Eicosanoid formation in the rat cerebral cortex. Contribution of neurons and glia.

Despite the extensive literature on brain eicosanoids, no information is available on the cellular source of individual compounds in the mature organ and the relative contribution of different cell types to the total synthetic product. To address this problem, neurons and glia were isolated from the cerebral cortex of the adult rat by a process comprising, in order, trypsinization, selective sieving, differential centrifugation, and density gradient centrifugation. Enrichment of cells in the appropriate fractions was verified by morphological, immunocytochemical, and biochemical criteria. Both neuron- and glia-rich fractions retained synthetic activity throughout the period of incubation (max. 60 min). Among the eicosanoids examined, prostaglandin (PG) EZ was the predominant compound, followed by leukotriene (LT) E4 and thromboxane (TX) BZ, whereas LTC 4 occurred in minimal amounts. Although the rank order of eicosanoids did not vary with the cell type, absolute values of PGE Z and TXB Z were greater with neurons. PGE, synthesis was increased by supplementation of the medium with arachidonic acid (2.6 g.M), whereas indomethacin (5.6 p.M) had the opposite effect. Conversely, LT synthesis was not altered by arachidonic acid and was only marginally reduced by the 5-lipoxygenase inhibitor, U-60,257 (10 µM). Several agonists (12-0-tetradecanoyl-phorbol-13-acetate, TPA; Ca ionophore A23187; plateletactivating factor; endotoxin; recombinant IL-1) were tested on both neuron- and glia-rich fractions but none of them had an effect. We