应激诱发的海马神经元突触增强参与大鼠的新环境学习

Involvement of stress-induced hippocampal synaptic potentiation in the novelty acquisition

本文旨在研究应激对海马新环境空间学习记忆的损伤作用机制。在大鼠海马CA1区埋植电极,刺激Schaffer侧枝记录CA1区树突层的兴奋性突触后场电位(field excitatory postsynaptic potential,fEPSP),探索应激对大鼠新环境空间学习的突触可塑性的影响。同时研究了再次新环境空间学习时,应激对动物海马的突触可塑性的影响。结果显示,在未给予外源性强直刺激(高频或低频刺激)诱导的前提下,应激适应大鼠首次探索新环境时诱发了海马神经元的突触抑制;而应激未适应大鼠首次探索新环境时却诱发了海马神经元的突触增强。在首次探索新环境24h后,再次将应激未适应大鼠放入"新环境"时,大鼠海马的突触传递却未发生显著变化。以上结果表明,应激通过产生突触增强来实现对海马新环境空间学习过程的损害,但是海马可通过再次接触经验对应激产生适应。

To study the influence of behavioral stress on hippocampal spatial learning and memory,we used the freely moving rats that had undergone chronic implantation of a recording electrode in the hippocampus CA1 region and a bipolar stimulating electrode in the ipsilateral Schaffer collateral-commissural pathway.The field excitatory postsynaptic potentials（fEPSPs） were recorded in the absence of exogenous induction of high-frequency stimulation（HFS） or low-frequency stimulation（LFS） and reflected the effect of stress on the hippocampal spatial learning.And we also investigated the change of hippocampal synaptic plasticity when rats were re-exposed to the same environment at 24 h after novelty acquisition.We found that exploration of a novel environment induced the hip-pocampal synaptic depression in the rats with stress-adaption,whereas exposure to the novel environment induced the hippocampal synaptic potentiation in the behavioral stress rats.Furthermore,re-exposure to the same environment no longer elicited the hippocampal synaptic potentiation or depression at 24 h after the first novel acquisition in the behavioral stress rats.These results demonstrate that behavioral stress induces the hippocampal synaptic potentiation under novelty acquisition and further damages the hippocampal spatial learning and memory.However,the stress can be adapted by re-exposure to the novelty and thus does not further damage the hippocampal spatial learning and memory.