Mechanism of neurological and cognitive side effects of sevoflurane anesthesia at

描述(申请人提供)：与新生儿麻醉相关的细胞毒性和延迟性行为/认知异常的细胞机制知之甚少。由麻醉剂抑制的神经元活动引起的神经发生改变一直是一个占主导地位的概念。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加剧GABA诱导的未成熟神经元的去极化和钙内流，导致即刻(癫痫，细胞毒性)和迟发性脑缺陷(将通过评估突触可塑性、声惊厥的脉冲前抑制(PPI)、梳理行为来研究)；2)癫痫发作不是其他缺陷发生的先决条件；3)不同的迟发性缺陷取决于给定麻醉剂的持续时间；4)给定麻醉剂引起的GABAA受体介导的副作用的类型和严重程度取决于其增强GABAA受体介导的信号转导的效果；此外，GABAA受体介导的副作用可通过其对钠和钙内流的直接作用而改变；5)抑制NKCC1活性可减轻这些麻醉剂对新生大鼠的副作用。使用七氟醚和异氟醚，这两种普通的挥发性麻醉剂共享GABAA的作用成分，该提案旨在验证上述假设。目的1：研究七氟醚和异氟醚对出生后4-24天(P4-P24)幼鼠大脑皮质神经元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性钙通道的影响。目的#2：测定七氟醚和异氟醚诱导P4-P24仔鼠大脑皮层癫痫发作的能力。目的#3：确定七氟醚和异氟醚麻醉对新生大鼠的细胞毒性和迟发性神经元副作用。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危重新生儿和婴儿的护理通常涉及外科和非外科手术，需要短期或长时间的麻醉。本研究的结果将有助于：1)确定七氟醚和异氟醚麻醉在脑发育早期产生不良反应的机制；2)为该年龄段选择更安全的麻醉剂或麻醉方案提供标准；3)提供方法，通过改变氯-稳态来提高现有的具有GABAA/甘氨酸能作用成分的麻醉药的有效性和安全性。 公共卫生相关性：使用新生大鼠，本研究测试了一种假设，即由增强GABAA/甘氨酸受体活性的麻醉剂产生的兴奋可能会影响全身麻醉的安全性，并可能导致新生儿和小婴儿的长期神经和认知风险。这项研究还验证了抑制NKCC1活性可能会减少这些副作用并增加麻醉药安全性的假设。

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.