Postnatal development of the juxtaoral organ as a muscle receptor of masticatory muscles

用电生理和形态技术研究了大鼠口旁器官功能和结构的发育关系。为了进行功能分析，从10天到10周的Wistar大鼠分离的口旁器官记录了对坡道和保持伸展的持续放电。10-12日龄动物的所有感觉单位在伸展动态期结束时仅表现为短暂的放电。在10天至3周期间，口旁器官伸展持续放电的阈值幅度显着下降，在5周龄时达到成人值。另一方面，静态敏感性在出生后2~4周显著增加，电子显微镜检查显示，出生后2~4周，由于外囊的完成，囊腔明显扩张。此外，在1-4周龄，感觉单位的终末前分支的数量、沿着末梢轴突的静脉曲张样肿胀的大小以及核心结构周围的胶原和弹性纤维的密度都随着年龄的增长而增加。免疫组织化学研究表明，内囊和外囊之间的包膜间隙含有透明质酸根离子。用透明质酸酶去除囊腔内的透明质酸离子时，该器官的持续放电消失。在浴液中加入6 mM-KCl，可再次出现持续放电，提示口旁器官囊腔内带负电荷的透明质酸离子参与了感觉终末膜的去极化，从而增加了该器官的兴奋性。

The developmental relationship between function and structure of the juxtaoral organ in rats was investigated using the electrophysiological and morphological techniques. For functional analysis, sustained discharges in response to ramp-and-hold stretches were recorded from the juxtaoral organs isolated from Wistar rats aged 10 days to 10 weeks. All sensory units of the animals of 10-12 days old showed nothing but brief discharges at the end of the dynamic phase of stretch. The threshold amplitude of stretch of the juxtaoral organ for a sustained discharge fell significantly between 10 days and 3 weeks reaching adult values at 5 weeks of age. On the other hand, the static sensitivity increased conspicuously between 2 and 4 weeks after birth.Electron microscopic examination revealed a conspicuous expansion of the capsular space caused by completion of the outer capsule between 2 and 4 weeks after birth. Moreover, between 1 and 4 weeks of age, age-dependent increases were observed in the number of preterminal branches in a sensory unit, in the size of the varicose-like swellings along the terminal axon, and in the density of collagen and elastic fibers around the core structure. Immunohistochemical investigation showed that the capsular space between inner and outer capsules contained hyaluronate ions. When hyaluronate ions in the capsular space were removed with a treatment of hyaluronidase, the sustained discharge of the organ was disappeared. The sustained discharge was appeared again by addition of 6 mM-KCl in the bathing solution.These results suggested that the negatively charged hyaluronate ions in the capsular space of the juxtaoral organ contributed to the depolarization of sensory terminal membranes resulting in an increase in the excitability of this organ.