Mechanism of neurological and cognitive side effects of sevoflurane anesthesia at

描述（由申请人提供）：与新生儿麻醉相关的细胞机制介导细胞毒性和延迟行为/认知异常尚不清楚。由麻醉抑制的神经元活动引起的神经发生改变一直是一个主流的概念。根据我们的初步结果和文献数据，我们假设：1)增强GABAA/甘氨酸受体活性的麻醉剂可能会加剧gaba诱导的去极化和Ca2+内流在未成熟神经元中导致立即（癫痫发作、细胞毒性）和延迟性脑缺陷（将通过评估突触可塑性、声惊吓的脉冲前抑制（PPI）、梳理行为来研究）；2)癫痫不是其他缺陷发生的前提；3)不同的延迟缺陷取决于给定麻醉剂的持续时间；4)特定麻醉剂引起的GABAA受体介导的副作用的类型和严重程度取决于其增强GABAA受体介导的信号传导的功效；此外，这种麻醉剂的GABAA受体介导的副作用可以通过其对Na+和Ca++流入的直接作用而得到改善；5)抑制NKCC1活性可减少这些麻醉药在新生大鼠中的副作用。使用七氟烷和异氟烷这两种具有相同GABAA作用成分的一般挥发性麻醉剂，本提案旨在验证上述假设。目的1：确定七氟醚和异氟醚对出生后第4-24天（P4-P24）大鼠幼鼠新皮质神经元GABAA/甘氨酸受体介导的反应、神经元放电、自发兴奋性突触后电流和电压门控钙离子通道的影响。目的2：确定七氟醚和异氟醚诱导P4-P24大鼠幼鼠皮质癫痫发作的能力。目的3：确定七氟醚和异氟醚麻醉对新生大鼠幼崽的细胞毒性和延迟性神经元副作用。这项研究对人类健康的影响是显而易见的。对越来越多的早产儿和重症足月新生儿和婴儿的护理通常涉及需要短期或长期麻醉的手术和非手术治疗。本研究结果将有助于：1)确定七氟醚和异氟醚麻醉在大脑发育早期的不良反应机制；2)为该年龄组提供选择更安全麻醉剂或方案的标准；3)通过改变Cl-稳态，为目前可用的具有GABAA/甘氨酸能成分的麻醉药提供提高疗效和安全性的方法。

DESCRIPTION (provided by applicant): Cellular mechanisms mediating cytotoxicity and delayed behavioral/cognitive abnormalities associated with neonatal anesthesia are poorly understood. Altered neurogenesis caused by anesthetic-depressed neuronal activity has been a predominant concept. Based on our preliminary results and literature data we hypothesize: 1) anesthetics that enhance GABAA/glycine receptor activity may exacerbate GABA-induced depolarization and Ca2+ influx in immature neurons resulting in immediate (seizures, cytotoxicity) and delayed brain defects (will be studied by evaluating synaptic plasticity, prepulse inhibition (PPI) of acoustic startle, grooming behavior); 2) seizures are not the prerequisite for other defects to occur; 3) distinct delayed defects are differently depend on duration of a given anesthetic; 4) types and severity of the GABAA receptor-mediated side effects caused by a given anesthetic depend on its efficacy to enhance GABAA receptor-mediated signaling; in addition, the GABAA receptor-mediated side effects of this anesthetic can be modified by its direct effects on Na+ and Ca++ influxes; 5) inhibition of NKCC1 activity diminishes side effects caused by these anesthetics in neonatal rats. Using sevoflurane and isoflurane, two general volatile anesthetics that share a GABAA component of action, this proposal aims to test the above hypotheses. The specific aims are as follows: Aim #1: Determine effects of sevoflurane and isoflurane on GABAA/glycine receptor-mediated responses, neuronal firing, spontaneous excitatory postsynaptic currents and voltage-gated Ca++ channels in postnatal day 4-24 (P4-P24) rat pup neocortical neurons. Aim #2: Determine the ability of sevoflurane and isoflurane to induce cortical seizures in P4-P24 rat pups. Aim #3: Determine the cytotoxic and delayed neuronal side effects of sevoflurane and isoflurane anesthesia in neonatal rat pups. The impact of this study on human health is obvious. Care for increasing numbers of preterm and critically ill term neonates and infants often involves both surgical and non-surgical procedures that require short-term or prolonged administration of anesthesia. The results of the current study will help: 1) to determine the mechanisms of the adverse effects of anesthesia with sevoflurane and isoflurane at early stages of brain development; 2) to provide criteria for choosing safer anesthetic agents or regimens for this age category; 3) to provide approaches to increase efficacy and safety of currently available anesthetics with a GABAA/glycine-ergic component of actions by modifying Cl- homeostasis. PUBLIC HEALTH RELEVANCE: Using neonatal rats this study tests the hypothesis that the excitation, generated by anesthetics that enhance GABAA/glycine receptor activity, may affect safety of general anesthesia and may result in long- term neurological and cognitive risks in neonates and small infants. This study also tests the hypothesis that inhibition of NKCC1 activity may diminish these side effects and increase safety of the anesthetics.