The medicines we take are reflected in our urine and animals on the receiving end of sewage can sometimes bear the brunt of drug use (such as the plight of London’s eels). New research published in the journal Proceedings of the Royal Society B has found however that the side effects aren’t always bad, as it was found that the water fleas (Daphnia magna) that had been exposed to antidepressants in human waste experienced a veritable baby boom.
Dopamine-regulating drugs, colloquially known as “happy pills,” are often prescribed to boost the mood of patients suffering from depression. They are widely prescribed and can be detected in human urine, making them one of the leading contributors to dopamine in the environment. Human waste does get processed by treatment plants to remove harmful pathogens, but dopamine doesn’t fit into this bracket and as such flows freely into the environment.
The researchers in the new study wanted to investigate how this influx of dopamine was affecting a type of water flea, specifically Daphnia magna. These organisms are zooplankton, which are extremely common in freshwater and are a vital ingredient in maintaining its health as they keep algae and bacteria in check as well as providing food for many other aquatic species.
They exposed the Daphnia to both dopamine and the dopamine reuptake inhibitor bupropion (a drug used to reduce depression and support smoking cessation) and recorded how it changed the fleas' life cycle trends including growth and reproduction rate across two experimental controls, one with lots of food and one with less. Both treatments induced changes but the control with less food had a more pronounced effect on the Daphnia making them grow faster and produce more babies.
While a dopamine-induced baby boom might sound like a benefit, the researchers urge it’s not yet known if this is a plus or a negative for the species. A faster growth and reproduction rate is usually a sign of stress in these organisms and rapid growth can compromise their immunity as it reduces the amount of available energy leaving them vulnerable to parasites and disease.
“In this study, we examined how dopamine mediates the responses of life-history traits to food abundance in D. magna, through aqueous exposure to dopamine and the antidepressant bupropion, a dopamine reuptake inhibitor,” said the study authors. “Our findings emphasize the role of the dopamine system as regulator of trait responses to food abundance and demonstrate that low but environmentally relevant concentrations of bupropion can alter the life history of D. magna, with possible consequences to individual fitness.”
[H/T: Norwegian SciTech News]