Lazarewicz J W, Wroblewski J T, Costa E
Fidia-Georgetown Institute for the Neurosciences, Georgetown University School of Medicine, Washington, D.C.
J Neurochem. 1990 Dec;55(6):1875-81. doi: 10.1111/j.1471-4159.1990.tb05771.x.
In primary cultures of cerebellar granule cells, glutamate, aspartate, and N-methyl-D-aspartate (NMDA) induced a dose-dependent release of [3H]arachidonic acid ([3H]AA) which was selective for these agonists and was inhibited by NMDA receptor antagonists. The agonist-induced [3H]AA release was reduced by quinacrine at concentrations that inhibited phospholipase A2 (PLA2) but affected neither the activity of phospholipase C (PLC) nor the hydrolysis of phosphoinositides induced by glutamate or quisqualate. Thus, the increased formation of AA was due to the receptor-mediated activation of PLA2 rather than to the action of PLC followed by diacylglycerol lipase. The receptor-mediated [3H]AA release was dependent on the presence of extracellular Ca2+ and was mimicked by the Ca2+ ionophore ionomycin. Pretreatment of granule cells with either pertussis or cholera toxin failed to inhibit the receptor-mediated [3H]AA release. Hence, in cerebellar granule cells, the stimulation of NMDA-sensitive glutamate receptors leads to the activation of PLA2 that is mediated by Ca2+ ions entering through the cationic channels functioning as effectors of NMDA receptors. A coupling through a toxin-sensitive GTP-binding protein can be excluded.
在小脑颗粒细胞的原代培养中，谷氨酸、天冬氨酸和N-甲基-D-天冬氨酸（NMDA）诱导了[3H]花生四烯酸（[3H]AA）呈剂量依赖性释放，这种释放对这些激动剂具有选择性，并被NMDA受体拮抗剂抑制。喹吖因在抑制磷脂酶A2（PLA2）的浓度下可降低激动剂诱导的[3H]AA释放，但既不影响磷脂酶C（PLC）的活性，也不影响谷氨酸或quisqualate诱导的磷酸肌醇水解。因此，AA生成增加是由于PLA2的受体介导激活，而非PLC作用后再经二酰基甘油脂肪酶作用所致。受体介导的[3H]AA释放依赖于细胞外Ca2+的存在，并可被Ca2+离子载体离子霉素模拟。用百日咳毒素或霍乱毒素预处理颗粒细胞未能抑制受体介导的[3H]AA释放。因此，在小脑颗粒细胞中，NMDA敏感的谷氨酸受体的刺激导致PLA2的激活，这是由通过作为NMDA受体效应器的阳离子通道进入的Ca2+离子介导的。可以排除通过毒素敏感的GTP结合蛋白的偶联。
