Nagao T, Alonso A, Avoli M
Montreal Neurological Institute, McGill University, QC, Canada.
Neuroscience. 1996 May;72(2):399-408. doi: 10.1016/0306-4522(95)00534-x.
An in vitro slice preparation of combined hippocampus and entorhinal cortex from adult rats was used to study the modalities of generation and propagation, as well as the pharmacological properties of the epileptiform activity induced by the muscarinic agonist pilocarpine (10 microM). Simultaneous field potentials recordings were made from the medial entorhinal cortex and from the dentate gyrus, CA3 and CA1 subfields. Pilocarpine application induced two types of interictal epileptiform discharges. The first occurred in the entorhinal cortex and consisted of bursts of population spikes lasting 408 +/- 135 ms (n = 20 slices) and repeating at a rate of 0.26 +/- 0.07 Hz (n = 20); this interictal activity propagated to the hippocampus via the perforant path. The second type was only observed in CA3 and CA1 subfields, had shorter duration (82 +/- 16 ms; n = 20) and occurred at a higher rate (1.42 +/- 0.7 Hz; n = 20) than the first type. Ictal epileptiform discharges (duration: 11.5 +/- 4.1 s; rate: 0.002 +/- 0.0009 Hz; n = 10) were also seen in the entorhinal cortex, from where they propagated to the dentate, CA3 and CA1 via the hippocampal trisynaptic loop as revealed by latency analysis and lesion experiments. Ictal and interictal discharges of entorhinal origin disappeared in the hippocampal sectors, but continued to occur in the entorhinal cortex following a cut of the perforant path (n = 5). Fast interictal discharges observed solely in the hippocampus originated in CA3, since sectioning the Schaffer collaterals made them disappear in CA1 (n = 7). All types of epileptiform activity disappeared during application of the non-N-methyl-D-aspartate receptor antagonist 6-cyano-7-nitroquinoxaline-2, 3-dione (10 microM; n = 7). By contrast, the N-methyl-D-aspartate receptor antagonist 3-3(2-carboxy-piperazine-4-yl) propyl-1-phosphonate (10 microM) abolished ictal discharges in the entorhinal cortex and reduced the duration of the interictal events recorded in this area (n = 7). Interictal discharges originating from CA3 continued to occur at a higher rate than in control during application of this N-methyl-D-aspartate receptor antagonist. Our study confirms that the combined hippocampal-entorhinal slice preparation represents a suitable model for understanding the modalities of origin and propagation of epileptiform activity within the limbic system. In this in vitro preparation, the entorhinal cortex is the site of origin for ictal discharges. Moreover, the different types of epileptiform activity induced by this muscarinic agonist have specific, structure-dependent pharmacological profiles. These results are discussed in relation to those obtained in vivo.
采用成年大鼠海马与内嗅皮质联合的体外脑片制备物，研究毒蕈碱激动剂毛果芸香碱（10微摩尔）诱导的癫痫样活动的产生和传播方式以及药理学特性。在内嗅皮质、齿状回、CA3和CA1亚区同时进行场电位记录。应用毛果芸香碱诱导出两种类型的发作间期癫痫样放电。第一种出现在内嗅皮质，由持续408±135毫秒（n = 20个脑片）的群体锋电位爆发组成，重复频率为0.26±0.07赫兹（n = 20）；这种发作间期活动通过穿通通路传播至海马。第二种类型仅在CA3和CA1亚区观察到，持续时间较短（82±16毫秒；n = 20），且发生率高于第一种类型（1.42±0.7赫兹；n = 20）。发作期癫痫样放电（持续时间：11.5±4.1秒；频率：0.002±0.0009赫兹；n = 10）也见于内嗅皮质，通过潜伏期分析和损伤实验表明，它们从这里经海马三突触回路传播至齿状回、CA3和CA1。内嗅起源的发作期和发作间期放电在海马区消失，但在切断穿通通路后（n = 5），在内嗅皮质仍继续出现。仅在海马观察到的快速发作间期放电起源于CA3，因为切断Schaffer侧支后，它们在CA1消失（n = 7）。在应用非N - 甲基 - D - 天冬氨酸受体拮抗剂6 - 氰基 - 7 - 硝基喹喔啉 - 2,3 - 二酮（10微摩尔；n = 7）期间，所有类型的癫痫样活动均消失。相比之下，N - 甲基 - D - 天冬氨酸受体拮抗剂3 - 3(2 - 羧基 - 哌嗪 - 4 - 基)丙基 - 1 - 膦酸酯（10微摩尔）消除了内嗅皮质的发作期放电，并缩短了该区域记录的发作间期事件的持续时间（n = 7）。在应用这种N - 甲基 - D - 天冬氨酸受体拮抗剂期间，起源于CA3的发作间期放电继续以高于对照的频率发生。我们的研究证实，海马 - 内嗅联合脑片制备物是理解边缘系统内癫痫样活动的起源和传播方式的合适模型。在这种体外制备物中，内嗅皮质是发作期放电的起源部位。此外，这种毒蕈碱激动剂诱导的不同类型的癫痫样活动具有特定的、依赖结构的药理学特征。结合体内研究结果对这些结果进行了讨论。
