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MOLECULAR MECHANISM OF SIGNAL TRANSDUCTION IN VISUAL AND NEURAL SYSTEM OF ASCIDIAN BRAIN

海鞘脑视觉和神经系统信号传导的分子机制

基本信息

批准号：
07408019
负责人：
TSUDA Motoyuki
金额：
$ 24.13万
依托单位：
HIMEJI INSTITUTE OF TECHNOLOGY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1998
项目状态：
已结题

项目摘要

Ascidian tadpole larvae change swimming behavior during the course of development. The photic behavior of the larvae of Ciona intestinalis was monitored by a computerized cell-tracking system with a time resolution of 0.1 s. Newly hatched larvae swim at an average speed of 1.4 mm/s, but show no response to light stimuli. The larvae were induced to swim more rapidly by a sudden decrease in light intensity 4 h after hatching. During the course of development the maximal speed of swimming behavior increased with time until 8h after hatching and then plateaued. The action spectrum for the step-down photophobic response of the larvae was determined at around 8 h after hatching and was fitted to Dartnall's nomogram with the absorbance maximum of the pigment located at 505 nm. These results suggest retinal proteins in the ocellus of the larvae are the photoreceptors for the photobehavior. Encephalic photoreceptors that are coupled to a biological clock for reproduction drive annual changes in gonadal activity of the preoptic-hypothalamic GnRH system in many animals.Photoreceptor and GnRH system in the cerebral ganglion of ascidians, primitive chordate, were examined and two light-evoked responses were recorded extracellularly from the cerebral ganglion of ascidian, Halocynthia roretzi. A light-evoked slow potential is assumed to originate from the photoreceptor cell and high frequency spontaneous discharges recorded in the dark were completely inhibited by light. Immunohistochemical study shows the cells bearing retinal proteins were found in the peripheral cellular cortex mainly at the dorsal surface. GnRH-immunoreactive cell bodies and fibers were distributed entire part of the cerebral ganglion and the part of those located close to the photoreceptor cells. Since the GnRH neuron exhibits a regular spontaneous beating discharge pattern, these results suggest photoreceptor cell coupled to GnRH neuron and pacemaker signal of GnRH neuron was controlled by light.

海鞘蝌蚪幼体在发育过程中会改变其游泳行为。用时间分辨率为0.1s的计算机细胞跟踪系统监测了玻璃海鞘幼虫的光行为。刚孵化的幼虫以1.4 mm/s的平均速度游泳，但对光刺激没有反应。孵化后4小时，突然降低光照强度，诱导幼虫游泳更迅速。在整个发育过程中，最大游泳速度随时间的延长而增加，至孵化后8h达到稳定。在孵化后约8 h测定幼虫的步降厌气反应的作用光谱，并拟合Dartnall诺模图，色素的最大吸收位于505 nm处。这些结果表明，视网膜蛋白在单眼的幼虫的光行为的光感受器。研究了海鞘脑神经节的光感受器和GnRH系统，并在细胞外记录了两种海鞘脑神经节的光诱发反应。光诱发的慢电位被认为是起源于感光细胞和高频自发放电记录在黑暗中被完全抑制的光。免疫组化结果显示，视网膜蛋白阳性细胞主要分布于背侧的外周细胞皮质。GnRH免疫反应阳性胞体和纤维分布于整个大脑神经节和靠近感光细胞的部分。由于GnRH神经元具有规则的自发搏动放电模式，这些结果表明光感受器细胞与GnRH神经元耦合，GnRH神经元的起搏信号受光控制。