GPR7 and GPR8 (G-protein-coupled Receptors) are two recently discovered and structural- ly related orphan receptors linked to protein G. They are present both in central nervous system and in peripheral organs. Recently, endogenous ligands of these receptors have been identified. One of them is a 29 amino acid residues long, uniquely modified with bromine and, thus, termed the neuropeptide B (NPB). The other, neuropeptide W (NPW), has been identified in two molecular forms of, respectively, 23 and 30 amino acids (NPW23 and NPW30).

Cerebellin is a relatively new and little-known neuropeptide, built of 16 amino acids. It is now known about the existence of four precursor proteins termed precerebeliny. Within a single species for each precerebellins genes located on different chromosomes, but in each case consist of three exons. Comparison between precerebellins between different species reveals their very high homology.