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Effects of ethanol on rates of heartbeat in Daphnia


The cladoceran Daphnia is well established as a model for ecotoxicology. Here, we show that Daphnia is also useful for investigating the effects of alcohol on heart rate. The results may then be extrapolated to determine the effect of alcohol on human heart rate and the possible heart diseases that may result from too much alcohol consumption. Daphnia heart was shown to respond to ethanol in the bathing medium. Ethanol decreased the heart rate when in concentration of 0.05% and above. Three measurements of the heart rate for each concentration of ethanol using three different Daphnia for each measurement was taken and the mean determined. Though the sample size was small and the results cannot be conclusive due to such a small sample size, the results show that Daphnia can be used as a novel model system for studying the effects of alcohol on heart rate and it may be used in further studies to determine the possible receptors that an alcohol molecule may bind to bring about an effect on the heart rate.

Once ethanol enters the Daphnia, it interferes with the heart rate. The method of action is probably by interfering with the nerves as mentioned above. (If the quality of the heart beat was affected, we might consider the cardiac muscle to be the site of action. In this case, however, only the rate is involved, so it's most likely the nerves that are affected.) It may be possible that the nerve fibers conducting pulses to the hearts of Daphnia may contain receptors that inappropriately bind to ethanol (or a product of ethanol after it is broken down) causing an inappropriate decrease in nerve activity.

To further confirm these findings and to determine the possible receptors found on the heart that are involved in binding of ethanol, further studies have to be carried out with a larger sample size.

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