Visualization of endogenous glycine in cat retina: an immunocytochemical study with Fab fragments.

Fab fragments of a glycine antiserum were prepared and used for immunocytochemical visualization of glycine in the cat retina. The use of Fab fragments in conjunction with Fab-specific secondary and tertiary antisera improved tissue penetration and made it possible to identify a number of the immunoreactive neurons. Staining was observed in several subpopulations of amacrine cells, including the A7(AII) rod amacrine. Multiple subpopulations of cone bipolar cells were also seen to be immunoreactive. Many neurons exhibited no detectable immunostaining, indicating that general metabolic levels of glycine do not interfere with the visualization of those cells that contain large amounts of endogenous glycine. The distribution of immunostaining appears to parallel the pattern of glycine labeling seen previously with autoradiographic techniques and implicates these cells in glycine-mediated neurotransmission.