Central Distribution and Efferent origins of facial nerve branches in the chicken

Abstract

The central afferent distribution and the origins of visceromotor and somatomotor components of greater superficial petrosal (GSP), chorda tympani (CT), and hyomandibular (Hy) branches of the facial nerve were analyzed by the transganglionic and retrograde transport of horseradish peroxidase. Labelled sensory afferent fascicles of the GSP collected dorsomedial to the spinal trigeminal complex and passed caudally as the tractus solitarius. Fine-grain terminal fields were evident in ipsilateral n. sensorius n. facialis, nuclei ventrolateralis anterior (Vla), centralis anterior and presulcalis anterior of the solitary complex, and n. glossopharyngei et n. motorius dorsalis nervi vagi (n. IX–X). Minor contralateral projections to these nuclei occasionally were observed. CT sensory afferents exhibited similar ipsilateral projections, and specifically, the projection to Vla was qualitatively sparser than that from the GSP. Small multipolar and spindle-shaped somata of visceromotor n. salivatorius were labelled retro-gradely from the GSP and CT. Large, oval somatomotor cells of the three subdivisions of the facial motor nucleus were labelled retrogradely from Hy, with no evidence of sensory afferent or visceromotor connections.