Related Experiment Videos
Relationship between light sensitivity and intracellular free Ca concentration in Limulus ventral photoreceptors. A
The Journal of General Physiology
|June 1, 1985
Summary
Calcium ions (Ca) play a role in light adaptation of Limulus photoreceptors, but are not the sole factor limiting dark adaptation. Changes in intracellular Ca concentration (Cai) correlate with sensitivity changes, but can become uncoupled under certain conditions.
Area of Science:
- Neuroscience
- Cell Biology
- Vision Science
Background:
- Light adaptation in photoreceptors involves a decrease in sensitivity.
- Calcium ions (Ca) are known to be involved in cellular signaling pathways.
- The precise role of intracellular free Ca concentration (Cai) in Limulus photoreceptor light adaptation requires further elucidation.
Purpose of the Study:
- To investigate the role of Ca ions in mediating the sensitivity drop during light adaptation in Limulus ventral photoreceptors.
- To simultaneously measure light sensitivity and intracellular free Ca concentration (Cai).
Main Methods:
- Simultaneous measurement of light sensitivity and intracellular free Ca concentration (Cai) using Ca-selective microelectrodes.
- Recording of Cai in dark-adapted photoreceptors and during light stimulation (brief flashes and maintained illumination).
- Experimental manipulation using EGTA injection and altering extracellular Ca2+ concentration (Cao).
Main Results:
- Resting Cai showed no correlation with absolute sensitivity between cells.
- Light-induced Cai rise was region-dependent and saturated at high light intensities.
- Steady Cai increases correlated with steady desensitization during maintained illumination, but Cai was not rate-limiting for dark adaptation recovery.
- EGTA injection affected response kinetics but not resting Cai, suggesting Ca binding capacity is key.
- Altering extracellular Ca2+ demonstrated conditions where Cai and sensitivity become uncoupled.
Conclusions:
- Intracellular Ca concentration (Cai) changes are associated with light adaptation and desensitization in Limulus photoreceptors.
- Cai is not the sole determinant of sensitivity changes and is not the rate-limiting factor for dark adaptation recovery.
- Ca binding capacity, rather than resting Cai, influences response kinetics, and Cai can become uncoupled from sensitivity under specific conditions.