Density of retinal dopaminergic cells and indoleamine-accumulating cells in different-sized carp.

Abstract

Density and total number of dopaminergic (DA-) cells and indoleamineaccumulating (IA-) cells were studied by means of a histofluorescence technique in relation to specimen size in the retina of carp (Cyprinus carpio), ranging from 9.2 to 37.5cm in body length (tip-to-tip). Both classes of cells were simultaneously visualized in retinal flat-mounts following intravitreal injection of a mixture of noradrenaline and 5, 6-dihydroxytryptamine. Central, intermediate, peripheral and marginal regions of the retina were examined. The densities of both classes of cells were found to be higher in the peripheral than in the central retina, and higher in all the regions in smaller fish as compared to larger ones. The density reduction with growth appeared to be more pronounced in the central than in the peripheral retina. The density ratio of DA-cells to IA-cells was approximately 1:1 in any region of differentsized specimens. The total numbers of both classes of cells per retina, on the other hand, increased with growth (approximately 260 cells each per cm of body length) as a result of cell proliferation at the retinal margin.