KATP CHANNEL MODULATION OF BRAINSTEM NEURONS IN HYPOXIA

在过去的5年里，我们专注于旨在理解 脑干神经元对缺氧的反应和适应。我们的 结果表明，脑干神经元对低氧的反应是 与大脑皮层神经元不同。缺氧时，脑干神经元 去极化并增加它们的兴奋性以增加运动神经元的输出， 而大脑皮层神经元的兴奋性降低。这一下降在 神经元兴奋性可能延缓大脑皮层神经元的损伤，但不是 明确脑干神经元如何保护自己免受过度 去极化和缺氧性损伤。在这方面，我们的初步数据 已经证明，对ATP敏感的K+(KATP)通道发生激活 在低氧期间，这可能减弱低氧诱导的去极化 并限制神经元兴奋性的增加。我们认为这是一次 重要的发现，因为它的影响不仅限于脑干 神经元，但也适用于所有被赋予这些 频道。尽管如此，中枢神经元上的KATP通道调节 不能很好地理解，尤其是在缺氧时。为了确定 这些KATP通道在缺氧过程中的作用及其调节 一些细胞质和膜因子，我们已经开发出了这个 试验性提案。将检验三个主要假设：1)低氧 激活脑干神经元上的KATP通道，从而改善 缺氧后这些神经元的功能恢复；2)KATP的激活 低氧时的通道是几个 胞浆和膜因子；3)KATP通道活性受调控 通过内源性神经递质以G蛋白依赖的方式。几个 将使用的技术包括单声道记录在节选和 细胞贴附贴片，全细胞电压钳，急性分离 神经元，用离子选择法测量离子浓度 脑干切片的微电极和细胞内记录。所有的 这些技术目前正在我们的实验室中使用。两组 神经元(舌下神经元和实质中的非呼吸性神经元 将在这些实验中使用，这两个实验都具有高密度 KATP频道。我们相信，我们提议的研究将产生 重要的新信息将提高我们对这些 KATP通道在中枢神经元热和低氧时被调节。 我们希望这一新知识将导致更有效的设计 预防或减少缺氧/缺血的治疗策略- 诱发性脑损伤。

Over the past 5 years, we have focused on studies aiming at understanding the response and adaptation of brainstem neurons to O2 deprivation. Our results have indicated that the response of brainstem neurons to hypoxia is different from that of cortical neurons. During hypoxia, brainstem neurons depolarize and increase their excitability to raise motoneuronal output, while excitability of cortical neurons decreases. This decrease in neuronal excitability may delay injury in cortical neurons, but it is not clear how brainstem neurons protect themselves from excessive depolarization and hypoxic damage. In this regard, our preliminary data have shown that activation of ATP-sensitive K+ (Katp) channels occurs during hypoxia and this may attenuate the hypoxia-induced depolarization and limit the increased neuronal excitability. We believe that this is an important finding as its implications are not limited only to brainstem neurons, but also applied to all neurons that are endowed with these channels. In spite of this, Katp channel regulation in central neurons is not well understood, especially during hypoxia. In order to determine the role of these Katp channels during O2 deprivation and their regulation by a number of cytosolic and membrane factors, we have developed this experimental proposal. Three major hypotheses will be tested: 1) hypoxia activates Katp channels in brainstem neurons and this improves the functional recovery of these neurons post hypoxia; 2) activation of Katp channels during hypoxia is a result of interactive changes in several cytosolic and membrane factors; and 3) Katp channel activity is modulated by endogenous neurotransmitters in a G protein-dependent manner. Several techniques will be used including single channel recordings in excised and cell-attached patches, whole-cell voltage clamp in acutely dissociated neurons, measurements of ionic concentrations with ion-selective microelectrodes and intracellular recordings from brainstem slices. All of these techniques are currently operative in our laboratory. Two groups of neurons (hypoglossal neurons and non-respiratory neurons in the substantia nigra) will be used in these experiments, both of which have a high density of Katp channels. We believe that our proposed studies will yield important new information that will improve our understanding of how these Katp channels are regulated in central neurons at zest and during hypoxia. We wish that this new knowledge will lead to a design of more effective therapeutical strategies in preventing or diminishing hypoxia/ischemia- induced brain injury.