Number, size, and regional distribution of motor neurons in the dorsolateral and retrodorsolateral nuclei as a function of sex and neonatal stimulation.

Motor neurons were measured in the retrodorsolateral nucleus (RDLN) and the dorsolateral nucleus (DLN) of adult male and female rats that were reared with normal or reduced levels of maternal anogenital stimulation. In contrast with findings for the spinal nucleus of the bulbocavernosus, which is located in the same spinal segments, reduced stimulation had no effect on neuron number in either nucleus. However, several regional and sex differences were observed. Rostrally located neurons were larger in both the RDLN and the DLN; these location effects were greater in females. There was no sex difference in RDLN neuron size, but DLN neurons were larger in females, particularly in the rostral region. Females had significantly more cells in the RDLN, a nucleus previously considered nondimorphic, whereas males had more DLN neurons. Both regional and sex differences may reflect local differences in trophic factors from targets or afferents.