It has been assumed previously that the sympathetic nervous system (SNS) serves to antagonize bronchoconstrictor stimuli. To assess the homeostatic regulatory effect elicited by exogenously induced bronchoconstriction, we studied the effect of inhaled @entity2710 on the SNS response in 12 normal and 9 @entity748 @entity1 . Exogenous SNS response was assessed as change in plasma @entity1425 and @entity1063 concentrations from basal levels during inhalation challenge. A 74 +/- 3% decrease in specific airway conductance (SGaw) (p less than 0.001) was induced in normal subjects and a 78 +/- 7% decrease in asthmatics by @entity2710 challenge (p less than 0.001). Neither plasma @entity1425 nor @entity1063 increased significantly from basal concentrations in normal or @entity748 subjects after maximal challenge (p greater than 0.33). To determine if physiologically achievable @entity1425 concentrations potentially could modulate bronchoconstriction, the effect of intravenously infused @entity1425 was measured in 11 of these subjects. After the highest dose of @entity2710 , a 15-min intravenous infusion of @entity1425 (0.06 micrograms/kg/min) caused an 85 +/- 7% increase in SGaw in normal subjects (p less than 0.02). In asthmatics, a 319 +/- 68% increase in SGaw (p less than 0.002) was observed with similar changes in plasma @entity1425 . Plasma @entity1425 concentrations after infusion were comparable to those obtained in 4 normal and 1 @entity748 subject undergoing 60-degree, head-up tilt 1 h after volume depletion with intravenously administered @entity1483 . We conclude that physiologic concentrations of @entity1425 can modulate moderately severe bronchoconstriction. However, the SNS does not regulate bronchomotor tone during mild to moderate bronchoconstriction.

Homeostatic regulation of bronchomotor tone by sympathetic activation during bronchoconstriction in normal and @entity748 XXXX .

@entity748 :: ('MESH:D013224', 'Disease') :: ['asthmatic'] @entity1 :: ('9606', 'Species') :: ['humans'] @entity1425 :: ('MESH:D004837', 'Chemical') :: ['epinephrine'] @entity1483 :: ('MESH:D005665', 'Chemical') :: ['furosemide'] @entity1063 :: ('MESH:D009638', 'Chemical') :: ['norepinephrine'] @entity2710 :: ('MESH:D016210', 'Chemical') :: ['methacholine']
@entity1 :: (9606,Species) :: ['humans']
