Mild brain ischemia produces bladder hyperactivity without brain damage in rats.

INTRODUCTION

The influence of brain ischemia without cerebral infarction on voiding function is unknown. To investigate the effects of a reduction in cerebral blood flow on voiding function, the influence of chronic cerebral hypoperfusion (CH) on bladder activity was examined in rats.

MATERIALS AND

METHODS

CH was induced in each of 11 female Sprague-Dawley rats by anastomosis between the right external jugular vein and the right common carotid artery with partial obstruction of the left common carotid artery. Twelve intact animals comprised a control group. Voided volume per micturition was assessed in a metabolic cage for 24 h on weeks 2, 4, and 8. Eight weeks after the operation, the rats were tested in a hippocampus-related learning paradigm, the Morris water maze. Bladder activity was monitored in 13 rats with continuous infusion cystometrography (CMG) at 2 weeks. After evaluation, the rats' brains were stained by perfusion with 2% 2,3,5-triphenyltetrazolium chloride (TTC).

RESULTS

Voided volume per micturition was significantly reduced and voiding frequency was significantly increased in CH rats 2 weeks after CH as compared to the control group (p < 0.05). Bladder capacity on CMG of CH rats was significantly reduced 14 days after CH as compared to the controls (p < 0.05). Although TTC staining of the CH rat brain did not show cerebral infarction, CH induced impairment of water maze learning.

CONCLUSIONS

These results indicate that mild forebrain ischemia without infarction results in the development of bladder hyperactivity and impairment of memory. Mild brain ischemia with aging may induce bladder overactivity in humans. Further studies of the nervous system related to bladder hyperactivity using this animal model may lead to pharmacological therapy or prevention of bladder overactivity in the aging individual with an unidentified origin of voiding dysfunction.