<prompt> Substrate P, actions all exceptVasoconstrictionPain transmissionAxon reflexPeristalsis  <response>: Substance P a peptide composed of 11 amino acids, present in nerve cells scattered throughout the body and in special endocrine cells in the gut; it increases the contractions of gastrointestinal smooth muscle and causes vasodilatation; it is one of the most potent vasoactive substances known, and it seems to be a sensory neurotransmitter involving pain, touch, and temperature.Ref: Ganong;s review of medical physiology 23rd edition Page no: 143 