Testosterone's role in sex-specific outcomes after early anesthesia

描述(由申请人提供)：儿童早期麻醉后认知结果的性别差异研究很少，而且这种差异的机制尚不清楚。该实验室的长期目标是通过消除麻醉剂引起的发育中大脑变化的持久认知影响，提高给儿童提供麻醉的安全性。这项建议的目的是确定导致雄性和雌性啮齿动物认知结果不同的特定性别相关因素。中心假说是，早期麻醉后不同性别的认知结果是由于睾酮介导的KCC2表达延迟，从而减缓了雄性大鼠海马区从兴奋性GABA能信号到抑制性GABA能信号的转变，导致神经元棘细胞丢失，最终导致认知功能障碍。这一假说将在两个特定的目标中得到验证：1)确定睾酮在新生大鼠麻醉后树突棘形成和认知结果中的作用。2)确定睾酮在KCC2表达中的作用，并确定兴奋性GABA能神经传递是否在麻醉介导的脊柱丢失和认知障碍中是必需的。第一个目标是比较雄性和雌性大鼠在性腺切除和/或外源性睾酮治疗后，麻醉暴露后海马锥体神经元树突棘密度和认知功能。在第二个目标下，第2.1节，将定义睾酮在对照组、性腺切除后的雄性和雌性大鼠或外源性睾酮治疗后KCC2性别特异性时间表达中的作用。和第2.2节，将使用宫内电穿孔，通过早期表达KCC2或内向整流Kir2.1(两种抑制GABA能去极化的机制)来遗传操纵海马区兴奋信号，然后评估早期麻醉暴露后树突棘的形态和密度以及认知功能。这种方法是创新的，因为细胞水平的机制研究是由认知功能测试来指导和解释的， 可以在动物身上测量的最相关的结果。这些研究的预期贡献是详细了解导致早期麻醉暴露后男性与女性识别记忆缺陷的性别特有因素。这项研究意义重大，因为1)出生前三年被麻醉的儿童中约有男性，2)很少有其他研究调查性别在早期麻醉后认知结果中的作用，3)儿童早期麻醉暴露后性别特异性认知结果的机制尚不清楚。从拟议的研究中获得的结果将导致最终的试验，以改善风险分层，并指导围绕必须接受麻醉的最年轻患者的决策。

DESCRIPTION (provided by applicant): Sex differences in cognitive outcome after early childhood anesthesia have been poorly studied and no mechanism for such differences is known. The long-term goal of this laboratory is to improve the safety of anesthesia delivered to children by eliminating lasting cognitive effects from anesthetic-induced changes in the developing brain. The objective of this proposal is to identify specific sex related factors that lead to divergent cognitive outcomes in male and female rodents. The central hypothesis is that sex-specific cognitive outcomes after early anesthesia are due to testosterone-mediated delay of KCC2 expression which slows the transition from excitatory to inhibitory GABAergic signaling in the hippocampus of male rats leading to loss of neuronal spines and eventual cognitive dysfunction. This hypothesis will be tested in two specific aims: 1) Establish the role of testosterone in dendritic spinogenesis and cognitive outcome after neonatal anesthesia in rats. 2) Establish the role of testosterone in KCC2 expression and determine whether excitatory GABAergic neurotransmission is necessary for anesthetic-mediated spine loss and cognitive deficits. The first aim will compare dendritic spine densities of hippocampal pyramidal neurons and cognitive function following anesthesia exposure in male and female rats after gonadectomy and/or treatment with exogenous testosterone. Under the second aim, section 2.1, will define the role of testosterone in sex-specific temporal expression of KCC2 in control, male and female rats after gonadectomy or treatment with exogenous testosterone. And section 2.2, will use in utero electroporation, to genetically manipulate hippocampal excitatory signaling by early expression of KCC2 or the inward rectifying Kir2.1 (two mechanisms that inhibit GABAergic depolarization) then assess dendritic spine morphology and density as well as cognitive function after early anesthesia exposure. The approach is innovative because cellular level mechanistic studies are guided by and interpreted in light of cognitive function testing, the most relevant outcome that can be measured in animals. The expected contribution from these studies is a detailed understanding of the sex-specific factors leading to deficits of recognition memory in males' vs females after early anesthesia exposure. The proposed research is significant because 1)~ T of children anesthetized in the first three years of life are male, and 2)few other studies have investigated the role of sex in cognitive outcome after early anesthesia, and 3)there is no known mechanism for sex-specific cognitive outcomes after early childhood anesthesia exposure. The results obtained from the proposed research will lead to eventual trials to improve risk stratification and guide decision making around the youngest patients that must be exposed to anesthesia.