SPINAL CORD ORGANIZATION OF MICTURITION REFLEX AFFERENTS

A coordinated micturition reflex capable of total evacuation of intravesical content has previously been demonstrated in the cat by cystometry to be dependent upon a complex arrangement of pelvic visceral and somatic afferent input to brain stem and spinal cord. By electrical stimulation of detrusor muscle afferents and the portion of pudendal nerve supplying the external urinary sphincter and recording of pelvic detrusor motor nerve responses the routing of these impulses was documented in the decerebrate and spinal cat. Pelvic detrusor muscle afferents evoked long-latency, long-duration responses in pelvic motor nerves in the decerebrate cat. These responses have been suggested by Shimamura as relaying via spino-bulbo-spinal pathways. Somatic afferents in the pudendal nerve relayed to pelvic detrusor motor nerve efferents by both propiospinal and spino-bulbo-spinal pathways. There was extensive contralateral crossing of both visceral and somatic afferent inputs. Crossing of visceral afferents was demonstrable in the decerebrate cat, whereas, somatic afferent crossing was demonstrable in the decerebrate and spinal animal. The evidence was consistent with proposal that micturition is a brain-stem reflex with final common pathway in caudal brain stem. Depression of the micturition reflex was displayed by antidromic stimulation of the pelvic detrusor motor nerve fibers and was evident contralaterally and ipsilaterally. This response may contribute to the development of local sign in organization of afferent input. © 1968.