Figure 2. NMB effect on breathing.

a-c, Breathing activity of anesthetized rat following bilateral NMB injection (100nl, 3μM) into preBötC. Note increased sighing (spikes in tidal volume (V_T), integrated diaphragm activity (∫Dia)) but little change in respiratory rate (frequency, f). Bar, 1 min. b,c, Similar, stereotyped waveforms of spontaneous (b) and NMB-induced (c) sighs (from a; also ED Fig. 3a,c-f). Bar, 2s. d, Quantification of (a). Top: raster plots of sighs (tics) in five rats following NMB injection (grey); numbers, highest instantaneous sigh rate (red tics). Bottom: instantaneous sigh rate of bottom raster plot; numbers, average instantaneous sigh rate before and maximum (and fold increase) after injection. e, Integrated hypoglossal nerve (∫XII; black) and preBötC neural activity (∫preBötC; grey) in preBötC slices containing indicated NMB concentrations. NMB increases doublets (*), a sigh signature in slices. Bar, 10s. f, Quantification of (e) (n=7; *, p<0.05). g, Basal sigh rate in C57BL/6 wild-type (WT) and Nmbr^−/− mice. n=4; bars, standard deviation of mean; *, p<0.001. h, Effect on sighing in anesthetized rats of bilateral preBötC injection (grey) of NMBR antagonist BIM23042 (100nl, 6μM). Top: raster plots; numbers, longest intersigh intervals (s, seconds) following injection. Bottom: sliding average sigh rate (bin 4 min; slide 30s); numbers, average rate before (left) and minimum binned rate after injection (right).