The conduction velocity and segmental distribution of afferent fibers in the rectal nerves of the female rat.

The conduction velocity and segmental distribution of afferent fibers in the rectal nerves of the female rat were determined. These afferent fibers had conduction velocities ranging from 0.5-23.5 m/s (Mode = 0.5 m/s; Median = 1 m/s). Sixty-six percent of the fibers had conduction velocities less than 2.5 m/s and were thus considered to be unmyelinated. Of a total of 135 afferent fibers studied, only 5 (4%) were found in the L6 dorsal root, whereas 130 (96%) were found in the S1 dorsal root. Neuroanatomic tracing studies (Fluoro-Gold applied to the transected rectal nerves) labelled an overwhelming majority of neurons in the S1 dorsal root ganglion, confirming the results of the conduction velocity experiments. Although the conduction velocity distribution of afferent fibers in the rectal nerves is similar to that of the afferent fibers innervating the bladder, the segmental distribution is quite different since most of the bladder afferent fibers (84%) were found in the L6 dorsal root.