Impact of Early-Life Seizures on Synaptic Plasticity

关于发展性癫痫的机制，即从生命早期的发作性癫痫发展到成年期的慢性癫痫，人们知之甚少。这一过程可能会导致儿童学习障碍，如果能更好地了解这一过程，就能预防这种障碍。学习、长期抑郁（LTD）的体外相关表达与癫痫发生的后果之间存在机制联系：LTD通过n -乙基-丙烯酰亚胺敏感融合蛋白（NSF）依赖机制诱导突触中特定GluR亚基（GluR2）的几乎完全去除，而体外癫痫样放电可以产生LTD，癫痫发生导致LTD受损。我假设这两个过程，LTD的表达和癫痫发生，使NSF-GIuR2相互作用饱和，从而减少突触GIuR2受体的数量，导致慢性LTD损伤。首先，采用现场记录技术研究对照组和癫痫大鼠海马切片LTD的发育过程。采用海马下破伤风毒素注射法诱导发育性癫痫发生。假设癫痫大鼠海马LTD的表达会发生进行性损害。其次，我们将利用全细胞膜片钳记录GluR介导的突触电流，以及调节不同年龄癫痫大鼠和对照大鼠片制剂中G1uR2-NSF相互作用的药物，研究GluR与NSF的发育相互作用。据推测，癫痫发生将饱和，从而阻断GluR2-NSF相互作用的进一步药理破坏。最后，发展性癫痫发生引起的LTD损伤可能是GluRs单通道和/或动力学特性改变的结果。假设通过全树突膜片钳记录GluR介导的突触电流和非平稳噪声分析来测量癫痫大鼠的G1uR单通道电导和动力学，将与对照大鼠的测量值相似。

Little is understood about the mechanisms developmental epilepsy, i.e., the progression from episodic seizures in early-life to chronic epilepsy in adulthood. This progression likely causes childhood learning impairment that could be prevented by a better understanding of the process. A mechanistic connection exists between the expression of an in vitro correlate of learning, long-term depression (LTD), and the consequences of epileptogenesis: LTD induces a near complete removal of a specific GluR subunit (GluR2) from synapses by an N-ethyl-maleimide-sensitive fusion protein (NSF) -dependent mechanism while epileptiform discharges in vitro can produce LTD and epileptogenesis leads to impaired LTD. I hypothesize that these two processes, the expression of LTD and epileptogenesis, saturate the same NSF-GIuR2 interaction that decreases the number of synaptic GIuR2 receptors and results in chronic LTD impairment. First, the developmental progression of LTD in hippocampal slices from control and epileptic rats will be studied using field-recording techniques. Developmental epileptogenesis will be induced with the infra-hippocampal tetanus toxin injection method. It is hypothesized that epileptic rats will develop a progressive impairment in the expression of hippocampal LTD. Second, the developmental interaction of GluRs with NSF will be studied using whole-cell patch-clamp recordings of GluR mediated synaptic currents along with pharmacological agents that modulate the G1uR2-NSF interaction in slice preparations from epileptic and control rats at different ages. It is hypothesized that epileptogenesis will saturate and thus occlude further pharmacological disruption of the GluR2-NSF interaction. Lastly, the impairment of LTD caused by developmental epileptogenesis could alternatively be the result of alterations in the single-channel and/or kinetic properties of GluRs. It is hypothesized that G1uR single- channel conductance and kinetics in epileptic rats, measured by whole- dendrite patch-clamp recordings of GluR mediated synaptic currents and non-stationary noise analysis, will be similar to values measured in control rats.