Matrine (50, 100, and 200 mg/kg, intragastrically administrated for seven days) [99] upregulated the expression of KCNB1 (encoding Kv 2.1) and KCNJ2 (encoding Kir2.1) in myocardial tissues of rats with myocardial infarction and prevented the occurrence of arrhythmia after myocardial infarction. The gene discussed is KCNJ2; the disease is cardiac arrhythmia.