Galanin (119418-04-1)

Galanin is a neuropeptide that has not been established as a member of any known family of neuropeptides despite repeated efforts to discover related peptides. Its actions are mediated via Gi-protein-coupled receptors and ion channels, usually producing inhibition of secretion of a transmitter or hormone in the nervous and endocrine system. In many respects, these inhibitory actions of galanin remind us of those of gamma-aminobutyric acid (GABA) and of neuropeptide Y (NPY). Galanin coexists with GABA, noradrenaline, 5-hydroxytryptamine (5-HT), and NPY in several regions of the brain. Galanin is a 29-amino acid neuropeptide not homologus with any other known peptide. High concentrations of galanin and its receptor subtypes are present in the hypothalamus and central administration of the neuropeptide increases food consumption in fed rats,a highly reproducible result. Although galanin appears to play a minor role in normal feeding behavior it is possible that under abnormal physiological conditions it may exert profound effects. Preliminary reports demonstrate unusual endogenous peptide levels in human appetite disorders but other studies have been inconclusive. It is possible that more targeted investigations involving subtype-selective non-peptide galanin receptor ligands may have clinical implications in appetite disorders.