Bombesin is a 14 amino acid endogenous mammalian neurotransmitter which activates three different G-protein-coupled receptors, bombesin receptor (BBR) 1, -2, and -3. Bombesin exhibits many biological effects including hormone release, stimulation of pancreatic enzyme secretion, inhibition of gastric emptying and modulation of gastric acid secretion. Bombesin also activates these receptors in the brain and together with cholecystokinin, it is the second major source of negative feedback signals that stop eating behaviour. Bombesin is also a tumour marker for small cell lung carcinoma, gastric cancer, pancreatic cancer, and neuroblastoma.
