Sympathetic neurons deprived of nerve growth factor (NGF) die by apoptosis. Chronic depolarization with elevated concentrations of extracellular potassium ([K⁺]_E) supports long-term survival of these and other types of neurons in culture. While depolarization has long been used to support neuronal cultures, little is known about the mechanism. We explored how chronic depolarization of NGF-deprived mouse sympathetic neurons in culture blocks apoptotic death. First, we determined the effects of elevated [K⁺]_E on proapoptotic BH3-only proteins reported to be upregulated in sympathetic neurons after NGF withdrawal. Upregulation of BIM_EL was blocked by depolarization while upregulation of PUMA was not. BMF levels did not increase after NGF withdrawal, and elevated [K⁺]_E had no effect on its expression. dp5/HRK was not detectable. A large increase in production of mitochondria-derived reactive species (RS), including reactive oxygen species (ROS), occurs in NGF-deprived sympathetic neurons. Suppressing these RS prevents cytochrome c release from mitochondria and apoptosis. The addition of high [K⁺]_E to cultures rapidly blocked increased RS and cytochrome c release. Elevated [K⁺]_E caused an increase of the cellular antioxidant glutathione (GSH). Preventing this increase prevented the elevated [K⁺]_E from blocking cytochrome c release and death. While suppression of BIM_EL upregulation by elevated [K⁺]_E may contribute to high [K⁺]_E pro-survival effects, we conclude that elevated [K⁺]_E prevents apoptotic death of NGF-deprived sympathetic neurons primarily via an antioxidant mechanism.

缺乏神经生长因子 (NGF) 的交感神经元因细胞凋亡而死亡。细胞外钾 ([K ⁺ ] _E )浓度升高的慢性去极化支持这些和其他类型神经元在培养中的长期存活。虽然长期以来一直使用去极化来支持神经元培养，但对该机制知之甚少。我们探索了培养中缺乏 NGF 的小鼠交感神经元的慢性去极化如何阻止细胞凋亡。首先，我们确定了 [K ⁺ ] _E升高对据报道在 NGF 停用后交感神经元中上调的促凋亡 BH3-only 蛋白的影响。BIM _EL的上调被去极化阻断，而 PUMA 的上调则没有。NGF 停用后 BMF 水平没有增加，[K ⁺ ] _E升高对其表达没有影响。dp5/HRK 无法检测。在缺乏 NGF 的交感神经元中，线粒体衍生的活性物质 (RS)，包括活性氧 (ROS) 的产生大量增加。抑制这些 RS 可防止细胞色素c从线粒体和细胞凋亡中释放。向培养物中添加高 [K ⁺ ] _E会迅速阻止 RS 和细胞色素c释放的增加。升高 [K ⁺ ] _E导致细胞抗氧化剂谷胱甘肽（GSH）的增加。防止这种增加可以防止升高的 [K ⁺ ] _E阻止细胞色素c 的释放和死亡。虽然通过升高的 [K ⁺ ] _E抑制 BIM _EL上调可能有助于高 [K ⁺ ] _{E 的}促生存作用，但我们得出结论，升高的 [K ⁺ ] _E主要通过抗氧化机制防止缺乏 NGF 的交感神经元的凋亡.