study on the development, aging and the regulation factors of the maintenance of the masticatory organs

咀嚼器官的发育、衰老和维持涉及多种因素。在本研究中，我们研究了由于牙齿脱落导致的牙周韧带感觉末梢的感觉输入缺失以及性激素对三叉神经运动核（Mo5）的影响。此外，我们还研究了咬肌和三叉神经运动神经元中雌激素和/或雄激素受体的出生后外观。缺乏来自感觉末梢的感觉输入导致支配咬肌的Mo5神经元数量减少。在发育中的小鼠咬肌中，我们观察到小鼠出生后第5天的免疫反应核阳性。免疫反应性无性别差异。在Mo5中，分别在出生后第5天和第20天检测到雌激素和雄激素受体特异性免疫反应阳性。给雌性小鼠注射5a-二氢睾酮使M05运动神经元的数量增加到雄性比例。相比之下，在雄性小鼠中，用17β-雌激素治疗，运动神经元数量下降到雌性小鼠的典型水平。雄激素拮抗剂醋酸环丙孕酮（cyproterone acetate）可显著降低未成熟雄性小鼠Mo5中运动神经元的数量。Me5中的感觉神经元不受任何治疗的影响。由此可见，雄性激素和雌性激素参与了出生后Mo5运动神经元数量的变化，而不参与Me5数量的变化。

The various factors are involved in the development, aging and maintaenance of the masticatory organs. In the present study, we investigated effects of the lack of the sensory input from the sensory endings in the periodontal ligament, resulted from tooth loss , and those of sex hormones on the trigeminal motor nucleus (Mo5) . Moreover, we studied the postnatal appearance of the oestrogen and/or androgen receptors in the masseter muscle and trigeminal motor nuerones.The lack of the sensory input from the sensory endings caused decrease in the number of Mo5 neurones that innervate the masseter muscle. In the masseter muscle of developing mice, we observed the positive immunoreactive nuclei by the 5th postnatal day in mice. No sex difference in the immunoreactivity was detected. In the Mo5, positive immunoreactivities specific for estrogen and androgen receptors were detected on the 5th and 20th postnatal days, respectively.Administration of 5a-dihydrotestosterone to female mice increased the number of motoneurones in the M05 to masculine proportions. By contrast, in male mice , treated with 17β-oestrogen, motoneurone numbers decreased to levels more typical of females. Treatment of cyproterone acetate , an androgen antagonist, significantly decreased the number of motoneurones in the Mo5 of immature male mice . Sensory neurones in the Me5 were unaffected by any of the treatment. Thus, androgenic and oestrogenic hormones are involved in the postnatal changes in motoneurone numbers of the Mo5, but not in the number of the Me5.