[Primary trigeminal projection to the brain stem-reticular formation. Experimental study in the rat].

By means of a transauricular approach, the trigeminal ganglion of the rat was lesioned in order to study the presence and distribution of the primary trigeminal afferents to the brain stem reticular formation. We could observe such projections to the reticular formation close to the trigeminal nuclei (lateral part of the n. reticularis ventralis and dorsalis, n. reticularis parvocellularis, reticular zone between the trigeminal n. principalis and the n. motorius trigemini) and also to the reticular formation more medially situated (medial part of the n. reticularis dorsalis and ventralis, n. reticularis gigantocellularis and n. reticularis pontis caudalis). Topographically, those projections correlated fair well with the extent of the trigeminal nuclei more related with sensorial transmission (n. principalis and subnuclei oralis and caudalis), specially the most medial of them. Moreover, although in a very much lesser intensity, we could see projections on the nuclei pallidus and magnus of the raphe system, and on the caudodorsal part of the central grey matter. The possible modulatory actions on the sensorial transmission and motor coordination of those projections are discussed.