Relationship between central actions of bradykinin and prostaglandins in the conscious rat

Intraventricular injection of bradykinin produced a dose-dependent increase in the mean arterial blood pressure of conscious rats. With 5 nmol of bradykinin, a dual pressor response was observed, which was associated with a biphasic behavioral change. With repeated hourly injections of bradykinin, tachyphylaxis developed to the pressor and central nervous system (CNS) stimulating effect. Indomethacin, given intraventricularly, reduced the hypertension and the behavioral excitation caused by bradykinin in a dose-dependent manner. When prostaglandin E2 was injected into the cerebral ventricles, it induced hypertension and behavioral sedation similar to the secondary response to bradykinin. These results suggest that bradykinin has a dual action on the CNS, and this is mediated by prostaglandin-related systems in the brain.