Hardie R C, Peretz A, Pollock J A, Minke B
Department of Physiology, Hadassah Medical School, Hebrew University, Jerusalem, Israel.
Proc Biol Sci. 1993 Jun 22;252(1335):223-9. doi: 10.1098/rspb.1993.0069.
The development of the light response was followed in Drosophila photoreceptors at 25 degrees C. In whole-cell recordings from dissociated ommatidia, responses to light were first detected at 82 h post-puparium formation; over the next 8 h sensitivity to light increased exponentially by 5 or 6 orders of magnitude. The end of this phase coincided with the maturation of the rhabdomere as measured by whole-cell capacitance. There was a modest 5-10fold further increase in sensitivity over the final 10 h of pupal development (90-100 h). During a narrow developmental time window (82-87 h) no responses could be detected using non-invasive recording techniques (electroretinogram or suction electrode), and responses to light could only be elicited in whole-cell recordings when micromolar concentrations of Ca2+ are included in the pipette. It seems unlikely that cytosolic Ca2+ per se is the limiting factor, and we suggest instead that the failure to respond to light is due to the lack of Ca2+ in the InsP3-sensitive intracellular stores and that the presence of Ca2+ in these stores is an absolute requirement for phototransduction in Drosophila.
在25摄氏度下跟踪果蝇光感受器中光反应的发育情况。在分离的小眼进行的全细胞记录中，在化蛹后82小时首次检测到对光的反应；在接下来的8小时内，对光的敏感度呈指数增长，增加了5到6个数量级。这一阶段的结束与通过全细胞电容测量的视小杆的成熟同时发生。在蛹发育的最后10小时（90 - 100小时）内，敏感度又适度进一步增加了5到10倍。在一个狭窄的发育时间窗口（82 - 87小时）内，使用非侵入性记录技术（视网膜电图或吸电极）无法检测到反应，并且只有当移液管中包含微摩尔浓度的Ca2+时，在全细胞记录中才能引发对光的反应。胞质Ca2+本身似乎不太可能是限制因素，相反，我们认为对光无反应是由于肌醇三磷酸敏感的细胞内储存库中缺乏Ca2+，并且这些储存库中Ca2+的存在是果蝇光转导的绝对必要条件。
