IONIC HOMEOSTASIS AND SEIZURE REGULATION

虽然癫痫是一种常见的神经学问题，但人们对癫痫放电的启动和终止机制知之甚少。这项研究的长期目标是了解神经元如何同步进入癫痫放电，并了解大脑如何终止同步，从而使癫痫结束。在这一授权期内，重点将放在离子环境在神经元同步中的作用。首先，将通过测量正常成年大鼠和星形胶质细胞抑制剂治疗的大鼠在电刺激、化学惊厥药物诱导的癫痫发作期间和之后以及在扩散性抑制期间和之后的体内[K+]0的上限水平和恢复率来测试神经元Na+/K+ATPase作为摄取机制在神经元活动期间和之后从升高的[K+]0水平恢复中的作用。这一假说将在齿状回、非突触场爆发和扩散性抑制期间、对照条件下以及旨在改变神经胶质和神经元摄取机制的治疗后的体外实验中进一步验证。为确定幼龄大鼠脑内[K+]0的异常调节是否与神经元Na+/K+ATPase发育不成熟有关，我们将比较成年大鼠和幼年大鼠(PN10-25)体内和体外[K+]0的上限水平和恢复率。最后，将对[K+]0中迄今已测量并将在此授权期内收集的依赖活动的变化进行定量解释。有待检验的第二个假设是，颗粒细胞细胞内pH的变化对于终止齿状回的癫痫放电至关重要。首先，在正常大鼠和用星形胶质细胞抑制剂治疗的大鼠中，将确定体外细胞内和细胞外pH的波动，以及它们与癫痫放电和对正常神经胶质功能的依赖的对应关系。最后，为了确定细胞内pH的变化是否是终止癫痫放电的基础，将在体外进行改变癫痫持续时间和组织泵入氢离子的能力的操作，同时测量细胞内的pH。

Although epilepsy is a common neurological problem, the mechanisms involved in the initiation and termination of seizure discharges are poorly understood. The long-term goal of this research is to understand how neurons become synchronized into seizure discharges and to understand how the brain terminates the synchronization allowing the seizure to end. In this grant period the focus will be on the role of the ionic environment in neuronal synchronization. First, the role of the neuronal Na+/K+ ATPase as an uptake mechanism in the recovery of the [K+]0 from elevated levels during and after neuronal activity will be tested by measuring the ceiling level and rate of recovery of the [K+]0 in vivo in normal adult rats and in rats treated with astrocyte inhibitors during and after seizures induced by electrical stimulation, administration of chemical convulsants and during and after spreading depression. This hypothesis will be further tested in vitro in the dentate gyrus during non-synaptic field bursts and during spreading depression in control conditions and after treatments designed to alter glial and neuronal uptake mechanisms. To determine whether the abnormal regulation of the [K+]0 in the immature brain is due to developmental immaturity of the neuronal Na+/K+ ATPase, the ceiling level and rate of recovery of the [K+]0 in vivo and in vitro in adult and juvenile rats (PN 10-25) will be compared. Finally, a quantitative interpretation of activity-dependent changes in [K+]0 that have been measured to date and that are to be gathered during this grant period will be developed. A second hypothesis to be tested is that alterations of the intracellular pH of the granule cells are critical for the termination of seizure discharges in the dentate gyrus. First, the intracellular pH fluctuations in vitro and extracellular fluctuations in pH in vivo and in vitro and their correspondence with the seizure discharges and dependence on normal glial function will be determined in normal rats and in rats treated with astrocyte inhibitors. Finally, to determine whether alterations in intracellular pH underlies the termination of the seizure discharges, manipulations that alter the seizure duration and the ability of the tissue to pump hydrogen ions will be carried out in vitro while measuring intracellular pH.