Abstract
Normal electroretinograms (ERG), consisting of a- and b-waves and wavelets, were recorded from isolated rat retinae which were mounted in a chamber and continuously perfused with a modified extracellular medium. The normal steady-state characteristics of the ERG were observed. The effects of altering the temperature, pH, and oxygen concentration on the ERG were reported. The receptor potential ( a-wave) was isolated by exposing the retina to high (20 mM) magnesium solutions. Except at low concentrations, the amplitude of the a-wave varied in proportion to the logarithm of the external sodium concentration and in inverse proportion to the logarithm of the external potassium concentration. A decrease of external chloride was without effect on the a-wave. Calcium depletion increased the amplitude of the a-wave. Deficiencies in glucose and oxygen produced a decrease in a-wave amplitude. It was concluded that the primary effect of light is to cause a decrease of the sodium conductance of the photoreceptor membrane. An electrical model of the receptor cell's outer and inner segments was proposed to explain the effects of ionic concentration changes.
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