A new study has shown that small pond worms, called planaria, respond to psychiatric drugs like rodents – offering a promising new way of studying mental health conditions such as schizophrenia and addiction.
Tiny pond worms, known as planaria, could provide new ways to treat schizophrenia and test medicines for mental illnesses – while reducing the number of mice and rats used in early-stage research.
Scientists from the University of Reading report 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, mimicking the effects observed in mice and rats.
Previous studies have already used planaria to research epilepsy treatments and investigate drug addiction – as the flatworms display signs of withdrawal. The new study, published in Pharmaceutical Research, could contribute to the development of treatments for mental health conditions such as schizophrenia and hallucinations.
“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,” said Professor Vitaliy Khutoryanskiy, who led the study.
“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.”
Haloperidol and the role of rodents in research
Haloperidol works by calming overactive brain activity in people whose minds are working too fast. Scientists often test this medicine on animals to better understand its effects and improve treatments. According to UK government data, 882,000 mice and 144,060 rats were used in animal research in 2023. A 2016 study also showed that the use of rodents in neuroscience rose from 20 percent in the 1980s to over 50 percent by the 2010s.
Despite growing efforts to make research more ethical, rodents remain central to neuroscience experiments. Using flatworms to study brain conditions could potentially reduce the number of mice and rats that are used in such research.
Testing new drug delivery methods
The research team also tested special ring-shaped sugar molecules called cyclodextrins, which act like tiny containers to hold medicines and help them dissolve better in water. Haloperidol normally doesn’t mix well with water – but when placed in these sugar containers – it dissolved 20 times more effectively. When trapped inside the containers – the drug could not reach the worm’s bodies – demonstrating that planaria could be useful, not only for testing different drugs, but also for exploring new ways of delivering them.
A more ethical future
The study highlights how planaria could transform mental health research. By responding to psychiatric drugs in ways similar to rodents, these flatworms offer an ethical alternative for early-stage testing. Beyond reducing reliance on mice and rats, planaria could help scientists explore new drug formulations and better understand conditions like schizophrenia and addiction – supporting the development of more effective treatments in the future.