The mesencephalic trigeminal nucleus receives proprioceptive sensory afferent of the trigeminal nerve from the jaw-closing muscle spindles and Ruffini nerve ending of the periodontal ligaments, and also send their axons to the motor trigeminal nucleus. Also in recent years, elucidation of glial cell-neuron network advances, the fact that the glia cells in the hippocampus and the cerebellum have responded variously in neural network has been shown. But, detailed research concerning the distribution and role of the glia cells in the brain stem such as the pons and the medulla has not been shown. The aim of this study was to investigate the distribution of the glia cell in the mesencephalic trigeminal nucleus. In this study, we used two types of the glial marker, glial fibrillary acidic protein (GFAP) and NG2 (maker of NG2 glia (expression of NG2 proteoglycan on their surface)). As a result, GFAP and NG2 immunoreactivity was observed in many regions of the brain stem including the mesencephalic trigeminal nucleus. They made contacts with mesencephalic trigeminal nucleus neuronal cell body on the same focal place. Thus, these results suggest possibility the GFAP or NG2 positive cells in the mesencephalic trigeminal nucleus participate in the jaw-jerk reflex and the periodontal-masseteric reflex.