Perez-Velazquez J L, Valiante T A, Carlen P L
Playfair Neuroscience Unit, Toronto Hospital Research Institute, Ontario, Canada.
J Neurosci. 1994 Jul;14(7):4308-17. doi: 10.1523/JNEUROSCI.14-07-04308.1994.
To date, there is little experimental evidence supporting or refuting electrotonic interactions through gap junctions in the generation and/or spread of seizure activity in the mammalian brain. We have studied gap junctional mechanisms in the in vitro calcium-free induced model of epilepsy using electrophysiological and staining techniques in the CA1 area of the hippocampus. Lucifer yellow staining of CA1 pyramidal neurons revealed that dye coupling was increased 2.3 times in hippocampal slices made hyperexcitable by perfusion with calcium-free artificial cerebrospinal fluid (aCSF). Furthermore, multiple neuronal dye coupling (triplets, quintuplets) was observed in these conditions but never in control (standard aCSF). Under conditions that reduce gap junctional conductance (intracellular acidification, octanol, halothane), seizure-like activity was suppressed in the CA1 area in this epilepsy model, whereas increasing gap junctional conductance by intracellular alkalinization increased the frequency and duration of field burst events. Intracellular acidification also reduced dye coupling as well as the frequency of fast prepotentials (electrotonic potentials) without altering neuronal firing frequency. Simultaneous extracellular field and single whole-cell recordings revealed suppression of synchronization between neuronal firing and spontaneous field burst activity during acidification. These observations indicate an apparent increase in electrotonic coupling during calcium-free induced spontaneous rhythmic field burst activity in the CA1 area of the hippocampus and that electrotonic coupling may contribute substantially to the synchronization of neuronal firing underlying seizure-like events.
迄今为止，几乎没有实验证据支持或反驳缝隙连接介导的电紧张相互作用在哺乳动物大脑癫痫活动的产生和/或传播中的作用。我们利用海马CA1区的电生理和染色技术，研究了体外无钙诱导癫痫模型中的缝隙连接机制。对CA1锥体细胞进行荧光黄染色显示，在用无钙人工脑脊液（aCSF）灌注使海马切片变得高度兴奋时，染料偶联增加了2.3倍。此外，在这些条件下观察到了多个神经元染料偶联（三联体、五联体），而在对照（标准aCSF）条件下从未观察到。在降低缝隙连接电导的条件下（细胞内酸化、辛醇、氟烷），该癫痫模型中CA1区的癫痫样活动受到抑制，而通过细胞内碱化增加缝隙连接电导则增加了场爆发事件的频率和持续时间。细胞内酸化还降低了染料偶联以及快速预电位（电紧张电位）的频率，而不改变神经元的放电频率。细胞外场和单个全细胞同步记录显示，酸化过程中神经元放电与自发场爆发活动之间的同步性受到抑制。这些观察结果表明，在海马CA1区无钙诱导的自发节律性场爆发活动期间，电紧张偶联明显增加，并且电紧张偶联可能在很大程度上促进了癫痫样事件背后神经元放电的同步化。
