Fig. 1

Timeline of the experimental protocol. The guinea pigs received 7 inhalation exposures (2 per week over 4 weeks) with aerosols of saline (SAL group) or ovalbumin solution (OVA group) containing an increasing dose of the antigen. From the 1st to the 4th exposures, the animals received 1 mg/mL ovalbumin (first two weeks). In the 5th and 6th exposures (third week), the animals received 2.5 mg/mL ovalbumin, and in the 7th exposure (beginning of the fourth week), a dose of 5 mg/mL of antigen was used. The solution of ovalbumin or saline was continuously aerosolized for either 15 min or until respiratory distress occurred. After the 5th exposure, the guinea pigs in the Rho-kinase inhibitor group received Y-27632 (1 mM; 2 min) by inhalation (OVA-RHO group) and/or dexamethasone (2 mg/kg-1/day i.p.) (OVA-C groups or ORC groups) 10 min before each exposure to OVA or SAL until the end of the experimental protocol. Seventy-two hours following the seventh exposure, the animals were anesthetized and exsanguinated, the exhaled nitric oxide was collected, and the mechanics of the respiratory system (Ers and Rrs) and the oscillatory parameters of the distal lung tissue (Et and Rt) were evaluated under basal conditions and after challenge with OVA (0.1 %). Afterwards, lung slices were removed and submitted to histopathological evaluation