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.