[Synergistic interaction between anti-allergic drugs and beta 2-stimulants on neurogenic contractions of guinea-pig isolated bronchial muscle]

Abstract

The inhibitory effect of beta 2-stimulants on neurogenic contractions of guinea-pig isolated bronchial strip-chain was examined after or without pretreatment with sodium cromoglycate (SCG, 10(-5) M). Electrical field stimulation (8 Hz, 0.5 msec, 30 V, 40 pulses) evoked a biphasic contraction of the bronchial muscle, consisting of an initial phasic component followed by a sustained one which was mediated by cholinergic and peptidergic nerve stimulations, respectively. Both terbutaline and clenbuterol caused a concentration-dependent inhibition in the height of the electrically-induced biphasic contraction. Concentration-response curves for the inhibitory actions of these beta 2-stimulants were shifted to the left by pretreatment with SCG or tranilast, and the peptidergic contractions were more potently inhibited than the cholinergic contractions. Terbutaline and clenbuterol also inhibited submaximal contractions to exogenously applied acetylcholine (2 x 10(-6) M) or substance P (2 x 10(-7) M), but the actions were not modified by pretreatment with SCG or tranilast. These results indicate that combined treatments with anti-allergic drugs and beta 2-stimulants can synergistically inhibit neurogenic contractions of guinea-pig bronchial muscles.