Morphological and functional characteristics of motoneurons including facial motoneurons playing in mastication and swallowing.

咀嚼和吞咽是由几种肌肉的一系列收缩组成的。然而，目前尚不清楚控制目标运动神经元的前运动神经元(Premo)是如何调节这些运动的。因此，在这笔赠款的第一年，即2004年，我们试图揭示Premo的位置以及这些Premo与皮质神经元之间的联系。实验动物为成年大鼠。我们发现投射到三叉神经运动核的Premo神经元位于三叉神经口侧核(Vo)，桥侧网状结构中有后指运动神经元和茎舌骨运动神经元，在三叉神经口侧核和网状结构的两部分都有皮质神经元发出轴突终末。在2005年的第二年，我们试图推动2004年的研究，发现有两种Vo神经元同侧投射到闭口运动核和开巴运动核，并且在具有同侧投射的Vo神经元中，一些神经元也投射到对侧的闭合或张开运动核。此外，我们发现Vo神经元接受初级和次级躯体感觉皮质吻部神经元的直接下行投射，并且下行投射是双侧的，对侧占优势。如上所述，本研究成功地产生了吞咽的中枢神经机制的有用信息，并对口腔生物学的进步做出了巨大贡献。

Mastication and swallowing are consisted of a series of contractions of several kinds of muscles. However it is still unclear how premotoneurons (preMo) controlling their target motoneurons are regulated for these movements. Therefore, in the first year, 2004,of this grant, we tried to reveal locations of the preMo and connection between these preMo and the cortical neurons. Adult rats were used. We revealed that preMo projecting to the trigeminal motor nucleus are located in the trigeminal oral (Vo) nucleus, the pontine lateral reticular formation where posterior digastic motoneurons and stylohyoid motoneurons exist, and that there are cortical neurons giving off their axon terminals in the trigeminal oral nucleus and the two parts of the reticular formation.In the second year,2005,of this grant, we tried to promote the study done in 2004,and revealed that there exist two kinds of Vo neurons which project ipsilaterally to either the jaw-closing or -opening motor nucleus, and that, in the Vo neurons with the ipsilateral projection, some neurons also project to the contralateral jaw-closing or -opening motor nucleus. Further, we revealed that the Vo neurons receive direct descending projections from neurons in the rostral part of the primary and secondary somatosensory cortex and that the descending projections are bilateral with a contralateral predominance.As described above, this study succeeded in producing a useful information of the central neuronal mechanisms of the swallowing and in contributing greatly to the progress of oral biology.