Effect of electroacupuncture preconditioning on bupivacaine-induced cardiotoxicity in rats

Objective To evaluate the effect of electroacupuncture(EA)preconditioning on bupivacaine-induced cardiotoxicity in rats. Methods Sixteen SPF adult male Sprague-Dawley rats, weighing 180-240 g, aged 2 months, were randomly assigned into either bupivacaine group(group B, n=8)or EA preconditioning group(group EP, n=8). Bilateral Neiguan(PC6), Zusanli(ST36)and Fenglong(ST40)acupoints were stimulated with an electric stimulator(dense-sparse waves, frequency 2 Hz, voltage 1 mA, wave length 0.2-0.6 ms)for 30 min, followed by another 30 min stimulation after a 1 h interval.At 3 h after the end of electric stimulation, 0.5% bupivacaine 10 mg/kg was injected intravenously, and the rats suffering heart arrest received cardiopulmonary resuscitation.The duration of QRS and QT interval increased by 20% of baseline value, the time for apnea and cardiac arrest and resuscitation time were recorded.The left ventricular myocardial tissues were harvested at 25 min after bupivacaine administration in successfully resuscitated rats and immediately after death in unsuccessfully resuscitated rats for measurement of carnitine content in the myocardial cytoplasm and mitochondria by enzyme linked immunosorbent assay. Results In B and EP groups, the incidence of cardiac arrest was 8/8 and 4/8, respectively, and the rate of successful resuscitation was 3/8 and 4/4, respectively.Compared with group B, the incidence of cardiac arrest was significantly decreased, the rate of successful resuscitation was increased, the duration of QRS and QT interval increased by 20% of baseline value and time for apnea were prolonged, the resuscitation time was shortened, carnitine content in the myocardial cytoplasm was decreased, and carnitine content in the myocardial mitochondria was increased in group EP(P<0.05). Conclusion EA preconditioning can increase the tolerance to bupivacaine-induced cardiotoxicity, and the mechanism is related to elevated level of mitochondrial carnitine in rats. Key words: Electric stimulation therapy; Ischemic preconditioning; Bupivacaine; Drug toxicity; Myocardium