Effects of various drugs on bladder function in conscious rats

In the present study, we attempted to evaluate the effects of various intravenous administered drugs, which had been shown to influence bladder function in anesthetized animals, on the cystometrogram in conscious rats placed in a restraining cage. Thiopental, diazepam, baclofen, clonidine and flavoxate, considered to act on the micturition center in the brain stem, hardly increased bladder capacity (time to micturition in cystometrogram) in conscious rats, but morphine, indomethacin and lidocaine, considered to act on the micturition center in the sacral cord or bladder mechanoreceptors, increased it. In a chronic conscious rat, histopathological findings show that the bladder tissue at 2 days after implantation of the catheter to the bladder showed experimental cystitis characterized by severe edema in the submucosa and an increase in prostaglandin E2 content, which is thought to stimulate directly and/or indirectly the capsaicin-sensitive sensory fiber in the afferent branch of the micturition reflex, and there was hyperreflexia characterized by decreases in both bladder capacity and urine volume. In conclusion, cystometrography in conscious rats placed in a restraining cage is thought to be a useful model for evaluating the true effect of a newly developed agent on bladder function.