Koh J Y, Goldberg M P, Hartley D M, Choi D W
Department of Neurology, Stanford University Medical School, California 94305.
J Neurosci. 1990 Feb;10(2):693-705. doi: 10.1523/JNEUROSCI.10-02-00693.1990.
The neurotoxicity of 3 non-NMDA glutamate receptor agonists--kainate, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA), and quisqualate--was investigated quantitatively in dissociated murine cortical cultures. Five minute exposure to 500 microM kainate, but not AMPA, produced widespread acute neuronal swelling. Kainate-induced swelling was resistant to 2-amino-5-phosphonovalerate (APV) or replacement of extracellular sodium with choline but attenuated by either kynurenate or low concentrations of quisqualate. Unlike NMDA agonists, kainate or AMPA did not produce much late neuronal loss after a 5 min exposure. In contrast, 5 min exposure to 500 microM quisqualate produced both acute neuronal swelling and widespread late neuronal degeneration. This acute swelling was blocked by APV or by replacement of extracellular sodium by choline, consistent with mediation by NMDA receptors; we speculate that high concentrations of quisqualate may directly activate NMDA receptors or induce the release of endogenous glutamate. Quisqualate-induced late neuronal degeneration may be due to another unexpected process: cellular quisqualate uptake and delayed release, converting brief addition into prolonged exposure. Hours after thorough washout of exogenously added quisqualate, micromolar concentrations could be detected in the bathing medium by high performance liquid chromatography. With lengthy exposure (20-24 hr), all 3 non-NMDA agonists were potent neurotoxins, able to destroy neurons with EC50's of about 20 microM for kainate, 4 microM for AMPA, and 1 microM for quisqualate. Kynurenate and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), but not APV or L-glutamate diethyl ester, were effective in attenuating the neuronal degeneration induced by these agonists. CNQX was about 3 times more selective than kynurenate against kainate-induced neuronal injury, but CNQX was still nearly equipotent with APV against NMDA-induced injury. Gamma-D-glutamylaminomethyl sulfonate exhibited partial antagonist specificity for AMPA-induced toxicity.
在解离的小鼠皮质培养物中，对3种非NMDA谷氨酸受体激动剂——海藻酸、α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）和喹啉酸的神经毒性进行了定量研究。暴露于500微摩尔/升的海藻酸5分钟会导致广泛的急性神经元肿胀，但暴露于AMPA则不会。海藻酸诱导的肿胀对2-氨基-5-磷酸戊酸（APV）有抗性，或者用胆碱替代细胞外钠也不能阻止，但可被犬尿氨酸或低浓度的喹啉酸减弱。与NMDA激动剂不同，暴露于海藻酸或AMPA 5分钟后，不会导致大量晚期神经元死亡。相反，暴露于500微摩尔/升的喹啉酸5分钟会导致急性神经元肿胀和广泛的晚期神经元变性。这种急性肿胀可被APV或用胆碱替代细胞外钠所阻断，这与NMDA受体介导一致；我们推测高浓度的喹啉酸可能直接激活NMDA受体或诱导内源性谷氨酸的释放。喹啉酸诱导的晚期神经元变性可能是由于另一个意想不到的过程：细胞对喹啉酸的摄取和延迟释放，将短暂添加转化为长时间暴露。在外源性添加的喹啉酸彻底洗脱数小时后，通过高效液相色谱法可在培养液中检测到微摩尔浓度的喹啉酸。长时间暴露（20 - 24小时）后，所有3种非NMDA激动剂都是强效神经毒素，能够破坏神经元，海藻酸的半数有效浓度（EC50）约为20微摩尔/升，AMPA为4微摩尔/升，喹啉酸为1微摩尔/升。犬尿氨酸和6-氰基-7-硝基喹喔啉-2,3-二酮（CNQX）可有效减弱这些激动剂诱导的神经元变性，但APV或L-谷氨酸二乙酯则无效。CNQX对海藻酸诱导的神经元损伤的选择性比对犬尿氨酸高约3倍，但CNQX对NMDA诱导的损伤仍与APV几乎等效。γ-D-谷氨酰氨基甲基磺酸盐对AMPA诱导的毒性表现出部分拮抗剂特异性。
