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|Title:||Generation of the electroretinogram M-wave and PII components in the amphibian retina|
|Author(s):||Katz, Bradley Jay|
|Doctoral Committee Chair(s):||Oakley, Burks, II|
|Department / Program:||Biology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
Biology, Animal Physiology
|Abstract:||The electroretinogram (ERG) is a field potential generated by the electrical activity of the retina in response to a flash of light. The ERG is measured in humans and is useful in the diagnosis of retinal pathologies. The investigations reported in this thesis were undertaken with the expectation that a more thorough characterization of ERG generation would enhance the diagnostic utility of the ERG and aid in understanding of the pathophysiology of retinal diseases.
The ERG was studied in the dark-adapted, isolated retina preparation of the toad, Bufo marinus. K$\sp+$-sensitive microelectrodes, as well as conventional intra- and extracellular microelectrodes, were used to record (K$\sp+$) $\sb0$ changes, the intraretinal ERG, the vitreal ERG, and Muller cell responses.
Using the aspartate receptor agonist, N-methyl-DL-aspartate, the M-wave was identified in the vitreal ERG. This represents the first report of this potential in a vitreal ERG recording. From the data, it is concluded that the M-wave is generated by a Muller cell response to the proximal K$\sp+$ increase. The M-wave was also found to be the principal component of the threshold ERG. A model of M-wave generation was constructed that is useful for understanding the contribution of the proximal K$\sp+$ increase to the ERG and that can account for the differences between the M-waves of amphibian and cat.
By exploiting the different neuropharmacologies of retinal neurons, the PII component was also isolated. To the knowledge of the author, this is the first report of the isolation of a PII component in the ERG of a non-mammalian species. The results presented strongly support the hypothesis that the PII component is generated by a Muller cell response to the distal K$\sp+$ increase, analogous to that which generates the ERG b-wave. In addition, it was found that at photopic levels, an orange (600 nm) flash enhanced the DC component of PII when compared with a rod-matched, green (500 nm) flash. This result indicates that it may be possible to study the isolated DC component in the human ERG without pharmacological means.
|Rights Information:||Copyright 1991 Katz, Bradley Jay|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI9136633|