MOLECULAR-IDENTIFICATION OF A DOPAMINE D(1)B RECEPTOR IN BOVINE RETINAL-PIGMENT EPITHELIUM

The rhythmic daytime inhibition of phagocytosis of shed photoreceptor outer segments (OS) by the retinal pigment epithelium (RPE) is related to increased cAMP in RPE cells. Dopamine (DA), the fight-adaptive sig nal of the retinal oscillator can activate adenylyl cyclase through it s D-1-like receptors. It reduces OS phagocytosis by cultured bovine RP E, but a DA receptor was not demonstrated. Using primers selected from alignment of D-1-like receptor genes already cloned, we have amplifie d by PCR two sequences in bovine genomic DNA. Phylogenetic analysis de monstrated that they correspond to D-1a and D-1b receptors. These rece ptors were then searched for using the reverse transcription-polymeras e chain reaction (RT-PCR) in cultured bovine RPE. Only the D-1b recept or subtype was demonstrated. It could mediate the DA-induced inhibitio n of phagocytosis. (C) 1997 Elsevier Science Ireland Ltd.