Aggarwal Yogesh, Dixit Aparna Banerjee, Siraj Fouzia, Tripathi Manjari, Chandra P Sarat, Banerjee Jyotirmoy
Department of Biophysics, All India Institute of Medical Sciences, New Delhi, India.
Dr. B. R. Ambedkar Centre for Biomedical Research, University of Delhi, New Delhi, India.
Exp Neurol. 2025 Jul;389:115265. doi: 10.1016/j.expneurol.2025.115265. Epub 2025 Apr 15.
Focal cortical dysplasia (FCD) is a developmental abnormality of cortex commonly linked with drug-resistant seizures. Altered GABAergic activity is a key contributor to interictal discharges in FCD. In FCD, GABA receptor associated epileptogenicity is dependent upon the age at seizure onset, as differential epileptogenic networks are observed in early and late onset FCD patients. But the contribution of GABA receptor alteration to epileptogenic networks during development is unclear. We hypothesize that GABAergic signaling in FCD undergoes age-dependent molecular alterations, contributing to the development of distinct epileptogenic networks. In this study, we investigated age-dependent changes in GABA neurotransmitter levels, GABA receptor α subunit expression, and GABA receptor-mediated synaptic activity using the BCNU-rat model of FCD. GABA levels, mRNA, and protein expression of GABA receptor α subunits were determined by HPLC, qPCR and western blot and spontaneous GABAergic activity from pyramidal neurons was recorded using whole cell patch-clamp technique. At postnatal days (P) 12 and 21, reduced expression of α1, 2 and 4 subunits were observed in FCD rats compared to control. Consistent with this, decreased amplitude and frequency of GABAergic events were observed in FCD rats. In contrast, at P30 and P65, decreased GABA levels, without changes in receptor expression, were observed in FCD rats. Consistently, reduction in the frequency of GABAergic events was observed in FCD rats compared to the control. Furthermore, treatment with tetrodotoxin (TTX) revealed that the observed alterations in GABAergic activity were predominantly action potential (AP)-dependent. Our findings indicate that distinct epileptogenic networks exist in FCD during early and late developmental stages. These networks are driven primarily by altered GABAergic activity, with early age changes linked to aberrant GABA receptor configurations and late age changes associated with abnormal GABA levels.
局灶性皮质发育不良（FCD）是一种常见的与药物难治性癫痫发作相关的皮质发育异常。GABA能活性改变是FCD发作间期放电的关键因素。在FCD中，GABA受体相关的致痫性取决于癫痫发作起始的年龄，因为在早发型和晚发型FCD患者中观察到不同的致痫网络。但GABA受体改变在发育过程中对致痫网络的作用尚不清楚。我们推测FCD中的GABA能信号传导经历年龄依赖性分子改变，促成不同致痫网络的形成。在本研究中，我们使用FCD的BCNU大鼠模型研究了GABA神经递质水平、GABA受体α亚基表达以及GABA受体介导的突触活动的年龄依赖性变化。通过高效液相色谱法（HPLC）、定量聚合酶链反应（qPCR）和蛋白质免疫印迹法测定GABA水平、GABA受体α亚基的mRNA和蛋白质表达，并使用全细胞膜片钳技术记录锥体神经元的自发性GABA能活性。在出生后第（P）12天和21天，与对照组相比，FCD大鼠中α1、α2和α4亚基的表达降低。与此一致，在FCD大鼠中观察到GABA能事件的幅度和频率降低。相比之下，在P30和P65时，FCD大鼠中GABA水平降低，而受体表达无变化。同样，与对照组相比，FCD大鼠中GABA能事件的频率降低。此外，用河豚毒素（TTX）处理表明，观察到的GABA能活性改变主要依赖于动作电位（AP）。我们的研究结果表明，在发育早期和晚期，FCD中存在不同的致痫网络。这些网络主要由GABA能活性改变驱动，早期变化与异常的GABA受体构型有关，晚期变化与异常的GABA水平有关。
