Figure 2.
Effect of repetitive stimulation of inhibitory neurons in the preBötC depends on the stimulation frequency. (a) Thoracic chest wall movements recorded by a piezo-sensor (inspiration upward) and the pulse wave (gray trace). Repetitive 33 Hz stimulation (duration of each light pulse: 20 ms; blue bars). Asterisks show heart beat artifacts. (b) During 33 Hz light stimulation, the respiratory rate is reduced in all mice, yielding an overall statistically significant reduction during stimulation (* p < 0.001; n = 12; One way RM ANOVA). The rate recovered to a slightly higher frequency compared with the baseline level (p = 0.033). (c) Stimulation with a light pulse frequency of 6 Hz. The expanded trace shows that some deflections coincide with light pulses (‡; breaths), while others do not (*; heart beat). (d) Statistical analysis of 6 Hz stimulation reveals a significant increase in the rate of chest wall movement (p < 0.05: n = 13; RM ANOVA on Ranks). Of note, 3 mice showed a reduced respiratory rate. (e) Modulation of the respiratory rate by light stimulation with different stimulation frequencies. Data are from n= 7 mice and normalized to the pre-stimulus conditions (set as 1). (f) The stimulation frequency that leads to an increase in the respiratory rate depends on the baseline respiratory rate (p = 0.030, R2 = 0.362).