According to sources close to the news, researchers at the Netherlands Institute of Neuroscience have made a groundbreaking discovery by observing neural plasticity in the moving axon for the first time. This finding sheds light on the brain’s ability to create new connections and structures, which is crucial for learning and memory.
Nerve cells in our brain communicate through electrical signals called action potentials. These action potentials originate from a small area of the cell known as the axon initial segment (AIS). The AIS acts as a control center, deciding when an action potential should be initiated before transmitting it along the axon.
Previously, scientists discovered that plasticity also occurs in the AIS. Plasticity refers to the brain’s capacity to adapt and form new connections to increase electrical activity. Changes in brain network activity can lead to alterations in AIS length. Excessive activity can shorten the segment, while little activity can lengthen it.
To understand how this adaptability works within the axon and identify its molecular mechanisms, researchers Amélie Fréal and Nora Jamann from Maarten Kole’s laboratory observed real-time changes in AIS structure. They found that sodium channels, which are essential for transmitting electrical signals, play a vital role in this process.
The team developed new tools to study these sodium channels and their supporting proteins. They discovered that within just an hour, the number of sodium channels in the AIS can change rapidly through endocytosis—a process where they are taken up into vesicles within cells.
This adaptability acts like an amplifier for adjusting input levels. A longer AIS requires less current and enhances cell output. If not appropriately adjusted, learning processes may be compromised.
The researchers conducted experiments with mice that demonstrated this adaptability. When a mouse had its whiskers trimmed, reducing sensory input, more sodium channels appeared in its AIS to maintain balance. Conversely, excessive sensory input caused by placing mice in highly active environments resulted in slightly shorter AIS segments with fewer sodium channels.
To capture plasticity in vivo, the researchers used two new tools. First, they utilized a special mouse model with fluorescently labeled AIS, allowing them to observe temporal changes in brain slices. Second, molecular tools made sodium channels visible in cell cultures, enabling the team to follow their live behavior.
The plasticity observed in the AIS closely resembles synaptic plasticity—the ability of connections between nerve cells to change strength—which is directly linked to learning and memory. The AIS acts as a decision-making center where relevant information is transmitted to the next nerve cell.
This study brings together different areas of specialization and highlights collaboration’s importance in advancing knowledge. By considering changes in the AIS when studying plasticity, scientists can gain a broader perspective on this fundamental process.
The essence of the matter, the groundbreaking research conducted by Fréal and Jamann sheds light on how neural plasticity occurs within moving axons. This discovery has significant implications for understanding learning and memory processes in the brain. By uncovering the molecular mechanisms behind AIS adaptability, scientists can further explore ways to enhance cognitive function and potentially develop therapeutic interventions for memory-related disorders.
Fréal A, Jamann N, Ten Bos J et al. Sodium channel endocytosis drives axon initial segment plasticity. Advanced science. 2023;9(37):eadf3885.
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