Fig. 4.
Loss of central 5-hydroxytryptamine (5-HT) increases cardiac vagal tone in females. Typical responses of mean arterial pressure (MAP) and heart rate (HR) to atropine for male wild-type (WT) and TPH2−/− pups (A) and female WT and TPH2−/− pups (B). Note that atropine injection (at vertical dashed line) induced a larger HR increase in the female TPH2−/− pup vs. its WT counterpart, an effect not seen in the male pups. C: change in HR in response to atropine (top) of WT (open bars; n = 5 male, 7 female) and TPH2−/− pups (closed bars; n = 6 male, 6 female) and atenolol (bottom) (WT: n = 8 male, 6 female; TPH2−/−: n = 10 male, 10 female) in quiet sleep (QS) and active sleep (AS). †Significant genotype × sex interaction (2FA, P = 0.016 QS; P = 0.028, AS). D: intrinsic HR (HRINT) of male and female WT (open bars) and TPH2−/− pups (closed bars). *Significant effect of genotype (2FA, P < 0.001).