Acute injury to superficial cortex leads to a decrease in synaptic inhibition and increase in excitation in...

Area of Science:

• Neuroscience
• Cellular and Molecular Neuroscience
• Epilepsy Research

Background:

• Superficial cerebral cortex injury alters synaptic responses, potentially promoting seizures.
• Understanding specific synaptic strength changes post-cortical injury is crucial for epilepsy research.

Purpose of the Study:

• To investigate synaptic changes in layer V pyramidal cells after superficial cortical injury.
• To determine the impact of cortical trauma on inhibitory and excitatory synaptic transmission.

Main Methods:

• Whole-cell voltage-clamp recordings from surgically traumatized and intact rat neocortical slices.
• Analysis of evoked and spontaneous inhibitory postsynaptic currents (IPSCs) and excitatory postsynaptic currents (EPSCs).
• Peak-scaled nonstationary fluctuation analysis to estimate receptor channel properties.

Main Results:

• Traumatized slices showed disinhibition with lower peak evoked IPSC amplitudes and decreased spontaneous IPSC frequency, indicating reduced GABA release.
• Enhanced synaptic excitation was observed, with larger peak amplitudes and higher frequencies of spontaneous EPSCs.
• Increased AMPA receptor unit conductance (+25%) in EPSCs was found in traumatized slices, while channel numbers remained unchanged.

Conclusions:

• Acute superficial neocortical injury leads to cortical disinhibition.
• Reduced GABA release, likely from interneuron loss, and enhanced AMPA receptor conductance contribute to hyperexcitability and seizure development.