Purpose: The aim of the experiments described here was to show whether Daphnia pulex could be used to investigate the effects of sleeping pill on the heart and to establish D. pulex as a model for investigating the side effect in human disease. Methods: The research used the 5(superscript th) generation water flea cultivated by the laboratory itself as the experiment material, adopted the nature-imitating water (hard water), and selected two representative sleeping pills to prepare for a density series, to carry out a series of experiments, including: acute toxicity test for LC50, EC50 values and measurement of the heart beat rate, after Zolpidem and Benzodiazepine treated. Results: D. pulex neonate 48h-LC50 values of two pharmaceuticals tested in the present study were 72.783 mg/L for Zolpidem tartrate (Stilnox) and 67.906 mg/L for Benzodiazepine (BZD). D. pulex embryo 48h-EC50 values of two pharmaceuticals tested in the present study were 4.572 mg/L for Stilnox and 0.739 mg/L for BZD. The acute toxicity to D. pulex increased with the duration of exposure for both the sleeping pills, which present a dose response reaction. The sleeping pills effects on the Daphnia heart beat rate are significantly different with the control group. Stilnox could decreased 3-25% of heart beat rate than the control group, and BZD decreased 6-41% of heart beat rate than the control group. The effect on Daphnia heart beat rate of BZD was unexpectedly higher than Stilnox. Conclusion: Here, we report that sleeping pill, at concentrations found in Zolpidem and Benzodiazepine, caused a dramatic decrease in D. pulex heart beat rate and induced severe arrhythmia. Our results provide further evidence of D. pulex as a unique model system in biology and medicine.
