This week in science: giving mice PTSD and then curing it

Post-traumatic stress disorder, or PTSD, affects around 4% of the world. It can be brought on by traumatic experiences such as attacks, natural disasters and serious accidents, and is currently treated with therapy and medication. However, these techniques do not work for many people, so researchers have been searching other ways to treat the condition.

Researchers at the Universities of Toronto and Kyushu have been monitoring the brain activity of mice. The study, led by Professor Paul Frankland in Toronto and Assistant Professor Risako Fujikawa in Kyushu, looks at neurogenesis, the creation of new brain cells, and how it helps us forget things.

“We think this happens because when new neurons integrate into neural circuits, new connections are forged and older connections are lost, disrupting the ability to recall memories,” says Fujikawa.

“We wanted to see if this process could help mice forget stronger, traumatic memories too.”

Mice were given shocks in dark, alcohol-scented boxes, and from that began exhibiting PTSD-like symptoms. They reacted in the same way to a second shock in another environment. For example, they became scared of dark places, and explored less (suggesting anxiety as well).

The mice were then split into two groups, one of which received exercise wheels. After four weeks, the exercising mice had more newly-formed brain cells and fewer PTSD-like symptoms. Exercise before the second shock also prevented the symptoms from developing.

To make sure this wasn’t in fact being caused by something other than exercise, the researchers used genetic engineering to make neurons grow faster in some mice.

By adding light-sensitive proteins to the neurons, they could shine blue light on some mice to speed up their neurogenesis and compare it to the rest of the animals. They also removed a protein that slows down neuron growth, and both these techniques did reduce the PTSD-like symptoms in the mice that had them. However, the effect this had on recovery was not as strong as the effect exercise had, and did nothing to reduce anxiety, proving that running on the wheel was helping the mice get better. Fujikawa points out “exercise also has broader physiological effects, which may contribute to the stronger outcomes seen.”

The researchers then took this a step further, to test if exercise and neurogenesis could also combat drug dependency. The mice were placed in two rooms, one containing cocaine, and when presented with both rooms some time later would spend more time with the cocaine. Fortunately, the effect of doing exercise here was that mice stopped preferring to go in the cocaine room.

In the experiments, the researchers found that exercise and genetic manipulation helped the mice forget traumatic memories. They also saw the techniques work against drug-associated memories, which could lead to better ways of combatting addiction.

We already know that exercise is good for you, but the extent to which it can reduce PTSD symptoms in humans still needs research. That being said, this study is a promising sign.

Going forward, Risako Fujikawa hopes to create a drug that can boost neurogenesis in humans, but she stresses the importance of exercise - something you can do now, no clinical trial or trauma necessary!

by Louis Davies @louis.on.air

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Source:

Risako Fujikawa, Adam I. Ramsaran, Axel Guskjolen, Juan de la Parra, Yi Zou, Andrew J. Mocle, Sheena A. Josselyn & Paul W. Frankland, Molecular Psychiatry (2024) "Neurogenesis-dependent remodeling of hippocampal circuits reduces PTSD-like behaviors in adult mice." https://doi.org/10.1038/s41380-024-02585-7