CRH神经元在应激致七氟烷暴露后新生大鼠远期认知功能损伤中的作用及机制

The neurotoxicity of anesthetics is a hot and difficult issue currently. In the previous study, our team first showed that a single short-time sevoflurane exposure did not induce long-term cognitive impairments in neonatal rats, but combined with delayed stress could lead to significant cognitive impairments. However, the underlying mechanism is unclear. Given that 1) the expression of corticotropin-releasing hormone (CRH) is significantly increased when GABAAR is activated; 2) the expression of nectin3 is significantly decreased when CRH is increased; and 3) these changes are closely related to cognitive impairments. Our preliminary results suggested that a single short-time sevoflurane exposure elicited an increased expression of CRH in neonatal rats. Therefore, we hypothesize that a single short-time sevoflurane exposure activates the GABAAR, moreover delayed stress further activates GABAAR. Both sevoflurane exposure and stress over-activates CRH neurons and induce an increase in CRH release, then reduce the expression of nectin3 in the postsynaptic membrane, lead to long-term cognitive impairments of the developing brain eventually. To test this hypothesis, we will establish the model of single sevoflurane exposure combined with stress firstly, focus on the over-activation of GABAAR and CRH neurons, and then apply a lot of technology to reveal the mechanism of this model. The proposed study will provide a new angle for the neurotoxicity of anesthetics.

全身麻醉药物神经毒性是目前麻醉学研究的热点和难点。前期研究中，本课题组率先发现：单次短时间七氟烷暴露并不损伤新生大鼠远期认知功能，而复合延迟应激则明显损伤远期认知功能，但机制不清。鉴于1）GABAAR兴奋时，促肾上腺皮质激素释放激素（CRH）表达增加；2）CRH增加时，突触后膜nectin3表达减少；3）这些变化与认知功能损伤密切相关。结合预实验结果：单次短时间七氟烷暴露增加新生大鼠CRH水平，我们推测：单次短时间七氟烷暴露部分激活GABAAR，延迟应激则进一步激活GABAAR，两者共同作用引起CRH神经元过度活化并释放CRH，进而降低突触后膜nectin3表达，最终导致发育期大脑远期认知功能损伤。本课题建立七氟烷暴露联合应激致新生大鼠远期认知功能损伤模型，以GABAAR及CRH神经元过度活化为切入点，采用多种神经生物学技术研究该模型的发病机制，为全身麻醉药物神经毒性的防治提供新视角。

全身麻醉药物神经毒性是目前麻醉学研究的热点和难点。全世界范围内每年有成千上万的婴幼儿因各种原因暴露于麻醉药物之中，其中超过 1/4 的儿童在其出生后一年暴露于全麻药之下。全麻药是一把“双刃剑” ，虽然在手术过程中发挥着麻醉镇痛作用， 但其所致认知功能等损伤日益受到临床医师、神经科学家和公众的关注。1-4 岁前暴露于麻醉药物的儿童，其青少年时智力较没有接触过麻醉药的儿童差，但亦有研究发现，与清醒下区域麻醉相比， 1小时内七氟烷全身麻醉对患儿2岁后智力无明显影响，这可能与成长的环境差异相关。尽管关于全麻药神经毒性机制研究多种多样，但很少有将麻醉和环境应激因素联合起来的研究，故本项目中我们将麻醉和应激联系起来建立新的模型，以探讨其可能的机制。.通过本项目研究，我们初步得出了一些结果：.（1）验证单次短期七氟烷暴露联合母婴分离致新生大鼠远期认知功能损伤的模型；（2）NKCC1抑制剂布美他尼可改善单次短期七氟烷暴露联合母婴分离所致的新生大鼠远期认知功能损伤；（3）单次短期七氟烷暴露联合母婴分离可致海马MR表达降低和下丘脑CRH表达增加，而NKCC1抑制剂布美他尼可改善以上变化；（4）艾司氯胺酮多次暴露对新生大鼠认知功能或许没有影响。.本项目建立七氟烷暴露联合应激致新生大鼠远期认知功能损伤模型，揭示了LHPA轴活化和GABAAR异常在其中发挥着重要作用，为全身麻醉药物神经毒性的防治提供新视角。