Projections from the caudal spinal trigeminal nucleus to commissural interneurons in the supratrigeminal region: an electron microscope study in the rat.

Electron microscopic double-labeling study in the rat indicated that projection fibers from the caudal spinal trigeminal nucleus (Vc) were distributed ipsilaterally within the supratrigeminal region (STR) capping the trigeminal motor nucleus (Tm) and made synaptic contact with neurons projecting to the contralateral Tm. Nociceptive inputs to the Vc may reflexly control, via interneurons in the STR, the activities of Tm neurons innervating the masticatory, tensor tympani, and/or tensor veli palatine muscles.