Ghrelin is a 28 amino acid peptide, acylated on a serine residue which is essential for its biological activity. In rodents, an additional form of the peptide could be purified. The peptide is released from the stomach and exerts its effect to ghrelin receptor (GHS-R). GHS-R is a member of the G-protein coupled receptor (GPCR) superfamily. Like all members, the receptor has seven transmembrane spanning domains and upon activation it stimulates phospholipase C, thereby increasing IP3 and intracellular Ca2+ levels. GHS-R is expressed in the hypothalamus, pituitary and hippocampus.