Effects of trigeminal tractotomy on facial thermal nociception in the rat.

Wire knife-cuts lesioning the descending trigeminal tract and trigeminal sensory nuclear complex at the level of subnucleus interpolaris significantly elevated response latencies to noxious thermal stimuli applied to one perioral locus of facial skin. Group analyses of four other ipsilateral sites did not reveal significant effects. Medial cuts, extensively damaging the sensory nuclear complex as well as the tract, were more likely to produce significant elevations than were lateral cuts. These results suggest that tractotomy does not result in complete facial analgesia in the rat, and that the effectiveness of tractotomy may in part be due to interruption of intranuclear trigeminal projections.