Peretz A, Suss-Toby E, Rom-Glas A, Arnon A, Payne R, Minke B
Department of Physiology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Neuron. 1994 Jun;12(6):1257-67. doi: 10.1016/0896-6273(94)90442-1.
Photoreceptors of dissociated Drosophila retinae were loaded with the fluorescent Ca2+ indicators, fluo-3 and Calcium Green-5N. In fluo-3-loaded, wild-type photoreceptors, a rapid increase in fluorescence (Ca2+ signal) accompanied the light-evoked inward current. Removal of extracellular Ca2+ greatly reduced the Ca2+ signal, indicating Ca2+ influx as its major cause. In Calcium Green-5N-loaded trp mutants, which lack a large fraction of the Ca2+ permeability underlying the light-evoked inward current, the Ca2+ signal was smaller relative to wild-type photoreceptors. Fluo-3-loaded norpA mutant photoreceptors, which lack a light-activated phospholipase C, generated no light-evoked inward current and no Ca2+ signal. The phosphoinositide pathway therefore appears necessary for both excitation and changes in cytosolic free Ca2+ concentration.
将分离的果蝇视网膜光感受器用荧光钙指示剂fluo-3和钙绿-5N进行装载。在装载了fluo-3的野生型光感受器中，荧光（钙信号）的快速增加伴随着光诱发的内向电流。去除细胞外钙可大大降低钙信号，表明钙内流是其主要原因。在装载了钙绿-5N的trp突变体中，其光诱发内向电流所依赖的大部分钙通透性缺失，相对于野生型光感受器，钙信号较小。装载了fluo-3的norpA突变体光感受器缺乏光激活的磷脂酶C，不产生光诱发的内向电流和钙信号。因此，磷酸肌醇途径似乎对于兴奋和胞质游离钙浓度的变化都是必需的。
