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. 1978 Feb;275:345–355. doi: 10.1113/jphysiol.1978.sp012193

Ionic effects on the membrane potential of hyperpolarizing photoreceptor in scallop retina

A L F Gorman *, John S McReynolds †
PMCID: PMC1282548  PMID: 633125

Abstract

1. The effects of different external ionic conditions and of metabolic inhibitors on the membrane potential of hyperpolarizing photoreceptors in the retina of the scallop Pecten irradians were examined in the presence and absence of light.

2. Changes in extracellular K+ have a greater effect on membrane potential in the light than in darkness. The receptor potential is increased in amplitude when [K]o is reduced and decreased when [K]o is elevated. It is hyperpolarizing when [K]o is less than the estimated value for [K]i and depolarizing when this condition is reversed.

3. The complete replacement of [Na]o causes a significant hyperpolarization of membrane potential in darkness, whereas it has a much smaller hyperpolarizing effect on the peak of the receptor potential.

4. The ratio of Na+ to K+ permeabilities (PNa/PK) decreases during bright illumination. Our results suggest that PK is seven times that for PNa in the dark but is 57 times greater than PNa in light.

5. The metabolic inhibitors DNP and NaCN cause membrane potential in the dark to hyperpolarize. This hyperpolarization is associated with a decrease in the PNa/PK ratio similar to that found during illumination.

6. High [Ca+]o also causes membrane potential in the dark to hyperpolarize. This hyperpolarization is associated with an increase in membrane conductance.

7. The results indicate that the hyperpolarizing receptor potential of the distal photoreceptor is produced by a light-evoked increase in K+ permeability.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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