Supplemental Figure 7 shows representative ECG and atrial cardiogram traces with AF in a null mouse in response to carbachol administration. In a separate experiment, we administered atropine (1 mg/kg) to null mice in which AF was found to be inducible under basal conditions. Atropine administration prevented subsequent pacing-induced AF episodes in 5 of 6 null mice tested, with 1 mouse still showing AF episodes (Figure 3E). These data suggest that, in addition to fibrosis, altered vagal tone may contribute to the high incidence of atrial arrhythmia in Scn1b-null animals. Here, SCN1B is linked to atrial fibrillation.