Functional and morphological correlates of amacrine cells in carp retina

Neurofibrillar long-range amacrine cells in mammalian retinae

A distinct population of wide-field, unistratified amacrine cells are shown to be selectively stained by using neurofibrillar methods in rabbit and cat retinae. Their cell bodies may be located in the inner nuclear, inner plexiform or ganglion cell layers and they branch predominantly in stratum 2 of the inner plexiform layer. Characteristically, each cell has two or more long-range distal processes which extend for 2-3 mm beyond a more symmetrical, proximal dendritic field of 0.6-0.8 mm diameter. Although the neurofibrillar long-range amacrines account for less than 1 amacrine in 500, they achieve effective coverage of the retina by both the proximal and distal dendrites.

Physiological and morphological characterization of OFF-center amacrine cells in the turtle retina

OFF-center amacrine cells were intracellularly recorded and stained with Lucifer yellow to investigate the cell correlations between photoresponses and morphological features. All OFF-amacrine cells were monostratified and branched within the outer half of the inner plexiform layer. In the flat-mounted retina, however, three distinct morphological classes were distinguishable, which correlated with observed physiological differences. Class 1 consisted of wide-field, stellate amacrine cells with long, thin processes, which branched only close to the soma. The diameter of the circular dendritic field ranged from 0.8 mm to 2.0 mm. Their photoresponse to spot stimulation was a hyperpolarization during light-ON and a small depolarization after light-OFF. They showed strong antagonistic center-surround organization of the receptive field. Its size was approximately equal to the dendritic field size. Class 2 consisted of wide-field, giant amacrine cells with a "central" dendritic field formed by thick dendrites, and a "peripheral" dendritic field formed by a few long and thin, "axonlike" processes. The shape of the dendritic field was elongated, with the long axis parallel to the visual streak. Their receptive field size was considerably smaller than their dendritic field size, which was several millimeters of diameter along the long axis. Their photoresponse to spot stimulation was a fast depolarization after light-OFF, and about 50% of these cells showed strong antagonistic center-surround receptive field organization. Class 3 consisted of small- or medium-field, "starburstlike" amacrine cells with circular dendritic fields of 0.1 mm to 0.6 mm diameter. Their fine, beaded dendrites branched predominantly in the distal parts of the dendritic field. their photoresponses to light were similar to those of the giant amacrine cells; however, their receptive field size exceeded the dendritic field size. Radial sections of the retinas with labeled cells were incubated in antisera to reveal the putative transmitters GABA, serotonin, neurotensin, met-enkephalin and glucagon. No immunoreactivity with these antisera was detected within the stained OFF-center amacrine cells.

Regional difference in the dendritic morphology of dopamine cells in carp retina

The dendritic morphology of dopamine (DA) cells in the inner plexiform layer of the retina of carp (body length, ca. 33 cm) was investigated by identifying their fluorescent cell bodies in isolated, aldehyde-fixed flat-mounts and injecting them iontophoretically with Lucifer yellow CH under microscopic control. Attention was paid to clarifying regional differences in their dendritic morphology. In the marginal zone within 0.25 mm from the retinal edge, the density of DA cells was extremely high (120 cells/mm2), their dendrites tended to extend in parallel with the retinal circumference, and the dendritic field size was small (2.5 X 10(-2) mm2). As the injection point was shifted centrally by steps, the dendrites of DA cells tended to extend toward the optic disc and subsequently toward the margin, finally forming a round or oval dendritic field for each cell. Concomitantly with such changes in the dendritic field, the cell density sharply decreased to about 30 cells/mm2, and the dendritic field size increased to 10 X 10(-2) mm2 in a zone 2-3 mm interior to the margin. However, the dendritic coverage factor was consistently about 3.0 over the entire retinal field. Such morphological changes observed sequentially from the retinal margin to the intermediate region represent a developmental course of DA cells in the carp retina.

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 found or oval covering an area of 0.18 +/- 0.05 mm2 (510 +/- 80 microns in diameter). Cell density in this region was about 32 cells/mm2 and, therefore, their dendritic field coverage was approximately 6.0.