Current source density analysis of the electroretinographic d-wave of frog
retina.
Xu, Xijing, Chester Karwoski.
Vision Research Laboratory, Department of Psychology, University of
Georgia, Athens, GA 30602, (706) 542-3102.
APStracts 2:0033N, 1995.
SUMMARY AND CONCLUSIONS
1. Dark flashes were used to evoke spatiotemporal profiles of the d-wave of
the electroretinogram (ERG) in frog retina. The current source density (CSD)
technique was used to compute the extracellular current sinks and sources
underlying the d-wave. 2. The largest d-wave current was a sink at the outer
plexiform layer (OPL-sink) and a source at the inner plexiform layer (IPL-
source). Several properties of this sink/source, including its relative
insensitivity to Ba 2+ , suggest that it arises from hyperpolarizing bipolar
cells. 3. There was a slower IPL-sink, along with a source at the inner
limiting membrane (ILM-source). Its properties, along with its sensitivity to
Ba 2+ and enhancement by picrotoxin, suggest it arises from the K + spatial
buffer currents of Muller cells. This IPL-sink/ILM-source underlies the M-
wave. 4. A small photoreceptor sink/source also contributes to the d-wave.
This is most significant during the very beginning of the d-wave. 5. Our
results indicate that, in frog retina and at the stimulus conditions used in
this paper, the d-wave originates primarily and directly from the
hyperpolarizing bipolar cells. Photoreceptors likely contribute a small
amount, especially during the initial portion of the d-wave. There is possibly
a small Muller cell contribution.
Received 14 October 1994; accepted in final form 10 February 1995.
APS Manuscript Number J637-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 3 April 1995.