长时间暗适应和弱背景光对鲤鱼视网膜视锥水平细胞的影响——形态和生理的相关研究

本工作利用电子显微镜及细胞内记录技术研究了在暗适应和弱背景光下鲤鱼视锥与水平细胞间突触部位超微结构及视锥水平细胞光反应的变化。在长时间暗适应(>2h)后,视锥水平细胞对光反应受到强烈压抑,其突起末端则外形光滑、圆钝。在施加弱背景光(15min)后,这些细胞的反应显著增大,其末端出现大量深陷于视锥小足内部的刺形结构,这种刺形结构增加了视锥与水平细胞间的突触传递效率,可能是视锥水平细胞光反应性增高的形态学基础。

EFFECTS OF PROLONGED DARKNESS AND BACKGROUND ILLUMINATION ON CONE HORIZONTAL CELLS IN CARP RETINA:A CORRELATIVE STUDY OF MORPHOLOGY AND PHYSIOLOGY

Using intact, immobilized carp preparations, changes in light responsiveness ofcone horizontal cells and untrastructures of their terminals in cone pedicles(HCTs)were correlatively examined in prolonged (>2h)darkness and after the presentationof a dim background light. Following background illumination cone horizontalcells exhibit high light responsiveness and HCTs give rise to a lot of long, finger-like or ball-like extensions, called slender or round spinules. When the retina isleft in the dark for more than 2h, the light responsiveness of these cells is depressed,which is accompanied by a dramatic decrease of spinules. Thus light responsive-ness of the cone horisontal cells seems to be well correlated with the number of spi-nules. The results suggest that spinules may play an important role in regulatinglight responsiveness of cone horizontal cells following background illumination byaltering the efficacy of signal transfer across the synapses between cone photorece p-tors and cone horizontal cells.