[The role of galanin in the endocrine system]

Galanin, a 29-30 amino-acid neuropeptide is distributed in the central and peripheral nervous systems, the pituitary gland, the gastrointestinal tract and also in the pancreas. The endogenous and exogenous effects of galanin are mediated by three receptor subtypes, which are termed: GALR1, GALR2, and GALR3. Galanin has a significant role in physiological and pathological processes in adults as well as in children. It has an ability to contract smooth muscles in GI (facilitation and inhibition), stimulates reflexes in the CNS, decreases pancreatic amylase secretion, changes transport of electrolytes Na+ and CL-. It takes part in etiopathogenesis of depression, Alzheimer's disease and diarrhoea, exerts tonic inhibition of nociceptive input to the central nervous system and regulates a function of hypothalamic-pituitary system. Galanin decreases insulin and somatostatin secretion, increases glucagon secretion, takes part in prolactin release, stimulates growth hormone-releasing hormone, hypothalamic gonadotropin releasing hormone and corticotropin releasing hormone. It causes increase of somatotropin secretion, luteinizing hormone and foliculotropin release and adrenocorticotropin secretion. The hypothalamic galanin takes part in etiopathogenesis of obesity not only in human reproductive period, but also in adolescence, increasing the appetite and changing fat metabolism. This variety of actions emphasizes the potential importance of this peptide in the regulation of cells function and the need to understand the mechanism by which they act.