This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pharmacology, Subject name: Pharmacology
[{'content': 'Which of the following receptor has an ion channel? \nSelect and explain. \nA. GABA A receptor, B. Insulin receptor, C. Vitamin A receptor, D. GABA B receptor', 'role': 'user'}, {'content': 'Answer: A \nExplanation: GABA receptors are divided into two main types: GABA A and GABA B. GABA A receptors are ionotropic receptors and, like glycine receptors, are pentameric structures that are selectively permeable to Cl-. GABA B receptors are metabotropic receptors that are selectively activated by the antispastic drug baclofen. These receptors are coupled to G proteins that, depending ontheir cellular location, either inhibit Ca 2+ channels or activate K + channels. Ref: Katzung; 13th edition; Page no: 369', 'role': 'assistant'}]