Effects of atropine on bladder capacity and instability in rats with bladder hypertrophy

Abstract

AbstractCystometries were performed in conscious normal rats and in rats with infravesical outflow obstruction in the absence and presence of atropine. The effects were evaluated with regard to bladder capacity, bladder compliance, threshold pressure, micturition volume, residual volume, micturition pressure, and spontaneous contractile activity. In control rats following the administration of atropine, bladder capacity increased in six of seven experiments, but this effect was not statistically significant. No other cystometrical variable was changed in control rats by muscarinic receptor blockade. Bladder capacity in obstructed rats was clearly larger than in control rats (mean 4.4 ± 1.1 and 0.20 ± 0.02 ml, respectively). In obstructed rats atropine significantly increased bladder capacity from 4.4 ± 1.1 to 7.9 ± 1.2 ml. Further, the obstructed rats were characterized by an increase in threshold pressure and residual volume, and a decrease in micturition volume after atropine administration. Micturition pressure in obstructed rats was higher than in control rats (131 ± 29 and 33 ± 6 cm H2O, respectively). In obstructed rats, administration of atropine decreased micturition pressure, indicating a cholinergic component participating in bladder contraction. A clear‐cut bladder instability was observed in all obstructed rats, and part of the contractions remained after atropine, suggesting a myogenic or a noncholinergic nervous origin.