Cardiopulmonary Effects of Vagus Nerve Stimulation in Mice

Figures

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  Figure 1.. VNS decreases HR in anesthetized mice. A, Diagram illustrating cuff construction of in-house manufactured VNS electrodes for mouse implantation. Micro-renathane tubing is cut open along the longitudinal access (dashed line); two platinum:iridium leads (cyan arrowheads) are sewn into place and secured with UV cure glue; suture is sewn into place on both sides of the cuff (gold arrowheads) at the longitudinal midpoint to facilitate cuff manipulation during assembly and for secure cuff closure during implantation. B, Photograph of assembled mouse VNS cuff electrode (arrowheads denote leads and sutures as in A). C, Cuff electrodes were acutely implanted around the right or left cervical vagus nerve in anesthetized mice. D, VNS (10 s trains of 0.4 mA, 30 Hz pulses) produced a significant decrease in HR; ****p < 0.0001, paired t test. E, No significant differences were observed in VNS-evoked HR changes between right and left nerve stimulation or between male and female mice.

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  Figure 2.. VNS decreases BR in anesthetized mice. A, Video-based breathing analyses were validated in two mice using simultaneously recorded ECG. B, Example breathing signals extracted from ECG (top, cyan) and video (bottom, gold) during a single 30 s recording from one mouse. Gray horizontal lines indicate the thresholds used to detect breaths in each trace, arrows indicate the times of detected breaths in each signal; shaded gray box indicates timing of VNS delivery. C, Across ten 10 s recording epochs, the timing of detected breaths was highly correlated between ECG and video recording methods (R2 = 0.9999, p = 0.0000, Pearson's linear correlation); filled circles, Mouse 1 data; open circles, Mouse 2 data. D, VNS produced a significant decrease in BR; ****p < 0.0001, paired t test. E, No significant differences were observed in VNS-evoked BR changes between right and left nerve stimulation or between male and female mice. F, The majority of mice exhibited both HR and BR reductions in response to VNS, though in approximately one-third of animals, only one type of response was observed. G, There was no correlation between the VNS-evoked change in HR and the change in BR. Legend for panels…

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  Figure 3.. VNS-evoked decreases in HR depend on activation of efferent vagal fibers. A, Transection of afferent (Aff.) vagal fibers was performed in eight mice (n = 2 ML, 2 MR, 2 FL, 2 FR). B, Prior to afferent fiber transection, VNS-evoked robust decreases in HR. C, VNS-evoked HR decreases were not altered by transection of afferent vagal fibers. D, Transection of efferent (Eff.) vagal fibers was performed in eight mice (n = 2 ML, 2 MR, 2 FL, 2 FR). E, Prior to efferent fiber transection, VNS evoked robust HR reductions. F, After efferent fiber transection, VNS-driven decreases in HR were abolished. ****p < 0.0001, paired t test.

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  Figure 4.. VNS-evoked decreases in BR depend on activation of afferent and efferent vagal fibers. A, Transection of afferent (Aff.) vagal fibers was performed in eight mice (same mice as in Fig. 3A–C). B, Prior to afferent fiber transection, 7/8 mice (87.5%) exhibited VNS-evoked decreases in BR; **p < 0.01, paired t test. C, VNS-evoked decreases in BR were abolished by transection of afferent vagal fibers. D, Transection of efferent (Eff.) vagal fibers was performed in eight mice (same mice as in Fig. 3D–F). E, Prior to efferent fiber transection, 7/8 mice (87.5%) exhibited significant VNS evoked decreases in BR; **p < 0.01, paired t test. F, After efferent fiber transection, VNS-driven decreases in HR were abolished. Legend for panels B and C and E and F is shown in Figure 3B.