Topolnik Lisa, Steriade Mircea, Timofeev Igor
Laboratoire de Neurophysiologie, Faculté de Médecine, Université Laval, Québec, Canada G1K 7P4, Canada.
Eur J Neurosci. 2003 Aug;18(3):486-96. doi: 10.1046/j.1460-9568.2003.02742.x.
Cortical trauma can lead to development of electrographic paroxysmal activities. Current views of trauma-induced epileptogenesis suggest that chronic neuronal hyperexcitability and extensive morphological reorganization of the traumatized cortex are required for the generation of electrographic seizures. However, the mechanisms responsible for the initiation of electrographic seizures shortly after cortical injury are poorly understood. Here we show that, in the experimental model of partially deafferented (undercut) cortex, an increase in intrinsic and synaptic excitability of neurons in areas adjacent to the undercut cortex is sufficient for the generation of electrographic paroxysmal activity within few hours after partial cortical deafferentation. Locally increased and spatially restricted neuronal excitability arose from the increased incidence of intrinsically bursting neurons, enhanced intrinsic and synaptic neuronal responsiveness, and slight disinhibition. These mechanisms only operate in neurons located in the vicinity of partially deafferented sites because, after the cortical injury, partially deafferented neurons are mostly silent and hypoexcitable. Our results suggest that trauma-induced electrographic seizures first arise in cortical fields that are closest to the site of injury and such seizures do not require long-term neuronal reorganization.
皮质创伤可导致脑电图阵发性活动的发生。目前关于创伤性癫痫发生的观点认为，慢性神经元过度兴奋和受创伤皮质的广泛形态重组是脑电图癫痫发作产生的必要条件。然而，对于皮质损伤后不久脑电图癫痫发作起始的机制，人们了解甚少。在此我们表明，在部分去传入（切断）皮质的实验模型中，切断皮质区域相邻部位神经元的内在兴奋性和突触兴奋性增加，足以在部分皮质去传入后数小时内产生脑电图阵发性活动。局部增加且空间受限的神经元兴奋性源于内在爆发性神经元发生率的增加、内在和突触神经元反应性的增强以及轻微的去抑制作用。这些机制仅在位于部分去传入部位附近的神经元中起作用，因为皮质损伤后，部分去传入的神经元大多处于静息状态且兴奋性降低。我们的结果表明，创伤性脑电图癫痫发作首先出现在最接近损伤部位的皮质区域，并且这种癫痫发作不需要长期的神经元重组。
