The c-wave in the erg of albino rat

Abstract

The ERG of the dark adapted pigmented rat demonstrates a c-wave which develops in association with photoreceptor activity: the spectral sensitivity curve of this wave coincides with the absorption curve for rhodpsin. In albino rats, placed under identical experimental conditions, this wave is lacking and in turn is replaced by a slow negative wave which succeeds the b-wave. The magnitude of the c-wave resulting from the algebraic sum of P-I and P-III depends on the relative amplitude of these two components. We have demonstrated that the absence of the c-wave in the albino rat does not necessarily imply the non-existence of the P-I component. Under the influence of sodium azide the latter is amplified and a c-wave therefore appears, whereas under the influence of iodate, the P-I component is abolished and the recordings show a larger (in amplitude and duration) late negative wave. The elimination of P-I and P-II following temporary ischemia of the retina permits the isolation of P-III, whose form takes account of the negative wave unmasked by iodate. Superposing the ERG under iodate and the normal ERG, it was possible to reconstruct the curve of the P-I component.