The hypotensive action of Desmodium styracifolium and Clematis chinensis.

The cardiovascular pharmacology of aqueous extracts of Desmodium styracifolium (DSE) and Clematis chinensis (CCE) were studied in rats both in vivo and in vitro. DSE produced two successive hypotensive actions: the first one via cholinergic receptor stimulation, while the second one potentiated by blockades of autonomic ganglion and alpha-adrenoceptor. In contrast to DSE, CCE produced only one hypotensive response which was mediated through histaminergic activity. Furthermore, both extracts relaxed isolated methoxamine preconstricted helical tail artery strips. CCE also produced both negative chronotropic and inotropic effects on isolated atria, while DSE was positive chronotropic without apparent effect on the contractile force.