All indoleamine-accumulating cells in the rabbit retina contain GABA

J Comp Neurol. 1992 Aug 8;322(2):275-91. doi: 10.1002/cne.903220213.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

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
  • Retina / metabolism*
  • gamma-Aminobutyric Acid / metabolism*


  • Biogenic Monoamines
  • Indoles
  • Muscimol
  • 5,7-Dihydroxytryptamine
  • gamma-Aminobutyric Acid