Amiodarone, adrenoceptor responsiveness and ischaemia- and reperfusion-induced arrhythmias.
Experiments were performed in rats which had been pretreated with amiodarone 50 mg kg-1 day-1 p.o. for 4 weeks. In anaesthetized animals subject to 25 min of coronary artery occlusion, the rats which had received amiodarone had fewer ischaemia-induced ventricular premature beats than the controls (381 +/- 106 compared with 815 +/- 215, P = 0.070). The duration of arrhythmias induced by reperfusion following 5 min of ischaemia was also less in the rats which had received amiodarone than in the controls (43.8 +/- 6.8 and 16.0 +/- 3.1 s respectively). Pretreatment of rats with amiodarone reduced the maximum driving frequency of both isolated left atria and papillary muscles. There were no differences between the responses to alpha- or beta-adrenoceptor agonists or to calcium in papillary muscle preparations from amiodarone-pretreated and control rats. These results suggest that the antiarrhythmic activity of chronic amiodarone seen in the present study does not depend on changes in ventricular adrenoceptor responsiveness.
Coker
S J
SJ
Department of Pharmacology and Therapeutics, University of Liverpool, U.K.
Chess-Williams
R
R
D000638:Amiodarone / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000517:prevention & control*; D003327:Coronary Disease / Q000150:complications*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D015428:Myocardial Reperfusion Injury / Q000150:complications*; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*
D011943:Receptors, Adrenergic, beta; D000638:Amiodarone