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: Physiology
In peristalsis following are involved except ? 
Select and explain. 
A. NO, B. Substance P, C. Noradrenaline, D. VIP
C: Noradrenaline
Answer: C: Noradrenaline 
Explanation: Ans. is 'c' i.e., Noradrenaline Peristalsis requires an active myenteric (Auerbach's) plexus. Local stretch by chyme releases serotonin, which activates myenteric plexus. Cholinergic neurons of this plexus passing in a retrograde direction release substance P and acetylcholine, causing smooth muscle contraction. Cholinergic neurons passing in an antegrade direction activate neurons that secrete NO, VIP, and ATP, produing relaxation ahead of the stimulus.