A peptide neurotransmitter believed to be important in the control of appetite and feeding behaviour, especially in response to leptin.
One of the most abundant peptides found in the central and peripheral nervous system. Serves as a vasoconstrictor in conjunction with norepinephrine. It is released by the GI tract and signals hunger. It plays an unknown role in the placenta where its level rises early in pregnancy and remains high for the duration of the pregnancy. Leptin reduces its synthesis.