<s>[INST] You are an assistant for question-answering tasks. Use the following pieces of retrieved context to answer the question. If you don't know the answer, just say that you don't know. Use three sentences maximum and keep the answer concise. Question:  Explain the role of neurotransmitters in the brain. Context: Neurotransmitters in the brain transmit signals between nerve cells as chemical messengers. Answer: [/INST]They are chemical messengers that transmit signals between nerve cells in the brain.</s>