Effects of gallanilide on isolated rabbit atria, thoracic aorta and portal vein

On isolated rabbit atria preparations,the new antiarrhythmic compound gallanilide (N-(2-dithylaminoethyl)-N-O-tolyl-3,4,5-trimethoxybenzaminde maleate, GA) as well as verapamil(Ver) antagonized the actions of isoprenaline in a non-competitive manner. They shifted the dose-response curves of isoprenaline to the right with the reduced crest values. The pD2 values of GA and Ver were 3.91+0.14 and 6.15+0.17,repectively. Ver 0.25 microM also significantly antagonized CaCl2-induced positive chronotropic responses in isolated rabbit atria. GA 10-50 microM showed similar through weaker antagonism. On isolated rabbit thoracic aorta preparations. GA inhibited the contraction induced by both KCl and noradrenaline (NA) in normal Krebs solution. After the preparations had been exposed to calcium-free Krebs solution for 2 h,the NA-induced responses were inhibited by the GA, whereas the KCl-induced reponses were not affected. On isolated rabbit portal vein preparations,GA inhibited the contractions induced not only by KCl and NA in normal Krebs solution, but also by CaCl2 in calcium-free depolarizing solution. These results suggested that GA had a calcium antagonistic effect.