Yang Xiaofeng, Bognar Joseph, He Tianyu, Mohammed Mouhari, Niespodziany Isabelle, Wolff Christian, Esguerra Manuel, Rothman Steven M, Dubinsky Janet M
Department of Neurology, University of Minnesota Medical School, Minneapolis, Minnesota, U.S.A.
Electrophysiology Laboratory, Xuanwu Hospital, Capital Medical University, Beijing, China.
Epilepsia. 2015 Dec;56(12):1899-909. doi: 10.1111/epi.13223. Epub 2015 Oct 30.
Brivaracetam (BRV) decreases seizure activity in a number of epilepsy models and binds to the synaptic vesicle glycoprotein 2A (SV2A) with a higher affinity than the antiepileptic drug levetiracetam (LEV). Experiments were performed to determine if BRV acted similarly to LEV to induce or augment short-term depression (STD) under high-frequency neuronal stimulation and slow synaptic vesicle recycling.
Electrophysiologic field excitatory postsynaptic potential (fEPSP) recordings were made from CA1 synapses in rat hippocampal slices loaded with BRV or LEV during intrinsic activity or with BRV actively loaded during hypertonic stimulation. STD was examined in response to 5 or 40 Hz stimulus trains. Presynaptic release of FM1-43 was visualized using two-photon microscopy to assess drug effects upon synaptic vesicle mobilization.
When hippocampal slices were incubated in 0.1-30 μm BRV or 30 μm-1 mm LEV for 3 h, the relative CA1 field EPSPs decreased over the course of a high-frequency train of stimuli more than for control slices. This STD was frequency- and concentration-dependent, with BRV being 100-fold more potent than LEV. The extent of STD depended on the length of the incubation time for both drugs. Pretreatment with LEV occluded the effects of BRV. Repeated hypertonic sucrose treatments and train stimulation successfully unloaded BRV from recycling vesicles and reversed BRVs effects on STD, as previously reported for LEV. At their maximal concentrations, BRV slowed FM1-43 release to a greater extent than in slices loaded with LEV during prolonged stimulation.
BRV, similar to LEV, entered into recycling synaptic vesicles and produced a frequency-dependent decrement of synaptic transmission at 100-fold lower concentrations than LEV. In addition, BRV slowed synaptic vesicle mobilization more effectively than LEV, suggesting that these drugs may modify multiple functions of the synaptic vesicle protein SV2A to curb synaptic transmission and limit epileptic activity.
布瓦西坦（BRV）在多种癫痫模型中可降低癫痫发作活动，且与抗癫痫药物左乙拉西坦（LEV）相比，它以更高的亲和力与突触囊泡糖蛋白2A（SV2A）结合。开展实验以确定在高频神经元刺激和缓慢的突触囊泡循环过程中，BRV的作用是否与LEV类似，可诱导或增强短时程抑制（STD）。
在大鼠海马脑片的CA1突触处进行电生理场兴奋性突触后电位（fEPSP）记录，在内在活动期间加载BRV或LEV，或在高渗刺激期间主动加载BRV。针对5或40 Hz的刺激串检测STD。使用双光子显微镜观察FM1-43的突触前释放，以评估药物对突触囊泡动员的影响。
当海马脑片在0.1 - 30μm的BRV或30μm - 1mm的LEV中孵育3小时时，与对照脑片相比，在高频刺激串过程中，相对CA1场兴奋性突触后电位下降得更多。这种STD具有频率和浓度依赖性，BRV的效力比LEV高100倍。两种药物的STD程度均取决于孵育时间的长短。用LEV预处理可阻断BRV的作用。如先前关于LEV的报道，重复的高渗蔗糖处理和刺激串成功地使BRV从循环囊泡中卸载，并逆转了BRV对STD的影响。在最大浓度下，与在长时间刺激期间加载LEV的脑片相比，BRV在更大程度上减缓了FM1-43的释放。
与LEV类似，BRV进入循环突触囊泡，并在比LEV低100倍的浓度下产生频率依赖性的突触传递递减。此外，BRV比LEV更有效地减缓突触囊泡动员，这表明这些药物可能会改变突触囊泡蛋白SV2A的多种功能，以抑制突触传递并限制癫痫活动。
