[Afferent projections to the uvula in the cat. II. Mossy fiber projections]

The mossy fiber projections to the uvula of the cerebellum were studied by means of retrograde axonal transport of horseradish peroxidase (HRP) in the cat. Following large and small injections into the uvula, distribution of the labeled cells in the brainstem nuclei was investigated. The results showed different afferent projections between the dorsal and ventral uvula. Major sources projecting to the dorsal uvula were the peduncular, paramedian, and lateral nuclei of the pontine nuclei. Labeled cells found in the pontine nuclei amounted to 81.6% of the total number of labeled cells in cat 1. On the other hand, major sources projecting to the ventral uvula were the caudal aspect of the medial and inferior vestibular nuclei, the x- and f-groups of the vestibular nuclei, the dorsal and central aspect of the superior vestibular nucleus, the rostral dorsomedial aspect of the paramedian nucleus of the pontine nuclei, the caudal aspect of the prepositus hypoglossal nucleus, and the infratrigeminal nucleus. Labeled cells in the vestibular nuclei amounted to 72.1% of the total number of the labeled cells in the cat 40. It was revealed that the lateral aspect of the ventral uvula receives inputs from the pontine nuclei, whereas the medial part of the ventral uvula receives inputs from the vestibular nuclei. Mediolateral differences were not found in the dorsal uvula. These mossy fiber zones were mediolaterally wide, and the dorsal uvula was different from the ventral uvula with regard to mossy fiber projection.