LOCALIZATION OF THE ERG BY AID OF HISTOLOGICAL METHOD

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Abstract
The ERG potential was recorded from within the frog''s isolated retina through the differentially connected inner and outer pipettes of a pencil-type microelectrode, the inner pipette being protruded a fixed distance of 50 [mu] out of the tip of the outer pipette. The insertion of the electrode was made from the receptor side. At the depth where a maximal ERG potential was obtained between the 2 pipettes, ferricyanide ions in the inner pipette were expelled electro-phoretically to combine with ferrous ions applied from outside the retina and to form a small spot of Turnbull''s blue in the tissue around the tip of the inner pipette. The blue spot was regularly detected in the distal half of the inner plexiform layer, indicating that the main ERG layer lies between this depth and the depth 50 [mu]. nearer to the receptors. This corresponded roughly to the bipolar cell layer. The whole ERG layer showed a wider distribution to both sides of this main layer. At the retinal region where the rod outer segments were removed, only the PIII component was obtained, isolated from the PII. Depth recording from such a region by means of the differentially connected pipettes and later histological location of the site of recording reaffirmed our earlier conclusion that the PIII originates from about the same depth as the PII.