Effects of dexamethasone on airway hyper‐responsiveness to the adenosine A1 receptor agonist cyclo‐pentyl adenosine in an allergic rabbit model

New Zealand White (NZW) rabbits were immunized within 24 h of birth with Alternaria tenuis in aluminium hydroxide (Al (OH)3) (i.p.) or sham immunized (saline plus Al (OH)3 i.p.) and subsequently injected with the allergen (i.p.) or sham‐immunized for the next 3 months. At 3 months of age, baseline airway responsiveness was assessed using cyclo‐pentyl adenosine (CPA). Bronchoalveolar lavage (BAL) was performed in all animals and samples of peripheral blood were collected from some animals for estimation of dexamethasone levels. In some animals, blood was collected at the end of the experiment and cellular function was assessed by measurement of ex vivo proliferation of mononuclear cells in response to phytohaemagglutinin (PHA). Allergen immunization significantly increased baseline airway responsiveness to inhaled CPA (P