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. 2017 Dec 27;596(15):3029–3042. doi: 10.1113/JP274357

Figure 6. Carotid body activation rapidly restores breathing during RTN inhibition.

Figure 6

A, representative breathing response to instant bilateral optogenetic inhibition of RTN in a conscious rat. Under normoxia, the nadir occurs within 5 s and is followed by a gradual recovery. A brief overshoot occurs when the laser is switched off. Under hyperoxia, to silence the carotid bodies, the recovery phase is not observed and breathing inhibition persists for some time after the light is switched off. Recovery and overshoot of f R are therefore attributable to carotid body stimulation. Adapted from Basting et al. (2016). B, mean breathing response to bilateral opto‐inhibition of RTN in conscious rats (N = 6). Left panel: frequency response before and 7 days after bilateral CB denervation (same 6 rats). Middle panel: tidal volume (V T) response before and after CB denervation. Note that, contrary to f R, V T inhibition is unaffected by CB denervation. Right panel: under hyperoxia, the breathing response to RTN opto‐inhibition is no longer affected by CB denervation. From Basting et al. (2016). Confidence intervals removed for clarity. C, sequence of events (schematic): RTN inhibition reduces both f R and V T causing a decrease in alveolar ventilation and subsequent carotid body activation via the ensuing changes in blood gases. In rats, the carotid bodies stimulate breathing by increasing breathing frequency primarily; this effect quickly mitigates the hypoventilation elicited by RTN inhibition.