Trigeminal primary afferents project bilaterally to dorsal horn and ipsilaterally to cerebellum, reticular formation, and cuneate, solitary, supratrigeminal and vagal nuclei

Horseradish peroxidase (HRP) applied to the transected mandibular division of the trigeminal ganglion was transported anterogradely to previously well known primary afferent terminal zones in the dorsal brainstem trigeminal nuclear complex of the rat, and retrogradely to cell bodies in the trigeminal motor, supratrigeminal and mesencephalic nuclei. Primary trigeminal afferents were also visible in the ipsilateral cerebellar cortex and paraflocculus, and the dentate, cuneate, solitary, supratrigeminal, and dorsal motor vagal nuclei, parvicellular reticular formation, area postrema, and C1–C6 dorsal horn. The contralateral medulla and cervical dorsal horn were also innervated by primary afferents which crossed in the posterior commissure. These projections were also labeled when HRP was applied to individual sensory branches of the mandibular nerve.