Histamine and early ischemic arrhythmia in anesthetized cats

Ligation of left anterior descending coronary artery caused various arrhythmias and reduced histamine content in ischemic myocardium in anesthetized cats. Intracoronary injection of compound 48-80 100 micrograms shortened the onset of VT and VF from 13 +/- 5, 18 +/- 5 min (n = 7) in control to 7.2 +/- 1.1 (P less than 0.01), 11 +/- 5 min (P less than 0.05) (n = 6) respectively, elevated the histamine concentration of plasma after acute coronary artery occlusion (15 +/- 3, 26 +/- 10 ng/ml, P less than 0.05, before and after ligation respectively). Iv chlorpheniramine (5, 10 mg/kg) or cimetidine (20, 40 mg/kg) dose-dependently reduced arrhythmia score, incidence of VF and mortality after myocardial ischemia, but with little influence on histamine content in ischemic myocardium and plasma. These results suggest that release of histamine from the ischemic myocardium is involved in the generation of early arrhythmias through H1 and H2 receptors in anesthetized cats subjected to acute coronary artery occlusion.