The research comes from the RIKEN Brain Science Institute. Here the researchers looked at several factors: serotonin levels, brain circuitry, and behavior in mice. The mice were bred to have a genetic mutation. This was based on one of the most frequent genetic patterns in people with autism, a type of gene copy variation. This led to the mice displaying various behavioral traits along the autism spectrum. This included low interactivity with others and inflexible behavior. The modified mice were examined alongside unaltered control mice.
The scientists then considered where in the brain the highest number of serotonin neurons were less active in the model mice compared with unaffected control mice. Following this they next considered the sensory region of the brain that receives input from these serotonergic neurons. This showed that normally inactive neurons were somehow active it was later found that the genetically modified mice possessed fewer inhibitory synapses and had a lower frequency of naturally occurring inhibitory inputs in the sensory region (again compared with the control mice). This led to the conclusion that abnormality in cortical excitatory/inhibitory balance was a determining factor.
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The subsequent experiments, carried out on infant mice that were given serotonin therapy (serotonin reuptake inhibitor), revealed that increasing serotonergic activity in the brain led to more balanced brain activity and improved the abnormal sociability of the mice. This was provided the treatment was performed during early stage development.
Principal scientist Dr. Toru Takumi outlines this further in communication to Digital Journal: “Although abnormalities in the serotonin system have been thought to be part of the pathophysiology in patents with autism spectrum disorder, the functional impact of serotonin deficiency in autism spectrum disorder was totally unknown.”
He adds: “Our work shows that early serotonergic intervention rescues regional excitatory/ inhibitory abnormalities in the brain as well as behavioral abnormalities.”
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Later studies showed that the serotonin intervention also improved the social behavior of the model mice in adulthood. While such results are promising, further research is required testing out further genetic models. A therapy suitable for humans may one day be possible.
The research findings have been published in the journal Science Advances. The research is titled “Serotonin rebalances cortical tuning and behavior linked to autism symptoms in 15q11-13 CNV mice.”
