ApoE4对大鼠在体海马L-LTP的影响及其分子机制的分析

Effects of Apolipoprotein E4 on Hippocampal Late-phase Long-Term Potertiation of Rats in vivo and Analysis of Molecular Mechanism

探讨载脂蛋白E4(apolipoprotein E,apoE4)的神经毒性作用。将12只健康雄性SD大鼠随机分成对照组和实验组两组(n=6)。采用电生理手段,利用海马给药装置和刺激/记录绑定电极记录大鼠在体海马CA1区场兴奋性突触后电位(fEPSP)和高频刺激(HFSs)诱导的晚期长时程增强(L-LTP),观察急性注射apoE4后对大鼠海马CA1区L-LTP的诱导及维持的影响。并且通过Western Blotting检测cAMP应答元件结合蛋白(CREB)的表达及其磷酸化水平,探讨apoE4影响L-LTP的分子机制。结果表明,HFSs前注射0.2μg apoE4并没有改变突触传递,对双脉冲易化(PPF)没有影响。但显著抑制L-LTP的诱导和维持,降低CREB的磷酸化水平。说明apoE4可以损伤海马L-LTP。这种神经毒性不是突触前神经递质释放所介导,而是通过降低突触后CREB活性实现的。

To investigate the neurotoxicity of apolipoprotein E4 （apoE4） and the underlying mechanisms, we recorded in vivo late-phase long-term potentiation （L-LTP） of field excitatory postsynaptic potentials （fEPSPs） in hippocampal CA1 region of rats. Twelve male SD rats were used and the L-LTP was induced by three groups of high frequency stimulations （HFSs）. ApoE4 solution （0. 1μg/μL, 2 μL, n=6） was injected into the CA1 region of hippocampus 30 min before HFS. Control rats （n=6） received only saline （2μL, n=6）. The paired pulse facilitation （PPF） was also recorded. The expression and phosphorylation levels of cAMP response element-binding protein （CREB） were measured by Western Blotting. The results show that apoE4 did not change the base line synaptic transmission and the PPF, but significantly impair the induction and the maintenance of L-LTP. In addition, the apoE4 decreasd the phosphorylation levels of the CREB in the hippocampus. These results strongly suggest that the neurotoxicity of ApoE4 on the synaptic plasticity was mainly involved in the suppression of L-LTP. And the attenuation of L- LTP was not mediated by presynaptic neurotransmitter release, but by the postsynaptic signaling. The decrease of the CREB phosphorylation in the hippocampus seemed to be related to the neurotoxicity.