Autistic kids have 'too' many synapses in brain

A new study has revealed that autistic children and adolescents have extra synapses in the brain.

The researchers at Columbia University Medical Center (CUMC) found that people with autism have a surplus of synapses in the brain, and this excess was due to a slowdown in a normal brain "pruning" process during development. Because synapses are the points where neurons connect and communicate with each other, the excessive synapses may have profound effects on how the brain functions.

Although, the drug, rapamycin, has side effects that might preclude its use in people with autism. It was established that a drug that restored normal synaptic pruning could improve autistic-like behaviors in mice even when the drug was given after the behaviors have appeared.

Using mouse models of autism, the researchers traced the pruning defect to a protein called mTOR. When mTOR was overactive, they found, brain cells lose much of their "self-eating" ability. And without this ability, the brains of the mice were pruned poorly and contained excess synapses.

The researchers could restore normal autophagy and synaptic pruning and reverse autistic-like behaviors in the mice, by administering rapamycin, a drug that inhibits mTOR. The drug was effective even when administered to the mice after they developed the behaviors, suggesting that such an approach might be used to treat patients even after the disorder has been diagnosed.

Alan Packer, PhD, said that the current view was that autism was heterogeneous, with potentially hundreds of genes that could contribute but that's a very wide spectrum, so the goal now would be now to understand how those hundreds of genes cluster together into a smaller number of pathways; that would give them better clues to potential treatments.

The study is published in the journal Neuron.