[Rabbit immunization to induce experimental asthma--relationship between antigens and airway reactivity]

Japanese white rabbits were immunized with either alternaria or ragweed starting at birth to induce experimental asthmatic model. We studied the characteristics of contractile responses of tracheal smooth muscle isolated from these sensitized animals and compared them with non-sensitized control animals. Both sensitivity and reactivity of contraction induced by acetylcholine (ACh) were increased in the alternaria sensitized group, but only sensitivity was increased in the ragweed group. Contractile responses to electrical field stimulation were enhanced in both sensitized groups, and responses in the alternaria group were significantly greater than those in the ragweed group. In the alternaria group, atropine suppressed the contractile response to KCl, indicating that the contraction was mediated partially through a muscarinic mechanism. In the ragweed group, atropine suppressed responses to 20 mM KCl. Stimulation of the intramural nerve plexus facilitated the release of neurotransmitters, especially ACh. This was more obvious in the alternaria group than in the ragweed group. These results suggest that alternaria sensitization of rabbits produces a better model for studying changes in interaction between nerves and smooth muscle in the airway.