Facial nerve injury induces facilitation of responses in both trigeminal and facial nuclei of rat.

A study was made of the effects of facial nerve transection on trigeminal stimulation- evoked field potentials in the principal trigeminal (Pr5) and facial nuclei (7) in rats. Although the transected branch of the facial nerve contains pure motoric efferents, it resulted in enhanced responses in both Pr5 and 7. These electrophysiological results suggest a functional circuitry involving the whiskers, trigeminal nerve, Pr5 and 7 and the facial nerve as efferent. The disconnection (opening) of this loop results in enhanced responsiveness of the neurons in both Pr5 and 7.