CENTRAL-NERVOUS-SYSTEM SITE OF ACTION OF BOMBESIN TO ELEVATE PLASMA-CONCENTRATIONS OF CATECHOLAMINES

To identify the central nervous system site of bombesin to elevate plasma concentrations of catecholamines, this peptide has been injected into numerous brain ventricular and parenchymal sites. Low doses of bombesin (1-10 ng) injected into the region of the rostral nucleus tractus solitarius (NTS) elicited an elevation of plasma catecholamines greater than those observed following an injection of bombesin into other brain regions. Bombesin-induced (10 ng) elevation of plasma epinephrine but not norepinephrine was prevented by co-administration of somatostatin-28 (100 ng). Mean arterial pressure (MAP) and heart rate (HR) were measured following injection of bombesin into the NTS. Bombesin injected into the NTS resulted in prolonged decreases in HR without significantly altering MAP. These studies demonstrate that bombesin injected into the dorsal medulla resulted in significant changes of plasma catecholamine levels and HR. Based on these actions of bombesin and the neuroanatomic distribution of bombesin-like peptide, it is suggested that this peptide may play an important role in regulation of sympatho-adrenal and cardiac functions.