The role of dopaminergic agnonists or antagonists on the regulation of intraocular pressure is poorly understood. There is conflicting literature as to the effects these classes of drugs have on aqueous humor dynamics. Speculation about the possible cellular mechanisms is limited due to the absence of information concerning the identification of these receptors in the anterior segment of animal or human eyes. The specific aim of this study is to obtain pilot data on the presence and characterization of membrane bound dopamine receptors in the anterior segment of human autopsy and rabbit eyes utilizing radiologand binding techniques. Direct binding studies of receptor saturation will provide estimates of the number of receptors present, while indirect binding assays employing several competing ligands will help characterize the subtypes of the dopamine receptors.