Chevassus-Au-Louis N, Congar P, Represa A, Ben-Ari Y, Gaïarsa J L
Institut National de la Santé et de la Recherche Médicale U29, Université Paris 5 René Descartes, 123 Boulevard de Port Royal, 75 674 Paris cedex 14, France.
Proc Natl Acad Sci U S A. 1998 Aug 18;95(17):10263-8. doi: 10.1073/pnas.95.17.10263.
Neuronal migration disorders have been involved in various pathologies, including epilepsy, but the properties of the neural networks underlying disorders have not been determined. In the present study, patch clamp recordings were made from intrahippocampal heterotopic as well as from neocortical and hippocampal neurons from brain slices of rats with prenatally methylazoxymethanol-induced cortical malformation. We report that heterotopic neurons have morphometrical parameters and cellular properties of neocortical supragranular neurons and are integrated in both neocortical and hippocampal networks. Thus, stimulation of the white matter induces both antidromic and orthodromic response in heterotopic and neocortical neurons. Stimulation of hippocampal afferents evokes a monosynaptic response in the majority of heterotopic neurons and a polysynaptic all-or-none epileptiform burst in the presence of bicuculline to block gamma-aminobutyric acid type A inhibition. Furthermore, hippocampal paroxysmal activity generated by bath application of bicuculline can spread directly to the neocortex via the heterotopia in methylazoxymethanol-treated but not in naive rats. We conclude that heterotopias form a functional bridge between the limbic system and the neocortex, providing a substrate for pathological conditions.
神经元迁移障碍与包括癫痫在内的多种病理状况有关，但这些障碍背后神经网络的特性尚未确定。在本研究中，对产前经甲基偶氮甲醇诱导造成皮质畸形的大鼠脑片的海马内异位神经元以及新皮质和海马神经元进行了膜片钳记录。我们报告称，异位神经元具有新皮质颗粒上层神经元的形态测量参数和细胞特性，并整合于新皮质和海马神经网络中。因此，对白质的刺激在异位神经元和新皮质神经元中均诱发了逆向和顺向反应。刺激海马传入神经在大多数异位神经元中诱发单突触反应，并在存在荷包牡丹碱以阻断A型γ-氨基丁酸抑制作用时诱发多突触全或无癫痫样爆发。此外，通过在浴槽中应用荷包牡丹碱产生的海马阵发性活动可通过甲基偶氮甲醇处理的大鼠而非未处理的大鼠中的异位灶直接扩散至新皮质。我们得出结论，异位灶在边缘系统和新皮质之间形成了一个功能桥梁，为病理状况提供了一个底物。
