Direct contacts between glossopharyngeal afferent terminals and hypoglossal motoneurons revealed by double labeling with cobaltic-lysine and horseradish peroxidase in the Japanese toad.

Glossopharyngeal (IX) afferents and hypoglossal (XII) motoneurons of the Japanese toad were simultaneously labeled with cobaltic-lysine and horseradish peroxidase, respectively. Some of the terminal branches of the IX afferents had direct contacts with the dorsal dendrites, the lateral dendrites and the somata of the XII motoneurons, but not with the medial dendrites. Such direct contacts mainly occurred in the rostral region of the dorsomedial XII nucleus, where tongue-retractor motoneurons predominate, but not in the caudal region nor in the ventrolateral XII nucleus.