A quantitative analysis of the afferent and extrinsic efferent innervation of specific regions of the bladder and urethra in the cat

Using the fluorescent tracer dyes bisbenzimide, nuclear yellow and fast blue, the possibility of differential innervation of various regions of the bladder and urethra was tested in cats. The dyes were injected into the lateral detrusor, bladder base, and urethra. Fluorescent cell bodies were counted in serial 48 μm sections of dorsal root, inferior mesenteric, sympathetic chain and pelvic plexus ganglia. Several dorsal root ganglia, primarily S₂, were the principal source of afferent innervation to all locations injected. The bladder and urethra received significant efferent innervation from both the inferior mesenteric ganglia and sympathetic chain ganglia (particularly L₇ to S₂) however, pelvic plexus ganglia made only small contribution to the innervation of these areas. The sympathetic chain and inferior mesenteric ganglia contributed equally to the innervation of the detrusor and bladder base but the sympathetic chain made double the contribution of the inferior mesenteric ganglia to the innervation of the urethra. There was a very low incidence (<1%) of neurons which projected to more than one injection site.