Abstract
In 77 children with broncial asthma, inhalation tests with acetylcholine and house dust extract were carried out. 1) The levels of respiratory threshold of acerylcohline were less than 97×2^7μg in 88% of the asthmatics and 97×2^7μg or more in non-asthmatics. 2) There was apparently no correlation between respiratory threshold of acetylcholine and the decreases of FEV_<1.0> with house dust extract, but lower levels of respiratory threshold were found with house dust extract in asthmatics with positive than in those with negative response (p<0.005). 3) Regarding the late response in the inhalation tests with house dust extract, lower levels of respiratory threshold of acerylcholine were observed in the positive than in the negative group (0.01<p<0.025). 4) there was no correlation between respiratory thresholds of acerylcholine and the age at the onset of asthma or the period of the disease. 5) Severe asthmatics were likely to have lower levels of respiratory threshold of acetylcholine in comparison with the moderate or mild asthmatics (p<0.1). 6) There was a significant correlation between the levels of respiratory threshold of acetylcholine and histamine (r=0.5, p<0.005).
