NA+ CHANNELS AND EXCITABILITY IN HYPOXIA

缺氧时的 NA 通道和兴奋性

• 批准号: 6108754
• 负责人: GARBIEL G HADDAD
• 金额: $ 19.08万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-12-01 至 1999-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6108754
• 关键词: G protein; age difference; autoradiography; biological signal transduction; cellular pathology; confocal scanning microscopy; flash photolysis; hypoxia; in situ hybridization; laboratory rat; microelectrodes; neural inhibition; neurons; neurophysiology; phosphorylation; receptor binding; sodium channel; statistics /biometry; voltage /patch clamp; voltage gated channel

In the past several years, one main focus of our laboratory has been to examine the response of central neurons in a number of brain regions to acute and chronic O2 deprivation. We are particularly interested in the mechanisms that can led to neuronal injury and those that, when activated, can prevent or delay injury. Recently, we have made interesting observations regarding membrane ionic events that link metabolism to excitability. One of these observations pertains to the voltage-sensitive Na+ channels in central neurons. An early event during anoxia in mature (adult) neocortical neurons seems to be a profound inhibition of the steady-state availability of these channels with a major reduction in Na+ current (iNa) and a decrease in neuronal excitability. This observation is important because this may be an adaptive strategy in the adult in that the decrease in excitability will lessen O2 consumption and minimize the mismatch between demand and supply. We are not sure how the immature neocortical cells will respond in terms of INa. We therefore focus in this proposal on the study of the Na+ current in neocortical neurons during graded hypoxia and examine 4 separate hypotheses: 1+ Neocortical neurons decrease their excitability during graded hypoxia by inhibiting INa in a graded manner in the mature but not in the immature; 2) the alterations in INa kinetics during O2 deprivation in neocortical neurons are due to changes in specific cytosolic factors and these are more pronounced in the mature than in the immature; 3) O2 deprivation alters INa via mechanisms that are either membrane-delimited or dependent on phosphorylation and 4) long term hypoxia modulates the expression of Na+ channels. These experiments will involve the use of the in-vitro slice and microelectrode technique as well as patch clamp with whole-cell and single channel recordings in freshly dissociated neurons. Optical measurements of Ca++ i and H+ i using confocal microscopy will also be performed. All techniques are available and routinely performed in the PI's laboratory. Our long term view and efforts are focussed on understanding the events that occur during anoxia in central neurons so that we can manipulate cell behavior and possibly render mammalian neurons more tolerant to lack of O2. This will have major implications on a vast number of diseases or conditions that span the age spectrum from the fetus to old age.

在过去的几年中，我们实验室的一个主要重点是 检查许多大脑区域中中央神经元对 急性和慢性O2剥夺。 我们对 可能导致神经元损伤的机制以及 激活，可以预防或延迟受伤。 最近，我们做了 关于链接的膜离子事件的有趣观察 兴奋性的代谢。 这些观察之一与 中央神经元中的电压敏感Na+通道。 早期事件 成熟（成人）新皮质神经元中的缺氧似乎是深刻的 抑制这些通道的稳态可用性 Na+电流（INA）的主要降低和神经元减少 兴奋性。 这个观察很重要，因为这可能是 成年人的自适应策略，因为兴奋性的降低将 减少O2的消耗并最大程度地减少需求和需求之间的不匹配 供应。 我们不确定未成熟的新皮层细胞会如何反应 就ina而言。 因此，我们将重点放在该建议上 Na+在分级缺氧期间新皮质神经元中的电流并检查4 单独的假设：1+新皮质神经元降低其兴奋性 在渐变低氧期间，通过以成熟的方式抑制INA 但不成熟； 2）O2期间INA动力学的改变 新皮质神经元的剥夺是由于特定的变化 胞质因子和这些因素在成熟中比在 不成熟； 3）O2剥夺通过机制来改变INA 膜限制或依赖于磷酸化，4）长期 缺氧调节Na+通道的表达。 这些实验会 涉及使用体外切片和微电极技术作为 以及带有整个细胞和单个通道记录的贴片夹 新鲜分离的神经元。 Ca ++ I和H+ I的光学测量值 还将使用共聚焦显微镜进行。 所有技术都是 在PI的实验室中可用并经常执行。 我们的长期 观点和努力的重点是理解发生的事件 在中央神经元的缺氧期间，我们可以操纵细胞行为 并且可能使哺乳动物神经元更宽容缺乏O2。 这 将对大量疾病或状况产生重大影响 从胎儿到老年的年龄频谱。