Identification and characterization of tyrosine hydroxylase immunoreactive amacrine cells.

Using immunohistochemical techniques and antiserum directed to the enzyme tyrosine hydroxylase, dopaminergic amacrine cells have been directly visualized in the rabbit retina. Tyrosine hydroxylase-like (TH) immunoreactive somata are observed only within the proximal inner nuclear layer (INL). These cells give rise to varicose processes, which are distributed to laminae 1, 3, and 5 of the inner plexiform layer. TH immunoreactive amacrine cells as observed from flat mounted, whole retina preparations have a medium- to large-sized somata. Their processes have extensive fields that provide at least a threefold coverage of any retinal region. As a population, these cells are located in all areas of the retina and are distributed in a sparse, nonrandom manner. These general features of the rabbit dopaminergic cell population appear to be representative of dopaminergic cell systems in other vertebrate retinas.