Carrageenan-induced pleurisy

Carrageenan-induced pleurisy was performed according to the method described in a previous report but with slight modification [24]. Briefly, mice were anesthetized with 3% isoflurane in a mixture of N₂O/O₂ gas and submitted to a skin incision at the level of the left sixth intercostal space. Sterile phosphate buffer saline (PBS; vehicle, 200 µL) or PBS containing 2% of λ-carrageenan (Sigma, USA) was injected into the pleural cavity by using a 24-gauge flexible catheter. Twenty-four hours after carrageenan injection, the animals were sacrificed and the chest was carefully opened. The pleural cavity was rinsed with 1 mL of sterile PBS with heparin (20 IU/mL), and the pleural exudate collected by aspiration. Any exudate contaminated with blood was discarded, and the amount of exudate was calculated by subtracting the volume of injected PBS from the total volume of collected fluids. The exudate fluid was diluted with Turk's solution at a ratio of 1:20 and the total number of leukocytes were counted by using an optical microscope and a Neubauer counting chamber. Animals were randomly assigned to experimental groups, and subsequent drug treatment and analyses were performed blindly.