Levetiracetam normalized E/I imbalance in the hippocampus after cortical stroke in aged mice

Stroke is a prevalent disorder representing the third leading cause of death and major cause of disability. Post-stroke epilepsy (PSE) has been recognized as a common clinical issue after stroke, accounting for 30-40% of the causes of epilepsy among older adults. In this study, we determined GABAA receptor-mediated seizure susceptibility after PT cerebral stroke in aged mice. Young adult mice around 10 weeks of age are widely used in stroke experiments. However, as most strokes are diagnosed in the elderly and PSE has been recognized as a common clinical incidence after stroke, we utilized photothrombosis (PT) model of cerebral ischemia and examined seizure susceptibility. To investigate in vitro drug-induced seizure susceptibility (E/I imbalance) of GABAA receptor antagonist, gabazine (GZ), voltage-sensitive dye (VSD) imaging techniques were used in hippocampal brain slices. One month after PT stroke, in vivo aged PT stroke mice exhibited severe convulsive seizures (late-onset). in vitro GZ-induced E/I imbalance in hippocampus of aging mice increased compared to young adults. In addition, Anti-seizure medication (levetiracetam) normalized in vitro GZ-induced E/I imbalance in hippocampus of aging mice. These findings exhibited that GABAA receptor-mediated seizures susceptibility (E/I imbalance) in hippocampus after cortical PT stroke in aging mice, but not in young adults. Photothrombosis (PT) model of cerebral ischemia was created by irradiating with LED light (wavelength; 565 nm, output; 200 mW) in a circle region with a diameter of 3.5 mm in the left parietal lobe region for 30 minutes after administration of rose bengal (35 mg/kg, i.p.) to C57BL/6N male mice (8-10 and 65-85 weeks old). One month after PT, mice were treated with anti-seizure medication, levetiracetam (LEV, free drinking, 5 mg/mL) for 2 weeks, and were withdrawn for 1 week after administration with LEV. An in vitro seizure susceptibility (E/I balance) was determined by voltage-sensitive dye (VSD) imaging techniques in hippocampal brain slices. By employing this approach, we investigated the in vitro GABAA receptor antagonist, gabazine (GZ).

脑卒中是一种高发疾病，位列全球致死原因第三位，同时也是成年人致残的首要诱因。卒中后癫痫（Post-stroke epilepsy, PSE）已被证实为卒中后常见的临床并发症，在老年人群的癫痫病因中占比达30%~40%。本研究旨在明确老年小鼠大脑光血栓（photothrombosis, PT）性卒中后，γ-氨基丁酸A型受体（GABAA receptor）介导的癫痫易感性变化。
既往脑卒中相关实验多采用约10周龄的青年成年小鼠，但临床中绝大多数脑卒中患者为老年人，且卒中后癫痫已是公认的高发临床事件，因此本研究采用大脑缺血光血栓（PT）模型，对癫痫易感性进行检测。
为探究γ-氨基丁酸A型受体拮抗剂加巴嗪（gabazine, GZ）诱导的体外癫痫易感性（兴奋/抑制失衡，E/I失衡），本研究采用电压敏感染料（voltage-sensitive dye, VSD）成像技术对海马脑片开展检测。
PT卒中造模1个月后，老年小鼠体内出现严重的迟发性惊厥性发作。与青年成年小鼠相比，老年小鼠海马脑片中GZ诱导的E/I失衡更为显著。此外，抗癫痫药物左乙拉西坦（levetiracetam, LEV）可使老年小鼠海马脑片中GZ诱导的E/I失衡恢复至正常水平。
上述结果表明，老年小鼠大脑皮层PT卒中后，海马组织中γ-氨基丁酸A型受体介导的癫痫易感性（E/I失衡）显著升高，而青年成年小鼠未出现该异常变化。
本研究的造模流程如下：对C57BL/6N雄性小鼠（分为8~10周龄青年组与65~85周龄老年组）腹腔注射孟加拉玫瑰红（rose bengal，35 mg/kg, i.p.）后，在左侧顶叶直径3.5 mm的圆形区域照射波长565 nm、输出功率200 mW的LED光源，持续30分钟，以此构建大脑缺血光血栓（PT）模型。PT造模1个月后，小鼠通过自由饮水方式给予左乙拉西坦（LEV，5 mg/mL），持续给药2周后停药1周。随后采用电压敏感染料（VSD）成像技术检测海马脑片的体外癫痫易感性（E/I平衡状态），以此探究γ-氨基丁酸A型受体拮抗剂加巴嗪（GZ）的作用效果。