Cardiovascular inhibitory effects of Hyoscyamus niger.

This study describes the hypotensive, cardiosuppressant and vasodilator activities of Hyoscyamus niger crude extract (Hn.Cr). Hn.Cr, which tested positive for alkaloids, coumarins, flavonoids, sterols, tannins and terpenes, caused a dose-dependent (10-100 mg/kg) fall in the arterial blood pressure (BP) of rats under anesthesia. In guinea-pig atria, Hn.Cr exhibited a cardiodepressant effect on the rate and force of spontaneous atrial contractions. In isolated rabbit aorta, Hn.Cr (0.01-1.0 mg/ml) relaxed the phenylephrine (PE, 1 microM) and K(+) (80 mM)-induced contractions and suppressed PE (1 microM) control peaks obtained in Ca(++)-free medium similar to that caused by verapamil. The vasodilator effect of Hn.Cr was endothelium-independent as it was not opposed by N (omega)-nitro-L-arginine methyl ester in endothelium-intact rat aortic preparations and also occurred at a similar concentration in endothelium-denuded tissues. These data indicate that Hyoscyamus niger lowers BP through a Ca(++)-antagonist mechanism.