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KMID : 1235920100020020068
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Medical Journal of Catholoc University of Daegu
2010 Volume.2 No. 2 p.68 ~ p.73
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Fine Structure and Synaptic Organization of the Genioglossus Motoneurons in the Rat
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Moon Yong-Suk
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Abstract
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Purpose: The hypoglossal nucleus is composed of many motoneurons that innervates the intrinsic and the extrinsic tongue muscles. The genioglossus muscle as an one of the extrinsic tongue muscles plays an important role in maintaining upper airway patency during inspiration.
Materials and Methods: We retrogradely labeled these neurons by injection of horseradish peroxidase (HRP) into the genioglossus muscle and investigated fine structure and synaptic organization of these neurons in the rat.
Results: Almost all genioglossus motoneurons had the appearance of α-motoneurons, i.e., large, oval or polygonal cells containing well developed organelles, Nissl bodies, and a prominent spherical nucleus. More than 65% of the somatic membrane was covered with terminals. More than half of the axosomatic terminals (53.5%) contained round vesicles and made asymmetric synaptic contacts (Gray’ type I), while 46.5% of them contained oval and pleomorphic vesicles and made symmetric synaptic contacts (Gray’ type II) with the genioglossus motoneurons. A few Cterminals were present on the genioglossus motoneurons. About 67.0% of the axodendritic terminals were Gray’ type I, while 33.0% of them were Gray’ type II in the genioglossus motoneurons. The percentage of synaptic covering of Gray’s type I erminals increased from soma to dendrite, while Gray’s type II terminals decreased in dendrite.
Conclusion: These results indicate that the genioglossus motoneurons in the hypoglossal nucleus have different synaptic organization in soma and dendrites.
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KEYWORD
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Genioglossus motoneuron, Horseradish peroxidase, Gray’s type I terminal, Gray’s type II terminal
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