Immunofluorescent identification of endogenous neurotransmitter content in Golgi-impregnated neurons

A combined Golgi-impregnation/immunocytochemistry procedure was developed to identify the endogenous neurotransmitter content of morphologically characterized neurons. Golgi-impregnated retinal amacrine cells in the lizard Anolis carolinensis were characterized morphologically in thick resin sections. Cells of interest were remounted, resectioned at 1 micron thickness and subjected to a postembedding immunofluorescence procedure to visualize the amino acid neurotransmitters gamma-aminobutyric acid (GABA) or glycine. Double-labeled cells were identified by opaque Golgi deposits in the cytoplasm under bright-field illumination and nuclear immunofluorescence under ultraviolet illumination. Twenty-seven Golgi-impregnated amacrine cells, exhibiting morphological features of GABA-immunoreactive (GABA-IR) cells, were tested for GABA-IR; 21 showed double labeling. Glycine-IR amacrine cells also were identified using the Golgi/immunocytochemistry procedure. This double-labeling procedure allows rapid assessment of endogenous neurotransmitter content in large samples of morphologically characterized neurons.