INHIBITORY EFFECTS OF CYANIDE ON MECHANICAL AND ELECTRICAL-ACTIVITIESIN THE CIRCULAR MUSCLE OF GASTRIC ANTRUM OF GUINEA-PIG STOMACH

Effects of cyanide (CN) on spontaneous mechanical and electrical activ ities were studied in the circular muscle of the guinea-pig gastric an trum. CN (0.05-0.5 mm) inhibited both mechanical and electrical activi ties, but the inhibition was stronger in the former than the latter (s low wave). When glucose was removed for more than 30 min, slow wave wa s also blocked by CN. It is likely that ATP necessary for the generati on of spontaneous activity can be supplied through either glycolysis o r oxidative phosphorylation. CN slightly depolarized the membrane and the inhibition by CN was not affected by glibenclamide, a blocking age nt of ATP-regulated K+ channel, suggesting that this channel is not ac tivated by CN treatment. Basal level of intracellular Ca2+ measured wi th fura-2 tended to increase during the mechanical inhibition by CN. T his was also clearly demonstrated in excess (60 mm) K+ solution. These results suggest that intracellular Ca2+ regulation is impaired and th at there is uncoupling between intracellular Ca2+ and tension developm ent in the presence of CN.