Inhibitory effects of cyanide on mechanical and electrical activities in the circular muscle of gastric antrum of guinea-pig stomach.

Effects of cyanide (CN) on spontaneous mechanical and electrical activities were studied in the circular muscle of the guinea-pig gastric antrum. CN (0.05-0.5 mM) inhibited both mechanical and electrical activities, but the inhibition was stronger in the former than the latter (slow wave). When glucose was removed for more than 30 min, slow wave was also blocked by CN. It is likely that ATP necessary for the generation of spontaneous activity can be supplied through either glycolysis or oxidative phosphorylation. CN slightly depolarized the membrane and the inhibition by CN was not affected by glibenclamide, a blocking agent of ATP-regulated K+ channel, suggesting that this channel is not activated by CN treatment. Basal level of intracellular Ca2+ measured with fura-2 tended to increase during the mechanical inhibition by CN. This was also clearly demonstrated in excess (60 mM) K+ solution. These results suggest that intracellular Ca2+ regulation is impaired and that there is uncoupling between intracellular Ca2+ and tension development in the presence of CN.