Abstract: Capsaicin, the pungent principle of hot peppers of the plant genus Capsicum simulates and in large concentrations desensitizes sensory and vagal nerve fibers which express transient receptor potential cation channel vanilloid subfamily member 1 (TRPV1) or the capsaicin receptor. Repetitive administration of capsaicin also produces a desensitization and an inactivation of sensory receptors. The aim of this study was to investigate the effect of single or repeated intraperitoneal (i.p.) administration of capsaicin on electrocardiographic parameters and cardiac histology in normal anesthetized rats. Capsaicin was i.p. administered at doses of 0.01, 0.1 or 1 mg/kg to separate animals. Other groups were treated with repeated i.p. injections of 0.01, 0.1 or 1 mg/kg capsaicin, at 5 min intervals between each application. Results showed that compared with the saline control, capsaicin given at doses of 0.01, 0.1 or 1 mg/kg produced negative chronotropic effect with significant decrease in the heart rate by 6%, 8.7% and 10% along with significant prolongation of the RR interval by 6.8%, 10.2% and 11.6%. The R wave showed a dose-dependent decrease by 9.9%, 18.4% and 19.8% following capsaicin application at 0.01, 0.1 or 1 mg/kg, respectively. Capsaicin given at 1 mg/kg shortened the PR, QT and QTc intervals. Capsaicin given at 0.1 or 1 mg/kg caused narrowing of the QRS complex duration by 9.3% and 18.6%. The P wave duration did not change after capsaicin. In contrast, T wave duration and amplitude decreased by capsaicin at 1 mg/kg. The responses to repeated i.p. doses of capsaicin were qualitatively similar to its single dose application with no evidence of reduced responses after repeated dosing. Meanwhile, a single or repeated i.p. administration of capsaicin did not induce arrhythmia or cardiac histologic damage. These findings suggest that stimulation of abdominal TRPV1 channels by i.p. capsaicin causes different electrocardiac changes.

Keywords: capsaicin, sensory receptors, abdominal afferents, electrocardiogram

Pages: 77-91

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