Effects of anesthetics on thalamic excitability

项目摘要 丘脑是感觉信息从外周流向皮层和大脑的主要通道。 丘脑皮质连接中断可能是安眠药催眠作用的一个基本共同特征 全身麻醉剂(气)多。此外，最近的研究确定了中央银行的重要作用 丘脑的内侧核(CEM)和腹基底核(VB)控制觉醒和自然睡眠。 尽管丘脑T型钙通道(T通道)在自然睡眠中的作用相当好 虽然已被证实，但这些通道在麻醉中的作用仍然知之甚少。另外，在过去 在这项资助的周期中，我们确定了大鼠仔鼠暴露于临床相关气体中会导致T- 丘脑网状核(NRT)的电流密度，进而导致持久的超兴奋性 以及在体外和体内丘脑皮质网络的病理性振荡。神经元的这些变化 选择性拮抗T通道可逆转其功能。 我们推测，使用针对T通道的药物抑制剂可能会促进GA诱导的丢失 因此，可能会减少手术所需的有效挥发性气体的使用。整体而言 这项应用的目的是检验中心假设，即T通道的CaV3.1亚型在 丘脑CEM和Vb核在麻醉催眠中起重要作用。 为了验证这一假设，我们将使用急性脑片和重组人的体外膜片钳记录。 选择性CEM和Vb核的体外细胞和体内脑电记录 药理T通道抑制剂，以及具有全球和区域特异性沉默的小鼠遗传学 丘脑中的CaV3.1通道追求以下特定目标： 目的1：确定重组和天然CaV3.1通道的生物物理和分子机制 异氟醚(ISO)和七氟烷(SEVO)两种常见气体的体外抑制作用及其对神经细胞的影响 CEM的区域兴奋性。我们还将使用新的方法与ISO的光亲和配体(AZI-ISO)和 SEVO(AZI-SEVO)以确定挥发性气体在CaV3.1通道上的特定分子结合位点。 目的2：确定大脑中皮层CaV3.1通道是否参与丘脑皮质的改变 挥发性气体镇静催眠及选择性T通道给药过程中的网络功能 抑制剂TTA-P2，通过活体脑电记录进行评估。 目的3：确定CEM和Vb丘脑CaV3.1通道的区域特异性沉默是否会 ISO和Sevo对体内镇静催眠和丘脑皮质振荡的不同影响 这项拟议的工作是创新的，因为麻醉剂引起的意识丧失的新机制将是 特色化的。它具有重要的医学意义，因为它描述了靶向电压门控的药物的重要性 钙通道的潜在发展更安全的做法在临床麻醉。

Project Summary The thalamus is the major gateway for the flow of sensory information from the periphery to the cortex and the disruption of thalamocortical connectivity may be an essential common feature of the hypnotic effects of many general anesthetic (GAs). Furthermore, recent studies have identified important roles of the central medial nucleus (CeM) and ventrobasal (VB) nucleus of the thalamus in control of arousal and natural sleep. Although the role of thalamic T-type calcium channels (T-channels) in natural sleep is reasonably well established, the role of these channels in anesthesia remains poorly understood. In addition, in the past cycle of this grant we established that exposure of rat pups to clinically-relevant GAs causes increased T- current densities in the reticular thalamic nucleus (nRT), which in turn contributes to lasting hyperexcitabil- ity and pathological oscillations in thalamocortical networks in vitro and in vivo. These changes in neuronal function were reversed by selective antagonism of T-channels. We postulate that the use of pharmacological inhibitors that target T-channels may facilitate GA-induced loss of consciousness and hence may reduce usage of potent volatile GAs needed for surgery. The overall objective of this application, is to test the central hypothesis that the CaV3.1 isoform of T-channels in the CeM and VB thalamic nuclei is important for anesthetic-induced hypnosis. To test this hypothesis, we will use in vitro patch-clamp recordings from acute brain slices and recombinant cells in vitro and electroencephalographic (EEG) recordings in vivo from the CeM and VB nuclei, selective pharmacological T-channel inhibitors, and mouse genetics with global and region-specific silencing of CaV3.1 channels in the thalamus to pursue the following specific aims: Aim 1: To determine the biophysical and molecular mechanism of recombinant and native CaV3.1 channel inhibition in vitro by two common GAs, isoflurane (ISO) and sevoflurane (SEVO), and their effect on neu- ronal excitability of CeM. We will also use new approach with photoaffinity ligands of ISO (AZI-ISO) and SEVO (AZI-SEVO) to identify specific molecular binding sites on CaV3.1 channels for volatile GAs. Aim 2: To determine whether CaV3.1 channels in the CeM contribute to the alterations in thalamocortical network function during sedation/hypnosis with volatile GAs and administration of the selective T-channel inhibitor TTA-P2, as assessed by in vivo EEG recordings. Aim 3: To determine if region-specific silencing of CaV3.1 channels in the CeM and VB thalamus will have differential effects on sedation/hypnosis and thalamocortical oscillations in vivo induced by ISO and SEVO. The proposed work is innovative in that new mechanisms of anesthetic-induced loss of consciousness will be characterized. It is medically significant because it describes the importance of drugs that target voltage- gated calcium channels for potential development of safer practices in clinical anesthesia.