"With calorie restriction, we saw reversal of all aspects of the synapse disassembly. With exercise, we saw a reversal of most, but not all," Sanes says.

Because of the study's structure -- mice were on calorie-restricted diets for their whole lives, while those that exercised did so for just a month late in life -- Sanes cautions against drawing conclusions about the effectiveness of exercise versus calorie restriction. He notes that longer periods of exercise might have more profound effects, a possibility he and Lichtman are now testing.

Though much of Sanes and Lichtman's work focuses on brain synapses, both have investigated neuromuscular synapses for many years. Neuromuscular junctions are large enough to be viewed by light microscopy, and can be a jumping-off point for brain study, highlighting areas of inquiry and potential techniques.

"These findings in neuromuscular synapses make us curious to know whether similar effects might occur in brain synapses," Sanes says.

While the changes to the synapses through caloric restriction and exercise were clear in the images the researchers obtained, Sanes cautioned that their work was structural, not functional, and they have not yet tested how well the synapses worked.

Source: Harvard University