NMDA receptors and nitric oxide regulate prostaglandin D2 synthesis in the rabbit hippocampus in vivo

Abstract

The aim of this in vivo micro dialysis study was to characterise the regulation of prostaglandin D₂ (PgD₂) synthesis by NMDA receptors in the rabbit hippocampus in relation to changes in extracellular Ca2+ concentration (Ca2+e) and nitric oxide (NO) levels. Samples of dialysate were analysed for changes in PgD₂ concentration, in Ca2+e and in the level of NO. The results demonstrated that a 20-min pulse application of 0.1-2.5 mM NMDA via a micro dialysis probe induced a prolonged stimulation of PgD₂ release that was sensitive to competitive NMDA receptor antagonists. An inhibitor of voltage-sensitive N/ channels, tetrodotoxin, did not influence this effect but significantly suppressed basal PgD₂ production, whereas a NOS inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME), prevented NMDA-evoked NO release and inhibited NMDA-induced PgD₂ release in an L-arginine-sensitive manner. NO donors, S-nitroso-N-acetylpenicillamine and sodium nitroprusside, stimulated PgD₂ release. NMDA-evoked decrease in Ca2+e was insensitive to TTX and L-NAME. These results demonstrate an in vivo NMDA receptor-mediated modulation of PgD₂ synthesis in the brain, in which NO participates.