Brain sites projecting to the spinal nucleus of the bulbocavernosus

Motoneurons of the spinal nucleus of the bulbocavernosus (SNB) occupy a distinct dorsomedial position in the ventral horn of lumbar segments 5 and 6 and innervate sexually dimorphic striated muscles of the rat perineum, including the bulbocavernosus and levator ani. To begin the study of brain influences upon SNB function, we used retrograde tracers to identify brain regions that project to the area of SNB motoneurons. Our findings provide strong evidence that lateral vestibular and several reticular nuclei innervate the SNB. Additional possible afferents include the superior and medial vestibular nuclei, raphe nucleus, red nucleus, interstitial nucleus of the medial longitudinal fasciculus, and paraventricular nucleus.