid, with electrical stimulation). In the last group bilateral electrodes were implanted into the S1 dorsal foramina and electrical stimulation applied for 8 h/day for 3 weeks. Acetic acid was instilled into the bladder to induce c-fos expression. After 3 weeks the rats were perfused with 4% paraformaldehyde, spinal segments dissected out and an immunocytochemical method used to stain the segments for fos protein encoded by c-fos. Results: The mean (SEM) micturition frequency (voids/17 h) in the sham groups increased from 10.8 (2.7) to 23.4 (3.4) 3 weeks after the intravesical instillation of HCl. The micturition frequency in the stimulated group, at 16.2 (2.7), was significantly less than in the sham group (P= 0.04) after electrical stimulation for 3 weeks. There was no significant difference in the mean (SEM) number of fos-positive neurones in the L6 spinal cord segment between the stimulated and the sham + acetic acid group, at 43.6 (9.4) and 35.8 (7.8) cells/section, respectively (P= 0.32). Conclusions: In rats with HCl-induced cystitis, electrical stimulation reduced the micturition frequency, but not by inhibiting afferent c-fibre activity.