EFFECTS OF 2 IMIDAZOLINES (ST-91 AND ST-93) ON THE CARDIAC-ARRHYTHMIAS AND LETHALITY INDUCED BY OUABAIN IN GUINEA-PIG

Two imidazoline derivatives (St-91 and St-93) were studied for their h aemodynamic effects and action on the cardiac arrhythmias and lethalit y induced by slow intravenous infusion of ouabain (8 mug min-1) in gui nea-pigs. St-91 (5.0, 10.0 and 20.0 mug kg-1) produced significant ris e in blood pressure associated with a reduction in heart rate. It fail ed to induce any significant increase in the doses of ouabain required to produce ventricular premature beats (VPB), ventricular tachyarrhyt hmias (VT) and lethality (L). St-93 (1.25, 2.5 and 5.0 mug kg-1) induc ed an initial rise in blood pressure followed by a fall in blood press ure and heart rate. St-93 at doses of 2.5 and 5.0 mug kg-1 increased t he doses of ouabain required to induce VPB, VT and L significantly. It is possible that the differential effects of these clonidine analogue s are due to their differential distribution in the central nervous sy stem.