Spasmolytic effects of tetrazepam on rat duodenum and guinea-pig ileum

This study was designed to examine the inhibitory effects exerted by tetrazepam isolated rat duodenum and guinea pig ileum contractive responses and to further clarity the mechanisms involved. Tetrazepam produced concentration-dependent and complete relaxation of muscle contractions induced by KCl (80 mM) in guinea-pig ileum and this relaxant action was not antagonized by pretreatment with hexamethonium (0.1 mM), antagonist for nicotinic receptors, or atropine (1 microM), antagonist for muscarinic receptors, or PK 11195 (1 microM) antagonist for peripheral-type benzodiazepines receptors. Tetrazepam also modified the concentration-response curves of CaCl2 in calcium-free and high K/ depolarizing medium as soon as concentration-response curves of acetylcholine in Tyrode solution. The results suggested that tetrazepam inhibits the contractile responses to guinea-pig ileum and rat duodenum, probably through a reduction of calcium influx by way of calcium channels and these events are not related to high-affinity peripheral benzodiazepine binding sites.