STUDIES OF THE MINOR COMPONENTS OF THE FROG'S ELECTRORETINOGRAM

Abstract

With a strong flash from a xenon discharge lamp the electroretinogram (ERG) and retinal action potentials recorded by intraretinal lead were investigated.1. The normal ERG of the frog consisted of an initial negative potential (the a-wave) and an initial positive potential (the b-wave) on which a series of oscillatory potentials was superimposed. The frequency of the oscillatory potentials was independent of the stimulus intensity used. With intensive illumination a notch was observed along the falling slope of the a-wave. Thus the a-wave in the frog's ERG seemed to develop two phases. The size of the late deflection (the late a-wave) usually surpassed that of the early one (the early a-wave).2. Effects of metabolic inhibitors on the ERG were studied. When 1.0 mM iodoacetate-Ringer's solution was perfused through the eye -ball, the ERG including the oscillatory potentials was abolished in a relatively short time. The rhythm of the oscillatory potentials, however, was not affected by iodoacetate.When 1.0 mM KCN-Ringer's solution or 1.0 mM azide-Ringer's solution was perfused through the eye-ball, the oscillatory potentials were slowed in the rhythm and depressed in amplitude from the end of the train. The late a-wave as well as the b-wave was found to be susceptible to KCN and azide. The a-wave withstood inhibitors-of cellular respiration. Anoxia also appeared to exert almost the same effect on the ERG components as respiratory inhi-bitors.3. With the eye-cup preparations intraretinal recordings were obtained from retinal layers.The bipolar cell layer was found to be the optimal site for recording the oscillatory potentials. Judging from this finding and the vulnerability of the oscillatory potentials to anoxia as well as respiratory inhibitors, the oscillatory potentials were tentatively assumed to originate in the bipolar cell layer primarily.The depth-experiments in this study indicate that an origin of the early a-wave is located in the receptor layer, and that of the late a-wave in the bipolar cell layer behind the visual cells. Hence the early a-wave may be specified as the distal a-wave, and the late a-wave as the proximal a-wave.The initial part of the deep response exhibited a rather complex mor phology: The deep electrode frequently detected a sharp positive potential appearing upon the proximal a-wave. This positive potential was proved to arise evidently after the notch which apparently segregates the a-wave into two components.In the light of the present investigation, the duplex nature of the a-wave in the human ERG was discussed.