EFFECTS OF L-TETRAHYDROPALMATINE ON ISOLATED GUINEA PIG ATRIA
Sun Feng & Li Dexing ( Dept. of Pharmacology, Nanjing Medical College)
L-tetrahydropalmatine (THP) verapamil ( Ver ) antagonized CaCl2-induced positive chronotropic response in spontaneously beating right atria of guinea pig, and noncompetitively antagonized CaCl2 - isoprenaline ( Iso ) -induced positive inotropic effects of the left atria electrically driven at 1.5 Hz Iso-induced positive chronotro-pic effects of the right atria. THP Ver had dose-dependent frequency-dependent inhibitory effects on contraction of the left atria, and inversed the frequency-contraction curve from positive staircase into negative staircase,but had only slight inhibitory effects on postrest potentiation. The results suggest that THP, similar to Ver, has inhibitory effects on isolated guinea pig atria, which might be related to antagonizing Ca2+ via blockade of Ca2+ influx.