Localization of trigeminal sensory innervation to the tongue and pharynx of the cat using horseradish peroxidase as tracer.

Trigeminal sensory innervation to the tongue and pharynx was investigated in the cat, using horseradish peroxidase (HRP) as a retrograde tracer. Following HRP application to the tongue, cells were labeled primarily in the posterolateral portion of the trigeminal ganglion. The pharynx was divided according to classical methodology into three regions: the epipharynx (nasopharynx), mesopharynx (oropharynx), and hypopharynx. When HRP was applied to the epipharynx and mesopharynx, HRP-labeled cells were found in the anteromedial and posterolateral portions of the trigeminal nerve, respectively. When HRP was applied to the hypopharynx, a single labeled cell was found in the trigeminal ganglion. These results indicate that trigeminal sensory nerve fibers in the cat branch to the tongue, epipharynx, and mesopharynx, but rarely to the hypopharynx.