Synaptic remodeling in mouse motor cortex after spinal cord injury

Area of Science:

• Neuroscience
• Spinal Cord Injury Research
• Synaptic Plasticity

Background:

• Spinal cord injury (SCI) disrupts neural communication between the central and peripheral nervous systems.
• The long-term effects of SCI on motor cortex synaptic structure remain poorly understood.
• Understanding synaptic reorganization is crucial for developing effective SCI therapies.

Purpose of the Study:

• To investigate synaptic reorganization within the motor cortex following SCI.
• To characterize changes in postsynaptic dendritic spines and presynaptic axonal boutons after SCI.
• To determine the temporal dynamics of synaptic remodeling in the motor cortex post-injury.

Main Methods:

• Established mouse models of T12 spinal cord hemi-section.
• Utilized in vivo monitoring of postsynaptic dendritic spines and presynaptic axonal boutons.
• Focused on pyramidal neurons in the hindlimb area of the motor cortex.
• Analyzed synaptic changes over time post-injury.

Main Results:

• SCI induced bilateral dendritic spine remodeling in the motor cortex, with dynamic changes over time.
• Previously stable dendritic spines became unstable, and eliminated spines showed reduced re-emergence.
• A significant increase in new spine formation was observed in the contralateral motor cortex.
• Newly formed dendritic spines exhibited a low survival rate, indicating fragility.
• No significant changes were detected in presynaptic axonal boutons.

Conclusions:

• Spinal cord hemi-section triggers synapse remodeling in the motor cortex.
• The primary impact of SCI on motor cortex synapses is on postsynaptic dendritic spines.
• Presynaptic axonal boutons appear less affected by SCI-induced synaptic remodeling.
• The fragile nature of new spine formation suggests limited spontaneous recovery of synaptic structure post-SCI.