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S Nymark, C Haldin, H Suominen, K Donner, A Koskelainen; Light-adaptation In Rat Rods At Different Temperatures . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1419.
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Purpose: Mammalian rods have been reported to light-adapt much less efficiently than rods of lower vertebrates. Our hypothesis is that this difference may be largely due to the different temperatures at which the experiments have been done. We therefore wanted to study how light-adaptation in rat rods changes with temperature. Methods: Aspartate-isolated rod photoresponses to 519 nm flashes were recorded by electroretinogram (ERG) technique across isolated rat (Rattus norvegicus) retinas. Fractional sensitivities (defined by the half-saturating flash intensity) were determined from five-point intensity-response data in darkness and under steady background illuminations (up to 103 Rh*/s, 503 nm) in the temperature range 12-36 °C. Results: At 36 °C the background intensity producing 10-fold sensitivity reduction (I10) was 500-800 Rh*/s, in agreement with the value 500-1000 Rh*/s obtained from the intact human eye (Friedburg et al. 2001, J. Physiol. 534.1, 217-242). As temperature was lowered, I10 decreased as follows: ca. 200 Rh*/s at 28 °C, 40 Rh*/s at 20 °C and 7 Rh*/s at 12 °C. In frog (Rana temporaria) at 16.5 °C, I10 is about 20 Rh*/s (Donner et al. 1995, Vision Res. 35, 2255-2266). Conclusion: At body temperature, I10 was similar to that in human rods. At similar (lower) temperatures, I10 of rat rods was comparable to that of frog rods. The results contradict the idea that there are basic differences in rod light-adaptation between mammals and amphibians.
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