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Title: Concentration-dependent desensitization of isolated porcine coronary arterial segments to acetylcholine.
Austin Authors: Tanz, R D;Nayler, W G
Affiliation: Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg, Victoria, Australia
Issue Date: 8-Jul-1991
Publication information: Archives Internationales De Pharmacodynamie Et De The´rapie; 312(): 110-25
Abstract: Acetylcholine elicited an increase in developed tension on isolated porcine coronary arterial rings at concentrations exceeding 1.1 x 10(-7) M. However, at concentrations greater than 3.3 x 10(-6) M, desensitization occurred with repeated exposures to acetylcholine. When rings were first exposed to 3.3 x 10(-6) M, then washed and subsequently exposed to 3.3 x 10(-5) M, tension was either unchanged or significantly reduced, giving rise to two different population effects. Although atropine completely antagonized the effect of acetylcholine, pretreatment with methysergide (5-HT2), mepyramine (H1) and prazosin (alpha 1) did not attenuate acetylcholine-induced desensitization, indicating that the phenomenon is unrelated to either serotonin, H1- or alpha-adrenergic receptor activation. Diltiazem and nifedipine significantly reduced or completely inhibited contractions produced by K+ depolarization, but not those produced by acetylcholine. Moreover, ryanodine did not alter the tension developed by repeated exposures to acetylcholine. Our results suggest that acetylcholine activates specific receptor-operated channels which are less sensitive to calcium antagonists than K(+)-activated voltage-dependent channels. Moreover, acetylcholine-induced contractions in this model do not appear to be the result of calcium release from the sarcoplasmic reticulum since ryanodine failed to attenuate contractions.
Gov't Doc #: 1663335
Journal: Archives internationales de pharmacodynamie et de thérapie
Type: Journal Article
Subjects: Acetylcholine.pharmacology
Coronary Vessels.drug effects
Dose-Response Relationship, Drug
Muscle Contraction.drug effects
Muscle Relaxation.drug effects
Muscle, Smooth, Vascular.drug effects.physiology
Potassium Chloride.pharmacology
Receptors, Adrenergic, alpha.drug effects
Appears in Collections:Journal articles

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