1. Alterations of A-type potassium channels in hippocampal neurons after traumatic brain injury.
- Author
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Lei Z, Deng P, Li J, and Xu ZC
- Subjects
- Animals, Brain Injuries pathology, Brain Injuries physiopathology, Disease Models, Animal, Epilepsy chemically induced, Epilepsy metabolism, Epilepsy pathology, Epilepsy physiopathology, Hippocampus pathology, Hippocampus physiopathology, Male, Nerve Degeneration metabolism, Nerve Degeneration pathology, Nerve Degeneration physiopathology, Neurons pathology, Rats, Rats, Sprague-Dawley, Shal Potassium Channels deficiency, Shal Potassium Channels genetics, Brain Injuries metabolism, Hippocampus metabolism, Neurons metabolism, Shal Potassium Channels antagonists & inhibitors
- Abstract
Traumatic brain injury (TBI) is associated with cognitive deficits, memory impairment, and epilepsy. Previous studies have reported neuronal loss and neuronal hyperexcitability in the post-traumatic hippocampus. A-type K+ currents (I(A)) play a critical role in modulating the intrinsic membrane excitability of hippocampal neurons. The disruption of I(A) is reportedly linked to hippocampal dysfunction. The present study investigates the changes of I(A) in the hippocampus after TBI. TBI in rats was induced by controlled cortical impact. The impact induced a reproducible lesion in the cortex and an obvious neuronal death in the ipsilateral hippocampus CA3 region. At one week after TBI, immunohistochemical staining and Western blotting showed that the expression of I(A) channel subunit Kv4.2 was markedly decreased in the ipsilateral hippocampus, but remained unchanged in the contralateral hippocampus. Meanwhile, electrophysiological recording showed that I(A) currents in ipsilateral CA1 pyramidal neurons were significantly reduced, which was associated with an increased neuronal excitability. Furthermore, there was an increased sensitivity to bicuculline-induced seizures in TBI rats. At 8 weeks after TBI, immunohistochemical staining and electrophysiological recording indicated that I(A) returned to control levels. These findings suggest that TBI causes a transient downregulation of I(A) in hippocampal CA1 neurons, which might be associated with the hyperexcitability in the post-traumatic hippocampus, and in turn leads to seizures and epilepsy.
- Published
- 2012
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