Axon images in biology textbooks have long been depicted as smooth, cylindrical tubes. However, new research suggests that axons may appear more like strings of tiny bubbles, also known as “non-synaptic varicosities.” These bulges are naturally occurring and can influence the speed of electrical signals.
Researchers at Johns Hopkins used advanced imaging techniques to study the structure of axons in healthy neurons. They discovered that the axon surface can wobble and form natural bulges due to physical forces like tension or pressure, which is known as “pearling instability.”
The study found that the shape and size of these pearl-like shapes are influenced by factors such as membrane composition, sugar concentration, and physical properties. Changes in these conditions altered the size of the pearls, with added sugar making them smaller and relaxing membrane tension having a similar effect.
In experiments, the researchers applied high-frequency electrical stimulation to the mouse neurons, which made the pearl-like segments swell and increase the speed of electrical signaling. However, if the membrane was cholesterol-depleted, the pearls didn’t swell, and the signaling speed didn’t improve.
The discovery challenges a century of understanding about axon structure and suggests that these axon pearl shapes may be adaptive features that help neurons function more efficiently. The study’s findings have implications for our understanding of brain function and disease, particularly in neurodegenerative diseases like Parkinson’s.
Source: https://www.earth.com/news/study-debunks-understanding-of-what-brain-cells-axons-look-like-pearl-structure