Mechano-electric transduction and dynamics of cytoskeletons in mechanoreceptor cells

众所周知，昆虫的机械感受器有三种类型，它们在结构和形态上彼此不同。本研究利用电子显微镜快速冷冻技术研究了三种昆虫机械感受器的机电转导形态学基础。1)研究了蟑螂触角、果蝇和蝗虫股骨的声带器官结构。它们的感觉纤毛与运动纤毛有一定的相似性，纤毛细长，具有轴突臂。机械刺激纤毛与未刺激纤毛的形态学比较表明，感觉纤毛的主动搏动或被动摆动可能参与了机械-电转导。2)对蟑螂触角和果蝇触角的钟形感受器结构进行了研究。它们的感觉纤毛的特点是远端有管状体，被称为一束微管。速冻标本的观察表明，肌动蛋白丝出现在管状体的微管之间。这两种纤维的规则排列可能构成了钟形感受器机电转导的形态学基础。这种细胞骨架的解聚导致受体敏感性的降低。3)对蝗虫翅膀拉伸受体的结构进行了研究。拉伸受体的细胞体很大（可达50 μ m），并延伸出许多树突，这些树突必须是受体的位置。肌动蛋白丝密集分布于树突区。4)本研究数据表明，三种昆虫机械感受器都有其特定的机电转导初级过程，这与受体区细胞骨架的特定组织密切相关。

It is widely known that there are three types of mechanoreceptors in insects, which structurally and morphologically differ from each other. In the present study morphological basis of mechano-electric transduction has been examined in the three types of insect mechanoreceptors by means of rapid freezing techniques for electron microscopy.1) The structure of the chordotonal organ was examined in cockroach antennae, Drosophila halteres, and locust femurs. Their sensory cilia show some similarity to motile cilia, being thin and long and possessing axoneme with dyenin arms. Morphological comparison between mechanically stimulated cilia and un-stimulated ones suggests that active stroke or passive waving of the sensory cilia may be involved in the mechano-electric transduction.2) The structure of the campaniform sensillum was examined in cockroach antennae and Drosophila halteres. Their sensory cilia are characterized by the tubular body in the distal tip, which is known as a bundle of microtubules. The observation of rapid frozen specimens revealed that actin filaments occur among microtubules in the tubular body. Regular arrangement of the two types of filaments may comprise morphological basis of mechano-electric transduction in the campaniform sensilla. Depolymerization of such cytoskeleton resulted in reduction of receptor sensitivity.3) The structure of the stretch receptor was examined in locust wings. The cell body of the stretch receptors is large (up to 50 mum) and extends many dendrites, which must be receptor sites. Actin filaments were densely localized in the dendritic regions.4) The data obtained in the present study suggest that three types of the insect mechanoreceptors possess their specific primary processes of the mechano-electric transduction, which is closely related to specific organization of cytoskeleton in the receptor region.