Effect of alpha-adrenergic receptor blockers on the vulnerability of cat heart to ventricular fibrillation.
Recently, alpha-adrenergic receptors have been implicated in the precipitation of arrhythmias associated with myocardial ischemia and reperfusion. The present investigation has been undertaken to study the effect of alpha-adrenoceptor antagonists on electrically induced ventricular fibrillation. The effect of ventricular fibrillation on the alpha-adrenergic receptor population in myocardium and its modification by phentolamine pretreatment has also been investigated. Phentolamine and prazosin raised the ventricular fibrillation threshold significantly. However, yohimbine was protective at high doses only (3 and 5 mg/kg). There was no change in alpha-receptor population and affinity after ventricular fibrillation. Cyclic AMP levels increased in the fibrillating myocardium. Pretreatment with phentolamine did not prevent the decrease in blood flow observed after electrically induced ventricular fibrillation. It is concluded that alpha 1-adrenergic receptor blockade is protective against ventricular fibrillation in cats.
Dikshit
M
M
Division of Pharmacology, Central Drug Research Institute, Lucknow, India.
Kar
K
K
Srimal
R C
RC
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002415:Cats; D003326:Coronary Circulation / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D004558:Electric Stimulation; D006801:Humans; D066298:In Vitro Techniques; D010646:Phentolamine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011869:Radioligand Assay; D014693:Ventricular Fibrillation / Q000503:physiopathology* / Q000517:prevention & control; D015016:Yohimbine / Q000494:pharmacology
D000319:Adrenergic beta-Antagonists; D015016:Yohimbine; D000242:Cyclic AMP; D011224:Prazosin; D010646:Phentolamine