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: Pharmacology
[{'content': 'Which of the following 5HT3 receptor blockers has highest receptor affinity \nSelect and explain. \nA. Ondansetron, B. Granisetron, C. Dolasetron, D. Palonosetron', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Palonosetron 5 HT3 subtypes of receptors are impoant for - Emesis - Gut peristalsis - Bradycardia - Transient hypotension - Apnea - Itch 5 HT3 receptor antagonists are: - Ondensetron - Granisetron - Pahmosetron "Among the 5 HT3 receptor blockers palonosetron is a new i.v. agent that has greatest affinity for 5 HT3 receptor and has a long serum half life".', 'role': 'assistant'}]