In peristalsis following are involved except ?
NO
Substance P
Noradrenaline
VIP
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.