Departments of Physiology and Cell Biology, Cognitive and Brain Sciences, Biomedical Engineering, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Department of Medical Neuroscience, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada.
Epilepsia. 2019 Feb;60(2):322-336. doi: 10.1111/epi.14631. Epub 2019 Jan 4.
Blood-brain barrier (BBB) impairment, redistribution of pericytes, and disturbances in cerebral blood flow may contribute to the increased seizure propensity and neurological comorbidities associated with epilepsy. However, despite the growing evidence of postictal disturbances in microcirculation, it is not known how recurrent seizures influence pericytic membrane currents and subsequent vasodilation.
Here, we investigated successive changes in capillary neurovascular coupling and BBB integrity during recurrent seizures induced by 4-aminopyridine or low-Mg conditions. To avoid the influence of arteriolar dilation and cerebral blood flow changes on the capillary response, we measured seizure-associated pericytic membrane currents, capillary motility, and permeability changes in a brain slice preparation. Arteriolar responses to 4-aminopyridine-induced seizures were further studied in anesthetized Sprague Dawley rats by using electrocorticography and tissue oxygen recordings simultaneously with intravital imaging of arteriolar diameter, BBB permeability, and cellular damage.
Within the preserved vascular network in hippocampal slice cultures, pericytes regulated capillary diameter in response to vasoactive agents and neuronal activity. Seizures induced distinct patterns of membrane currents that contributed to the regulation of pericytic length. During the course of recurrent seizures, individual vasodilation responses eroded and BBB permeability increased, despite unaltered neurometabolic coupling. Reduced vascular responsiveness was associated with mitochondrial depolarization in pericytes. Subsequent capillary constriction preceded BBB opening, suggesting that pericyte injury mediates the breach in capillary integrity. In vivo findings were consistent with slice experiments, showing seizure-related neurovascular decoupling and BBB dysfunction in small cortical arterioles, accompanied by perivascular cellular injury despite normoxic conditions.
Our study presents a direct observation of gradually developing neurovascular decoupling during recurrent seizures and suggests pericytic injury as an inducer of vascular dysfunction in epilepsy.
血脑屏障（BBB）损伤、周细胞重新分布以及脑血流紊乱可能导致癫痫相关的发作倾向增加和神经合并症。然而，尽管越来越多的证据表明发作后微循环存在紊乱，但尚不清楚复发性癫痫发作如何影响周细胞的膜电流以及随后的血管扩张。
在这里，我们通过 4-氨基吡啶或低镁条件诱导的复发性癫痫发作来研究毛细血管神经血管偶联和 BBB 完整性的连续变化。为了避免动静脉扩张和脑血流变化对毛细血管反应的影响，我们在脑片制备中测量了与癫痫发作相关的周细胞膜电流、毛细血管运动和通透性变化。在麻醉的 Sprague Dawley 大鼠中，通过同时进行皮层电图和组织氧记录以及动静脉直径、BBB 通透性和细胞损伤的活体成像，进一步研究了 4-氨基吡啶诱导的癫痫发作时的动静脉反应。
在海马片培养物中保留的血管网络中，周细胞调节毛细血管直径以响应血管活性物质和神经元活动。癫痫发作诱导了独特的膜电流模式，这些模式有助于周细胞长度的调节。在复发性癫痫发作过程中，尽管神经代谢偶联未改变，但单个血管扩张反应逐渐消失，BBB 通透性增加。血管反应性降低与周细胞中线粒体去极化有关。随后的毛细血管收缩先于 BBB 开放，表明周细胞损伤介导了毛细血管完整性的破坏。体内发现与切片实验一致，显示与癫痫发作相关的神经血管解偶联和小皮质动静脉的 BBB 功能障碍，尽管处于氧合条件下，但伴有血管周围细胞损伤。
我们的研究提供了在复发性癫痫发作期间逐渐发展的神经血管解偶联的直接观察，并表明周细胞损伤是癫痫发作中血管功能障碍的诱导因素。
