蝾螈椭圆囊毛细胞换能、编码和突触传递的形态学基础

本实验研究椭圆囊毛细胞换能、编码和突触传递的形态和显微力学基础。以幼年蝾螈为对象，光镜和电镜观察椭圆囊囊斑的微细和超微结构。实验结果：（１）只有毛细胞的高静纤毛和动纤毛的头部和耳石膜接触，耳石膜的剪切力由直接和间接两种途径传递至静纤毛；（２）耳石膜和表皮板组成纤毛束上下两端的致密板状结构，皮板下微管起固定和支撑下板作用，在两板之间的无定形物质有缓冲和利于上板滑动的功能，这种安排是纤毛受力后偏曲的基础；（３）囊斑上皮存在着动纤毛排列方向不同的四种毛细胞，感受器依靠这些分布不同的毛细胞群进行信号编码；（４）多根传入神经末梢和１～２ 根传出神经末梢与毛细胞构成传入和传出突触，存在于毛细胞底部胞液内和传出神经末梢内的囊泡是突触传递的物质基础。

MORPHOLOGICAL BASIS FOR TRANSDUCTION,CODING AND SYNAPTIC TRANSMISSION OF HAIR CELL IN THE NEWT UTRICLE

To investigate the morphological basis for transduction, coding and synaptic transmission, the fine structure of the utricular macula in the larva of the Japanese red bellied newt was examined by light and transmission electron microscopy. The utricle is located in a horizontal position at the ventral wall of the otic vesicle. The macula consists of a layer of sensory epithelium and a layer of covering tissue, the otolith membrane. The sensory epithelium contains an array of hair cells and supporting cells interposed. The otolith membrane, which supports the otolith mass, is composed of two layers of fibrillar substance, the dense stained otoconia membrane and the loosely organized supramacular material. Only the heads of the tallest stereocilia and the kinocilum attach the low surface of the otoconia membrane. Shear stress is delivered to the stereocilia through both of direct and indirect ways. The stereocilia bundles are intercalated between two rigid plates, the otoconia membrane and the cuticular plate. The microtubules, which are present in the supranuclear cytoplasm, provide a mechanical support to the cuticular plate. The supramacular material screens the stress transmitted to the stereocilia so that the stereocilia are subjected only to the stress that causes angular deflection of the bundle. Four types of hair cells on which the kinocilia are oriented in different directions are present in the macula. This structural polarization provides a morphological basis for the coding of message. Each hair cell has 5～7 afferent and 1～2 efferent nerve endings which appose to the basal cell membrane directly. Abundant synaptic vesicles are distributed in the basal cytoplasm of the hair cell and the efferent nerve endings. These vesicles contain neurotransmitters which are ready to be released into the synaptic space during transmission. (Figures 1～5 on plate 26)