Flatworms could replace rats for in vivo brain studies

Tiny pond worms could help find new ways to treat schizophrenia, develop an understanding of drug addiction and test new medicines for mental illnesses—all while reducing the number of mice and rats used in early medical research.

Scientists from the University of Reading say that planaria—harmless flatworms found in ponds and rivers—react to brain medicines in ways similar to rodents. When given haloperidol, a drug used to treat mental health conditions, the worms became much less active, just like mice and rats do.

Previous studies have used planaria to research epilepsy treatments and to investigate drug addiction, as the flatworms exhibit signs of withdrawal symptoms.

This new study, published in the journal Pharmaceutical Research, could help to develop treatments for mental health conditions such as schizophrenia and hallucinations. A 2024 study found one in 69 UK adults are using antipsychotic medication long-term.

Professor Vitaliy Khutoryanskiy, who led the study from the University of Reading, said, “This finding adds to growing evidence that tiny flatworms like planaria could play a valuable role in how we study the brain. They display certain responses to psychiatric drugs that resemble those seen in mammals, but using them involves far fewer ethical concerns.

“Close to a million mice and rats are used in UK research each year, but using planaria instead could potentially cut those numbers and still give us the answers we need to develop better treatments for people with serious mental health conditions. It’s good for science and it’s good for animal welfare.”

Lab rats could be replaced

Haloperidol works by calming overactive brain activity in people whose minds are working too fast or in confusing ways. Scientists often test this medicine on animals to understand how it affects the brain and to develop better treatments for patients. According to UK government data, 882,000 mice and 144,060 rats were used in animal research in 2023.

A 2016 study suggested the use of rats and mice in neuroscience had risen from 20% in the 1980s, to over 50% by the 2010s.

Despite growing efforts to make research more ethical, scientists still rely heavily on rodents for testing. Using flatworms for studying brain conditions could potentially reduce the number of rodents used in research.

The research team also tested special ring-shaped sugar molecules called cyclodextrins, which act like tiny containers that can hold medicines and help them dissolve better in water. Haloperidol normally doesn’t mix well with water, but when it was placed in the sugar containers, it dissolved 20 times better than normal.

When the drug was trapped inside these containers, they held onto the medicine so tightly that it couldn’t get to the worm’s bodies. This shows that the worms could be useful for testing not just different drugs, but also different ways of making those medicines.

The planaria research has already influenced teaching at the University of Reading, where the haloperidol effect on worms is now part of undergraduate pharmacology classes.