Reticulo-facial enkephalinergic pathway in the rat: an experimental immunohistochemical study.

Enkephalins have been detected in the cranial motor nuclei and may play a role in the motor system. The afferent source of leucine-enkephalin-like immunoreactive fibers in the facial nucleus was investigated using experimental immunohistochemistry. These leucine-enkephalin-containing fibers were markedly reduced on the operated side after the destruction of the ventrolateral part of the caudal medullary reticular formation, where a number of leucine-enkephalin-positive cell bodies were observed. This fact strongly suggests that these leucine-enkephalin-positive cells project ipsilaterally to the facial nucleus and so could have some effects on facial motoneurons.