Tidal breathing pattern differentially antagonizes bronchoconstriction in C57BL/6J vs. A/J mice.
There is abundant evidence that tidal breathing, and especially tidal breathing at elevated minute ventilation, antagonizes the development and persistence of airflow obstruction during bronchoconstrictor stimulation in normal animals and people. Here, we studied the antiobstructive effect of different tidal breathing patterns in C57Bl/6J and A/J mice during bronchoconstriction induced by continuous or bolus infusion of methacholine. Anesthetized, paralyzed mice were mechanically ventilated at 1,500 ml.kg(-1).min(-1), using each of three breathing patterns: 5 ml/kg, 300 breath/min; 10 ml/kg, 150 breath/min; or 20 ml/kg, 75 breath/min. Changing from 10 ml/kg, 150 breath/min to 20 ml/kg, 75 breath/min, breathing functionally antagonized bronchoconstriction, reducing the level of airflow obstruction induced by methacholine infusion or boluses equivalently in both strains. In marked contrast, changing from 10 ml/kg, 150 breath/min to 5 ml/kg, 300 breath/min, breathing substantially exacerbated methacholine-induced airflow obstruction in A/J mice, whereas it had no significant effect in C57Bl/6J mice. Our results therefore demonstrate that 1) even at moderate, fixed minute ventilation, the precise breathing pattern can influence the degree of airflow obstruction substantially, and 2) the influence of breathing pattern on bronchoconstriction differs considerably between genetically diverse inbred mouse strains. These findings imply that differences in antiobstructive effects of breathing can contribute to differences in apparent airway constrictor responsiveness. Much attention has been placed on dysregulation of contractile function of airway smooth muscle in human disease. We suggest that important pathophysiology might also be found in impairment of the functional antagonist effect of tidal breathing on airflow obstruction.
Section of Pulmonary and Critical Care Medicine, University of Chicago, 5841 S. Maryland Ave., MC6026, Chicago, Illinois 60637, USA.
Bohao
B
Chen
Gustine
G
Liu
Felix
F
Shardonofsky
Maria
M
Dowell
Oren
O
Lakser
Richard W
RW
Mitchell
Jeffrey J
JJ
Fredberg
Lawrence H
LH
Pinto
Julian
J
Solway
D000402:Airway Obstruction / Q000235:genetics / Q000503:physiopathology*; D000818:Animals; D016084:Bronchoconstriction / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016085:Bronchoconstrictor Agents / Q000494:pharmacology; D002799:Cholinergic Fibers / Q000502:physiology; D005260:Female; D006967:Hypersensitivity / Q000235:genetics / Q000503:physiopathology; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL / Q000235:genetics / Q000502:physiology*; D008815:Mice, Inbred Strains / Q000235:genetics / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D009130:Muscle, Smooth / Q000503:physiopathology; D012123:Pulmonary Ventilation / Q000187:drug effects / Q000502:physiology*; D015656:Respiratory Mechanics / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012137:Respiratory System / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology; D013990:Tidal Volume / Q000502:physiology
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride