This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
[{'content': 'Monoamine neurotransmitter in brains is \nSelect and explain. \nA. Serotonin, B. Glycine, C. GABA, D. Dopamine', 'role': 'user'}, {'content': "Answer: A \nExplanation: There are three main classes of chemical substances that serve as neurotransmitters and neuromodulators: small molecule transmitters large-molecule transmitters gas transmitters. Small molecule transmitters include amino acids (eg, glutamate, g-aminobutyric acid , and glycine, acetylcholine, monoamines (eg, norepinephrine, epinephrine, dopamine, and serotonin. Large-molecule transmitters include neuropeptides such as substance P, enkephalin, and vasopressin. Neuropeptides are often co-localized with one of the small-molecule neurotransmitters Ref: Ganong's Review of Medical Physiology 26th edition", 'role': 'assistant'}]