Activation of Phox2b-Expressing Neurons in the Nucleus Tractus Solitarii Drives Breathing in Mice
Activation of Phox2b-Expressing Neurons in the Nucleus Tractus Solitarii Drives Breathing in Mice
复制标题
孤束核中表达 Phox2b 的神经元的激活驱动小鼠呼吸
DOI：
10.1523/jneurosci.2048-18.2018
复制
发表时间：
2019-04-10
影响因子：
5.3
通讯作者：
Wang, Sheng
中科院分区：
文献类型：
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作者：
Fu, Congrui;Shi, Luo;Wang, Sheng
孤束核（NTS）与呼吸的控制有关，但参与这种生理功能的神经元表型和回路机制仍不完全清楚。本研究重点关注表达配对样同源框 2b 基因 (Phox2b) 的 NTS 神经元的呼吸作用，并试图确定选择性刺激这组神经元是否会激活雄性小鼠的呼吸。将编码 Gq 偶联人 M3 毒蕈碱受体 (hM3Dq) 的 Cre 依赖性载体显微注射到 Phox2b-Cre 转基因小鼠的 NTS 中。 hM3Dq 转导的神经元在清醒小鼠中被药物激活，同时通过体积描记法测量呼吸效应。我们证明，表达 Phox2b 的 NTS 神经元的化学遗传学刺激通过增加呼吸频率而不是潮气量来显着增加基线分钟通气量。化学遗传学刺激还与适度的二氧化碳刺激协同作用，以增强肺通气反应。选择性消融表达 Phox2b 的 NTS 神经元显着减弱高碳酸血症通气反应。此外，组织学证据表明，刺激表达 Phox2b 的 NTS 神经元会增加 preBötzinger 复合体的神经元活性。最后，我们提出了表达 Phox2b 的 NTS 神经元直接投射到假定的呼吸中枢模式发生器的神经解剖学证据。总体而言，这些发现表明，表达 Phox2b 的 NTS 神经元的选择性激活通过对呼吸中枢模式发生器的兴奋性驱动来增强基线肺通气，并且这组神经元也是高碳酸血症通气反应所必需的。意义陈述 孤束核（NTS）与呼吸的控制有关。配对样同源盒 2b 基因 (Phox2b) 是先天性中枢性通气不足综合征的疾病定义基因，并且限制性存在于脑干核中，包括 NTS。使用化学遗传学方法，我们在此证明，选择性刺激表达 Phox2b 的 NTS 神经元通过对啮齿类动物呼吸中枢模式发生器的兴奋性驱动，大力增强基线肺通气。这些神经元的基因消融减弱了高碳酸血症通气反应。我们还认为，一小部分表达 Phox2b 的神经元表现出 CO2 敏感性，并且可能具有中枢呼吸化学感受器的功能。该方法有望为患有睡眠相关通气不足或呼吸暂停的患者提供未来的适用性。
The nucleus tractus solitarii (NTS) is implicated in the control of breathing, but the neuronal phenotype and circuit mechanism involved in such a physiological function remain incompletely understood. This study focused on the respiratory role of paired-like homeobox 2b gene (Phox2b)-expressing NTS neurons and sought to determine whether selective stimulation of this set of neurons activates breathing in male mice. A Cre-dependent vector encoding a Gq-coupled human M3 muscarinic receptor (hM3Dq) was microinjected into the NTS of Phox2b-Cre transgenic mice. The hM3Dq-transduced neurons were pharmacologically activated in conscious mice while respiratory effects were measured by plethysmography. We demonstrate that chemogenetic stimulation of Phox2b-expressing NTS neurons significantly increased baseline minute volume via an increase in respiratory frequency rather than tidal volume. Chemogenetic stimulation also synergized with moderate CO2 stimulation to enhance pulmonary ventilatory response. Selective ablation of Phox2b-expressing NTS neurons notably attenuated a hypercapnic ventilatory response. Moreover, histological evidence revealed that stimulation of Phox2b-expressing NTS neurons increased neuronal activity of the preBötzinger complex. Finally, we presented the neuroanatomical evidence of direct projection of Phox2b-expressing NTS neurons to putative respiratory central pattern generator. Overall, these findings suggest that selective activation of Phox2b-expressing NTS neurons potentiates baseline pulmonary ventilation via an excitatory drive to respiratory central pattern generator and this group of neurons is also required for the hypercapnic ventilatory response. SIGNIFICANCE STATEMENT The nucleus tractus solitarii (NTS) has been implicated in the control of breathing. The paired-like homeobox 2b gene (Phox2b) is the disease-defining gene for congenital central hypoventilation syndrome and is restrictively present in brainstem nucleus, including the NTS. Using a chemogenetic approach, we demonstrate herein that selective stimulation of Phox2b-expressing NTS neurons vigorously potentiates baseline pulmonary ventilation via an excitatory drive to respiratory central pattern generator in rodents. Genetic ablation of these neurons attenuates the hypercapnic ventilatory response. We also suggest that a fraction of Phox2b-expressing neurons exhibit CO2 sensitivity and presumably function as central respiratory chemoreceptors. The methodology is expected to provide a future applicability to the patients with sleep-related hypoventilation or apnea.