The light response of Drosophila photoreceptors is accompanied by an increase in cellular calcium: effects of specific mutations.
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.
Peretz
A
A
Department of Physiology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Suss-Toby
E
E
Rom-Glas
A
A
Arnon
A
A
Payne
R
R
Minke
B
B
D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology*; D004594:Electrophysiology; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D008027:Light; D008564:Membrane Potentials / Q000528:radiation effects; D009154:Mutation; D017956:Photoreceptor Cells, Invertebrate / Q000502:physiology* / Q000528:radiation effects; D011679:Pupa; D012160:Retina / Q000502:physiology; D013050:Spectrometry, Fluorescence; D014966:Xanthenes
D000814:Aniline Compounds; D015220:Calcium Channels; D005456:Fluorescent Dyes; D014966:Xanthenes; C059715:Fluo-3; D002118:Calcium