The ultrastructure of two distinct neuron populations in the hypoglossal nucleus of the rat

Timothy B. Boone, L. D. Aldes

Research output: Contribution to journalArticle

77 Scopus citations

Abstract

An ultrastructural study of the hypoglossal nucleus (XII) in the rat has revealed two distinct neuronal populations. Hypoglossal motoneurons comprised the largest population of neurons in XII and were identified following injection of horseradish (HRP) into the tongue. Motoneurons were large (25-50 μ), multipolar in shape and distributed throughout XII. The nucleus was large, round and centrally located, and the cytoplasm was characterized by dense lamellar arrays of rough endoplasmic reticulum. In contrast, a second population of small (10-18 μ), round to oval shaped neurons was found restricted to the ventral and dorsolateral regions of XII. The nucleus was markedly invaginated and eccentric, the cytoplasm scant and filled with free ribosomes, and the absence of lamellar arrays of rough endoplasmic reticulum was conspicuous. Neurons of this type were never found to contain HRP reaction product. These results demonstrate that the hypoglossal nucleus does not consist solely of motoneurons, but includes a distinctly separate, presumably non-motoneuronal pool. Arguments are presented in favor of this second neuron population being interneurons. The functional significance of these findings in relation to tongue control is discussed.

Original languageEnglish (US)
Pages (from-to)321-326
Number of pages6
JournalExperimental Brain Research
Volume54
Issue number2
DOIs
StatePublished - Mar 1 1984

Keywords

  • HRP
  • Hypoglossal nucleus
  • Interneuron
  • Motoneuron

ASJC Scopus subject areas

  • Neuroscience(all)

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