STUDIES ON INTRARETINAL ACTION POTENTIAL WITH LOW-RESISTANCE MICROELECTRODE

Abstract

The capillary electrode, which had been used by one of the authors to record intraretinal slow action potential, was improved to minimize the internal resistance by filling up to its tip with a fine silver wire of about 5 u in diam. The improved microelectrode permitted simultaneous recording of the slow action potential and the spike discharge arising from the same region in a bullfrog''s retina. With the microelectrode introduced into the retina, spikes could be detected from the inner retinal layers occupied by the third neurones, while the receptors and the cells in the layer of bipolar cells appeared to react only with the slow potential. Application of strychnine upon the eye revealed that the intra-retinal negative potential, the most predominant component in the slow action potential, is closely related to the mechanism of spike discharge, the slower oscillations superimposed on it pacemaking the discharge. At a later stage of the strychnini-zation, the intraretinal negative potential disappeared, leaving behind a configuration of usually small but normal ERG even in a layer as deep as the outer plexiform layer, and this appeared to favor the view that at least one part of PII and PIII originates in the receptor elements themselves. This point was discussed, leaving the final conclusion to further investigation.