Immunohistochemical localization of adenosine deaminase in the retina of the rat.

Immunohistochemical procedures were used to determine the localization of adenosine deaminase (ADA) in the rat retina. Small ADA-immunoreactive neurons having a sparse but regular distribution pattern were detected in the ganglion cell layer (GCL) and in somewhat fewer numbers in the inner nuclear layer (INL). ADA-immunoreactive processes eminating from these two cell types were seen distributed in specific sublayers of the inner plexiform layer (IPL). In addition, a dense band of punctate ADA-immunostaining was observed in the IPL immediately adjacent to the GCL. Injections of the retrogradely transported dye, fast blue, into the optic nerve failed to label ADA-immunoreactive neurons in the GCL and unilateral enucleation had no effect on the density of ADA-immunostained fibers in the superior colliculus or lateral geniculate nucleus on the enucleated compared with the contralateral control side. In addition, ADA-immunoreactive cells in the GCL of the rat appeared not to correspond to the population of cells in this layer which in other species have been shown to accumulate 4,6-diamino-2-phenylindole (DAPI) following intraocular injection of this dye. These results indicate that subpopulations of intrinsic neurons in the rat retina express high levels of ADA.