TABLE 2.

Parameters of cardiac autonomic modulation before and after isoproterenol (ISO) administration in older conscious WT and R21C mice

Data are given as mean ± S.E. and are derived from 10 male R21C and 10 WT littermate mice (12 months old). HR, heart rate; RMSSD, root mean square of successive R-R differences; pNN6 percentage of adjacent R-R intervals that differ by a length of time exceeding the experimental threshold (6 ms); TP, total power; HF, high frequency component of the heart rate variability; LF, low frequency component of the heart rate variability. *, p < 0.05 versus WT −ISO; †, p < 0.01 versus WT −ISO; ‡, p < 0.05 versus WT −ISO; §, p < 0.01 versus WT −ISO.

Parameter	−ISO		+ISOa
	WT	R21C	WT	R21C
HR (bpm)	698 ± 16	763 ± 13†	770 ± 12‡	767 ± 7
RMSSD (ms)	3.9 ± 1.3	0.9 ± 0.2*	0.68 ± 0.1‡	0.8 ± 0.1
pNN6 (ms)	8.1 ± 0.9	2.9 ± 0.7†	2.9 ± 1.1‡	2.1 ± 1.0
TP (ms)	2.1 ± 0.4	0.2 ± 0.1†	1.0 ± 0.5‡	0.2 ± 0.1
HF (ms2)	1.97 ± 0.50	0.10 ± 0.06*	0.33 ± 0.08‡	0.05 ± 0.07
LF (ms2)	4.05 ± 0.60	0.10 ± 0.09†	0.12 ± 0.09§	0.10 ± 0.09

^a Intraperitoneal injection of isoproterenol (2.5 μg/g).