Melatonin’s Protective Heart Effects Not Antioxidant Related

Melatonin is known to have antiarrhythmic effects which were assumed to be due to its antioxidant effects. An international team of researchers have examined how melatonin affected hearts in rat models of heart attacks which suggest otherwise.  

Animals were either given a placebo or 10mg of melatonin daily for seven days, electrical activity was measured in their hearts before, during, and after a cardiac event; hearts were examined later for measures of oxidative stress and antioxidant activity.

Ventricular fibrillation and tachycardia are dangerous irregular electrical activity that can result in the heart from a heart attack; incidence of VF and VT were observed to be reduced in melatonin treated rats and a marker of antioxidant activity was also increased; however there was no association between presence of oxidative stress and incidence of irregular electrical activity.

Blocking melatonin specific receptors was previously observed to have removed antiarrhythmic benefits of melatonin. According to Jan Azarove, PhD of the Komi Science Center previous results in combination with these results suggest that the protective effect of melatonin for the heart "are related to its antiarrhythmic action, and this effect is related not to antioxidative properties but to melatonin receptor stimulation."