Abstract
Farfarae Flos, a traditional herb medicine, has been used in Korea and China for many centuries as a treatment for respiratory disease. The purpose of the present study was to determine the effect of Farfarae Flos on histamine-induced tracheal smooth muscle contraction in rats. Guinea pigs(500g, female) were killed by CO2 exposure and a segment (8-10mm) of the thoracic trachea from each guinea pig was cut into equal segments and mounted 'in pairs' in a tissue bath. Contractile force was measured with force displacement transducers under 0.5g loading tension. The dose of histamine which evoked 50% of maximal response (ED50) was obtained from cumulative dose response curves for histamine (10-7-10-4M). Contractions evoked by histamine(ED50) were inhibited significantly by Farfarae Flos. The mean percent inhibition was 8.7% after 1.5mg/ml Farfarae Flos, and 33.5% (p<0.05) after 5.0mg/ml Farfarae Flos. Propranolol (10-7M) slightly but significantly attenuated the inhibitory effects of Farfarae Flos. Following treatment with propranolol, the mean percent inhibition caused by 5.0mg/ml Farfarae Flos. Indomethacin and methylene blue (10-7M) did not significantly alter the inhibitory effect of Farfarae Flos. These results indicate that Farfarae Flos can relax histamine-induced contraction of guinea pig tracheal smooth muscle, and that this inhibition involves, in part, symphathetic nerve system.