Tapia-Arancibia L, Rage F, Récasens M, Pin J P
Unité de Neurobiologie Endocrinologique, CNRS URA 1197, Université de Montpellier II, France.
Eur J Pharmacol. 1992 Mar 12;225(3):253-62. doi: 10.1016/0922-4106(92)90027-s.
We have recently shown that glutamate exerts a stimulatory action on somatostatin secretion in cortical neurons essentially through NMDA receptor sites. Here, we investigated whether arachidonic acid release could be modified after NMDA receptor activation in cortical neurons in primary culture. We also studied whether pharmacological manipulation of phospholipase A2 could modify somatostatin release. We found that both glutamate and NMDA (N-methyl-D-aspartate) stimulated [3H]arachidonic acid release. NMDA-evoked arachidonic acid release was inhibited by MK-801 and TCP (two NMDA receptor-type antagonists), or by mepacrine, an inhibitor of phospholipase A2. NMDA-induced somatostatin release was inhibited by MK-801, mepacrine and by another phospholipase A2 inhibitor, p-bromophenacylbromide (pBPB). However, responses to NMDA were unaffected by H7, NDGA (nordihydroguaiaretic acid), indomethacin or by RHC 80267 (inhibitors of protein kinase C, lipooxygenase, cyclooxygenase and diacylglycerol lipase, respectively). Mepacrine (greater than or equal to 100 microM) decreased NMDA-stimulated phosphatidylinositol (PI) hydrolysis and at higher concentrations (250 microM) was also able to inhibit basal release whereas pBPB had no effect in the range of concentrations tested. Neomycin (which inhibits phosphatidylinositol metabolism by binding strongly and selectively to inositol phospholipids) reduced by 30% the NMDA-stimulated somatostatin release, although chronic treatment of neurons with the phorbol ester 12-myristate, 13-acetate (PMA) had no effect on this response. Melittin, an activator of phospholipase A2, was able to stimulate both arachidonic acid release and somatostatin secretion. High-performance liquid chromatography (HPLC) analysis of tritiated metabolites released from cortical neurons under basal or NMDA-stimulated conditions revealed that [3H]arachidonic acid was the only metabolite detectable. Furthermore, external addition of arachidonic acid increased somatostatin secretion. Our results show a correlation between the two parameters studied.
我们最近发现，谷氨酸主要通过NMDA受体位点对皮质神经元中的生长抑素分泌发挥刺激作用。在此，我们研究了原代培养的皮质神经元中NMDA受体激活后花生四烯酸释放是否会发生改变。我们还研究了磷脂酶A2的药理操作是否会改变生长抑素的释放。我们发现谷氨酸和NMDA（N-甲基-D-天冬氨酸）均能刺激[3H]花生四烯酸的释放。NMDA诱发的花生四烯酸释放受到MK-801和TCP（两种NMDA受体型拮抗剂）或磷脂酶A2抑制剂米帕林的抑制。NMDA诱导的生长抑素释放受到MK-801、米帕林以及另一种磷脂酶A2抑制剂对溴苯甲酰溴（pBPB）的抑制。然而，对NMDA的反应不受H7、去甲二氢愈创木酸（NDGA）、吲哚美辛或RHC 80267（分别为蛋白激酶C、脂氧合酶、环氧化酶和二酰甘油脂肪酶的抑制剂）的影响。米帕林（大于或等于100 microM）可降低NMDA刺激的磷脂酰肌醇（PI）水解，且在较高浓度（250 microM）时也能够抑制基础释放，而pBPB在所测试的浓度范围内无作用。新霉素（通过与肌醇磷脂强烈且选择性结合来抑制磷脂酰肌醇代谢）使NMDA刺激的生长抑素释放减少了30%，尽管用佛波酯12-肉豆蔻酸酯、13-乙酸酯（PMA）对神经元进行慢性处理对该反应无影响。蜂毒肽是一种磷脂酶A2激活剂，能够刺激花生四烯酸释放和生长抑素分泌。对基础或NMDA刺激条件下皮质神经元释放的氚化代谢产物进行高效液相色谱（HPLC）分析显示，[3H]花生四烯酸是唯一可检测到的代谢产物。此外，外源添加花生四烯酸可增加生长抑素分泌。我们的结果显示了所研究的两个参数之间的相关性。
