In Vitro Study of Bronchial Relaxation Mechanism of Coptosapelta Flavescens Korth Root’s Methanol Extract On Receptors

Objective: To evaluate the bronchorelaxation effect of methanol extract of Coptosapelta flavescens Korth. ischolar_main (MECFR) on cholinergic, histamine receptors and beta2-adrenoceptors, in vitro.

Method: The research design was experimental in which a 4-mm long guinea pig’s bronchus was kept in an isolated organ bath containing Kreb’s-Henseleit solution at 37°C, pH 7.4 and flooded with carbogen gas. The study was divided into 3 groups: in Group 1 and 2, the bronchial rings were incubated in 3 concentrations of MECFR, and then contracted with cumulative doses of methacholine and histamine, respectively; in Group 3, the bronchial ring was incubated in 3 concentrations of propranolol, contracted with a single dose of methacholine, and then the MECFR was administered in cumulative doses.

Results: In both Group 1 and Group 2, the dose-response curves of all 3 doses of MECFR shifted to the right with lower E_max (P<0.05) as compared to the negative control. In Group 3, the dose-response curves showed MECFR has bronchorelaxation effect on bronchial rings both in the presence of propranolol andwithout, with similar E_max (P>0.05).

Conclusion: MECFR exhibits bronchorelaxation effects by acting as non-competitive antagonist at the cholinergic and histamine1 receptors, and also by acting as beta₂-adrenoceptor agonist.