Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA; Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA.
Shanxi Key Laboratory of Innovative Drug for the Treatment of Serious Diseases Basing on the Chronic Inflammation/Neurobiology Research Center, Shanxi University of Chinese Medicine, Jinzhong, Shanxi, China.
Neurobiol Dis. 2023 Aug;184:106233. doi: 10.1016/j.nbd.2023.106233. Epub 2023 Jul 17.
Stroke is the most common cause of acquired epilepsy, but treatment for preventing the development of post-stroke epilepsy is still unavailable. Since stroke results in neuronal damage and death as well as initial loss of activity in the affected brain region, homeostatic plasticity may be trigged and contribute to an increase in network hyperexcitability that underlies epileptogenesis. Correspondingly, enhancing brain activity may inhibit hyperexcitability from enhanced homeostatic plasticity and prevent post-stroke epileptogenesis. To test these hypotheses, we first used in vivo two-photon and mesoscopic imaging of activity of cortical pyramidal neurons in Thy1-GCaMP6 transgenic mice to determine longitudinal changes in excitatory activity after a photothrombotic ischemic stroke. At 3-days post-stroke, there was a significant loss of neuronal activity in the peri-injury area as indicated by reductions in the frequency of calcium spikes and percentage of active neurons, which recovered to baseline level at day 7, supporting a homeostatic activity regulation of the surviving neurons in the peri-injury area. We further used optogenetic stimulation to specifically stimulate activity of pyramidal neurons in the peri-injury area of Thy-1 channelrhodopsin transgenic mice from day 5 to day 15 after stroke. Using pentylenetetrazole test to evaluate seizure susceptibility, we showed that stroke mice are more susceptible to Racine stage V seizures (time latency 54.3 ± 12.9 min) compared to sham mice (107.1 ± 13.6 min), but optogenetic stimulation reversed the increase in seizure susceptibility (114.0 ± 9.2 min) in mice with stroke. Similarly, administration of D-cycloserine, a partial N-methyl-d-aspartate (NMDA) receptor agonist that can mildly enhance neuronal activity without causing post-stroke seizure, from day 5 to day 15 after a stroke significantly reversed the increase in seizure susceptibility. The treatment also resulted in an increased survival of glutamic acid decarboxylase 67 (GAD67) positive interneurons and a reduced activation of glial fibrillary acidic protein (GFAP) positive reactive astrocytes. Thus, this study supports the involvement of homeostatic activity regulation in the development of post-stroke hyperexcitability and potential application of activity enhancement as a novel strategy to prevent post-stroke late-onset seizure and epilepsy through regulating cortical homeostatic plasticity.
中风是获得性癫痫最常见的病因，但目前仍缺乏预防中风后癫痫发生的治疗方法。由于中风导致神经元损伤和死亡以及受影响大脑区域的初始活动丧失，因此稳态可塑性可能被触发，并有助于增加网络超兴奋性，从而导致癫痫发生。相应地，增强大脑活动可能会抑制由增强的稳态可塑性引起的超兴奋性，并预防中风后癫痫发生。为了验证这些假设，我们首先使用活体双光子和介观成像技术，对 Thy1-GCaMP6 转基因小鼠的皮质锥体神经元的活动进行了研究，以确定光血栓性缺血性中风后兴奋性活动的纵向变化。在中风后 3 天，损伤周围区域的神经元活动明显减少，表现为钙峰频率和活性神经元百分比降低，在第 7 天恢复到基线水平，支持损伤周围区域存活神经元的稳态活动调节。我们进一步使用光遗传学刺激，从中风后第 5 天至第 15 天，特异性地刺激 Thy1 通道视紫红质转基因小鼠损伤周围区域的锥体神经元。使用戊四氮测试评估癫痫易感性，我们发现与假手术小鼠（潜伏期 107.1±13.6 分钟）相比，中风小鼠更容易发生 Racine 阶段 V 癫痫发作（潜伏期 54.3±12.9 分钟），但光遗传学刺激逆转了中风小鼠癫痫易感性的增加（114.0±9.2 分钟）。同样，从中风后第 5 天至第 15 天给予 D-环丝氨酸（一种可以轻度增强神经元活动而不会引起中风后癫痫发作的部分 N-甲基-D-天冬氨酸（NMDA）受体激动剂），也显著逆转了癫痫易感性的增加。该治疗还导致谷氨酸脱羧酶 67（GAD67）阳性中间神经元的存活率增加和胶质纤维酸性蛋白（GFAP）阳性反应性星形胶质细胞的激活减少。因此，这项研究支持稳态活动调节在中风后超兴奋性发展中的作用，以及通过调节皮质稳态可塑性，将活动增强作为一种预防中风后迟发性发作和癫痫的新策略的潜在应用。
