FUNCTIONAL AND MOLECULAR EXPRESSION OF PACAP VIP RECEPTORS IN THE RATRETINA/

Receptor binding sites for pituitary adenylate cyclase activating poly peptide (PACAP) and vasoactive intestinal polypeptide (VIP), positivel y coupled to adenylate cyclase, have been previously described in the retina of different mammalian species. In the present study, we determ ined the mRNA expression of PACAP/VIP receptor variants in the rat ret ina and investigated their coupling to phospholipase C in addition to adenylate cyclase. The two forms of PACAP, PACAP27 and PACAP38, induce d a dose-dependent (1-100 nM) increase of cAMP and [H-3]inositol monop hosphate levels, whereas VIP stimulated, with lower potency and effica cy, cAMP formation only. Reverse transcription-PCR analysis in the rat retina detected both type-I (PACAP-R and PACAP-HOP splice variants) a nd type-II(VIP-l and -2) receptor-mRNAs. These data indicate that PACA P and VIP may interact with multiple receptor subtypes and activate on e (VIP) or two (PACAP) signal transduction mechanisms in the rat retin a. (C) 1998 Elsevier Science B.V.