Effect of verapamil on Ca2+ influx to rat phrenic nerve-diaphragm preparation

The effect of verapamil on contractility and on influx of calcium (Ca2+) to the rat phrenic nerve-hemidiaphragm preparation was studied in vitro, at rest and during electrical stimulation at 0.2-100 Hz. Calcium content of the bathing solution was measured using the Technicon method (SMAC, Sequential Multiple Analyser/Computer). The results showed that verapamil (a) reduced the twitch and tetanic contractions in a non-competitive manner, and (b) reduced the influx of Ca2+ to the rat hemidiaphragm preparation. Greater reductions occurred as the rate of stimulation increased.