A study published in Nature Communications has shown that a single dose of rapamycin can produce rapid but short-lived improvements in brain function and behaviour in adult mice whose mothers experienced inflammation during pregnancy.
This maternal inflammation model generates lasting changes that echo aspects of autism: neuronal hyperexcitability, greater susceptibility to seizures, disrupted brain network patterns, repetitive behaviours and heightened sensory sensitivity. The new work demonstrates that these functional problems can be dialled back quickly in adulthood, without fixing the underlying structural alterations caused by the original inflammation.
Improvements in neuronal overactivity, seizure threshold, network connectivity, repetitive actions and sensory responses appeared within two hours of the rapamycin injection. The behavioural changes, however, proved temporary. Repetitive behaviour abnormalities returned after 72 hours. When the same mice received daily doses over five weeks, tolerance developed and the benefits on repetitive behaviours disappeared.
The findings point to a striking functional adaptability still present in the adult brain. They also illustrate the limits of that adaptability: the drug did not correct the structural brain changes set down earlier in development. Researchers determined that the acute effects were driven centrally in the brain rather than by any broad reduction in body-wide inflammation, since systemic cytokine levels barely changed two hours after treatment.
At the molecular level, the single dose coincided with shifts in the expression of genes linked to autism spectrum disorder, ion channels and epilepsy. These observations add weight to the idea that restoring balance between excitation and inhibition, or tweaking the modularity of sensory networks, could be fruitful therapeutic targets.
The rapid functional improvements occurred without correction of underlying structural brain changes produced by maternal inflammation.
While the work is rigorous and hypothesis-driven, it remains confined to one animal model. No correction of the original developmental insult was achieved, the benefits were transient, and repeated dosing led to tolerance. Rapamycin itself carries known side effects that would make it unsuitable for long-term human use.
