c-fos induction in the subnucleus oralis following trigeminal nerve stimulation.

Neurons with c-Fos protein-like immunoreactivity (fos-neurons) were examined in the rostral parts of the brainstem sensory trigeminal nuclear complex following intense electrical stimulation of the trigeminal nerves and noxious mechanical stimulation of the trigeminal receptive fields. Stimulation of all the examined nerves and receptive fields induced some fos-neurons at the medial edge of the subnucleus interpolaris but not in the principal sensory trigeminal nucleus. Stimulation of the primary neurons innervating the intraoral structures but not facial skin induced fos-neurons in the ipsilateral subnucleus oralis. These oralis fos-neurons were located in the dorsomedial nucleus that contained calcitonin gene-related peptide-like immunoreactivity. The oralis fos-neurons are considered to be involved in the processing of intraoral nociceptive signals.