<prompt> In peristalsis following are involved except ?NOSubstance PNoradrenalineVIP  <response>: Ans. is c i.e., Noradrenaline Peristalsis requires an active myenteric Auerbachs 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. 