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
Terlipressin can be used for hematemesis from oesophageal varices. The action is mediated by: 
Select and explain. 
A. V1a, B. V1b, C. V2, D. V4
A: V1a
Answer: A: V1a 
Explanation: Terlipressin causes vasoconstriction by acting on V1a/V1 receptor.
(V1b receptor is also called as V3 receptor)