Photostimulation of channelrhodopsin‐transfected rostral medullary Phox2b‐expressing neurons activates breathing in unaesthetized rats

The Phox2b‐positive neurons of the RVLM were made to synthesize channelrhodopsin‐2 (ChR2) fused to mCherry (ChR2‐mCherry) by injecting a lentivirus that expresses the transgene under the control of the artificial promoter PRSX8. Labeled neurons consisted of ~62% C1 cells and ~38% retrotrapezoid (RTN) neurons. After 3–4 weeks, we examined the effect of photostimulation (~9 mW; 20 Hz, 10 ms pulses, 30 s) on breathing using plethysmography (10 rats) or diaphragmatic EMG (dEMG) recordings (4 rats). Photostimulation increased dEMG amplitude (19.2±7.4 %) and frequency (104±5 to 125±6 bursts/min, P<0.01). Photostimulation increased all plethysmographic respiratory variables including rate (from 76±3 to 108±5 breaths/min, P<0.0001), tidal volume (from 1.7±0.1 to 2.1±0.1 ml, P<0.001) and peak expiratory flow (from 7.9±0.6 to 9.7±0.9, P<0.05). In sum, the Phox2b‐expressing neurons of the RVLM regulate all aspects of breathing including inspiration and active expiration. We attribute these respiratory effects to the activation of RTN neurons but a small contribution of the C1 cells to these effects is not excluded (NIH support: HL 074011 & 28785).

通过注射一种在人工启动子PRSX8控制下表达转基因的慢病毒，使延髓头端腹外侧网状核（RVLM）的Phox2b阳性神经元合成与mCherry融合的视紫红质通道蛋白2（ChR2 - mCherry）。标记的神经元约62%为C1细胞，约38%为斜方体后核（RTN）神经元。3 - 4周后，我们使用体积描记法（10只大鼠）或膈肌肌电图（dEMG）记录（4只大鼠）检测光刺激（约9毫瓦；20赫兹，10毫秒脉冲，30秒）对呼吸的影响。光刺激使膈肌肌电幅度增加（19.2±7.4%），频率增加（从104±5到125±6次爆发/分钟，P<0.01）。光刺激使所有体积描记呼吸变量增加，包括呼吸频率（从76±3到108±5次呼吸/分钟，P<0.0001）、潮气量（从1.7±0.1到2.1±0.1毫升，P<0.001）和呼气峰流量（从7.9±0.6到9.7±0.9，P<0.05）。总之，延髓头端腹外侧网状核中表达Phox2b的神经元调节呼吸的各个方面，包括吸气和主动呼气。我们将这些呼吸效应归因于斜方体后核神经元的激活，但不排除C1细胞对这些效应有少量贡献（美国国立卫生研究院资助：HL 074011和28785）