CNP, a member of the natriuretic peptide family, was first identified in porcine brain and later found in other mammals as well as non-mammals. Processing of the CNP precursor gives rise to CNP-22 and its N-terminally elongated form, CNP-53. The CNPs share considerable sequence homology with ANP and BNP within the disulfide loop and exert similar pharmacological actions, although with different relative potencies. CNP-22 is a potent and selective activator of the human BNP cell surface receptor, a transmembrane guanylyl cyclase. This ligand-receptor pair may be involved in the regulation of fluid homeostasis by the central nervous system.