Journal of Neurophysiology, Vol 38, Issue 1 210-216, Copyright © 1975 by APS
Modification of the frog's electroretinogram by transretinal direct current
R. W. Knighton
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.
