Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
J Neurophysiol. 2011 Feb;105(2):522-7. doi: 10.1152/jn.00456.2010. Epub 2010 Dec 8.
The epileptic hippocampus has an enhanced propensity for seizure generation, but how spontaneous seizures start is poorly understood. Using whole cell and field-potential recordings, this study explored whether repetitive perforant-path stimulation at physiological frequencies could induce epileptiform bursts in dentate gyrus minislices from rats with kainate-induced epilepsy. Control slices from saline-treated rats responded to single perforant-path stimulation with an excitatory postsynaptic potential (EPSP) and a single population spike in normal medium, and repetitive stimulation at different frequencies (0.1, 1, 2, 5, 10 Hz) did not cause significant increases in the responses. Most minislices (82%) from rats with kainate-induced epilepsy also responded to single perforant-path stimulation with an EPSP and a single population spike/action potential, but some slices (18%) had a more robust response with a prolonged duration and negative DC shift or responses with two to three population spikes. Repetitive perforant-path stimulation at 5-10 Hz, however, transformed the single-spike responses into epileptiform bursts with multiple spikes in half (52%) of the slices, while lower frequency (e.g., ≤ 1 Hz) stimulation failed to produce these changes. The emergence of epileptiform bursts was consistently associated with a negative field-potential DC shift and membrane depolarization. The results suggest that compared with the controls, the "gate" function of the dentate gyrus is compromised in rats with kainate-induced epilepsy, and epileptiform bursts (but not full-length seizure events) can be induced in minislices by repetitive synaptic stimulation at physiological frequencies in the range of hippocampal theta rhythm (i.e., 5-10 Hz).
癫痫海马体具有增强的发作产生倾向，但自发性发作如何开始仍知之甚少。本研究使用全细胞和场电位记录，探索在生理频率下重复穿通通路刺激是否会在海人酸诱导癫痫大鼠的齿状回小块中引起癫痫样爆发。来自生理盐水处理大鼠的对照切片在正常培养基中对单个穿通通路刺激的反应为兴奋性突触后电位 (EPSP) 和单个群体锋电位，而不同频率 (0.1、1、2、5、10 Hz) 的重复刺激不会导致反应显著增加。大多数来自海人酸诱导癫痫大鼠的小块 (82%) 也对单个穿通通路刺激的反应为 EPSP 和单个群体锋电位/动作电位，但一些小块 (18%) 具有更长持续时间和负直流偏移的更强烈反应或具有两个至三个群体锋电位的反应。然而，5-10 Hz 的重复穿通通路刺激将单峰反应转化为具有多个尖峰的癫痫样爆发，其中一半 (52%) 的切片发生这种变化，而较低频率 (例如，≤1 Hz) 的刺激则无法产生这些变化。癫痫样爆发的出现始终与负场电位直流偏移和膜去极化相关。结果表明，与对照组相比，海人酸诱导癫痫大鼠的齿状回“门控”功能受损，在生理频率范围内 (即 5-10 Hz) 的重复突触刺激可在小块中诱导癫痫样爆发 (但不是全长发作事件)。
