PREDOMINANT EXPRESSION OF PLATELET-ACTIVATING-FACTOR RECEPTOR IN THE RAT-BRAIN MICROGLIA

Cellular localization of platelet-activating factor (PAF) receptor in the rat brain was determined by (1) in situ hybridization, (2) Norther n blot analysis in primary cell cultures of neurons, microglia, astroc ytes, and fibroblasts, and (3) Ca2+ imaging in hippocampal culture. In situ hybridization revealed that the PAF receptor mRNA is expressed i ntensely in microglia and moderately in neurons, Northern blot analysi s revealed that PAF receptor mRNA is the most abundant in microglia. I n primary hippocampal cultures, PAF elevated intracellular Ca2+ concen tration in microglia and also in neurons, but to a lesser extent. Thes e results suggest predominant presence of PAF receptor in microglia. C ultured microglia also expressed cPLA(2) mRNA the most intensely. PAF- activated microglia released arachidonic acid in a Ca2+-dependent mann er and without conversion to its derivatives, We propose that microgli a as well as neurons contribute to PAF-related events in the CNS by re leasing arachidonic acid.