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

应用电生理和形态学技术研究了大鼠口旁器功能与结构的发育关系。对于功能分析，持续放电的斜坡和保持拉伸反应记录从10天至10周的Wistar大鼠分离的近口器官。10-12日龄的动物的所有感觉单位在牵拉的动态阶段结束时只显示短暂的放电。持续放电的近口器官的拉伸的阈值幅度显着下降之间的10天和3周达到成人值在5周龄。另一方面，静态敏感性在出生后2 - 4周显著增加，电镜检查显示出生后2 - 4周由于外囊的完成而引起囊腔明显扩张。此外，在1至4周龄之间，年龄依赖性增加观察到的数量preterminal分支的感觉单位，在大小的静脉曲张样sediment沿着的终端轴突，并在密度的胶原蛋白和弹性纤维的核心结构周围。免疫组织化学研究显示内外囊之间的囊隙含有透明质酸离子。当用透明质酸酶处理去除囊腔中的透明质酸离子时，器官的持续放电消失。结果表明，口旁器囊腔内带负电荷的透明质酸离子使感觉终末膜去极化，使该器官兴奋性增强。

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.