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J. C. Lau, R. A. Linsenmeier; Photoreceptor Oxygen Consumption in the Light- and Dark-Adapted Rat Retina. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2719.
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To investigate, for the first time using double-barreled oxygen/voltage microelectrodes, the oxygen distribution and consumption in the light- and dark-adapted rat retina.
PO2 depth profiles were recorded from retinas of intact, isoflurane/urethane anesthetized Long-Evans rats using double-barreled oxygen microelectrodes. Arterial blood parameters were monitored and kept within normal limits. Profiles were first obtained in dark-adaptation. Light-adapted profiles were then recorded under an illumination that was sufficient to at least saturate rod responses. The electroretinogram (ERG) was used to assess the position of the electrode in the retina as well as the condition of the retina. The three layer one-dimensional diffusion model previously used for cat and monkey retina was fitted to profiles to determine photoreceptor oxygen consumption per unit volume, Qav.
Light-adaptation reduced Qav in the outer retina of the rat to 48.1 ± 29.0% of the dark-adapted value (n= 8 rats). The minimum PO2 in the outer retina occurred at the photoreceptor inner segments in dark-adaptation and was 23.6 ± 7.0 mmHg. Light-adaptation increased the minimum PO2 to 36.0 ± 15.0 mmHg.
As expected, light-adaptation increased the minimum PO2 and decreased oxygen consumption in the rat retina as compared to dark-adaptation by a similar amount as in cat retina. However, minimum PO2 in the outer retina was higher in the dark-adapted Long-Evans rat than in either the dark-adapted cat or monkey retina, as has been previously found in Sprague-Dawley rats (Cringle et al, 2002).
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