摘要
采用大鼠海马脑片体外缺血模型,观察海马突触体内蛋白激酶C(PKC)活性的变化,以及这种变化对突触体谷氨酸(GLU)摄取的影响。结果显示:海马脑片体外“缺血”10min,其突触体内PKC活性基本不变,而缺血30min,突触体内PKC活性显著上升(P<0.01,n=6);非N-甲基-D-天门冬氨酸(NMDA)受体拮抗剂DNQX有效地抑制PKC活性的同时,可降低胞外GLU的堆积,而NMDA受体阻断剂AP_5无作用。进一步实验证明,PKC激动剂PDB浓度依赖性地抑制突触体对3H-GLU的摄取(IC50=131±10μmol/L),此抑制作用可由PKC抑制剂H-7(100μmol/L)抵消。提示脑缺血诱发GLU堆积的作用机理可能是:脑缺血引发钙内流导致GLU过量释放,GLU又通过突触前非NMDA受体激活PKC,抑制其自身摄取,正反馈性加重胞外GLU的堆积。
With a in vitro ischemic model, the activities of protein kinase C(PKC) and the effects of PKC on glutamate (GLU) uptake into synaptosomes in rat hippocampal slices were studied. The results showed that in synaptosomes, the PKC activity showed no changes under 10 min ischemic insult. However, the PKC avtivation was observed in presynaptic nerve terminals (from 1.30±0. 12 to 9. 34±0. 89U) following 30 min ischemia. DNQX, a nonNMDA receptor antagonist, potently reduced the PKC activation and decreased the ischemiainduced GLU accumulation, whereas NMDA receptor antagonist AP_5 showed no such effect.We further observed that the inhibition of 1- ̄3H-GLU uptake into synaptosomes by addition of PDB, a PKC stimulator, was dependent on PDB concentration. These results provide direct evidence to show that the accumulation of GLU induced by cerebral ischemic conditions was under the dual control of Ca ̄(2+) influx which enhances GLU release and PKC activation in presynaptic nerve terminals.
基金
江苏省自然科学基金
关键词
蛋白激酶
海马
突触体
缺血
谷氨酸
Protein kinase C
Excitatory amino acid receptor antagonists
Hippocampal slices
Synaptosomes
Ischemia
Glutamate uptake
Rats