Blocking effect of diltiazem in the isolated rat phrenic hemidiaphragm

The effects of diltiazem on indirectly and directly elicited twitch were studied in the isolated rat phrenic hemidiaphragm preparation. Diltiazem (30-500 microM) blocked the indirectly elicited twitch response and this effect was not affected by reducing the extracellular calcium from 2.5 to 1.25 mM. An effect on the directly elicited twitch was also observed (100-300 microM). Diltiazem (30-300 microM) blocked the peak tetanic tension and tetanic fade was present. The results were consistent with an action of diltiazem on the nicotinic receptor-ion channel complex.