Extracellular K+ activity changes related to electroretinogram components. II. Rabbit (E-type) retinas.
Electroretinogram (ERG) and extracellular potassium activity (K+o) measurements were carried out in isolated superfused rabbit eyecup preparations under control conditions and during the application of pharmacological agents that selectively modify the light-responsive retinal network. Light-evoked K+o changes in the rabbit (E-type) retina resemble those previously described in amphibian (I-type) retinas. Different components of the light-evoked K+o changes can be distinguished on the bases of retinal depth, V vs. log I properties, and their responses to pharmacological agents. We find two separable sources of light-evoked increases in extracellular K+: a proximal source and a distal source. The properties of the distal light-evoked K+o increase are consistent with the hypothesis that it initiates a K+-mediated current through Müller cells that is detected as the primary voltage of the electroretinographic b-wave. These experiments also support previous studies indicating that both the corneal-positive component of c-wave and the corneal-negative slow PIII potential result from K+-mediated influences on, respectively, the retinal pigment epithelium and Müller cells.
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Dick
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Miller
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Bloomfield
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D004596:Electroretinography; D000431:Ethanol / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D008027:Light; D008564:Membrane Potentials; D008839:Microelectrodes; D010775:Photic Stimulation; D011188:Potassium / Q000378:metabolism / Q000502:physiology*; D011817:Rabbits; D012160:Retina / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D013194:Staining and Labeling; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D000431:Ethanol; D005680:gamma-Aminobutyric Acid; D000109:Acetylcholine; D011188:Potassium