Andjus P R, Khiroug L, Yakel J L, Cherubini E, Nistri A
Biophysics Sector, International School for Advanced Studies (SISSA), Trieste, Italy.
Neurosci Lett. 1996 May 24;210(1):25-8. doi: 10.1016/0304-3940(96)12647-1.
Confocal laser scanning microscopy was used to study changes in intracellular free calcium concentration ([Ca2+]i) at the level of the soma of cultured hippocampal neurones following pressure application of glutamate or N-methyl-D-aspartate (NMDA). [Ca2+]i was imaged in the presence of tetrodotoxin after loading cells with the fluorescent dye indicator fluo-3/AM. Responses to glutamate were potently antagonized by 6-cyano-7 nitroquinoxaline-2,3-dione (CNQX: 20 microM). They were also strongly and reversibly depressed by 3-((+/-)-2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (CPP; 20 microM), leaving a small CNQX-sensitive component. Responses to NMDA were also blocked by CNQX. In the presence of saturating concentrations of glycine (100 microM), the depression of glutamate or NMDA responses by CNQX was greatly reduced. Exogenously applied glycine also potentiated the NMDA response. These data indicate that the glycine binding site of the NMDA receptor channel is not saturated in cultured hippocampal neurones and thus is susceptible to the action of agonists or antagonists.
采用共聚焦激光扫描显微镜，研究在对培养的海马神经元胞体施加谷氨酸或N-甲基-D-天冬氨酸（NMDA）压力后，细胞内游离钙浓度（[Ca2+]i）的变化。在用荧光染料指示剂氟-3/AM加载细胞后，在河豚毒素存在的情况下对[Ca2+]i进行成像。谷氨酸反应被6-氰基-7-硝基喹喔啉-2,3-二酮（CNQX：20微摩尔）有效拮抗。它们也被3-((+/-)-2-羧基哌嗪-4-基)-丙基-1-膦酸（CPP；20微摩尔）强烈且可逆地抑制，留下一个小的对CNQX敏感的成分。对NMDA的反应也被CNQX阻断。在饱和浓度的甘氨酸（100微摩尔）存在下，CNQX对谷氨酸或NMDA反应的抑制作用大大降低。外源性应用甘氨酸也增强了NMDA反应。这些数据表明，在培养的海马神经元中，NMDA受体通道的甘氨酸结合位点未饱和，因此易受激动剂或拮抗剂的作用影响。
