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
Tegaserod acts at the following receptor: 
Select and explain. 
A. Histamine, B. Serotonin, C. Thromboxane, D. None of the above
B: Serotonin
Answer: B: Serotonin 
Explanation: Tegaserod is a serotonin 5-HT4 paial agonist that has high affinity for 5-HT4 receptors but no appreciable binding to 5-HT3 or dopamine receptors. Tegaserod was approved for the treatment of patients with chronic constipation and IBS with predominant constipation. Ref: Katzung 11th edition Chapter 60.