This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Raphe nucleus, in the brain stem is responisble for the secretion of which of the following chemicals? \nSelect and explain. \nA. Histamine, B. Serotonin, C. Dopamine, D. Epinephrine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Raphe nucleus is a cluster of cells found in the brain stem, their main function is to secrete serotonin. Serotonin (5-hydroxytryptamine; 5-HT) is present in highest concentration in blood platelets and in the gastrointestinal tract, where it is found in the enterochromaffi n cells and the myenteric plexus. Lesser amounts are found in the brain and in the retina. Ref: Molecular and Cellular Signalling By Main Beckerman, Page 292', 'role': 'assistant'}]