The goal of the proposed research is to understand specific ionic and molecular mechanisms that act at the cellular level in the vertebrate retina during light- and dark-adaptation. Photic stimulation of the retina causes rod photoreceptors to remove K+ from the extracellular space, leading to a decrease in [K+]o. The Muller (glial) cells are likely to be affected directly by this light-evoked decrease in [K+]o. Moreover, the changes in [K+]o are likely to be accompanied by changes in the movements other important ions, such as Na+ and C1-, across cell membranes. The resulting changes in intracellular and extracellular ionic concentrations will affect rod function directly, and will affect Muller cell function indirectly. These ionic movements and interactions will be examined in the isolated retina of the toad, Bufo marinus. Experiments will identify ionic mechanisms that produce light-evoked changes in ionic concentration, and will determine the effects of these light-evoked changes in concentration upon rods and Muller cells. These experiments will involve intracellular measurement of membrane voltage, in combination with intra- and extracellular measurement of ionic concentrations using ion-selective microelectrodes, both in darkness and during periods of maintained illumination. Within rods, many biochemical reactions must participate in the transduction and adaptation processes. Experiments will use electrophysiologial methods to assess the role of certain of these biochemical reactions in the control of rod photoresponses. Proteins and other molecules that are thought to participate in these reactions will be pressure-injected into rods while recording membrane voltage. These experiments will help to elucidate molecular mechanisms involved in the biochemical control of electrophysiological responses in rods. The proposed experiments will provide basic knowledge of ionic and molecular mechanisms that function at the cellular level in rods and in Muller cells. Knowledge of these mechanisms may lead to better understanding of disease processes that disrupt function in the outer retina. Experiments that examine ionic mechanisms in Muller cells will help to determine the cellular origin of several components of the electro-retinogram (ERG), which may increase the diagnostic usefulness of the clinical ERG.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
2R01EY004364-04
Application #
3258729
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1982-08-01
Project End
1990-07-31
Budget Start
1985-08-01
Budget End
1986-07-31
Support Year
4
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of Illinois Urbana-Champaign
Department
Type
DUNS #
041544081
City
Champaign
State
IL
Country
United States
Zip Code
61820
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Oakley 2nd, B; Katz, B J; Xu, Z et al. (1992) Spatial buffering of extracellular potassium by Muller (glial) cells in the toad retina. Exp Eye Res 55:539-50
Tucker, J L; Wen, R; Oakley 2nd, B (1991) A deconvolution technique for improved estimation of rapid changes in ion concentration recorded with ion-selective microelectrodes. IEEE Trans Biomed Eng 38:156-60
Katz, B J; Wen, R; Zheng, J B et al. (1991) M-wave of the toad electroretinogram. J Neurophysiol 66:1927-40
Wen, R; Oakley 2nd, B (1990) Ion-selective microelectrodes suitable for recording rapid changes in extracellular ion concentration. J Neurosci Methods 31:207-13
Katz, B J; Oakley 2nd, B (1990) Evidence for Na+/H+ exchange in vertebrate rod photoreceptors. Exp Eye Res 51:199-207
Wen, R; Oakley 2nd, B (1990) K(+)-evoked Muller cell depolarization generates b-wave of electroretinogram in toad retina. Proc Natl Acad Sci U S A 87:2117-21
Oakley 2nd, B; Wen, R (1989) Extracellular pH in the isolated retina of the toad in darkness and during illumination. J Physiol 419:353-78
Oakley 2nd, B (1987) Measurement of potassium turnover in rod photoreceptors in toad isolated retina using ion-selective microelectrodes. Can J Physiol Pharmacol 65:1018-27
Shimazaki, H; Oakley 2nd, B (1986) Decline of electrogenic Na+/K+ pump activity in rod photoreceptors during maintained illumination. J Gen Physiol 87:633-47