Motor innervation of the mole and shrew snout muscles by means of horseradish peroxidase technique.

The axonal transport method of the horseradish peroxidase (HRP) was used for defining the anatomical background of the snout movements in 54 Japanese shrew-moles, Urotrichus talpoides, 4 Temminck's moles, Mogera wogura, and 21 big-clawed shrews, Sorex unguiculatus. Either snout muscle or proximal stump of the facial nerve on one side was exposed to HRP. The results obtained from this experimental study were as follows: HRP-containing cells were found either ipsilaterally or bilaterally in the facial motor nucleus in both the moles and shrews. The HRP-containing cells were grouped into 4 subnuclei: ventrolateral, ventromedial, dorsal and accessory. In case of the snout muscle being exposed to the HRP were the HRP-containing cells found in the ventral groups. A HRP-positive fiber bundle was found at the genu of the facial motor root extending toward the median raphe, when the proximal stump of the facial nerve was exposed to the HRP.