Localization of cytosolic phospholipase A2 messenger RNA mainly in neuronsin the rat brain

Ca2+-sensitive 85,000 mol. wt cytosolic phospholipase A2 plays an essential role in the selective and stimulus-dependent release of arachidonic acid f rom membrane phospholipids. Cytosolic phospholipase A2-catalysed lipid medi ators including arachidonic acid and its metabolites have been suggested to be involved in a variety of neuronal functions in the CNS. Since the cellu lar localization of cytosolic phospholipase A2 is still controversial and o bscure, we tried an improved method of rapid processing of each specimens a nd succeeded in obtaining intense signals of cytosolic phospholipase A2 mes senger RNA in the normal rat brain by northern blot analysis and in situ hy bridization. Northern blot analysis showed the abundant distribution of cyt osolic phospholipase A2 messenger RNA in most regions of the brain, with in tense signals observed in the pineal gland and pens. Macroautoradiographs p repared after in situ hybridization with three different antisense riboprob es gave essentially similar patterns of localization; significant signals w ere widely detected in the gray matter of various regions, i.e. the olfacto ry bulb, cerebral cortex, hippocampus, amygdala, several thalamic and hypot halamic nuclei and cerebellum. Microautoradiographs showed that most of the intense signals were predominant in neurons, and that faint signals were f rom glial cells and other non-neuronal cells in the choroid plexus, inner s urface cells of veins and the leptomeninges. In addition, the cycloheximide treatment increased the cytosolic phospholipase A2 messenger RNA level in the same cell populations originally possessing messenger RNA signals. Predominant expression of cytosolic phospholipase A2 messenger RNA in neuro ns may provide the basis for the contribution of cytosolic phospholipase A2 -catalysed lipid mediators to a variety of neurotransmission and synaptic f unctions in the CNS. (C) 1999 IBRO. Published by Elsevier Science Ltd.