[Inhibitory effect of bronchodilators on cholinergic and peptidergic contractions of guinea-pig isolated bronchial muscle].
The effect of bronchodilators on neurogenic contractions was studied using isolated bronchial strip-chain preparations from guinea-pigs. 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. All the beta-stimulants and xanthines tested caused a concentration-dependent inhibition in the height of the electrically-induced biphasic contraction, with the following order of potency: procaterol greater than fenoterol greater than salbutamol greater than isoproterenol greater than adrenaline greater than enprofylline greater than aminophylline greater than ephedrine. Ipratropium bromide selectively inhibited the electrically-induced cholinergic contraction. Submaximal contractions of the bronchial muscle evoked by exogenous substance P (2 X 10(-7)M) were less potently inhibited by these drugs than those evoked by exogenous acetylcholine (2 X 10(-6)M). These results indicate that in isolated guinea-pig bronchial muscle, bronchodilators may inhibit cholinergic and peptidergic neurotransmissions mainly by postsynaptic depression of the responsiveness and partly by presynaptic reduction of the transmitter release.
Kamikawa
Y
Y
D000818:Animals; D001980:Bronchi / Q000187:drug effects* / Q000294:innervation; D001993:Bronchodilator Agents / Q000494:pharmacology*; D003864:Depression, Chemical; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects; D010275:Parasympathetic Nervous System / Q000502:physiology*
D001993:Bronchodilator Agents