This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy & Physiology (Oesophagus), Subject name: Surgery
Lower esophageal sphincter tone is due to 
Select and explain. 
A. Vasoactive intestinal peptide, B. Nitrous oxide, C. Acetylcholine, D. Pancreatic polypeptide
C: Acetylcholine
Answer: C: Acetylcholine 
Explanation: Ans. (c) AcetylcholineRef: Bailey & Love 26th ed. / 988There are two types of control of LES via the Myenteric plexus:* Excitatory (cholinergic) ganglionic neurons* Inhibitory (nitric oxide) ganglionic neuronsFunctionally, inhibitory neurons mediate Deglutitive lower esophageal sphincter (LES) relaxation and the sequential propagation of peristalsis.