Airway hyperresponsiveness in anaesthetised guinea-pigs 18-24 hours after antigen inhalation does not occur with all intravenously administered spasmogens.

Actively sensitised guinea-pigs were exposed to inhalation challenges with ovalbumin aerosol (macro- and microshock) and airway responsiveness to six intravenously administered spasmogens was evaluated 18 to 24 hr later in the anaesthetised animal. An increase in airway sensitivity was defined as a significant leftward shift of the dose-response curve when compared with saline-challenged control sensitized animals. After ovalbumin-macroshock (1% ovalbumin for 2 min. with mepyramine cover against fatal anaphylaxis), airway hyperresponsiveness was seen to 5-HT, the thromboxane A2-mimetic, U-46619, and bradykinin but not to methacholine, histamine or substance P. A similar pattern was seen after ovalbumin-microshock (0.010% ovalbumin for 60 min.), with induction of airway hyperreactivity to 5-HT and U-46619 but not methacholine or histamine. When the U-46619 dose-response curve was constructed following treatment of the animals with atropine (1 mg/kg, intravenously), airway hyperresponsiveness was no longer significant. As an index of airway inflammation, lung weights were significantly heavier in ovalbumin-challenged animals, than in saline-challenged controls. The results of this study with intravenously administered spasmogens does not support claims that ovalbumin-induced airway hyperreactivity in the guinea-pig is a 'non-specific' phenomenon.