Figure 6. Specificity of HCRT-NMB circuit for confinement-induced sighing.

(A) Sigh rate of wild-type adult mice under tube confinement or hypoxia (10 % O₂) that were gavage fed with HCRTR antagonist ALM (+) or vehicle (−) for 2 hours before plethysmography. Note systemic HCRTR antagonism diminished confinement-induced but not hypoxia-induced sighing. Mean +/−SEM; sample size n=3; *, p<0.05 (unpaired t-test). (B) Respiratory rate before (−) and during (+) confinement of mice systemically treated with ALM (+, n=7) or vehicle (−, n=8) (Fig. 5 E to G). Note HCRTR antagonism reduced respiratory rate under basal and confinement conditions (mean +/−SEM; *, p<0.05, unpaired t-test). (C) Respiratory rate after bicuculline injection to activate LHA of anesthetized mice systemically treated 2 hours earlier with ALM (+, n=7) or vehicle (−, n=6) (Fig. 5H). Note HCRTR antagonism reduced tachypnea induced by pharmacologic LHA activation (mean +/−SEM; *, p<0.05, unpaired t-test). (D) Respiratory rate during optogenetic activation of Hcrt-IRES-Cre neurons (Hcrt*) of anesthetized mice injected with ALM (+, n=7) or vehicle (−, n=5) in RTN (Fig. 5I). Note local HCRTR antagonism in RTN did not affect tachypnea induced by Hctr neuron activation in LHA (mean +/−SEM; *, n.s., not significant, unpaired t-test).