GABA‐ergic pathways in the goldfish retina

Abstract

A high-affinity uptake mechanism for [3H]-gamma-aminobutyric acid (GABA) has been localized to type H1 cone horizontal cells and type Ab pyriform amacrine cells in the retina of the goldfish by light and electron microscopy autoradiography. By stimulating isolated retinas with colored lights during incubation we have been able to use [3H]-GABA uptake as a probe of light-evoked changes in membrane potential. All colors of lights increase and darkness decreases [3H]-GABA uptake by H1 cone horizontal cells. Our model of voltage dependence of GABA uptake predicts that all colors of light should hyperpolarize H1 cone horizontal cells and other investigators have shown by intracellular recording and dye-marking that type H1 cone horizontal cells hyperpolarize to all wavelengths of light. We have also obtained evidence that dark-induced depolarization of cone horizontal cells leads to release of GABA. Type Ab pyriform amacrine cells show maximal [3H]-GABA uptake in darkness and when exposed to green or blue lights, but red lights dramatically suppress uptake. We predict these neurons to be red-depolarizing, and recent intracellular recordings and dye-marking by Famiglietti et al. ('77) support our conclusions. Synaptic relations of apparently GABA-ergic neurons were investigated in the electron microscope. We propose type H1 cone horizontal cells to be both pre- and post-synaptic to red-sensitive cones and type Ab pyriform amacrine cells to be both pre- and post-synaptic to red-sensitive center-depolarizing bipolar cells.

GABA-mediated negative feedback from horizontal cells to cones in carp retina.

“…As cones are minute cells, the electrode did not stay intracellularly located long enough to observe slowly appearing effects from lower concentrations of GABA. If one also considers the high-affinity uptake mechanisms of GABA into horizontal cells (MARC et al, 1978), it is reasonable to suppose that the concentration of externally applied GABA is gradually reduced during diffusion en route to the GABA-sensitive site in cones, and that the final concentration does not differ greatly from the effective concentration at the invertebrate neuromuscular junction.…”

“…The early studies were reviewed by GRAHAM (1974) andVOADEN (1976). Our interest has been quickened by a series of reports published by Lam and others, in which they suggested that, in the fish retina, GABA is a neurotransmitter mediating the feedback synaptic pathways from horizontal cells to cones (LAM and STEINMAN, 1971;LAM, 1975LAM, , 1976MARC et al, 1978;LAM et al, 1979).…”

Synaptic transmission at retinal ribbon synapses

“…The delay and the polarity reversal seemed to indicate a chemical junction. In the lower vertebrates which were the main object of study in the 1970s and 1980s, horizontal cells are GABAergic (Marc et al, 1978) and much energy was expended in trying to prove that feedback to cones operated through a GABA-dependent mechanism. In spite of many claims and counterclaims, however (reviewed in Burkhardt, 1993;Kamermans and Spekreijse, 1999), a GABAergic basis for feedback could not be established firmly.…”

Glutamate transport by retinal Müller cells in glutamate/aspartate transporter‐knockout mice

“…Retinas were fixed in 2.5% glutaraldehyde/1% paraformaldehyde, dehydrated, embedded in epoxy resin, sectioned (250 nm), and processed for light microscope autoradiography as described by Marc and Liu (1985). In detail, 250-nm sections were placed at 25 mm from the end of a glass slide, dipped in 1:1 aqueous Kodak NTB-3 at 40°C and dried at an angle of 70°C, were exposed for 15 days, developed in 1:1 aqueous Kodak Dektol at 16°C, fixed, washed, dried, and stained with toluidine blue as specified in Marc et al (1978). This protocol allows for precise, quantitative comparisons of labeling across specimens.…”