Dendritic morphology of indoleamine cells revealed by intracellular injection of lucifer yellow in fixed carp retina

The dendritic morphology of indoleamine amacrine cells in carp retina was investigated by identifying their fluorescent cell bodies by preloading with noradrenaline followed by iontophoretic injection of Lucifer Yellow in isolated and aldehyde-fixed preparations under microscopic control. Although two subpopulations of serotonin-like immunoreactive amacrine cells (small and large in soma size) were found, small cells were not seen in aldehyde-fixed preparations. Cells preloaded with noradrenaline corresponded to large immunoreactive cells and were labeled with Lucifer Yellow. The cell bodies labeled were located at the innermost level of the inner nuclear layer, and gave rise to three to five primary dendrites which branched frequently and were found mainly in sublamina a of the inner plexiform layer. These cells examined in an intermediate region between the optic disc and the retinal periphery were pyriform in soma shape while dendritic fields were round or oval covering an area of 0.18 ± 0.05 mm² (510 ± 80μm in diameter). Cell density in this region was about 32 cells/mm² and, therefore, their dendritic field coverage was approximately 6.0.