Cardiovascular action of penta-O-ethylquercetin in the rat.

: Intravenous (i.v.) administration of penta-O-ethylquercetin (PQ) dissolved in glycerolformal (GF) induced a rapid and transient fall in arterial blood pressure of rats. The mechanism appears rather complex. Beside its inhibitory properties toward cardiac cyclic AMP phosphodiesterase, the drug seems to lower the adrenergic tone, thus acting both at the central (stimulation of the cardiomoderator medullary center) and peripheral (partial blockade of postsynaptic alpha-adrenergic receptors, decrease in noradrenaline liberation) levels. Repeated i.v. administration of variable dosages of PQ caused a decrease in the hypotensive effect of PQ/GF which might be related to a tachyphylaxy phenomenon. In marked contrast, continuous i.v. infusion of PQ/GF progressively increased arterial blood pressure, which very likely involves a quite different mechanism of action.