An improvement to the use of sulfur dioxide to induce cough in experimental animals

In this study a new method has been developed to administer sulfur dioxide to experimental animals in order to induce cough for testing antitussives. Sulfur dioxide was packed into aerosol cans equipped with a 75 microliter dosage nozzle. Sulfur dioxide was diluted with the fluorocarbon mixture and the content varied from 15-19% w/w. The dose of the sulfur dioxide aerosol used was 75-225 microliter. Guinea pigs breathed sulfur dioxide for 20 sec from a special muzzle connected to the aerosol can. The frequency of coughing was counted for 10 min after the sulfur dioxide challenge. The test procedure utilized an initial dose of sulfur dioxide as a basic stimulus in order to make the animals sensitive to sulfur dioxide. There were quite large differencies in cough caused by the baseline irritation by sulfur dioxide, but 1 hr after the baseline irritation, a further sulfur dioxide challenge evoked a reliable and reproducible incidence of cough.