Ion Channels in Epilepsy and as Targets for Antiepilepti

本项目的目的是基于抗癫痫药物与神经元离子通道系统的相互作用，探索合理开发抗癫痫药物的新策略。应用细胞电生理记录技术，研究了神经递质门控和电压激活离子通道在脑片、培养神经元和异种细胞中对离子通道亚单位基因的药物调节作用。相关研究在动物模型中进行。在本报告所述期间，我们完成了一个研究冷却作为癫痫治疗方法的可能性的项目。此前已有研究表明，降温可以终止实验性癫痫模型中的癫痫样活动，而不会对降温的大脑造成损伤，这表明降温可能代表着一种控制难治性局灶性癫痫发作的方法。我们试图确定在体外脑片模型中应用降温来终止自发癫痫样放电的最有效方法。用4-氨基吡啶(4-AP)、4-AP+荷包牡丹碱和无镁人工脑脊液(ACSF)在28~34℃诱导大鼠脑片自发癫痫样活动。用冷ACSF灌流降低切片温度。以2.5C/S的速率快速降温与以0.1C/S的慢速降温相比较，两种速率的降温都可逆地阻止了三种模型和所有记录点的癫痫样放电。在快速冷却的情况下，微小的温度下降在终止排放方面非常有效，只要保持降低的温度水平，这种效果就会持续下去。相比之下，缓慢冷却需要更大的温降来抑制放电。在缓慢冷却的情况下，绝对温度降至21~22℃可使事件发生频率减少90%，但需要冷却至14~15℃才能终止放电。我们的结论是，在体外癫痫模型中，快速降温和缓慢降温一样有效地终止了放电，但所需的温度变化幅度较小。如果降温足够迅速，抑制癫痫发作的实用设备可能只需要诱导很小的体温下降。

The objective of this project is to explore new strategies for the rational development of antiepileptic drugs based upon their interaction with neuronal ion channel systems. Cellular electrophysiological recording techniques are used to study drug modulation of neurotransmitter-gated and voltage-activated ion channels in brain slices, cultured neurons and heterologous cells transfected with cloned ion channel subunit genes. Correlative studies are carried out in animal models. In the present reporting period, we completed a project examining the potential of cooling as an epilepy treatment approach. Cooling has been previously shown to terminate experimentally induced epileptiform activity in models of epilepsy without causing injury to the cooled brain, suggesting that cooling could represent an approach to seizure control in intractable focal epilepsies. We sought to determine the most effective way to apply cooling to abort spontaneous epileptiform discharges in in vitro brain slice models. We induced spontaneous epileptiform activity in rat brain slices by exposure to 4-aminopyridine (4-AP), 4-AP plus bicuculline, and magnesium-free artificial CSF (aCSF) at 28?34 ?C. Extracellular field recordings were made at hippocampal or neocortical sites. Slice temperature was reduced by perfusion with cold aCSF. Rapid cooling at rates of 2?5 ?C/s was compared to cooling at slower rates of 0.1?1 ?C/s. Cooling at both rates reversibly aborted epileptiform discharges in all three models and at all recording sites. With rapid cooling, small temperature drops were highly effective in terminating discharges, an effect that was sustained for as long as the reduced temperature level was maintained. In contrast, slow cooling required much larger temperature drops to inhibit discharges. With slow cooling, absolute temperature drops to 21?22 ?C caused a 90% reduction in event frequency, but cooling to 14?15 ?C was required to terminate discharges. We conclude that rapid cooling as effectively aborts discharges in in vitro epilepsy models as does slow cooling, but the magnitude of the temperature change required is less. Practical devices to inhibit seizure activity may only need to induce small temperature drops, if the cooling can be applied sufficiently rapidly.