Novel neurosteroid anesthetics and developmental synaptogenesis

总结 幼儿暴露于全身麻醉药（GAs）在医学中很常见;然而， 这表明这种做法可能不利于大脑发育，导致长期的认知障碍。 损伤由于目前使用的已知对未成熟大脑具有神经毒性的GA通过以下方式发挥其作用： 调节两个主要的受体系统- GABA和NMDA -我们提出了一般假设， 具有不同细胞靶点的麻醉剂可能是安全且有前途的替代品。一种这样的替代 是已知对低电压激活的T型钙通道具有阻断作用的神经活性类固醇家族 对神经元的兴奋性和突触传递很重要。我们的长期目标是开发新的遗传算法 这将提供与现有产品相同的可靠性和有效性，但不会造成长期的破坏性影响。 后果我们有一个充满希望的开始，因为T通道阻断神经活性类固醇不仅 强效镇痛药，也是有效的催眠药。最重要的是，与其他注射剂（和 吸入）麻醉剂，它们似乎对发育中的大脑的伤害要小得多， 初步病理形态学和功能发现。我们的基本原理是， 用于儿童的麻醉剂应该以目前对机制的理解为指导， 导致目前使用的GA的发育神经毒性。为此，我们将使用体外和体内 GA诱导的发育神经毒性大鼠模型，以解决新的特定假设， 与临床使用的GA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剂。目的#1：表征以下物质的麻醉特性 新型神经活性类固醇类似物，其为T-通道阻断剂（例如3-OH和ECN）和GABAA激动剂 (e.g. ACN、CDNC 24和阿法沙酮），并将其在大鼠和小鼠中的麻醉特征与常用的 注射麻醉剂异丙酚初步数据表明，3-羟色胺是安全有效的， 与氯胺酮一起，当给予大鼠幼崽（出生后第7天）时，它表现出更高的功效和效力。目的 #2：检查神经活性类固醇类似物维斯维斯丙泊酚的神经毒性潜力（已知会引起显著的 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（例如急性凋亡性细胞死亡，突触形成/维持中的延迟损伤， 线粒体的完整性、神经元存活和突触传递的损伤）。目标#3：仔细检查长期- 早期暴露于新型神经活性类固醇类似物的长期功能结局，特别关注 海马离体切片制备中神经元通讯和认知功能的体内评估 发展我们的初步研究结果表明，在早期暴露于3毫克- 哦目标#4：通过检查麻醉剂的麻醉特性和安全性，将啮齿动物研究提升到一个新的水平。 选择的神经活性类固醇（如目的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.