Topographical representation of the hypoglossal nerve branches and tongue muscles in the hypoglossal nucleus, with special reference to the house musk shrew

Abstract

Representation of hypoglossal nerve branches and tongue muscles was examined in the hypoglossal nucleus of the house musk shrew (Suncus murinus) by the horseradish peroxidase method, and furthermore in the rat, rabbit and dog in order to find out the general organization of the hypoglossal nucleus in mammalian species. In the shrew, the nucleus was roughly divided cytoarchitectonically into dorsal and ventral divisions. The former was further divided into the dorsomedial and dorsolateral subnuclei, and the latter into the ventromedial, intermediate, ventrolateral and ventral subnuclei. The dorsal division mainly supplied the lateral branch of the hypoglossal nerve, and the ventral division the medial branch. The styloglossus and hyoglossus motoneurons were located in the lateral aspect of the dorsolateral subnucleus. The genioglossus and geniohyoid motoneurons were distributed in the dorsolateral aspect of the ventrolateral subnucleus, and in the ventral subnucleus, respectively. Patterns of the representation in the rat, rabbit and dog resembled that in the shrew.