Novel neurosteroid anesthetics and developmental synaptogenesis

摘要 幼儿接触全身麻醉剂(GAS)在医学上很常见；然而，新的数据显示 表明这种做法可能对大脑发育有害，导致长期认知 减损。由于目前使用的已知对未成熟大脑有神经毒性的气体通过 调节两个主要的受体系统--GABA和NMDA--我们提出了一个普遍的假设，即新的 具有不同细胞靶点的麻醉药可能是安全和有前途的替代药物。一种这样的选择 是一类对低电压激活的T型钙通道具有阻断作用的神经活性类固醇 对神经元兴奋性和突触传递很重要。我们的长期目标是开发新型天然气 这将提供与目前可用的相同的可靠性和有效性，但不会产生破坏性的长期影响 后果。我们有了一个充满希望的开始，因为阻断T通道的神经活性类固醇不仅 强效镇痛剂，但也是有效的催眠药。最重要的是，与其他可注射的(和 吸入麻醉剂，它们对发育中的大脑的危害似乎要小得多，根据我们的 初步的病理形态和功能发现。我们的理论基础是，更安全的设计 儿童使用的麻醉药应以目前对其作用机制的了解为指导 对目前使用的气体的发育神经毒性负责。为此，我们将使用体外和体内 GA诱导发育神经毒性的大鼠模型解决新的特定假设 与临床使用的GAS不同，对T通道具有阻断作用的神经活性类固醇是有效和安全的 在大脑发育的关键阶段使用的麻醉药。目标1：表征麻醉剂的特性 新型神经活性类固醇类似物，为T-通道阻滞剂(如3--OH和ECN)和GABA受体激动剂 (如ACN、CDNC24和Alphaxone)，并比较它们在大鼠和小鼠的麻醉情况 使用注射麻醉剂异丙酚。初步数据表明，3-OH是安全有效的，并与 对于氯胺酮，它在小鼠出生后(出生后7天)给药时显示出更高的疗效和效力。目标 #2：检查神经活性类固醇类似物与异丙酚的神经毒性潜力(已知会导致显著 发育神经毒性)，通过关注GA诱导的损伤的形态和功能特征 突触发生(如急性细胞凋亡性死亡，突触形成/维持迟发性损害， 线粒体的完整性、神经元存活和突触传递障碍)。目标3：仔细检查长期- 早期接触新的神经活性类固醇类似物的足月功能结果 海马区神经元通讯的体外脑片制备及在体认知功能评价 发展。我们的初步研究结果表明，早期接触3-后缺乏认知障碍。 噢。目标4：通过检查麻醉剂的特性和安全性，将啮齿动物研究提高到一个新的水平 在婴儿非人类灵长类动物中选择神经活性类固醇(如AIMS 1-3中所确定的)。

Summary Exposure of young children to general anesthetics (GAs) is common in medicine; however, emerging data suggest that this practice may be detrimental to brain development, resulting in long-term cognitive impairments. Since currently used GAs known to be neurotoxic to the immature brain exert their action by modulating two main receptor systems – GABA and NMDA – we suggest the general hypothesis that novel anesthetics with different cellular targets might be safe and promising alternative. One such alternative is a family of neuroactive steroids with blocking action on low-voltage-activated T-type calcium channels known to be important for neuronal excitability and synaptic transmission. Our long-term goal is to develop novel GAs that will provide the same reliability and efficacy as currently available ones but without devastating long-term consequences. We are off to a promising start since T-channel-blocking neuroactive steroids are not only powerful analgesics but also effective hypnotics. Most importantly, compared with other injectable (and inhaled) anesthetics, they appear to be much less harmful to the developing brain based on our preliminary pathomorphological and functional findings. Our rationale is that the design of safer anesthetics for use in children should be guided by the presently available understanding of the mechanisms responsible for developmental neurotoxicity of currently used GAs. To that end, we will use ex vivo and in vivo rat models of GA-induced developmental neurotoxicity to address the specific hypothesis that novel neuroactive steroids with blocking action on T-channels, unlike clinically-used GAs, are effective and safe anesthetics for use during critical stages of brain development. Aim #1: Characterizes anesthetic properties of novel neuroactive steroid analogs that are T-channel blockers (e.g. 3-OH and ECN) and GABAA agonists (e.g. ACN, CDNC24 and alphaxalone) and compares their anesthesia profile in rats and mice with commonly used injectable anesthetic, propofol. Preliminary data suggest that 3-OH is safe and effective and, compared with ketamine, it exhibits higher efficacy and potency when administered to rat pups (at post-natal day 7). Aim #2: Examines neurotoxic potential of neuroactive steroid analogs vis-à-vis propofol (known to cause significant developmental neurotoxicity) by focusing on morphological and functional features of GA-induced impairments of synaptogenesis (e.g. acute apoptotic cell death, delayed impairment in synapse formation/maintenance, integrity of mitochondria, neuronal survival and impairment in synaptic transmission). Aim #3: Scrutinizes long- term functional outcomes of an early exposure to novel neuroactive steroid analogs with particular focus on neuronal communication in hippocampal ex vivo slice preparation and in vivo assessment of cognitive development. Our preliminary findings suggest a lack of cognitive impairment after an early exposure to 3- OH. Aim #4: Takes rodent studies to the next level by examining the anesthetic properties and safety of a chosen neuroactive steroid (as determined in Aims 1-3) in infant non-human primates.