A novel animal model of underactive bladder: analysis of lower urinary tract function in a rat lumbar canal stenosis model.

AIMS: An animal model of neurogenic underactive bladder (UAB) has not been established. It was reported that a rat lumbar spinal canal stenosis (LCS) model created by cauda equina compression manifested intermittent claudication and allodynia. In this study, we examined the lower urinary tract function of the rat LCS model.

METHODS

One small hole was drilled at the fifth lumbar vertebral arch (sham), and a rectangular piece of silicone rubber was inserted into the L5-L6 epidural space (LCS). Before and after surgery, a metabolic cage study was performed. After surgery, awake cystometry (CMG) and an in vitro muscle strip study were performed. Bladder morphology was evaluated by hematoxylin and eosin staining.

RESULTS

The LCS rats showed a significant decrease in voided volume and a significant increase in postvoid residual volume and residual urine rate compared with Sham rats. CMG showed that the postvoid residual urine volume and numbers of non-voiding contractions significantly increased, while the voided volume, threshold pressure, and maximum intravesical pressure during voiding significantly decreased. There were no significant differences between sham and LCS rats in response to carbachol. In contrast, there was a significant increase in response to field stimulation, especially at lower frequencies, in LCS rats. LCS rats showed no obvious difference in detrusor morphology.

CONCLUSIONS

This rat model requires a relatively simple surgical procedure and has characteristics of neurogenic UAB. It seems to be useful in the pathophysiological elucidation of UAB and might have potential for assessment of pharmacotherapy of UAB.