β-淀粉样蛋白31-35片段对海马神经元分离膜片Ca^(2+)激活大电导钾通道的抑制

Suppression of large conductance Ca^(2+)-activated K^+ channels by amyloid β-protein fragment 31-35 in membrane patches excised from hippocampal neurons

为了确定β－淀粉样蛋白（ＡβＰ）在影响神经元电生理特性并导致神经毒作用时的最短活性序列，实验采用膜片钳技术，在急性分离的大鼠海马ＣＡＩ区锥体细胞的“内面向外”式膜片上，观察了ＡβＰＲ的３１－３５和２５－３５片段对Ｃａ２＋激活大电导钾（ＢＫ）通道活动的影响。结果显示，浴液中给予 ５μｍｏｌ／Ｌ的ＡβＰ ３１－３５后，ＢＫ通道的平均开放概率（Ｐｏ）和开放频率在１～３ｍｉｎ内分别减少了８５．８％（Ｐ＜０．０１）和７２．１％（Ｐ＜０．０１）；平均开放时间减少了４１．１％（Ｐ＜０．０１）；平均电流幅度则无明显改变（Ｐ＞０．０５）；给子同样摩尔浓度的ＡβＰ ２５－３５后，ＢＫ通道平均Ｐｏ减少了８５．５％（Ｐ＜０．０１），平均开放时间减少了５１．４％，（Ｐ＜０．０５）。结果提示，两种ＡβＰ片段对海马神经元ＢＫ通道具有抑制作用，这可能与ＡβＰ的神经毒性作用有关；ＡβＰ３１－３５片段可能是ＡβＰ分子中影响细胞电生理特性的最小活性序列。

To clarify the shortest essential active sequence in amyloid β-protein (AβP) responsible for affecting neuronal electrophysiological properties,the effects of fragments 31-35 and 25-35 of AβP on the large conductance Ca2+-activated potassium (BK) channels were investigated in the 'inside-out' membrane patches excised from hippocampal neurons of rats. After application of PβP 31-35 (5 μmol/L, n=l0),the mean Po and open frequency of BK channels decreased by 85.8±13.5%(P<0.01)and72.1± 22.8% (P<0.01), respectively, and the mean open time decreased by 41.1±18.5% (P<0.01), while the mean current am-plitude was ont significantly affected (P>0.05). Application of AβP 25-35 (5 μmol/L) also induced a decrease of 85.5±22.1% (P<0.01) in mean Pｏ and of 51.4±18.3% (P<0.05) in mean open time within 1-3 min after application. These results sug-gest that the functional alteration in BK channels elicited by AβP fragments may play an important role in the mechanisms underlying AβP neurotoxicity, and AβP 31-35 may be the shortest active sequence in AβP responsible for affecting the electrophysiological prop-erties of neurons.