Bordetella pertussis vaccination of rats resulted in impairment of relaxation to isoprenaline and histamine of partially contracted tracheal smooth muscle. The concentration range of carbachol (10(-6) to 5 x 10(-6) M) required for contraction (ED50) did not differ from the control group. Pretreatment of vaccinated animals with hydrocortisone was found to reverse the inhibition of spasmolytic activity.
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