Journal of neurophysiology
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Injury to the superficial layers of cerebral cortex produces alterations in the synaptic responses of local circuits that promote the development of seizures. To further delineate the specific changes in synaptic strength that are induced by this type of cortical injury, whole cell voltage-clamp recordings were used to examine evoked and spontaneous synaptic events from layer V pyramidal cells in coronal slices prepared from surgically traumatized rat neocortices in which the superficial third of the cortex (layers I, II, and part of III) was removed. Slices from intact neocortices were used as controls. ⋯ EPSC and IPSC channel numbers and IPSC unit conductance did not differ between traumatized and intact slices. However, the mean unit conductance of EPSCs was higher (+25%) in traumatized slices. These findings suggest that acute injury to the superficial neocortical layers results in a disinhibition of cortical circuits that stems from a decline in GABA release likely due to the loss of superficial inhibitory interneurons and an enhancement of synaptic excitation consequent to an increase in the AMPA receptor unit conductance.