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Pharmacological analysis of the rat cone electroretinogram

Published online by Cambridge University Press:  23 September 2003

LI XU
Affiliation:
Cole Eye Institute, Cleveland Clinic Foundation, Cleveland Present address: Department of Psychology, Columbia University, New York, NY 10027.
SHERRY L. BALL
Affiliation:
Cole Eye Institute, Cleveland Clinic Foundation, Cleveland Research Service, Cleveland VAMC, Cleveland Department of Psychology, Case Western Reserve University, Cleveland
KENNETH R. ALEXANDER
Affiliation:
Departments of Ophthalmology and Visual Sciences and Psychology, University of Illinois at Chicago College of Medicine, Chicago
NEAL S. PEACHEY
Affiliation:
Cole Eye Institute, Cleveland Clinic Foundation, Cleveland Research Service, Cleveland VAMC, Cleveland Department of Neurosciences, Case Western Reserve University, Cleveland

Abstract

The electroretinogram (ERG) of the cone system provides a useful noninvasive measure of the activity of the cone pathway. Despite a wide application of the cone ERG in the study of rodent models of human hereditary retinal disease, the cellular origins of the rat cone ERG have not been well defined. Here, we address this issue using a pharmacological approach that has been used previously to derive ERG response components. Agents that impair synaptic transmission at well-defined retinal loci were dissolved in saline and injected into the vitreous of adult Sprague-Dawley rats anesthetized with ketamine/xylazine, and cone ERGs were recorded approximately 2 h later. Analysis of the resulting waveforms indicated that the rat cone ERG includes a relatively small-amplitude component of negative polarity that is derived from the activity of cone photoreceptors, and perhaps retinal glial (Müller) cells. The cone depolarizing bipolar cell pathway contributes a positive potential of large amplitude to the rat cone ERG. In comparison, the contribution of hyperpolarizing bipolar cells is of negative polarity and of much smaller amplitude. The inner retina contributes a negative wave upon which higher frequency oscillations are superimposed. These results provide a foundation for interpreting changes in the waveform of the rat cone ERG that may be observed following genetic alteration or other experimental treatment.

Type
Research Article
Copyright
© 2003 Cambridge University Press

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