麻醉药调控cAMP-HCN信号通路介导的突触再可塑性减轻电休克学习记忆损伤的机制研究

ECT is the most effective treatment for depressive disorder, however, it also can induce learning and memory impairment. Clinical studies reported that low-dose ketamine combined propofol could alleviate the learning and memory impairment induced by ECT, but the mechanism is unclear. The learning and memory function is affected by intrinsic excitability mediated metaplasticity, which is closely related to Ih current conducted by cAMP-HCN channel signaling. Our previous research revealed that metaplasticity involved in the process of ECS (an analog of ECT to animals) and ECS with propofol and/or ketamine, additionally, the expression of cAMP, HCN1 and HCN2 in hippocampus were also changed. Therefore, we speculated that the neuroprotection of propofol and ketamine in ECS was possibly conducted by cAMP-HCN channel signaling mediated metaplasticity. To verify the hypothesis, this study aimed to investigate the effect of Ih current on the meaplasticity influenced by propofol and ketamine. Moreover, agonist and cDNA carried by lentivirus were used to demonstrate the key role of cAMP-HCN channel signaling in the metaplasticity involved in the process of ECS with propofol and/or ketamine. This study will provide new insight into optimation of anesthetic protocol of ECT and application foundation for preventing learning and memory impairment induced by ECT.

电休克（ECT）是治疗抑郁症最为有效的措施，但会造成患者学习记忆损伤。研究发现小剂量氯胺酮联合丙泊酚麻醉可有效地减轻ECT学习记忆损伤，其机制不清。神经兴奋性介导的突触再可塑性能影响学习记忆，cAMP-HCN信号通路调控的Ih电流与神经兴奋性密切相关。我们前期研究发现ECS（动物实验中模拟的ECT），丙泊酚和氯胺酮能够影响突触再可塑性，海马cAMP，HCN1及HCN2表达也发生了变化。因此，我们推测丙泊酚和氯胺酮可通过调控cAMP-HCN信号通路介导的突触再可塑性减轻ECS学习记忆损伤。基于此，本项目将应用分子生物学、膜片钳电生理等技术，研究Ih电流改变在丙泊酚和氯胺酮调控突触再可塑性中的作用；采用特异性激动剂和cDNA慢病毒调控cAMP和HCN，进一步阐明丙泊酚和氯胺酮调控突触再可塑性的分子机制。本项目将为优化临床ECT的麻醉方案，预防ECT学习记忆损伤，提供新思路和应用依据。

电休克（ECS）是治疗抑郁症最为有效的措施，但会造成学习记忆损伤。研究发现小剂量氯胺酮联合丙泊酚麻醉可有效地减轻ECS学习记忆损伤，其机制不清。本项目以抑郁大鼠为研究对象，给予不同麻醉下的ECS及干预处理，评价大鼠抑郁状态及空间学习记忆能力，检测cAMP-HCN通路相关蛋白，mRNA表达，检测突触再可塑性变化，相关神经元兴奋性及Ih电流大小。. 本项目原计划内容已大部分完成，并根据国内外前沿及实验实际进展情况，对部分研究内容做了调整。主要研究结果如下：（1）艾司氯胺酮联合丙泊酚可增强ECS抗抑郁效果，并进一步减轻ECS所致的学习记忆损伤；（2）艾司氯胺酮或丙泊酚均可下调ECS引起的HCN1/2蛋白，mRNA及cAMP表达上调，艾司氯胺酮联合丙泊酚能进一步下调HCN1，HCN2及cAMP表达量。给予腺苷酸环化酶激动剂Forskolin后再行不同麻醉药下ECS处理，大鼠表现为空间学习记忆能力进一步降低，但其HCN1，HCN2蛋白未发生改变；（3）Ih电流阻断剂ZD7288能够改善ECS所致的学习记忆损伤以及LTD/LTP诱导阈值增大。ZD7288可部分逆转ECS所致的自发和诱发AP频率下降。ECS亦可引起50%振幅时AP波宽，AP达峰时间，振幅以及后超极化电位变化，而ZD7288也能有效地抑制ECS所引起的上述变化。ZD7288亦可有效抑制ECS引起的Ih电流增大。扩展研究发现，内源性大麻素系统功能变化可能也是介导ECS学习记忆损伤的重要机制之一。. 本项目首次验证了Ih电流调控的神经兴奋性在ECS所致学习记忆损伤及突触再可塑性变化中的作用。该机制不仅可以有效地解释ECS抗抑郁效应和学习记忆损伤的双重效应，也可以进一步解释不同麻醉药在ECS中发挥神经保护功能的共同途径，为后续提出ECS最佳麻醉方案提供了重要的理论基础，亦为研究促进抗抑郁治疗和减轻学习记忆损伤的干预药物提供了新的靶点。