DOMINANT EXPRESSION OF RAT PROSTANOID DP RECEPTOR MESSENGER-RNA IN LEPTOMENINGES, INNER SEGMENTS OF PHOTORECEPTOR CELLS, IRIS EPITHELIUM, AND CILIARY PROCESSES

Prostaglandin (PG) D-2 is one of the major prostanoids in the mammalia n brain and eye tissues. Its function is mediated by the prostanoid DP receptor, which is specific for PGD, among the various prostanoids. I n this study, we cloned the full-length cDNA for the rat DP receptor a nd used it for detection of DP receptor mRNA in various rat tissues. N orthern blotting and RT-PCR analyses revealed that this DP receptor wa s expressed most intensely in the eye tissues, moderately in the lepto meninges and oviduct, and weakly in the epididymis. The tissue distrib ution profile of the mRNA for the rat DP receptor is overlapped with t hose of hematopoietic and lipocalin-type PGD synthases. Among rat eye tissues, the expression was the highest in the iris. In situ hybridiza tion and in situ RT-PCR revealed DP receptor mRNA to be localized in t he epithelium of the iris and ciliary body and in photoreceptor cells of the retina, suggesting the involvement of the receptor in the physi ological regulation of intraocular pressure and the vision process. In the brain, DP receptor mRNA was dominantly expressed in the leptomeni nges and was not detected in the brain parenchyma including the ventra l rostral forebrain, the surface area of which is reportedly involved in sleep induction by PGD(2).