Department of Mathematics and Center for the Neural Basis of Cognition, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
PLoS Comput Biol. 2019 Aug 30;15(8):e1006938. doi: 10.1371/journal.pcbi.1006938. eCollection 2019 Aug.
The mechanism(s) of action of most commonly used pharmacological blockers of voltage-gated ion channels are well understood; however, this knowledge is rarely considered when interpreting experimental data. Effects of blockade are often assumed to be equivalent, regardless of the mechanism of the blocker involved. Using computer simulations, we demonstrate that this assumption may not always be correct. We simulate the blockade of a persistent sodium current (INaP), proposed to underlie rhythm generation in pre-Bötzinger complex (pre-BötC) respiratory neurons, via two distinct pharmacological mechanisms: (1) pore obstruction mediated by tetrodotoxin and (2) altered inactivation dynamics mediated by riluzole. The reported effects of experimental application of tetrodotoxin and riluzole in respiratory circuits are diverse and seemingly contradictory and have led to considerable debate within the field as to the specific role of INaP in respiratory circuits. The results of our simulations match a wide array of experimental data spanning from the level of isolated pre-BötC neurons to the level of the intact respiratory network and also generate a series of experimentally testable predictions. Specifically, in this study we: (1) provide a mechanistic explanation for seemingly contradictory experimental results from in vitro studies of INaP block, (2) show that the effects of INaP block in in vitro preparations are not necessarily equivalent to those in more intact preparations, (3) demonstrate and explain why riluzole application may fail to effectively block INaP in the intact respiratory network, and (4) derive the prediction that effective block of INaP by low concentration tetrodotoxin will stop respiratory rhythm generation in the intact respiratory network. These simulations support a critical role for INaP in respiratory rhythmogenesis in vivo and illustrate the importance of considering mechanism when interpreting and simulating data relating to pharmacological blockade.
作用机制（S）最常用的药理阻滞剂电压门控离子通道都很清楚; 然而，这种知识很少被认为是在解释实验数据。封锁的影响往往被认为是等效的，而不管涉及的阻滞剂的机制。通过计算机模拟，我们证明这种假设可能并不总是正确的。我们模拟通过两种不同的药理机制来阻断持续钠电流（INaP）：（1）河豚毒素介导的孔阻塞和（2）通过利鲁唑改变失活动力学。在呼吸神经元中提出的预 - Botzinger 复合体（pre-BötC）呼吸神经元中产生节律的河豚毒素和利鲁唑的实验应用的报道效果是多种多样的，似乎是相互矛盾的，并且导致了该领域关于 INaP 在呼吸电路中的具体作用的相当大的争论。我们的模拟结果与从孤立的 pre-BötC 神经元水平到完整的呼吸网络水平的广泛的实验数据相匹配，并且还产生了一系列可进行实验测试的预测。具体来说，在这项研究中，我们：（1）为 INaP 阻断的体外研究中看似矛盾的实验结果提供了一种机制解释，（2）表明 INaP 阻断在体外制剂中的作用不一定等同于更完整制剂中的作用，（3）证明并解释为什么利鲁唑在完整的呼吸网络中不能有效地阻断 INaP，以及（4）得出预测，低浓度河豚毒素对 INaP 的有效阻断将停止完整的呼吸网络中的呼吸节律生成。这些模拟支持 INaP 在体内呼吸节律发生中的关键作用，并说明了在解释和模拟与药理学阻断相关的数据时考虑机制的重要性。
