[Medicamentous modification of gastrointestinal motility and secretion]

This article gives an overview on possible new pharmacological tools to modify gastrointestinal motility and/or secretion. The characterization of new subclasses of classical neurotransmitter receptors and of peptidergic receptors offer a new approach for the development of new therapeutic agents. Using molecular biology techniques a variety of receptor subclasses have been demonstrated for muscarinic and alpha 2-adrenergic receptors. Both receptor types are of major importance for the regulation of mucosal secretion in the submucosal plexus and specific ligands for these receptor subtypes could be of clinical interest. In the next paragraphs the possible therapeutic relevance of 5-HT3-receptor antagonists and of opiate agonist and -antagonists is discussed. 5-HT3-antagonists, which can be used as potent antiemetics, also demonstrate quite potent effects on upper gastrointestinal motility such as gastric emptying. Whereas the subclassification of opioids has so far no specific therapeutic consequences there is some evidence that casomorphin, a derivative of the casein of the milk, could be used as a possible antidiarhoic substance. The use of antagonist and agonists on peptidergic receptors with orally active ligands offer a further new therapeutic approach. This is discussed for CCK-antagonists and erythromycin-analogues which are agonists at the motilin receptor. Besides this experimental approach to modify defined receptor subclasses, there are new substances with so far not clearly defined mechanism of action, which, however, have potent therapeutic effects. Cisapride, a new potent prokinetic drug with little side effects, is now available for clinical use for a wide range of motility disorders.