1. Effects of increased intracellular pH-buffering capacity on the light response of Limulus ventral photoreceptor
- Author
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Joel E. Brown and Jonathan A. Coles
- Subjects
Light ,Brachyura ,Intracellular pH ,Biophysics ,Buffers ,Biochemistry ,Photoreceptor cell ,chemistry.chemical_compound ,medicine ,Animals ,Photoreceptor Cells ,Membrane potential ,HEPES ,Chromatography ,biology ,Chemistry ,Cell Biology ,Hydrogen-Ion Concentration ,biology.organism_classification ,Electric Stimulation ,MOPS ,Kinetics ,Electrophysiology ,medicine.anatomical_structure ,Limulus ,Intracellular - Abstract
Aspects of a possible involvement of hydrogen ions in the electrophysiological responses to light of Limulus ventral photoreceptors were investigated. A I M solution of either a zwitter-ionic pH buffer or a weakly-buffering control substance was pressure injected through a micropipette into a ventral photoreceptor cell. To estimate the amount injected, 35SO4 was included in the solution. Membrane currents induced by light flashes were measured by a voltage-clamp technique. The buffer-filled micropipette passed current and a 3 M KCl filled micropipette monitored membrane voltage. The sensitivity (peak light-induced current/stimulus energy) was measured, after dark adaptation, before and after injection. Injections of buffers, pH 6.3–7.2, to intracellular concentrations of at least 40–200 mM produced only a small mean decrease in sensitivity, approximately equal to that caused by injections of control substances. Excitation, therefore, apparently is not mediated by a change in intracellular pH. Buffers with pH values 5.4–8.4 were also injected. The time to peak of the response depended on pH, being shortened by up to 20% at pH values below 7.7 and lengthened at higher pH values. The time to peak of the response appeared to be shortened by an increase in intracellular pH-buffering capacity even when there was no change in intracellular pH.
- Published
- 1976