This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous General Anesthesia, Subject name: Anaesthesia
[{'content': 'Which of the following has antiemetic action? \nSelect and explain. \nA. Propofol, B. Thiopentone, C. Ether, D. Nitrous oxide', 'role': 'user'}, {'content': 'Answer: A \nExplanation: ANSWER: (A) PropofolREF: Miller\'s Anaesthesiology 7th Ed Ch 25"A unique action of propofol is its antiemetic effect, which remains present at concentrations less than those producing sedation/\'Propofol\'s antiemetic action may be explained by the decrease in serotonin levels it produces in the area postrema, probably through its action on GABA receptors. Two notable side effects of propofol are its antiemetic effect and a sense of well-being in patients. The antiemetic effect gives a special advantage in day care anaesthesia.', 'role': 'assistant'}]