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J. Bilotta, B. Bishop, E.V. Vukmanic, M.L. Risner, J. Souza; Examination of the Dark–Adaptation Functions of Adult and Young Zebrafish ERG Responses . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5689.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Previous anatomical studies have shown that in young zebrafish, rod photoreceptors mature later than cone photoreceptors. The purpose of this study was to determine whether these immature rods contribute to the ERG response in young zebrafish. To that end, dark–adaptation functions were derived from ERG b–wave responses of adult and young zebrafish under conditions favoring rod responses. Methods: Initially, adult and young (14–21 days postfertilization) zebrafish (Danio rerio) were light–adapted to a broadband background light. Following the termination of the background light, ERG responses to a single 200–ms flash at a constant irradiance were obtained every 2 min; stimulus wavelength was 500 nm, the wavelength of peak sensitivity of zebrafish rods. Dark–adaptation functions were derived by plotting b–wave amplitude versus time in dark (0–50 min). Following 50 min of dark–adaptation, spectral sensitivity functions were obtained by presenting stimuli of various wavelengths (320–640 nm) at several irradiances. Spectral sensitivity was derived by determining the stimulus irradiance at each wavelength required to reach a b–wave criterion response. Results: As expected, adult dark–adaptation functions based on the b–wave response displayed a rod–cone break at about 12 min following the onset of dark–adaptation; by 50 min of dark adaptation, the adult b–wave component had reached its maximum amplitude. However, the dark–adaptation function based on the b–wave response of young zebrafish did not show a rod–cone break. Initial dark–adaptation took longer in young zebrafish compared to adults. The dark–adaptation function of young subjects resembled what would be expected from only cone contributions; by 50 min of dark adaptation, the b–wave component of young subjects also reached its maximum amplitude but was significantly lower than those of adults. Spectral sensitivity functions based on the adult responses resembled the rod spectra. Spectral sensitivity of dark–adapted young zebrafish was more similar to the spectral sensitivity function of light–adapted young zebrafish than to that of the adult dark–adapted function. Conclusions: The physiological responses based on the ERG b–wave response correspond with previous anatomical work suggesting that rod photoreceptors are immature in young zebrafish. The results of this work show that developmental studies with zebrafish can be used to examine the relationship between retinal anatomy and physiology.
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