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β 淀粉样蛋白 (amyloidβ protein ,AβP)的神经毒性作用已被广泛报道 ,其毒性作用机制可能与改变细胞膜上原有离子通道尤其是钾通道的活动有关。目前 ,AβP对K+通道的作用报道不一 ;在单通道水平上AβP对K+通道产生的早期效应尚不清楚。本研究采用单通道膜片钳技术 ,观察了AβP的 31 35片段 (AβP31 35 )对急性分离的海马神经细胞内面向外式 (inside out)膜片的延迟整流钾电流 (IK)单通道活动的影响 ,旨在从通道水平揭示AβP的神经毒性机制。结果发现 :①IK 通道的电导较低 ,分布在 9～ 38pS范围之内 ,平均电导只有 (2 4.4± 7.9) pS (n =2 9) ;通道电流的翻转电位 (- 6 5mV)接近K+的平衡电位 ;140mmol/LCsCl取代溶液中KCl后 ,通道电流能立即消失 ,但含有EGTA的无Ca2 +浴液对通道活动没有影响。②经灌流系统给予膜片内侧 5 μmol/L的AβP31 35后 ,IK 通道平均开放频率和开放概率 (PO)分别下降了 (70 .45± 35 .75 ) % (P <0 .0 1)和 (86 .91± 1.13) % (P <0 .0 1) ,有些膜片甚至显示出通道活动的完全丧失 (PO=0 )。③给予 5 μmol/L的AβP31 35后 ,IK通道的平均开放时间减少了 (4 7.0 7± 38.8) % (P <0 .0 5 ) ;平均电流幅度虽有 (16 .6± 12 .6 ) %的增加 ,却无统计学意义 (P >0 .0 5 )。以上表明
The neurotoxicity of amyloid β protein (AβP) has been widely reported. The mechanism of its toxic effects may be related to the alteration of the activity of ion channels, especially potassium channels on the cell membrane. At present, the effects of AβP on K + channels are reported differently. The early effect of AβP on K + channels at the single channel level is not yet clear. In this study, single-channel patch-clamp technique was used to observe the delayed rectifier potassium current (IK) single channel activity of A 35P fragment of AβP (AβP31 35) in the inner outflow membrane of acutely isolated hippocampal neurons The aim is to reveal the neurotoxic mechanism of AβP at the channel level. The results showed that: (1) The conductance of IK channel is low and distributed in the range of 9 ~ 38pS with average conductance of (2 4.4 ± 7.9) pS (n = 29); channel current reversal potential (-65mV) The channel current disappeared immediately after KCl was replaced by 140 mmol / L HCl solution. However, Ca 2+ -free bath containing EGTA had no effect on channel activity. ② The average IK channel opening and opening probability of IK channels decreased by 70.45 ± 35.75% (P <0.01) and (3) after perfusion with 5 μmol / L AβP31 35 (86.91 ± 1.13)% (P <0.01), and some even showed a complete loss of channel activity (PO = 0). (3) The average opening time of IK channels decreased by (4 7.0 7 ± 38.8)% (P <0.05) after 5 μmol / L AβP31 35 administration; mean current amplitude was (16.6 ± 12.6) % Increase, but no statistical significance (P> 0.05). The above shows