In this study, whole cell patch clamp recording technique was employed to investigate the effect of Shenmai Injection (SMI) on L-type calcium current ofdiaphragmatic muscle in rats. The result showed that when the diaphragmatic muscle cell was held at —80 mV and depolarized to +60 mV, 10 μl/ml, 50 μl/ml and 100 μl/ml SMI enhanced the inner peak L-type calcium current from -(6.8±0.7) pA/pF (n=7) to -(7.3±0.8) pA/pF (P>0.05, n=7), -(8.6±1.0) pA/pF (P<0.05, n=7) and -(9.4±1.2) pA/pF (P<0.05, n=7), respectively. The rates of L-type calcium current were increased by (7.34±2.37) %, (25.72±5.94)% , and (38.16±7.33)% , respectively. However, it had no significant effect on maximal activation potential and reversal potential. Our results suggested that SMI could activate the calcium channel of the diaphragmatic fibers of the rats, increase the influx of Ca 2+, and enhance the contractility of diaphragmatic muscles.
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