Protective effect of insulin on suppressed electrical activity caused by ouabain in isolated frog retina

The reduction in amplitude of the a-wave of the frog ERGs in response to light at seven different intensities recorded from isolated frog retinas (Rana catesbeiana) caused by ouabain (10(-5) M) was partially prevented dose-dependently by the insulin pre-treatment (between 6.6 x 10(-8) and 6.6 x 10(-5) M). Inversely, however, the already suppressed a-waves by ouabain could not be recovered by the application of insulin. The preventive effect of insulin pretreatment was also significantly dependent upon the stimulus intensity, but not upon the presence of glucose in the external media. The effect of insulin itself on the amplitude of the a-wave was below significance level over the range of its concentrations employed in the present experiments. It was suggested that this effect of insulin on the a-wave can be explained by assuming that insulin enhanced the Na-K pump activity under its suppressed conditions in visual cell.