Inhibitory interactions between colonic and vesical afferents in the micturition reflex of the cat.

1. In anaesthetized cats in which the only intact autonomic pathways innervating the colon and bladder were in the pelvis nerves, distension of the colon resulted in a graded inhibition of spontaneous bladder motility, and a decrease in the reflexly evoked waves of activity in the vesical branches of the pelvic nerves. 2. Electrical stimulation with voltages sufficient to excite only the myelinated fibres in the colonic branches of the pelvic nerve caused inhibition of spontaneous bladder motility, an increase in micturition threshold, and a reduction in the reflexly evoked waves of activity in the vesical efferents of the pelvic nerve. 3. The results demonstrate that the pelvic nerve afferent inflow from the colon produces a marked central inhibitory influence on the micturition reflex.