Ghai R S, Bikson M, Durand D M
Neural Engineering Center, Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106, USA.
J Neurophysiol. 2000 Jul;84(1):274-80. doi: 10.1152/jn.2000.84.1.274.
It is well established that exogenous electric fields can suppress activity obtained in different models of epileptiform discharge such as penicillin and high potassium. In the low-calcium model of epilepsy, spontaneous epileptiform bursting is generated in the absence of synaptic transmission. It has been suggested that ephaptic interactions play a critical role in neuronal synchronization and burst propagation in this nonsynaptic model. We, therefore, tested the hypothesis that low-calcium bursting induced in the CA1 region of transverse and longitudinal hippocampal slices should be highly sensitive to exogenous electric fields. Uniform, low amplitude DC electric fields were applied during spontaneous low-calcium epileptiform activity. Modulation and full suppression of epileptiform activity was observed at field strengths between 1 and 5 mV/mm, a value significantly lower than in other in vitro models of epilepsy. We further investigated the hypothesis that the efficacy of electrical fields was related to changes in the extracellular space. Our results suggest that the osmolality of the perfusate can modulate the efficacy of electric fields. It was also observed that the ability of a field to suppress or modulate low-calcium activity was highly dependent on its orientation, polarity, as well as magnitude. Finally, it was observed that the extracellular potassium "waves" that normally accompany individual epileptiform events was abolished when the individual events were suppressed. These results suggest that DC fields modulate and suppress low-calcium activity by directly polarizing CA1 pyramidal cells.
众所周知，外源性电场可以抑制在不同癫痫样放电模型（如青霉素和高钾模型）中获得的活动。在低钙癫痫模型中，在没有突触传递的情况下会产生自发性癫痫样爆发。有人提出，在这个非突触模型中，电突触相互作用在神经元同步和爆发传播中起关键作用。因此，我们测试了这样一个假设，即在横向和纵向海马切片的CA1区域诱导的低钙爆发应该对外源性电场高度敏感。在自发性低钙癫痫样活动期间施加均匀的低振幅直流电场。在1至5 mV/mm的场强下观察到癫痫样活动的调制和完全抑制，该值明显低于其他体外癫痫模型。我们进一步研究了电场的功效与细胞外空间变化有关的假设。我们的结果表明，灌注液的渗透压可以调节电场的功效。还观察到，电场抑制或调节低钙活动的能力高度依赖于其方向、极性以及大小。最后，观察到当单个癫痫样事件被抑制时，通常伴随单个癫痫样事件的细胞外钾“波”消失了。这些结果表明，直流电场通过直接使CA1锥体细胞极化来调节和抑制低钙活动。
