Abstract

Central actions of bradykinin were studied by recording blood pressure and sympathetic nerve activity from the body of a recipient rat whose head was vascularly isolated and perfused by a donor rat. Intracarotid injections of bradykinin had biphasic effects consisting of initial inhibition followed by more prolonged stimulation. Initial vasodepression and sympathetic inhibition disappeared after intracerebroventricular injection of 6-hydroxydopamine. On the other hand, the secondary pressor response and its attendant sympathetic hyperactivity were reduced after inhibition of prostaglandin synthesis with indomethacin, and conversely, augmented after administration of the prostaglandin precursor, arachidonic acid. Pressor responses elicited by intracerebroventricular injection of bradykinin in awake rats were also inhibited by indomethacin. These results indicate that bradykinin has at least two centrally induced actions on blood pressure: an initial vasodepression caused by release of endogenous norepinephrine which activates alpha adrenergic vasodepressor mechanisms in supramedullary centers, and a secondary pressor effect that may be mediated via release of endogenous prostaglandins.