Further studies on mechanisms regulating the voiding cycle of the rat urinary bladder.

1. The effect of transection of pudendal or hypogastric nerves and of various pharmacological pretreatments on the bladder voiding cycle elicited by saline filling was investigated in urethane-anesthetized rats. 2. Sectioning of pudendal nerves reduced efficiency of the expulsive phase of the voiding cycle while sectioning of hypogastric nerves enhanced voiding efficiency and reduced residual volume. 3. An increased voiding efficiency was also observed in 6-hydroxydopamine-treated rats. 4. Atropine and physostigmine decreased and increased voiding efficiency, respectively. Indomethacin pretreatment produced a marked increase in residual volume. 5. These findings indicate that the autonomic innervation of the bladder and urethra as well as production of local factors such as prostanoids regulates not only the collecting phase of the cystometragram but also influence markedly voiding efficiency.