Projection cells of the superior colliculus to the facial nucleus in the rat Makoto ShinsenjiT he First Department of Anatomy, Nippon Medical School Projection cells of the superior colliculus to the lateral , intermediate or medial subnucleus of the facial nucleus were examined in the Wistar rat by the horseradish peroxidase (HRP) method. As to the size and form of the labeled cells, the following points were commonly observed in all of the experiments : Middle sized cells were far more

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... s than large -sized ones, and only a few were small-sized. Almost all of the labeled cells were multipolar . Vertical cells were slightly more numerous than horizontal cells . As to the distribution pattern of the labeled cells, the following facts were obtained : After HRP injection into the lateral subnucleus, the great majority of labeled cells were found in the rostrolateral part of the stratum griseum intermedium of the contralateral superior colliculus . After HRP injection into the intermediate or medial subnucleus , the labeled cells decreased in number to 20,°6 of the number after HRP injection into the lateral subnucleus . When the intermediate subnucleus received HRP, the great majority of labeled cells were seen in the rostrolateral part of the stratum griseum intermedium of the contralateral superior colliculus . When HRP was injected into the medial subnucleus, the labeled cells were observed sporadically within the central third of the caudal part of the superior colliculus in both sides , and the ipsilateral superior colliculus had slightly more labeled cells than the contralateral one . The labeled cells were localized in the stratum griseum profundum rather than in the stratum griseum intermedium in this case. In this report, the function of the projection cells of the superior colliculus to the facial nucleus was also discussed.