Noradrenaline, a stimulant of the adenylate cyclase, augmented the c-wave as much as ouabain and this effect was largest at 10-´N4. After augmentation of the c-wave by 10-´M noradrenaline, there was no additional augmenting effect of 10-´M ouabain. This fact suggests that the ouabain-induced augmentation of the c-wave may be due to the stimulation of adenylate cyclase. In the presence of 10 -´M ouabain, the light sensitivity of retina was elevated to 0.5 log unit and it was increased about 30% over the maximum response. This may be one of the signs of visual complications caused by ouabain, such as metachromatopsia.
The effect of ouabain on the ERC c-wave was investigated in the isolated chick retina. Although, the c-wave was abolished by a high dose of ouabain (10-´M), it increased in amplitude in the presence of ouabain at a low concentration of 10-´M, which was within the therapeutic range of clinical use for cardiac glycoside.
The standing potential of the retina did not change appreciably until 10 "M order and then decreased gradually at higher concentrations. In the presence of 10 _.}M ouabain, the level having a complete blocking effect of Na-K ATPase, both the c-wave and the standing potential were almost abolished. These effects of ouabain were more conspicuous when the drug was applied to the vitreous side than to the choroidal side.
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