Table 2.

HR variability during cardiovascular reactivity testing (4-wk DEHP exposure)

	Homecage Baseline (4-wk exposure)			Cardiovascular Reactivity Test 1 (4-wk exposure)
	Control	DEHP	P value	Control	DEHP	P value
HR, beats/min	431 ± 35	413 ± 31	0.629	780 ± 13	794 ± 15	0.279
RR, ms	139 ± 6.8	145 ± 7.5	0.642	76.9 ± 0.8	75.5 ± 0.5	0.279
SD1, ms	5.4 ± 0.9	3.7 ± 0.5	0.270	0.63 ± 0.08	0.63 ± 0.1	0.971
SD2, ms	17.2 ± 2.2	18.3 ± 3.3	0.832	3.19 ± 0.2	1.79 ± 0.2*	0.020
HF power, normalized units	353 ± 48	194 ± 23*	0.0001	47.7 ± 17	51.3 ± 28.8	0.935

All values reported as means ± SE. RR and heart rate (HR) variability parameters were computed from a 500-beat segment during a homecage basal period and again after the initiation of the first conditioned stimulus (tone)-unconditioned stimulus (shock) pair (cardiovascular test 1). High-frequency (HF) power was significantly lower in di-2-ethylhexyl-phthalate (DEHP)-treated animals before reactivity testing. SD from the major (SD1) and minor axis (SD2) were computed from Poincare plots computed in the same timeframe. SD2 was significantly lower (P < 0.05) in the DEHP-treated group than in the control group during the cardiovascular test, indicating heightened reactivity.

^*P < 0.05.