摘要
应用盲法脑片膜片钳记录方法 ,研究了幼年大鼠 (生后 6～ 2 1d)及成年大鼠 (生后 5 6～ 70d)离体海马脑片CA1锥体神经元N 甲基 D 门冬氨酸 (NMDA)及非NMDA受体介导的兴奋性突触后电流 (EPSCs)的生后发育变化。为阻断γ 氨基丁酸 (GABA)能抑制性突触活动 ,灌注液中常规应用GABAA受体拮抗剂荷包牡丹碱 (5 0μmol/L)。局部刺激海马辐射层 (0 .0 5～ 0 .1Hz)可引起EPSCs。结果显示NMDA受体拮抗剂AP5可减小EPSCs的幅值 ,减小的程度以幼年大鼠为显著。进一步灌注α 氨基 3 羧基 5 甲基异噁唑 4 丙酸 (AMPA)受体拮抗剂CNQX(2 0 μmol/L)可完全阻断残余EPSCs。分析给予AP5前、后EPSCs幅值的大小 ,可得到NMDA及非NMDA受体介导的EPSCs,显示非NMDA受体介导的EPSCs随着发育明显增加 ,而NMDA成分则降低。上述研究结果表明海马CA1神经元的兴奋性突触活动是由NMDA及非NMDA受体介导的 ,并且在生后一周内以NMDA成分为主 ,因此在发育的早期NMDA受体可能更多参与对发育的调节作用。
In vitro hippocampal slices were prepared from juvenile (6～21 days old) and young adult rats (56～70 days old). Whole cell voltage clamp recordings were used to study the postnatal development of N methyl D aspartate (NMDA) and non NMDA receptor mediated excitatory postsynaptic currents (EPSCs) in CA1 pyramidal neurons. GABA A receptor antagonist bicuculline (50 μmol/L) was routinely included in the perfusion solution in order to block the GABAergic inhibitory events. Focal stimulation of stratum radiatum at 0.05～0.1 Hz elicited EPSCs. Pharmacological separation of EPSCs into NMDA and non NMDA receptor mediated components was accomplished by application of the NMDA receptor antagonist, DL 2 aminophosphonopentanoic acid (AP5, 100 μmol/L). The depression of the EPSCs by AP5 was significantly greater in younger rats than in older rats. The residual EPSCs were blocked by further application of α amino 3 hydroxy 5 methyl 4 isoxazolepropionic acid (AMPA) receptor antagonist, CNQX (20 μmol/L). Analysis of EPSCs before and after AP5 showed a significant increase in the relative contribution of the non NMDA component with postnatal development, whereas the NMDA component decreased. The present results demonstrate that EPSCs in hippocampal CA1 neurons are mediated by NMDA and non NMDA receptors, and NMDA component of the evoked EPSCs is larger during the first postnatal week. The relative larger NMDA mediated component during the early postnatal period may contribute to the modulatory influence of NMDA receptors on development.
基金
国家重点基础研究规划"脑功能和脑重大疾病的基础研究"(G19990 5 40 0 0 )
