<prompt> Neurotransmitter for pain isDopamineSubstance PPAFNone  <response>: Substance P a polypeptide neurotransmitter that stimulates vasodilation and contraction of intestinal and other smooth muscles. It also plays a pa in salivary secretion, diuresis, natriuresis, and pain sensation. It has been isolated from ceain cells of the GI and biliary tracts.Ref: Ganong;s review of medical physiology 23rd edition Page no: 143 