Article date: 1992/8/8
PubMed ID: 1522254
Journal name: The Journal of comparative neurology (ISSN: 0021-9967)
The indoleamine-accumulating amacrine cells of the rabbit retina are wide-field and numerous. They form a dense plexus in sublamina 5 of the inner plexiform layer where they make reciprocal synapses with rod bipolar cells. To provide a quantitative test for the colocalization of serotonin (5-HT) and gamma-aminobutyric acid (GABA) in the rabbit retina, we designed two parallel double-label experiments. In the first series, the indoleamine-accumulating cells were labeled with 5,7-dihydroxytryptamine (5,7-DHT), which was subsequently visualized by photooxidation in the presence of diaminobenzidine. This was combined with autoradiography for 3H-muscimol. In the second and complementary series, 3H-5-HT uptake was combined with postembedding GABA immunocytochemistry. These two experiments provided essentially identical results: over 98% of the indoleamine-accumulating amacrine cells were double-labeled. This means that, within the limit of experimental error, all the indoleamine-accumulating amacrine cells are GABAergic. The indoleamine-accumulating amacrine cells account for 15-20% of a large diverse group of GABA amacrine cells. In addition, the rare type 3 indoleamine-accumulating cells and fine processes running in the optic fiber layer were double-labeled. If there is insufficient 5-HT to support a transmitter role in the rabbit retina, our results suggest that the indoleamine-accumulating cells may use GABA as a neurotransmitter. Thus, rod bipolar cells, in common with other bipolar cell types, receive extensive negative feedback at GABA-mediated reciprocal synapses.
Author List: Massey S C, Mills S L, Marc R E
Publication Types: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.
Substances mentioned in the article: Biogenic Monoamines; Indoles; Muscimol; 5,7-Dihydroxytryptamine; gamma-Aminobutyric Acid;
Mesh terms: 5,7-Dihydroxytryptamine/metabolism; Animals; Autoradiography; Biogenic Monoamines/metabolism; Female; Immunohistochemistry; Indoles/metabolism; Male; Muscimol/metabolism; Oxidation-Reduction; Photochemistry; Photoreceptor Cells/cytology; Rabbits; Retina/cytology; gamma-Aminobutyric Acid/metabolism;