Brain prostaglandins mediate the bombesin-induced increase in plasma levels of catecholamines.

Intracerebroventricular (i.c.v.) administration of bombesin (0.1, 1.0, 10.0 nmol/animal) in urethane-anesthetized rats induced long-lasting and dose dependent increases in plasma levels of adrenaline and noradrenaline. These effects of bombesin were inhibited by i.c.v. pretreatment with indomethacin (50-500 micrograms/animal), while the same dose of indomethacin by the intravenous route was without effect. The bombesin-induced increases in plasma levels of catecholamines were also inhibited by i.c.v. pretreatment with diclofenac (100-500 micrograms/animal), a cyclooxygenase inhibitor other than indomethacin. I.c.v. administration of thyrotropin releasing hormone (TRH) (10 nmol/animal) also induced increases in plasma levels of adrenaline and noradrenaline, however, these increases were not modified by i.c.v. pretreatment with indomethacin. The present results suggest that the bombesin-induced increases in plasma levels of catecholamines are probably due to prostaglandins synthetized in the brain with this neuropeptide. Furthermore, it is likely that prostaglandins are not always involved in central activation of sympatho-adrenomedullary system by other brain neuropeptides.