Suppression of the depressor cardiac reflex during coronary occlusion by lidocaine--evidence for a central nervous site of action.

Abstract

The effect of lidocaine (0.35 and 0.7 mg/kg/min i.v.) on reflex cardiovascular depression was studied during coronary occlusion in 10 chloralose-anesthetized cats. Twenty to 60 s occlusion of the left anterior descending coronary artery decreased heart rate, efferent cardiac sympathetic nerve activity and blood pressure by 33.8 ± 8.8%, 56.1 ± 31.8% and 48.4 ± 13.1% of control values, respectively. During infusion of 0.35 (0.7) mg/kg/min lidocaine the heart rate was decreased by 17.6±6.1% (10.2 ±6.9), the sympathetic activity by 46.2 ± 25.5% (30.2 ± 13.4) and blood pressure by 44.7 ± 13.6% (36.4 ± 16.6) compared to controls. The same reflex was elicited in 12 cats by afferent stimulation of cardiac vagal nerve branches, and the bradycardia and decrease of blood pressure were also inhibited by lidocaine. It is concluded, that the suppression of the reflex is due to a central nervous effect of lidocaine. A possible anticholinergic effect of the drug seems to play no major role, since the bradycardia during efferent vagal stimulation (eight animals) was not affected by 0.35 mg/kg/min lidocaine.