Drug temporarily reverses autism-like brain changes in adult mice within hours

by University of California, Los Angeles

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A new mouse study led by UCLA Health suggests that inflammation during pregnancy can trigger autism-like changes in offspring, but those brain and behavioral effects may be rapidly, though temporarily, reversible in adulthood with a single dose of the immunosuppressive drug rapamycin.

Even mild inflammation during midpregnancy has been shown to result in autism-like symptoms in offspring, abnormal brain growth, seizures and heightened sensitivity to everyday sensory input that persist into adulthood.

In the study published in the journal Nature Communications, UCLA researchers found that a single dose of rapamycin significantly improved brain signaling and behavioral symptoms in these offspring within about two hours, too short a time to correct underlying physical brain changes caused by maternal inflammation.

The study did not identify rapamycin as a viable treatment for these symptoms in humans, given its temporary effects and potential toxicity from repeated doses. Instead, researchers said the drug's effects revealed new therapeutic targets for the development of future treatments.

"The level of functional normalization achieved over this short time suggests new mechanisms by which possible treatments may act," said the study's senior author, Dr. Harley Kornblum, director of the UCLA Intellectual and Developmental Disabilities Research Center in the Semel Institute for Neuroscience and Human Behavior.

"It suggests the adult brain may be more adaptable than we assumed, even when the underlying structural changes from early development are still there. This points us toward the brain's functional circuitry, not just its physical structure, as a target for future treatment approaches."

What rapamycin could reveal

Previous studies have shown that offspring of mothers who experience inflammation while pregnant have a higher likelihood of developing autism-associated traits such as repetitive behaviors and difficulty with social interaction, as well as brain overgrowth and disrupted sensory processing that continue into adulthood.

Additionally, rapamycin has been shown in previous mouse autism studies to improve symptoms by suppressing an overactive pathway that signals cell growth and proliferation, known as the mTOR pathway.

What was less clear was whether these brain changes could still be modified in adulthood and whether rapamycin's benefits came from long-term structural repair or faster functional changes.

Rapid shifts in adult brains

In this study, researchers exposed pregnant mice to a mild inflammatory trigger early in gestation at a dose too low to make the mothers significantly ill. The resulting offspring developed chronic brain and bodywide inflammation, mild brain overgrowth, overactive cell signaling in the mTOR pathway, disorganized brain functional network connectivity and behaviors associated with autism.

When researchers gave adult offspring a single dose of rapamycin, they found rapid improvement across nearly every measure: neurons that had been firing abnormally calmed down, susceptibility to seizures dropped, brain regions that had been miscommunicating reorganized into more typical patterns, and repetitive behaviors and sensory over-responsivity eased.

These changes occurred within roughly two hours, too quickly to be explained by the kind of physical rewiring of brain synapses that typically takes longer.

"These results reframe how autism-associated symptoms might be treated. If the adult brain remains capable of functional normalization, then some features of autism may be successfully addressed without needing to correct underlying structural differences," said the paper's first author, Dr. Janel Le Belle, an associate professor in the UCLA Department of Neurosurgery.

Gene activity changed quickly

To understand the mechanisms behind rapamycin's rapid effects, researchers examined gene activity in brain cells before and after treatment. They found that rapamycin reversed abnormal expression of genes tied to autism, epilepsy and ion channel function, particularly in excitatory neurons, suggesting the drug works by quickly rebalancing brain cell excitability rather than by repairing structural brain differences.

The findings suggest that mTOR pathway activity, brain network organization and neuronal excitation levels may be potential targets for future therapies aimed at specific autism symptoms, such as sensory over-responsivity, a common but difficult-to-treat symptom of autism.

Limits of a temporary effect

Co-senior author Dr. Neil Harris, a professor in the UCLA Department of Neurosurgery, cautioned that the researchers also found the treatment effects to be temporary and that daily dosing produced tolerance over several weeks. This, along with rapamycin's potential for toxicity and the fact that these studies were performed in mice, makes it unsuitable for broad use in humans.

"This points toward new therapeutic targets like sensory circuit neuromodulation or balancing neuronal inhibition and excitation, rather than toward rapamycin itself as a treatment," Harris said.

Publication details

Acute rapamycin treatment reveals distinct mechanisms of dysfunction in a maternal inflammation mouse model, Nature Communications (2026). DOI: 10.1038/s41467-026-74958-1

Journal information: Nature Communications

Key medical concepts

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NeurologyPediatricsChildren's health Provided by University of California, Los Angeles Who's behind this story?

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →

Robert Egan

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