Abstract
1030 Both exercise and hypoxia activate the adrenergic nervous system causing an increase in circulating catecholamines that may enhance the ventilatory response to exercise. Previous studies indicate that beta-adrenergic stimulation does not enhance the ventilatory response to exercise in normoxia or hypoxia. Weil et al. (JAP 33:1972), proposed that α-adrenergic vasoconstriction during exercise may decrease carotid body blood flow, hence augmenting chemosensitivity. Thus, blocking α1-adrenergic receptors should prevent vasoconstriction and attenuate carotid body stimulation of exercise hyperpnea. We examined the role of α-adrenergic activation during exercise in 12 women at sea level (SL) and during 40 h at simulated high altitude (HA: PB 445 mmHg) once on placebo and on an α1-adrenergic blocker (prazosin: 3mg/d). Subjects performed graded intensity cycle ergometry to exhaustion. Results ( ± S.D.): (Table)TableExercise ventilation increased (p<0.01) at HA vs. SL. However, α1-adrenergic blockade did not alter the ventilatory response to exercise in normoxic or hypoxic conditions. Thus, in humans α-adrenergic activation does not appear to augment exercise ventilation by vasoconstriction of the carotid body vasculature. Supported in part by DOD grant #DAMD 17-95-C5110
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