GABA-like immunoreactivity in the cat retina: light microscopy.

Semithin sections of the cat retina were stained with antibodies against GABA conjugated to bovine serum albumin with glutaraldehyde. Labelled cells were visualized by means of the peroxidase-antiperoxidase method. In the outer plexiform layer both A- and B-type horizontal cells and the B-type axon terminal system expressed GABA-like immunoreactivity. Approximately 25-30% of all amacrine cells and the whole inner plexiform layer were heavily labelled. Two types of putative GABA-ergic interplexiform cells could be distinguished. One of them also expressed tyrosine-hydroxylase-like immunoreactivity. A few bipolar cells were also GABA-immunolabelled. GABA-like immunoreactivity and 3H-muscimol uptake were colocalized in 90% of the amacrine cells labelled. However, horizontal cells did not accumulate 3H-muscimol.