Colocalization of GABA-immunoreactivity in neuropeptide- and monoamine-containing amacrine cells in the retina of Bufo marinus.

Immunocytochemical study was performed in the Bufo marinus retina to reveal the localization of gamma-aminobutyric acid (GABA)-immunoreactivity in neuropeptide Y (NPY)-, substance P (SP)-, serotonin (5HT)-and tyrosine hydroxylase (TH)-immunoreactive amacrine cells. GABA-immunoreactivity was present in all NPY-, in some of the SP- and 5HT-containing amacrine cells, but not in TH-immunoreactive amacrine cells. Among the 5HT-immunoreactive amacrine cells, a population of 5HT-synthesizing and most of the 5HT-accumulating cells were GABA-immunoreactive. These results indicate that neuropeptide- and GABA-immunoreactivity are colocalized in amacrine cells of the anuran retina. We propose a possible co-transmission for two classical neurotransmitters (GABA and 5HT) in some of the 5HT-containing amacrine cells.