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，目前还不清楚前运动神经元（preMo）控制其目标运动神经元是如何调节这些运动。因此，在2004年的第一年，我们试图揭示前Mo的位置以及这些前Mo和皮层神经元之间的联系。使用成年大鼠。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核（Vo），即存在后消化运动神经元和茎突舌骨肌运动神经元的脑桥外侧网状结构，在三叉神经口核和网状结构的两个部分都有皮质神经元发出轴突终末。我们在2004年的研究基础上，发现在同侧存在两种投射到闭颌运动核或开颌运动核的Vo神经元，在投射到同侧的Vo神经元中，也有投射到对侧的闭颌运动核或开颌运动核的神经元。此外，我们还发现Vo神经元接受初级和次级躯体感觉皮层吻侧部分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有用的信息，吞咽的中枢神经元机制，并在口腔生物学的进步作出了巨大贡献。

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.