Table 1.

Hemodynamic responses to progressive, low-intensity LBNP

	Preinfusion	Baseline	LBNP, −5 mmHg	LBNP, −10 mmHg	LBNP, −15 mmHg	Drug	Time	Drug × Time
SBP, mmHg
Control		124 ± 7	130 ± 6	129 ± 6	130 ± 6	0.027	0.006	0.841
Phentolamine	125 ± 4	118 ± 5*	123 ± 6	126 ± 74	124 ± 7
DBP, mmHg
Control		64 ± 4	68 ± 3	74 ± 6	81 ± 4	0.043	0.004	0.001
Phentolamine	67 ± 4	53 ± 1*	55 ± 1†	55 ± 1†	53 ± 1†
MAP, mmHg
Control		84 ± 4	86 ± 4	85 ± 3	86 ± 4	0.296	0.029	0.253
Phentolamine	83 ± 2	79 ± 3	83 ± 3	84 ± 4	84 ± 4
HR, beats/min
Control		61 ± 2	61 ± 2	60 ± 2	63 ± 2	0.005	0.114	0.911
Phentolamine	66 ± 2	69 ± 2*	70 ± 3	70 ± 3	73 ± 2
RPP, beats/min·mmHg
Control		7,503 ± 325	7,808 ± 218	7,735 ± 212	8,194 ± 397	0.032	0.008	0.789
Phentolamine	8,449 ± 218	8,258 ± 349	8,613 ± 362	8,780 ± 518	9,056 ± 552

Data are means ± SE. Eight young healthy subjects underwent testing in the supine posture; each stage was 10 min in duration.

LBNP, lower-body negative pressure; SBP, systolic blood pressure; DBP, diastolic blood pressure; MAP, mean arterial pressure; HR, heart rate; RPP, rate-pressure product.

^*Significantly different from preinfusion;

^†significantly different from control condition.