The effects of intracellular iontophoretic injection of calcium and sodium ions on the light response of Limulus ventral photoreceptors.
During intracellular iontophoretic injection of Ca(++) into Limulus ventral photoreceptor cells, there is a progressive diminution of the light response. Following Ca(++) injection, the size of the light response slowly recovers. Similarly, there is a progressive diminution of the light response during intracellular injection of Na(+) and recovery after the injection is stopped. The rate of diminution during Na(+) injection is greater for higher [Ca(++)](out). In solutions which contain 0.1 mM Ca(++), there is nearly no progressive decrease in the size of the light response during Na(+) injection. Intracellular injections of Li(+) or K(+) do not progressively decrease the size of the light response. We propose that an increase in [Na(+)](in) leads to an increase in [Ca(++)](in) and that an increase in [Ca(++)](in) by any means leads to a reduction in responsiveness to light.
D000818:Animals; D001693:Biological Transport, Active; D003386:Brachyura; D002118:Calcium / Q000494:pharmacology* / Q000502:physiology; D002614:Chelating Agents; D066298:In Vitro Techniques; D008027:Light; D008564:Membrane Potentials; D009799:Ocular Physiological Phenomena; D010786:Photoreceptor Cells / Q000502:physiology / Q000528:radiation effects*; D011189:Potassium Chloride; D011830:Radiation Effects; D012623:Seawater; D012964:Sodium / Q000494:pharmacology* / Q000502:physiology; D012965:Sodium Chloride
D002614:Chelating Agents; D012965:Sodium Chloride; D011189:Potassium Chloride; D012964:Sodium; D002118:Calcium