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
GPCR that does not act through opening of potassium channels is? 
Select and explain. 
A. Muscarinic M2 receptor, B. Dopamine D2 receptor, C. Serotonin 5 HT1 receptor, D. Angiotensin 1 receptor
D: Angiotensin 1 receptor
Answer: D: Angiotensin 1 receptor 
Explanation: Ans. D. Angiotensin 1 receptor* Four G protein gated inwardly-rectifying potassium (GIRK) channel subunits have been identified in mammals: GIRK1, GIRK2, GIRK3, and GIRK4. The GIRK subunits come together to form GIRK ion channels.* Activation of the IKACh channels begins with release of acetylcholine (ACh) from the vagus nerve onto pacemaker cells in the hea.* ACh binds to the M2 muscarinic acetylcholine receptors, which interact with G proteins.