Neuropeptide Y immunoreactivity is preferentially located in rat lumbar sexually dimorphic nuclei

The distribution of neuropeptide Y-like immunoreactivity (NPY-LI) was examined in the ventral gray lumbar spinal cord of male and female rats. Fibers containing NPY-LI were distributed in a sexually dimorphic manner in three motor nuclei: the male cremaster nucleus (CN), spinal nucleus of the bulbocavernosus (SNB) and the dorsolateral nucleus, pars medialis (mDLN) receive a greater number of fibers with NPY-LI than females. Fibers with NPY-LI had the following ratios: males, mDLN greater than or equal to SNB greater than CN greater than dorsolateral nucleus, pars lateralis (1DLN) greater than remaining lumbar ventral gray horn motoneurons (VGH); females, mDLN greater than or equal to SNB greater than or equal to CN greater than VGH greater than or equal to 1DLN. In addition, a previously undescribed small column of motoneurons, located between mDLN and SNB, is outlined by fibers which contain NPY-LI in both sexes. The role of NPY in lumbar sexually dimorphic nuclei is presently unknown.