Response of rabbit detrusor muscle to total extract and major alkaloids of Hydrastis canadensis

Hydrastis canadensis L. (Ranunculaceae) is used in traditional medicine to treat numerous diseases, including bladder disorders and prostatitis. This study was designed to ascertain in bladder detrusor muscle the effects of an ethanol extract of the major alkaloids in Hydrastis canadensis. On rabbit bladder strips, the total extract of Hydrastis canadensis induced relaxation nearly comparable to the response evoked by isoproterenol (EC50); propranolol partly blocked relaxation induced by the extract. Conversely, when the major alkaloids in Hydrastis canadensis (berberine, beta-hydrastine, canadine and canadaline) were added to the bath separately at concentrations several times higher than those present in the extract, none of them induced relaxation. These findings suggest that the relaxing effect depends on components other than the tested alkaloids, that the extract induces relaxation only partly through beta-adrenoreceptors and that other mechanisms must be involved.