Here we report the effects of ammonium on the main biophysical features of neurons and astrocytes during the first minutes of exposure. We found that ammonium causes the depolarization of neurons, which leads to the generation of high-frequency action potentials (APs). The initial alkalization and subsequent acidification of the intracellular medium in neurons occur along with the generation of calcium oscillations. Moreover, although the kinetics of calcium response of neurons and astrocytes is different, the dynamics of changes in the intracellular pH (pH_i) is similar. The rate of superoxide production and mitochondrial membrane potential do not change in most neurons and astrocytes during ammonium exposure. At the same time, we observed an increased superoxide production and a decrease in the mitochondrial potential in some neurons in response to ammonium application. However, in both cases, the amplitude of the calcium response in these neurons is significantly higher compared to other neurons. Application of UK 14,304, an agonist of alpha-2 adrenergic receptors (A-2ARs), decreased the frequency of APs upon ammonium-induced high-frequency spike activity. Moreover, we also observed periods of hyperpolarization occurred in individual neurons. We suppose that this hyperpolarization contributes to the suppression of activity and can be mediated by astrocytic GABA release, which is stimulated upon activation of A-2ARs. Thus, our findings reveal a new possible mechanism of the protective action of alpha-2 adrenergic agonists against ammonium-induced hyperexcitation and demonstrate the correlation between intracellular calcium concentration, mitochondrial membrane potential, pH_i, the intensity of superoxide production in hippocampal cells under acute hyperammonemia.

在这里，我们报告了铵暴露在最初的几分钟内对神经元和星形胶质细胞的主要生物物理特征的影响。我们发现铵引起神经元的去极化，从而导致高频动作电位（AP）的产生。神经元中细胞内介质的初始碱化和随后的酸化与钙振荡的产生一起发生。此外，尽管神经元和星形胶质细胞的钙反应动力学不同，但细胞内pH（pH _i） 类似。在铵暴露期间，大多数神经元和星形胶质细胞中超氧化物的产生速率和线粒体膜电位不变。同时，我们观察到，响应于铵盐的施用，某些神经元中超氧化物的产生增加，线粒体电位降低。但是，在这两种情况下，与其他神经元相比，这些神经元中钙反应的幅度明显更高。UK 14,304（α-2肾上腺素受体（A-2ARs）的激动剂）的应用降低了铵诱导的高频尖峰活动后AP的频率。此外，我们还观察到个别神经元发生超极化的时期。我们认为这种超极化有助于抑制活性，并且可以由星形细胞GABA释放介导，在激活A-2AR时会刺激它。因此，我们的发现揭示了α-2肾上腺素能激动剂对铵诱导的过度兴奋的保护作用的新的可能机制，并证明了细胞内钙浓度，线粒体膜电位，pH值之间的相关性。_i，急性高氨血症下海马细胞中超氧化物产生的强度。