Recently, there has been an increasing interest in the involvement of adenosine as a mediator of allergic asthma. In the present study, we have employed an allergic rabbit model to study the airway responses to adenosine. The rabbit litter mates were injected i.p., within 24 h of birth, with ragweed pollen extract to preferentially produce ragweed-specific IgE. This allergic rabbit model demonstrates many clinical features of asthma similar to human allergic asthma. Aerosolized adenosine (0.156-10 mg/ml) caused a concentration-dependent bronchoconstriction. The normal rabbits (non-immunized) did not respond to adenosine within that concentration range. Theophylline significantly inhibited the adenosine-induced bronchoconstriction. These early studies suggest that adenosine differentiated asthmatic airways from normal airways and adenosine-induced bronchoconstriction in this model was mediated through specific cell surface receptor(s).