Yang S N, Wu J N, Liu D, Tung C S
Department of Physiology, National Defense Medical Center, Taipei, Taiwan, ROC.
Brain Res Bull. 1998 Aug;46(6):505-12. doi: 10.1016/s0361-9230(98)00046-x.
Effects of metabotropic glutamate (mGlu) receptors on calcium-induced long-term potentiation (LTP) of alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA) and N-methyl-D-aspartate (NMDA) receptor-mediated components were investigated in rat hippocampal slices using whole-cell patch-clamp recordings of excitatory postsynaptic currents (EPSCs). Calcium-induced LTP comprises a parallel, long-lasting increase of AMPA and NMDA receptor-mediated components. The calcium-induced LTP of the AMPA receptor-mediated component can be significantly attenuated by the use of a selective NMDA antagonist. (R.S)-alpha-methyl-4-carboxyphenylglycine (MCPG), a selective antagonist of mGlu receptors, abolished the long-lasting increase of both AMPA and NMDA receptor-mediated components observed in calcium-induced LTP. In current clamp mode, the application of a high calcium alone or Schaffer fiber stimulation alone (20 Hz) only generated a short-term increase in the firing rate of evoked action potentials. Conversely, a long-term increase in the firing rate was observed if Schaffer fiber stimulation (20 Hz) accompanied the perfusion of high calcium. These results suggest that calcium-induced LTP involves a parallel, long-lasting enhancement in ionotropic AMPA and NMDA receptor-mediated components. More importantly, the mGlu receptor plays a critical role in the establishment of both AMPA and NMDA receptor-mediated components underlying calcium-induced LTP. In addition, the present study also described an experimental condition in which the coapplication of the high calcium pulse and Schaffer fiber stimulation (20 Hz) can synergistically elicit a long-term increase of neuronal excitability.
使用全细胞膜片钳记录兴奋性突触后电流（EPSC），在大鼠海马切片中研究了代谢型谷氨酸（mGlu）受体对α-氨基-3-羟基-5-甲基-4-异恶唑丙酸（AMPA）和N-甲基-D-天冬氨酸（NMDA）受体介导成分的钙诱导长时程增强（LTP）的影响。钙诱导的LTP包括AMPA和NMDA受体介导成分的平行、持久增加。AMPA受体介导成分的钙诱导LTP可通过使用选择性NMDA拮抗剂而显著减弱。（R.S）-α-甲基-4-羧基苯甘氨酸（MCPG），一种mGlu受体的选择性拮抗剂，消除了在钙诱导LTP中观察到的AMPA和NMDA受体介导成分的持久增加。在电流钳模式下，单独应用高钙或单独进行Schaffer纤维刺激（20Hz）仅引起诱发动作电位发放率的短期增加。相反，如果Schaffer纤维刺激（20Hz）伴随着高钙灌注，则观察到发放率的长期增加。这些结果表明，钙诱导的LTP涉及离子型AMPA和NMDA受体介导成分的平行、持久增强。更重要的是，mGlu受体在钙诱导LTP的AMPA和NMDA受体介导成分的建立中起关键作用。此外，本研究还描述了一种实验条件，即高钙脉冲和Schaffer纤维刺激（20Hz）共同应用可协同引起神经元兴奋性的长期增加。
