The obligatory role of calcium in the development of antigen‐induced airway hyperreactivity to cold provocation in the rat isolated trachea

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Abstract
The effect of antigen challenge on cold provocation (30‐10°C) in isolated tracheal segments from control (normal) and ovalbumin‐sensitized rats was studied. Sensitization alone or acute cold provocation (10°C) alone was not sufficient to cause contraction of tracheal smooth muscle preparation. Following recovery from antigen‐induced responses (Schultz‐Dale phenomenon) in sensitized rat segments, cold provocation induced strong contractile responses. Both the antigen‐induced contractions and the subsequent development of airway hyperreactivity to cold were dependent on extracellular Ca2+ and inhibited by verapamil. The data in this study indicate that extracellular Ca2+ plays an obligatory role in the mediation of antigen‐induced contractile responses as well as the subsequent development of hyperreactivity to cold provocation in rat tracheal smooth muscle.