To study cardioprotective drugs, we developed a simple and efficient methodology to evaluate effects of drugs on cardiac electrical activity using electrocardiogram (ECG) in rats submitted to cardiac ischemia-reperfusion (I/R). Using adult male Wistar rats (14 -16-week-old) anesthetized (urethane 1.25 g/kg, i.p.) and kept under mechanical ventilation, we used surgical procedures to induce cardiac I/R by means mechanical occlusion of left anterior descendent coronary artery for 10 min (ischemia) with silk suture (tourniquet) followed by its removal to allow coronary recirculation (reperfusion). To evaluate the effects of surgical process, a group of rats (SHAM-operated) was submitted to surgical procedures previously described, but without coronary occlusion. To evaluate cardiac electrical activity in rats submitted to cardiac I/R and SHAM-operated, the ECG system was coupled to animal body to determine the incidence of ventricular arrhythmia (VA), atrio-ventricular blockade (AVB) and lethality (LET). To evaluate injury biomarkers production in rats submitted to cardiac I/R and SHAM-operated, serum concentrations of creatine kinase fraction (MB/CK-MB) and troponin I were determined by biochemical techniques. Using the methodology proposed in this work, we observed that VA, AVB and LET incidence was significantly higher in cardiac I/R group (85%, 79% and 70%, respectively) than in SHAM-operated group (0%, 0% and 0%, respectively). Serum levels of CK-MB and troponin I were also significantly higher in cardiac I/R (1,850 ± 222 U/L and 0.031 ± 0.009 ng/mL, respectively) compared to SHAM-operated group (808 ± 72 U/L and 0.200 ± 0.027 ng/mL). To evaluate efficiency of methodology proposed in this work to study the effect of cardioprotective drugs, the effects of the L-type Ca 2+ channel blocker (CCB) nifedipine (30 mg/kg, intravenously -IV) in rats submitted to cardiac I/R were studied. The treatment with nifedipine (before ischemia) significantly reduced the incidence of VA (from 85% to 28%), AVB (from 79% to 14%), and LET (from 70% to 14%). These results indicate that the methodology described in the present work is simple, and efficient, to evaluate cardiac functional and biochemical alterations induced by cardiac I/R, and also the study of cardioprotective drugs in rats. This methodology could contribute to the development of new pharmacological cardioprotective strategies for to treatment of ischemic cardiac diseases in humans, such as myocardial infarction.

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