![]() This is a surprising finding, because in most mammalian species studied to date, M cones outnumber S cones by a factor of approximately 10. 27 In this species, the densities of the cones expressing the M and the S cone opsin, respectively, were reported to be present in a 1:1 ratio over the entire retina. This finding makes these two species good models for the study of molecular control mechanisms in opsin coexpression in rodents, and renders them suitable as sources of dual cones for future investigations on the role and neural connections of this cone type.Īmong rodents, the Siberian hamster presents an interesting novel pattern of cone distribution. The retina of the Siberian hamster and the pouched mouse is the first example to show a uniform coexpression of M and S cone opsins in all cones, without any topographical gradient in opsin expression. No dorsoventral gradient in the differential expression of the two opsins is observed.Ĭonclusions. The immunocytochemical results demonstrate that in both the Siberian hamster and the pouched mouse all retinal cones contain two visual pigments. Opsin colocalization was also confirmed in consecutive semithin tangential sections. ![]() Topographical distribution was determined from retinal wholemounts, and the colocalization of visual pigments was examined using confocal laser scanning microscopy. Double-label immunocytochemistry using antibodies directed against short-wavelength (S)–and middle- to long-wavelength (M/L)–sensitive opsin were used to determine the presence of visual pigments in cones of two species of rodents, the Siberian hamster ( Phodopus sungorus) and the pouched mouse ( Saccostomus campestris) from South Africa. To decide whether the identical topography of short- and middle-wavelength cone photoreceptors in two species of rodents reflects the presence of both opsins in all cone cells.
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