Table 1.

EKG intervals and Response to Autonomic Stimuli

A
	Control n=4	iNICD n=8
Heart Rate	634 ±45	473 ±21*
P wave duration (msec)	7.61 ±0.34	9.35 ±0.53*
PR (msec)	33.5 ±1.6	36.9 ±1.2
QRS (msec)	9.57 ±0.88	11.59 ±0.99

B
	Control n=11	iNICD n=14
Baseline HR	649 ±21	559 ±35
Isoproterenol HR (% change)	728 ±14* (12.1)	649 ±26† (16.3)
Atropine HR (% change)	742 ±6* (14.2)	676 ±16‡ (21.1)
Carbachol HR (% change)	230 ±25§ (64.6)	227 ±13§ (59.4)

A. Controls are littermate tetO_NICD mice (n=4 males) and iNICD are αMHC-rtTA; tetO_NICD mice (n=4 females, n=4 males). Both genotypes were fed doxycycline chow at 8 weeks of age for 3 weeks with no washout. EKGs were performed on mice during isoflurane sedation. Statistics were performed using unpaired t tests with Welch’s correction.

^*P<0.05, data are expressed as mean ± SEM.

B. Controls are littermate αMHC-rtTA mice on dox (n=3 females, n=8 males), and iNICD are experimental αMHC-rtTA; tetO_NICD on dox group (n=8 females, n=6 males). All mice were fed doxycycline chow starting between 2–3 months of age for 3 weeks, followed by a washout period of 2 weeks. EKGs were performed on conscious mice. Adrenergic stimulation with isoproterenol was done by intraperitoneal injection of isoproterenol (0.2 mg/kg), inhibition of parasympathetic activity with atropine (1mg/kg), and carbachol injection was given intraperitoneally (0.3 mg/kg) to simulate increased vagal nerve activity. With repeated measures 2 way ANOVA there is a statistically significant genotype effect F(1,23)=10.6, p=0.0039. There is also a statistically significant drug effect across both genotypes F(3,69)=233.2, P<0.001. However, there is not a significant interaction between drug and genotype F(3,69)=1.739, P=0.17.

^*P<0.05,

^†P<0.01,

^‡P<0.001,

^§P<0.0001, data are expressed as mean ± SEM.