Zebrafish are physiologically and genetically remarkably similar to human beings, which has frequently made them the subject of scientific research. They have been studied before for research on mental health disorders and addictive behaviours to a variety of drugs, but this new study (video above) headed by Randall Peterson and Gabriel Bossé of Utah University may help scientists discover new ways to treat addiction.

It turns out that zebrafish resemble humans even in their addiction to drugs.

For 50 minutes each day for five days, the researchers placed the zebrafish in a white water tank with a small yellow platform with motion sensors to trigger the release of food. They trained the fish to swim over the yellow platform for food, and then replaced the food with hydrocodone, a kind of opioid.

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The tests show that the zebrafish grew very fond of the opioid painkiller. They ventured over the yellow platform more often than they did for food, especially when the doses of opioids were reduced.

Even when the water level was reduced in the tank – zebrafish normally avoid shallow waters to prevent themselves from becoming easy prey to birds – they abandoned caution to seek the drug. The water in the tank was regularly replaced to prevent build-up of the drug, compelling them to adopt active drug-seeking behaviour.

The fish also started to show signs of withdrawal such as anxiety after a few hours without a “hit”.

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The study can help in the development of new drugs to combat drug-seeking behaviour. Genetic tests may be conducted to check for specific mutations that influence such addictive, drug-seeking behaviour in zebrafish. It may also lead to the investigation of the biological pathways of the pleasure centres in the brain associated with addiction.

All of which can, of course, ultimately provide a better understanding of addiction and suggest ways to combat it.