ORIGIN OF THE GLYCINERGIC INNERVATION OF THE RAT TRIGEMINAL MOTOR NUCLEUS

In order to determine the localization of the glycinergic neurones res ponsible for the hyperpolarization of the rat trigeminal motoneurones during paradoxical sleep, we developed a new double immunohistochemica l method combining the b subunit of the cholera toxin (CTb), a very se nsitive retrograde tracer, with glycine immunohistochemistry. After io ntophoretic injections of CTb into the trigeminal motor nucleus (Mo5), a large number of double-labelled cells was observed bilaterally in t he parvocellular reticular nucleus alpha, dorsolateral to the descendi ng branch of the facial nerve. A moderate number of double-labelled ne urones was found in the ipsilateral parvocellular reticular nucleus at the level of the facial nucleus, and bilaterally in the raphe magnus and the gigantocellular reticular alpha nuclei. These results suggest that the glycinergic neurones hyperpolarizing the trigeminal motoneuro ns during paradoxical sleep might be localized in the parvocellular re ticular nucleus alpha.