Effects of intracerebroventricular administration of bradykinin on rat brain serotonin and prostaglandins.

Intracerebroventricular (ICV) administration of bradykinin (5, 10 and 20 micrograms) produced a dose-related increase in the concentration of serotonin in rat brain. The maximum increase was observed after 15 min of bradykinin administration. Thereafter, the augmented levels of serotonin declined and tended to come to normal value after 60 min. Bradykinin (20 micrograms) significantly increased the concentrations of serotonin specifically in cortex, hypothalamus, midbrain and pons-medulla but not in cerebellum and spinal cord. The time course of increase and subsequent decline of regional concentrations of serotonin in brain were similar to that noted with bradykinin-induced changes in serotonin levels in whole brain. Bradykinin (5, 10 and 20 mg, ICV) increased the concentration of prostaglandin E2 (PGE2) but not of PGF2 alpha of rat brain. The time course of bradykinin-induced changes in PGE2 concentrations were similar to the effects of bradykinin on the levels of serotonin in rat brain. The inhibitors of PG synthesis, hydrocortisone, diclofenac and paracetamol, antagonized the bradykinin-induced increase of serotonin in rat brain. These results have provided support for the contention that PGs may presumably mediate some of the central actions of bradykinin and that bradykinin-induced augmentation of central serotonergic activity could possibly account for PGE2-induced modulation of rat brain serotonin.