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Structural and functional alterations in rat corticospinal neurons after axotomy
1Department of Anatomy, National Taiwan University, Taipei.
Journal of Neurophysiology
|January 1, 1996
Summary
Spinal cord injury in rats alters corticospinal neurons (CSNs), reducing their size but increasing excitability. These functional changes in CSNs persist long-term after axotomy, impacting neural responsiveness.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
- Spinal Cord Injury Research
Background:
- Cervical spinal cord injury (axotomy) impacts neuronal function.
- Understanding long-term changes in corticospinal neurons (CSNs) is crucial for recovery research.
Purpose of the Study:
- To investigate the long-term electrophysiological properties of rat corticospinal neurons (CSNs) after cervical spinal cord axotomy.
- To assess functional and structural changes in CSNs at 3, 9, and 12 months post-axotomy.
Main Methods:
- In vitro neocortical slice technique with intracellular recordings.
- Double-labeling method to identify axotomized CSNs.
- Analysis of somatic size, dendritic morphology, axonal arborization, resting membrane potential, input resistance, spike parameters, and synaptic potentials.
Main Results:
- Axotomized CSNs showed progressive somatic shrinkage but maintained dendritic and axonal morphology.
- Input resistance increased, and the spike frequency-current (f-I) slope steepened over time post-axotomy.
- Reduced generation of slow afterhyperpolarizations and a significant decrease in inhibitory postsynaptic potentials (IPSPs) were observed.
Conclusions:
- Axotomized CSNs exhibit altered intrinsic membrane properties and impaired inhibitory synaptic function.
- These changes enhance neuronal responsiveness to excitatory inputs, potentially influencing motor control after injury.
- Long-term functional plasticity in CSNs following axotomy is significant.