Bombesin is a 13 amino acid peptide originally isolated from the skin of a frog. It has two known homologues in mammals called neuromedin B and gastrin releasing peptide. It works on the gastrointestinal tract neuroendocrine hormone and it stimulates gastrin release from G cells . It activates three different G-protein coupled receptors known as BBR1 2 & 3. It also activates these receptors in the brain.