Study of synaptic transmissions on hair cells

内耳的毛细胞是机械能的传递细胞。也就是说，声音、平衡和加速度信息被转换成电信号，然后传输到中枢神经系统。一些反馈信息从中枢神经系统返回到外周听力器官，以抑制毛细胞。在这项研究中，我的目标是通过使用耳蜗片标本来研究毛细胞的传入和传出突触。然而，由于硬结构和软结构的混合，制作好听力器官的切片是极其困难的。因此，我把重点放在了利用前庭器官的切开准备进行分析和分离毛细胞的实验上。在前庭器官切取标本中记录到传入性突触活动，观察到突触电位形态的差异，可能也是突触传递的机制。分离的毛细胞主要用于乙酰胆碱作用的分析。乙酰胆碱通过增加细胞内钙浓度和激活钾电导使毛细胞膜超极化。利用分离的毛细胞制剂和培养的具有高谷氨酸受体敏感性的神经元，推测毛细胞释放的递质很可能是谷氨酸。

Hair cells of the inner ear is the transducer cell of mechanical energy. Namely, the informations of sound, balance and accelerations are transduced into the electrical signal and then transmitted to the central nervous system. From the central nervous system some feedback informations are returned to the peripheral hearing organ to inhibit the hair cell. I have aimed in this research to investigate both the afferent and efferent synapses on to the hair cell, by utilizing a slice preparation of the cochlear. However, making a good slice of the hearing organ was extremely difficult, because of the mixture of hard and soft structures. I have therefore focused on the analysis by utilizing cutout preparation of vestibular organ and on the experiments with isolated hair cells. Afferent synapse activities were recorded in the cut-out preparation of vestibular organ, and the differences of the synaptic potential appearance, probably the mechanism of synapse transmission too, were detected between bouton type and calyx type synapses. The isolated hair cells were mainly studied in the analysis of acetylcholine effects. Acetylcholine hyperpolarized the hair cell membrane by increasing intracellular Ca concentration and by activating K conductance. The transmitter released from hair cell was concluded most likely as glutamate also by utilizing the isolated hair cell preparation together with cultured neuron with high glutamate receptor sensityvity.