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Kenkichi Fukurotani; Tetraphasic Horizontal Cell in the Retina of Goldfish. Invest. Ophthalmol. Vis. Sci. 2013;54(15):6145.
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© ARVO (1962-2015); The Authors (2016-present)
I previously reported at this meeting that tetrachromatic horizontal cell was common to many cyprinid species (ARVO 1984 annual meeting abstract, p.118). However, I could not identify the tetraphasic horizontal cell in the retina of goldfish at that time. Now I re-examined short-wave-sensitive horizontal cells in the retina of goldfish to find out the tetraphasic horizontal cell.
Intracellular spectral responses of horizontal cells were recorded by glassmicropipette from the retina of common goldfish, Carassius auratus. A white background light of visible spectrum was used to lower the sensitivities of R, G and B cone inputs but keep the sensitivity of UV cone input the same.
About half of triphasic horizontal cells (type 1 of H3 cells) exibited off-transient UV response, while the remainder (type 2 of H3 cells) did not. Under the white background, the type 1 responded to UV stimuli by depolarization but the type2 did by hyperpolarization. Spectral sensitivity curves of the UV response were fitted to spectral absorbance of UV cone. These results suggested that (1) The type 1 was intrinsically tetraphasic but small depolarizing input from UV cone was usually masked by larger hyperpolarizing input from B cone; (2) As the deporalizing UV cone input had longer delay time than that of the hyperpolarizing B cone input, UV response of the type 1, added the two inputs of opposite polarity, became off-transient like the known tetraphasic horizontal cells of other species did; (3) The type 2 was the usual triphasic horizontal cell receiving hyperpolarizing input from both UV cone and B cone. Other experiments on wild species, Carassius auratus langsdorfii and Carassius cuvieri showed that the tetraphasic horizontal cell of C. cuvieri had more prominently depolarizing UV phase than that of the common goldfish, while any UV cone input was not recognized in horizontal cell responses of C. auratus langsdorfii . C. cuvieri is plankton eater and prefers clear open water. C. auratus langsdorfii is benthic, omnivorous and inhabiting turbid creeks. Differences of their photo-environment and ecology might cause the variations of short-wave-sensitive system in the distal retina among even closely related species.
Goldfish possessed the tetraphasic horizontal cell whose depolarizing UV phase was small and degenerative.
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