Bradycardic and Antiarrhythmic Effects of the D-Limonene in Rats

BACKGROUND: D-limonene (DL) is a monoterpene and is the major component in the essential oil of citrus fruit. It presents antihyperglycemic and vasodilatation activities. OBJECTIVES: This study evaluated the cardiovascular effects and potential antiarrhythmic of DL in rats. METHODS: Hemodynamic and electrocardiographic (ECG) parameters were measured in male Wistar rats, which under anesthesia had been cannulated in the abdominal aorta and lower vena cava and had electrodes subcutaneously implanted. In the in vitro approach, the heart was removed and perfused using the Langendorff technique. The significance level adopted was 5% (p < 0.05). RESULTS: DL, in doses of 10, 20, and 40 mg/kg (i.v), produced intense and persistent bradycardia associated with hypotension. Bradycardia with prolonged QTc was observed in the ECG in vivo recording. In the in vivo model of arrhythmia induced by Bay K8644, DL (10 mg/kg) decreased the arrhythmia score from 15.33 ± 3.52 to 4.0 ± 2.64 u.a (p < 0.05, n = 4). In isolated perfused hearts, DL (10(-3) M) promoted significant reductions in heart rate (from 228.6 ± 8.5 ms to 196.0 ± 9.3 bpm; p < 0.05) and left ventricular development pressure (from 25.2 ± 3.4 to 5.9 ± 1.8 mmHg; n = 5, p < 0.05). CONCLUSIONS: DL produces bradycardia and antiarrhythmic activity in rat heart.