ISSN:
1432-1351
Keywords:
Phototransduction
;
Photoreceptor
;
Cytoplasmic calcium
;
Microfluorometry
;
Bee
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract We have measured Cai at rest and upon light stimulation in the photoreceptors of the honeybee drone microfluorometrically with the fluorescent Ca2+ indicator dyes fura-2, fluo-3 and Ca-green 5N. In darkness, Cai was ∼ 90 nM after 5 min of dark adaptation. A saturating light step caused Cai to rise in the bulk cytoplasm to ∼ 750 nM within 1 s. Our measurements with the low affinity dye Ca-green 5N showed that bright 1-s light flashes cause a rapid increase in Cai which was graded with stimulus intensity. Ca-green 5N fluorescence reached a peak in about 200 ms, and then decayed to a slightly lower sustained plateau. The fluorescence signal peaked, when the receptor potential was repolarizing from its peak to the plateau. This observation is in agreement with the proposal that the peak-to-plateau transition of the receptor potential is caused by the rise in Cai From our Fluo-3 measurements it appears that the latency of the Ca2+ increase is by 3–4 ms longer than the latency of the receptor potential elicited by bright 100-ms light flashes. This result provides no support for the proposal that Ca2+ mediates the opening of those membrane channels responsible for the upstroke of the receptor potential.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00191708
