In vitro uterine relaxant activity of Fire Ha Kong Recipe in rats

Fire Ha Kong recipe in a concentration range of 1040 μl/ml was used to test in an in vitro uterine contraction inhibition. Contraction frequencies and amplitudes of the normal uterine of estrogen-primed non-pregnant rats were monitored. A decline in the frequencies of uterine contractions of 43.8 93.6% was detected. Addition of Fire Ha Kong at the final concentrations of 20-40 μl/ml inhibited the amplitudes of uterus contraction by 57.1% and 85.7%, respectively. The reductions in area under the curve (AUC) of contractions were 57.1% and 85.7% for the added concentrations. Fire Ha Kong recipe revealed inhibitory effects on the uterine response to oxytocin (10-11 M) 31.9% and 29.3% only in frequency but not in amplitude and AUC in comparison to oxytocin alone. These results indicate that the tocolytic potential of Fire Ha Kong recipe may involve oxytocin receptor-dependent pathway or reduce the intracellular availability of calcium ions.