Distribution of GABA-immunoreactive amacrine cell synapses in the inner plexiform layer of macaque monkey retina

Abstract

The distribution patterns of G A B A immunoreactive ( + ) and immunonegative (-) amacrine cell synapses a n d profiles in the inner plexiform layer (IPL) were analyzed in three macaque monkey retinas using postembedding electron-microscopic (EM) immunogold cytochemistry. Synapses and profiles were counted at 5 % intervals throughout the I P L depth in three EM montages (total area = 6509 fim 2 ), with 0% depth at the inner nuclear l a y e r / I P L border. Nearly 7 0 % of all amacrine synapses were G A B A + , and they contacted all major classes of neurons that arborize in the I P L : bipolars (45%), ganglion cells (25%), and G A B A + (20%) a n d G A B A -(10%) amacrines. A major relationship was seen between G A B A + amacrine processes a n d bipolar terminals: 7 6 % of all amacrine-to-bipolar synapses were G A B A + , and 8 2 % of bipolar output dyads contained at least one G A B A + amacrine.G A B A + amacrine profiles (N = 2455) were concentrated in three wide bands at I P L depths of 0 -2 5 % , 4 0 -6 0 % , and 7 5 -1 0 0 % , corresponding to the dense bands seen with light-microscopic immunocytochemistry. In contrast, G A B A + amacrine synapses (N = 1081) were distributed evenly throughout the IPL depth, rather than being confined to the three dense bands. G A B Aamacrine synapses (N = 516) were concentrated at 4 0 % and 6 0 % depths.Each category of amacrine output synapses had a characteristic pattern of stratification in the I P L . G A B A + amacrine-to-bipolar synapses occurred throughout the I P L but were most frequent at 2 0 % and 8 0 % I P L depths, where the dendrites of midget cone bipolars arborize (Polyak, 1941). In contrast, G A B A + amacrine-to-ganglion cell synapses were concentrated at 3 0 % and 7 0 % I P L depths, near the dendritic arborizations of parasol ganglion cells (Watanabe & Rodieck, 1989). G A B A + synapses o n t o bipolars a n d amacrines were also concentrated at the level of rod bipolar terminals. G A B A + amacrines must play significant but different roles in O N and O F F midget and parasol pathways as well as the rod pathway.

Multiple ?-aminobutyric acid plasma membrane transporters GAT-1, GAT-2, GAT-3 in the rat retina

“…This conclusion is in agreement with previous GAT-1 and GAT-3 in situ hybridization and GABA uptake-autoradiographic findings (Neal and Iversen, 1972;Blanks and Roffler-Tarlov, 1982;Brecha and Weigmann, 1994;Ruiz et al, 1994;Durkin et al, 1995). However, the possibility that these GATS or a novel GAT are transiently expressed by horizontal cells of the developing rodent and rabbit retina (Schnitzer and Rusoff, 1984;Redburn and Madtes, 1986;Versaux-Botteri et al, 1989) and by the adult cat and primate retina (Grunert and Wassle, 1990;Koontz and Hendrickson, 1990;Vardi et al, 1994) remains an unresolved issue.…”

Synaptic Currents Generating the Inhibitory Surround of Ganglion Cells in the Mammalian Retina

“…Both conventional and reciprocal synapses have been observed (Chun and Wässle, 1989;Owczarzak, 1989, 1991a,b;Koontz and Hendrickson, 1990). At these synapses, bipolar cells express different isoforms of glycine, GABA A , and GABA C receptors (Sassoè-Pognetto et al, 1994;Grünert, 2000), and the presynaptic amacrine cells represent several different morphological classes (Masland and Raviola, 2000).…”

Synaptic input to small bistratified (blue-ON) ganglion cells in the retina of a New World monkey, the marmosetCallithrix jacchus

“…In marmoset retina, GABA immunoreactivity has been found in a population of amacrine and displaced amacrine cells (Wilder et al, 1996), and we assume that like in other primates GABA and glycine are the major inhibitory neurotransmitters in this species. GABA-and glycine-positive amacrine cell synapses onto ganglion cell processes are found throughout the IPL (Hendrickson et al, 1988;Grü nert and Wä ssle, 1990;Koontz and Hendrickson, 1990), and thus small bistratified ganglion cells probably receive input from both GABA and glycinergic amacrine cells. Whether the small minority of amacrine cells that do not contain GABA or glycine (Davanger et al, 1991;Martin and Grü nert, 1992;Koontz et al, 1993;Kalloniatis et al, 1996) provide input to small bistratified cells cannot be determined since their morphology is not known.…”