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.
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