Cardiac arrhythmia induced by hypothalamic stimulation in cardiac ischemic rabbits and the antiarrhythmic action of Panax ginseng

Frequent ventricular extrasystoles were recurrently provoked by electrical stimulation of right dorsal medial hypothalamic nucleus and anterior hypothalamic area near the medial margin of optic tract in anesthetized rabbits with 2 branches of anterior descending coronary artery cauterized. The stimulation employed was 30-min (sometimes 40—60 min) train of square wave pulses of 0.2 ms, 50 Hz and 3—6 mA through 2 insulated stainless steel electrodes with bare tips of 0.3—0.8 mm. Ventricular extrasystoles were elicited in nearly 90% the rabbits. It was ineffective to stimulate right medial preoptic area plus lateral preoptic area. In the first few stimulations at intervals of 10 min, the number of ventricular extrasystoles tended to decrease spontaneously (about 24 % in 0.5 h). The decreasing tendency of induced extrasystoles was lessened after succeeded longer interval. On this model the preparation of had an obvious anti-arrhythmic effect.