[Chemoreflexive drive of ventilation and noradrenaline stimulus in man]

O2 chemoreflex drive of ventilation was studied before and after an intravenous infusion of L-norepinephrine (9 microgram/min), inducing a plasmatic hormone concentration similar to that obtained during submaximal exercise. The ventilation increasing rapidly at the beginning of the infusion was stabilized after 30 min : the ventilation was two times the reference value. The O2 chemoreflex drive of ventilation increased during norepinephrine infusion. When man was transiently switched from hypoxia to pure O2 (O2 test) the maximal fall of ventilation was two times the reference response. This increase in the chemoreflex drive, although the physico-chemical blood state was unchanged, may be explained by a norepinephrine chemoreceptor sensitization. Such a mechanism could partly explain the increase of O2 chemoreflex drive observed during muscular exercise.