[Galanin: a new biologically active gastrointestinal neuropeptide]

The 29 amino acid containing neuropeptide galanin is localized in the intrinsic nervous system of the entire gastrointestinal tract and the pancreas. It was found in man and several animal species. Molecular biology studies revealed different molecular forms of galanin in several mammalian species including man. The galanin precursor was also found. Galanin shows several potent pharmacological actions: it inhibits gastrointestinal motility in man. It also has an inhibitory effect on intestinal smooth muscle contractility of several animal species. These actions are mediated directly by opening of potassium channels and indirectly by inhibition of acetylcholine release. In addition galanin inhibits pancreatic hormone secretion (i.e. hypoinsulinemia, hyperglycemia) and partly the release of hormones localized in the gastrointestinal tract. On exocrine glands in man (salivary glands) galanin has hydrokinetic actions. The physiological role of galanin might be regulation of gastrointestinal motility, control of secretory function of intestine and a regulatory role in endocrine and exocrine gland secretion.