EFFECTS OF SOME COMMON IONS ON THE TRANSRETINAL DC POTENTIAL AND THE ELECTRORETINOGRAM OF THE ISOLATED FROG RETINA

Abstract

1. In order to measure changes in the transretinal dc potential and the ERG, the isolated bullfrog's retina deprived of the pigment epithelium placed as a septum separating the modified Conway solution in the apparatus.2. From diffusion potentials between non-identical solutions, the relative permeability coefficients were: PNa: PK: Pcholine PCl: PSO4=0.33: 1.00: 0.27: 0.29: 0.11.3. The ‘half-times’ of the diffusion potential transients produced due to increasing the potassium concentration was 2.2 times longer for the vitreous surface than for the receptor surface. This suggests that the vitreous surface has a indiscriminate retarding force to potassium diffusion.4. Low sodium or high potassium solution on the receptor side induced the reduction in the ERG, while no change on the vitreous side. The reduction in the ERG with a low sodium solution related to the log of the sodium concentration.5. Decreasing chloride concentration on the receptor side to 15 or 0 mM, the amplitude of the ERG was reduced, whereas on the vitreous side it was increased. These light responses could be due to a direct effect of lack of chloride in the bathing solution rather than to a reduction of calcium ions or the effect of polarizing current across the retina.6. High potassium solution, azide or ouabain on the receptor side causedspontaneously a slow oscillatory dc potential change resembling Leao's spreadingcortical depression, whereas when either one side of the retina was exposedto a low chloride solution, the slow oscillatory potential induced following alight stimulation. On the basis of these results it is proposed that the slowoscillatory potential is the response of the scleral portion of the MULLER cells.