Topographical Representation of Motoneurons in Carnivora Lower Brainstem

用辣根过氧化物酶(HRP)逆行法研究了家麝鼠三叉神经支配肌肉运动神经元的分布。在细胞构筑学上，三叉神经运动核(TMN)大致分为大的背外侧区，遍布整个吻尾水平，小的腹内侧区位于其尾侧的一半。在背外侧区，翼外肌运动神经元分布于背、中、腹侧，翼外肌运动神经元与腭帆张肌运动神经元在内侧部几乎重叠，仅存在于核的吻侧半部。前二腹肌运动神经元和舌骨前运动神经元分别位于腹内侧部的背侧部和腹侧部。鼓膜张量运动神经元定位于靠近外侧丘系腹外侧核的网状结构。此外，还测量了HRP标记神经元的数目和大小，并在解剖显微镜下用盐酸咀嚼肌肉来计数每条肌肉的肌纤维数量。颞肌平均肌纤维数与标记运动神经元的比值为322，其中咬肌336个，翼内肌106个，翼外肌78个，前二腹肌136个，舌骨42个，腭帆张肌29个，鼓室张肌3个。

In the house musk shrew (insectivore), distribution of motoneurons of the trigeminal nerve innervating muscles was examined by a retrograde horseradish peroxidase (HRP) method. Cytoarchitectonically, the trigeminal motor nucleus (TMN) of the shrew was roughly divided into the large dorsolateral division throughout a whole rostrocaudal level of the nucleus, and small ventromedial divisions being in a caudal half of that. In the dorsolateral division, motoneurons of the temporal, masseter and medial pterygoid muscles were localized in dorsal, intermediate and ventral parts, respectively, and distribution are a of the lateral pterygoid and tensor veli palatini motoneurons were almost overlapped each other in the medial part which existed only at a rostral half of the nucleus. The anterior digastric and mylohyoid motoneurons situated respectively in the dorsal and ventral parts of the ventromedial division. The tensor tympani motoneurons was localized in the reticular formation near the lateral lemniscus ventrolateral to the nucleus. Additionaly, number and size of labeled neuron with HRP were measured, and number of muscle-fibers of each muscle was also counted by mascerarating muscle using hydrochloride under a dissection microscope. Ratio of mean muscle-fiber number to a labeled motoneuron of the temporal muscle was 322, masseter 336, medial pterygoid 106, lateral pterygoid 78, anterior digastric 136, mylohyoid 42, tensor veli palatini 29, tensor tympani 3.