Department of Neurosurgery, All India Institute of Medical Sciences, New Delhi, India.
Dr. B.R Ambedkar Center for Biomedical Research, University of Delhi, New Delhi, India.
Neurochem Int. 2021 Sep;148:105084. doi: 10.1016/j.neuint.2021.105084. Epub 2021 May 27.
Benzodiazepines are the first choice of anti-epileptic drugs used to treat seizures. However, it has been seen that their efficacy decreases with time leading to drug insensitivity, plausibly caused by an alteration in the expression of the benzodiazepine biding site on GABA receptors. This study was designed to investigate if the differential expression of GABA receptor subunits α1/α4/γ2/δ across the postsynaptic sites could contribute to benzodiazepine resistance in patients with focal cortical dysplasia (FCD), the most common cause of drug resistant epilepsy in pediatric population. Differential gene and cellular expression of GABA receptor subunits α1, α4, γ2 and δ were evaluated and validated using qPCR and immunohistochemistry. Whole cell patch clamp studies were performed on pyramidal neurons of resected cortical FCD samples to measure the spontaneous GABA receptor activity. Upregulation of α4-and γ2-subunits containing GABA receptors were observed at both mRNA and protein level. α1-and δ-subunits containing GABA receptors did not show any significant changes. Flumazenil treatment did not affect the kinetics of GABAergic events in FCD; however, it significantly reduced the frequency and amplitude of spontaneous GABAergic activity in non-seizure control samples. Our results demonstrate the enhanced expression of α4-containing GABA receptors and GABAergic activity in pyramidal neurons which in turn may contribute to benzodiazepine resistance in FCD patients.
苯二氮䓬类药物是治疗癫痫发作的首选抗癫痫药物。然而，已经观察到它们的疗效随着时间的推移而降低，导致药物不敏感，这可能是由于 GABA 受体上苯二氮䓬结合位点的表达改变所致。本研究旨在探讨 GABA 受体亚基 α1/α4/γ2/δ 在突触后位点的差异表达是否导致局灶性皮质发育不良（FCD）患者对苯二氮䓬类药物产生耐药性，FCD 是儿科人群中耐药性癫痫最常见的原因。使用 qPCR 和免疫组织化学评估和验证 GABA 受体亚基 α1、α4、γ2 和 δ 的差异基因和细胞表达。在切除的皮质 FCD 样本的锥体神经元上进行全细胞膜片钳研究，以测量自发 GABA 受体活性。在 mRNA 和蛋白质水平上观察到含有 α4 和 γ2 亚基的 GABA 受体的上调。含有 α1 和 δ 亚基的 GABA 受体没有显示出任何显著变化。氟马西尼治疗不会影响 FCD 中 GABA 能事件的动力学；然而，它显著降低了非惊厥对照样本中自发性 GABA 能活性的频率和幅度。我们的结果表明，FCD 患者的锥体神经元中 α4 包含的 GABA 受体和 GABA 能活性表达增强，这反过来可能导致对苯二氮䓬类药物的耐药性。
