Dopaminrezeptoren des Hornhautepithels und -endothels

Abstract

Dopamine is a major neurotransmitter and its two receptor subgroups, termed D1-like and D2-like receptors, are found both in the central and peripheral nervous systems. D1-like receptors signal through increases, D2-like receptors through decreases in cAMP production. Reports about the presence of dopamine receptors in the cornea are rare and inconsistant. The aim of this study was to examine if native bovine corneal epithelial and endothelial cells express dopamine receptors and whether these receptors belong to the D1-like or D2-like group. Dopamine receptors were studied using polyclonal antibodies. The cAMP concentration after receptor stimulation with dopamine was determined by means of an enzyme immunoassay. In bovine corneal epithelium and endothelium immunohistochemical staining was positive for D1-like receptors but not for D2-like receptors. Stimulation of corneal D1-like receptors with dopamine revealed a dose-dependent increase of the intracellular cAMP concentration which was blocked by SCH23 390 (a selective D1-like antagonist). Our data demonstrate that bovine corneal epithelium and endothelium express a functional D1-like receptor positively coupled to adenylyl cyclase and cAMP production. However, at the present time the physiological role of this receptor remains a matter of speculation.