Hyaluronidase-induced matrix remodeling contributes to long-term synaptic changes.

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• The neural extracellular matrix (ECM) is a crucial component of the brain's extracellular space.
• Hyaluronan, a key ECM polymer, plays roles in barrier functions and cellular signaling.
• The physiological impact of acute ECM enzymatic degradation remains largely unexplored.

Purpose of the Study:

• To investigate the immediate physiological consequences of enzymatic ECM removal.
• To elucidate the role of hyaluronan and associated receptors in neuronal function during ECM disruption.
• To examine changes in synaptic plasticity following acute ECM degradation.

Main Methods:

• Enzymatic degradation of the ECM using hyaluronidase.
• Electrophysiological recordings to measure membrane potential and calcium influx in neurons.
• Pharmacological blockade of N-methyl-D-aspartate (NMDA) receptors.
• Assessment of long-term potentiation (LTP) at CA3-to-CA1 synapses.

Main Results:

• Hyaluronidase treatment induced simultaneous neuronal membrane depolarization and calcium influx.
• A rapid increase in spontaneous action potential firing frequency was observed in interneurons, but not pyramidal neurons.
• Hyaluronidase-induced calcium entry was blocked by an NMDA receptor antagonist, identifying NMDA receptors as critical mediators.
• NMDA receptor-dependent long-term potentiation at CA3-to-CA1 synapses was enhanced during acute ECM removal.

Conclusions:

• Hyaluronan is a significant regulator of neuronal excitability and synaptic function.
• NMDA receptors are key mediators of the neuronal response to ECM degradation.
• Acute ECM removal acutely modulates synaptic plasticity, highlighting the dynamic role of the ECM in synaptic function.