Thursday September 10, 2026
EurekAlert! —
Many of the drugs that target human brain chemistry, such as antidepressants, are still biologically active when they leave the body. These substances and their metabolites can persist in wastewater and eventually end up in the sea, rivers, or other aquatic environments. Because fish also use the same neurotransmitters as humans, including serotonin, dopamine, and norepinephrine, pharmaceuticals designed to interact with these chemical signals in humans can also interfere with fish’s biological processes, potentially affecting both behavior and physiology.
However, observing behavioral changes in exposed fish does not by itself reveal how a given drug caused that effect. Antidepressants often act on proteins called monoamine transporters, which help clear serotonin, dopamine, and norepinephrine from the synaptic cleft. The three main transporters are known as SERT for serotonin, DAT for dopamine, and NET for norepinephrine. Although fish possess versions of these proteins, it remains unclear whether they respond to human-targeted pharmaceuticals in a similar way to their human counterparts. Moreover, most mechanistic research has focused on a small number of fish species, so scientists are not sure whether pharmaceutical sensitivity is broadly shared across fish.