咀嚼の神経機構

Neural Mechanisms of Mastication

咀嚼はエネルギー摂取の効率を上げ，哺乳類の高い代謝率を支える。咀嚼の運動パターンは，歯根膜感覚や閉口筋筋紡錘感覚をもとに咀嚼の中枢性パターン発生器が形成し，三叉神経上核や顔面神経背側の網様体などに存在するプレモーターニューロンを介して各運動ニューロンに送られる。また新生仔マウスからの摘出脳幹標本では，下顎と舌の協調運動指令は，舌筋運動ニューロンには同側性，顎筋運動ニューロンに交叉性に送られることが明らかとなった。

Abstract

Comminution of food by mastication contributes to an increase in the efficiency of energy intake from food, which supports the high metabolic rate of mammals. The central pattern-generating circuit for mastication produces motor commands for mastication by using sensory information from periodontal mechanoreceptors and muscle spindles in the jaw-closing muscles. The motor commands that are glutamatergic, glycinergic, and GABAergic are transmitted to motoneurons for the jaw, tongue, etc., through premotor neurons that are located in the supratrigeminal region, reticular formation dorsal to the facial nucleus, etc. Our previous studies of N-methyl-D-aspartate-induced fictive suckling using isolated brainstem-spinal cord preparations obtained from neonatal mice revealed that the neuronal network that contributes to the synchronized activity of the jaw and tongue muscles is located in both the right and left sides. The network of either side sends its command to the trigeminal motoneurons mainly via the commissural pathway, while the command is sent to the hypoglossal motoneurons on the same side.