Modification of the frog's electroretinogram by transretinal direct current.
1. Transretinal direct current modifies the amplitude and waveform of the frog's electroretinogram (ERG). Outward current (that flowing from vitreous to sclera) depresses the ERG while inward current enhances it. Outward current causes an apparent reversal of the polarity of the positive off-response (d-wave) of the ERG. 2. A true reversal does not actually occur. Rather, the outward current unmasks a negative off-response by depressing the positive off-response. 3. The positive off-response and the b-wave can be completely abolished by strong outward current, but cannot be reversed. 4. Treatment with ammonia abolishes the negative off-response, leaving a positive off-response which is affected by current in exactly the same way as the normal positive off-response. 5. Two possible mechanisms by which the current could be affecting the amplitude of the positive off-response would require that its amplitude be reversed for strong outward current. The absence of such reversal rejects these mechanisms.
D000641:Ammonia / Q000494:pharmacology; D000818:Animals; D004558:Electric Stimulation; D004596:Electroretinography; D005071:Evoked Potentials; D008027:Light; D010786:Photoreceptor Cells / Q000502:physiology; D010812:Physical Stimulation; D011894:Rana pipiens / Q000502:physiology; D011930:Reaction Time; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000502:physiology
D000641:Ammonia