Figure 6.
Selective activation of RVLM-CA neurons increases cardiorespiratory coupling and autonomic activation in conscious DβHCre/0 mice. A, Cardiovascular and respiratory effects of RVLM-CA neuron stimulation (5 ms pulse at 20 Hz). BP, arterial blood pressure; HR, heart rate. B1, B2, Expanded traces of resting (B1) and stimulated (B2) segments in A. During stimulation a marked increase in the synchronicity of the cardiac and respiratory cycles (sinus arrhythmia) is manifested by increased beat-to-beat variability. Broken vertical lines mark onset of inspiration and highlight sinus arrhythmia. C, Phase histogram plot of occurrence of BP nadirs (representing cardiac contraction) relative to the respiratory cycle (triggered from the rising phase of inspiration) plotted from A. Note that while the respiratory cycle was shortened by stimulation, the phase duration of inspiration was unchanged (resting, 0–130°; stimulated, 0–137°). D–H, Effects of photostimulation (5 ms, 20 Hz, 30 s) on MBP and HR after intraperitoneal injection of saline (D), methyl-atropine (E), propranolol (F), methyl-atropine plus propranolol (G), and prazosin (H). (*Overlapping lines reflect significant differences: one line, p < 0.05; two lines p < 0.01; three lines p < 0.001 by Dunnett's post test between drug and saline treatment.)