Voltage-Dependent Rhythmogenic Property of Respiratory Pre-Bötzinger Complex Glutamatergic, Dbx1-Derived, and Somatostatin-Expressing Neuron Populations Revealed by Graded Optogenetic Inhibition.
Voltage-Dependent Rhythmogenic Property of Respiratory Pre-Bötzinger Complex Glutamatergic, Dbx1-Derived, and Somatostatin-Expressing Neuron Populations Revealed by Graded Optogenetic Inhibition.
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DOI：
10.1523/eneuro.0081-16.2016
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发表时间：
2016-05
期刊：
影响因子：
3.4
通讯作者：
Smith JC
中科院分区：
文献类型：
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作者：
Koizumi H;Mosher B;Tariq MF;Zhang R;Koshiya N;Smith JC
哺乳动物的呼吸节律起源于脑干前 Bötzinger 复合体（前 BötC），据推测是由谷氨酸能神经元产生的，但这尚未得到直接证明。此外，转录因子 Dbx1 的发育表达或神经肽生长抑素 (Sst) 的表达已被提议作为节律发生前 BötC 谷氨酸能神经元的标记，但尚不清楚这两个表型定义的神经元群在节律生成方面是否在功能上等同于谷氨酸能神经元。为了解决这些问题，我们通过光遗传学方法比较研究了 BötC 前谷氨酸能、Dbx1 衍生和 Sst 表达神经元在体外新生转基因小鼠髓质切片以及更完整的成人灌注脑干脊髓制剂中呼吸节律生成中的作用。我们建立了三种不同的三重转基因小鼠品系，它们在谷氨酸能、Dbx1 衍生或 Sst 表达神经元中选择性表达 Cre 驱动的古视紫红质 3 (Arch)，以实现靶向光抑制。在每个细胞系中，我们通过体外髓质切片制剂中的全细胞记录，鉴定了有节律性活跃、表达 Arch 的前 BötC 吸气神经元亚群，并确定 Arch 介导的这些吸气神经元的超极化是激光功率依赖性的，且具有相同的功效。通过位点和群体特异性分级光抑制，我们证明了在所检查的呼吸网络的每种状态下，具有相同的神经元电压依赖性频率控制机制的每个群体都降低了吸气频率。我们推断足够多的节律性前 BötC 谷氨酸能神经元也具有 Dbx1 和 Sst 表达表型，因此所有三种表型都具有相同的电压依赖性频率控制特性。
The rhythm of breathing in mammals, originating within the brainstem pre-Bötzinger complex (pre-BötC), is presumed to be generated by glutamatergic neurons, but this has not been directly demonstrated. Additionally, developmental expression of the transcription factor Dbx1 or expression of the neuropeptide somatostatin (Sst), has been proposed as a marker for the rhythmogenic pre-BötC glutamatergic neurons, but it is unknown whether these other two phenotypically defined neuronal populations are functionally equivalent to glutamatergic neurons with regard to rhythm generation. To address these problems, we comparatively investigated, by optogenetic approaches, the roles of pre-BötC glutamatergic, Dbx1-derived, and Sst-expressing neurons in respiratory rhythm generation in neonatal transgenic mouse medullary slices in vitro and also more intact adult perfused brainstem-spinal cord preparations in situ. We established three different triple-transgenic mouse lines with Cre-driven Archaerhodopsin-3 (Arch) expression selectively in glutamatergic, Dbx1-derived, or Sst-expressing neurons for targeted photoinhibition. In each line, we identified subpopulations of rhythmically active, Arch-expressing pre-BötC inspiratory neurons by whole-cell recordings in medullary slice preparations in vitro, and established that Arch-mediated hyperpolarization of these inspiratory neurons was laser power dependent with equal efficacy. By site- and population-specific graded photoinhibition, we then demonstrated that inspiratory frequency was reduced by each population with the same neuronal voltage-dependent frequency control mechanism in each state of the respiratory network examined. We infer that enough of the rhythmogenic pre-BötC glutamatergic neurons also have the Dbx1 and Sst expression phenotypes, and thus all three phenotypes share the same voltage-dependent frequency control property.