Acetylcholine mediates learning-dependent AMPA receptor delivery into the CA3-CA1 synapses

通过结合体内基因传递和体外膜片钳记录，我们发现，海马依赖的抑制性回避(IA)学习推动AMPA受体亚单位重组GluR1进入CA3和CA1锥体神经元之间形成的突触。递送阻滞剂的双边表达进一步揭示，语境学习需要在CA1突触中递送AMPA受体。东莨菪碱的预处理不仅损害了IA的学习，而且阻断了AMPA受体的传递。在配对记录研究中，东莨菪碱预处理成功地阻断了GluR1胞浆尾部突变片段(GFP-MPR-DD)的作用，GFP-MPR-DD是一种抑制AMPA受体学习依赖性突触递送的结构。相反，控制片段(GFP-MPR-AA)的表达不影响学习依赖的交付。此外，在IA学习60min期间和之后，CA1区细胞外乙酰胆碱水平显著增加。对照组动物(如幼稚的、仅休克的或穿过老鼠的)没有表现出增加。这些结果表明，学习依赖型AMPA受体向CA3-CA1突触传递所需的胆碱能激活。

By combining in vivo gene delivery with in vitro patch-clamp recordings, we found that hippocampal-dependent inhibitory avoidance (IA) learning drives recombinant GluR1, an AMPA receptor subunit, into synapses formed between CA3 and CA1 pyramidal neurons. Bilateral expression of delivery blocker further revealed that contextual learning requires AMPA receptor delivery in CA1 synapses. Pretreatment of scopolamine, not only impaired the IA learning, but also blocked the AMPA receptor delivery. In paired-recording study, scopolamine pretreatment successfully blocked the effect of mutated fragment of GluR1 cytoplasmic tail (GFP-MPR-DD), a construct inhibits learning-dependent synaptic delivery of AMPA receptors. Conversely, expression of control fragment (GFP-MPR-AA) did not affect the learning-dependent delivery. Further, extracellular acetylcholine level at CA1 region significantly increased during and after IA learning for 60 min. Control animals (such as naive, shock only, or walk through rats) did not show the increase. These results suggest that cholinergic activation is required for learning-dependent AMPA receptor delivery into the CA3-CA1 synapses.