<Ul> <Li> Gastrin--cholecystokinin family: gastrin and cholecystokinin </Li> <Li> Secretin family: secretin, glucagon, vasoactive intestinal peptide and gastric inhibitory peptide </Li> <Li> Somatostatin family </Li> <Li> Motilin family </Li> <Li> Substance P . </Li> </Ul> <Li> Gastrin--cholecystokinin family: gastrin and cholecystokinin </Li> <Li> Secretin family: secretin, glucagon, vasoactive intestinal peptide and gastric inhibitory peptide </Li> <Li> Substance P . </Li>

Which substance present in the blood regulates contraction of stomach