Novel neurosteroid anesthetics and perioperative analgesia

项目摘要 背根神经节（DRG）和背角（DH）的痛觉神经元可被致敏 （过度兴奋）对手术诱导的外周组织损伤的反应。由于知识不足 关于这种致敏的机制，目前对术后疼痛的治疗仅限于 具有显著副作用或滥用可能性的某种非特异性全身性药物（阿片类药物）。最近 我们实验室的研究已经确定，CaV3.2（T型）钙通道和CaV2.3（R型）电压- 门控钙通道对疼痛反应的敏感性做出了以前未被认识的贡献， 增强外周伤害感受器的兴奋性并控制DH中的兴奋性突触传递， 脊髓我们以前发现，阻断伤害性DRG神经元的CaV3.2电流， 5β-还原的神经活性类固醇是其有效的外周抗伤害感受作用的基础。我们的新数据 证明了一种这样的类固醇，3β-OH [（3β，5 β，17 β）-3-羟基雄甾烷-17-腈]，除了 催眠性质，也显示出优异的脊髓介导的镇痛作用。我们还发现3β-OH抑制 重组CaV2.3电流。这一发现使我们假设：抑制神经元CaV3.2和 新型麻醉剂3β-OH和相关神经活性类固醇在疼痛通路中的CaV2.3电流 有效的镇痛。在目标1中，我们将使用临床相关的方法研究神经活性类固醇的镇痛效力。 皮肤和深部组织切口的啮齿动物模型。在目标2中，我们将定义神经活性类固醇在以下方面的作用： 调节伤害感受性DH神经元的突触传递和神经元兴奋性。这些研究将 定义了测试化合物在主要伤害感受途径中的全细胞神经生理学作用。我们将 我们还使用电子显微镜研究了CaV2.3和CaV3.2通道的细胞和亚细胞定位， 伤害感受性DH神经元。目的三是研究甾体类化合物的作用机制和构效关系 在伤害感受性DRG神经元中的重组和天然CaV2.3电流的抑制。这个的主要目标 目的是扩大目前可用的有限信息，并期望获得的信息 对于设计更有效和选择性的CaV2.3通道抑制剂非常重要， 在开发新的和更安全的麻醉剂和镇痛剂方面具有重要意义。这项工作具有创新性， 具有医学意义，因为我们预计我们的研究将确定围手术期疼痛的新疗法 这可能会大大减少对麻醉品的需求和药物滥用的可能性。

Project Summary Pain-sensing sensory neurons of the dorsal root ganglion (DRG) and dorsal horn (DH) can become sensitized (hyperexcitable) in response to surgically induced peripheral tissue injury. Because of insufficient knowledge about the mechanisms for this sensitization, current treatment for postoperative pain has been limited to somewhat non-specific systemic drugs (opioids) having significant side effects or potential for abuse. Recent studies in our laboratory have established that CaV3.2 (T-type) calcium-channels and CaV2.3 (R-type) voltage- gated calcium channels make a previously unrecognized contribution to sensitization of pain responses by enhancing excitability of peripheral nociceptors and controlling excitatory synaptic transmission in the DH of the spinal cord. We previously showed that the blockade of CaV3.2 currents in nociceptive DRG neurons by 5β-reduced neuroactive steroids underlies their potent peripheral anti-nociceptive effects. Our new data demonstrate that one such steroid, 3β-OH [(3β,5β,17β)-3-hydroxyandrostane-17-carbonitrile], in addition to hypnotic properties, also displays excellent spinally-mediated analgesia. We also found that 3β-OH inhibits recombinant CaV2.3 currents. This finding has led us to hypothesize that: inhibition of neuronal CaV3.2 and CaV2.3 currents in pain pathways with the novel anesthetic 3β-OH and related neuroactive steroids underlies effective analgesia. In Aim 1, we will study analgesic potency of neuroactive steroids using a clinically relevant rodent model of skin and deep tissue incision. In Aim 2, we will define the role of neuroactive steroids in modulating synaptic transmission and neuronal excitability of nociceptive DH neurons. These studies will define the whole-cell neurophysiological effects of test compounds in the major nociceptive pathway. We will also use electron microscopy to study cellular and subcellular localization of CaV2.3 and CaV3.2 channels in nociceptive DH neurons. In Aim 3, we will study mechanisms and structure-activity relationships of steroid inhibition of recombinant and native CaV2.3 currents in the nociceptive DRG neurons. The main goal of this aim is to expand the limited information currently available with the expectation that the information obtained will be important for the design of more potent and selective inhibitors of CaV2.3 channels that can be important in developing novel and safer anesthetics and analgesics. The proposed work is innovative and medically significant because we anticipate that our studies will identify novel therapies for perioperative pain that may greatly decrease the need for narcotics and potential for drug abuse.β