Recovery of food intake and change in the arrangement of the bilateral hypoglossal

2001 Fiscal Year Final Research Report Summary

• Project/Area Number: 11672019
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Surgical dentistry
• Research Institution: Nihon-University
• Principal Investigator: HORI Minoru Nihon-University, School of Dentistry, Lecturer, 歯学部, 講師 (60096899)
• Co-Investigator(Kenkyū-buntansha): ISHII Teruhiko Nihon-University, School of Dentistry, Research Assistant, 歯学部, 助手 (40267092) ; IWANARI Shinkichi Nihon-University, School of Dentistry, Research Assistant, 歯学部, 助手 (30168588) ; TANAKA Hiroshi Nihon-University, School of Dentistry, Professor, 歯学部, 教授 (30059555) ; HIRABA Hisao Nihon-University, School of Dentistry, Lecturer, 歯学部, 講師 (00156689)
• Project Period (FY): 1999 – 2001
• Keywords: severance of the hypergrossal nerve / masticatoryr muscles / genioglossus muscles / fluoresent dye / EMGs / hypergrossal nerve nuclei / trigeminal motor nuclei / cats

Research Abstract

We have studied changes in orofacial behavior and the arrangement of both hypoglossal nuclei after severance of the medial branch of the unilateral hypoglossal nerve. After the head holder surjery and training, the nerve was cut, and the resulting effects on food intake and changes in orofacial behavior were examined for about one month. After the cut, the cats' tongue deviated toward the cut side during tongue protrusion, and this tongue deviation did not recover throughout the experiment. Although food intake decreased up to 20% because of a drop of food, it recovered to 80% by about 10 days after nerve-cutting. Although the EMG activities of both sides of the genioglossus, masseter and the anterior digastric muscles fluctuated for about one month after severance, their mastication became well balanced thereafter in spite of the different activities in both sides.
In order to examine changes in the arrangement of both of the hypoglossal nerve and trigeminal motor nuclei at one month after severance, the two kinds of fluorescent dye (10% Evans blue, EB) and 3% Fast blue, FB) were injected into the bilateral genioglossus, masseter and anterior digastric muscles using syringes (0.15 ml in each). Injection of FB and EB into the bilateral genioglossus muscles in normal eats revealed cells positively stained with each dye in the hypoglossal nuclei. However, in cats one month after nerve-cutting, fluorescent dye injected into the genioglossus muscle on the cut side was observed in the hypoglossal nucleus on the opposite side. On the other hand, the arrangement of the trigeminal motor nuclei remained in normal.
These findings suggest that the impaired food intake and the change in balance between the genioglossus muscles on the cut and opposite sides during mastication may be compensated by reconstruction of the peripheral nerves on the uncut side.