Kim Do Young, Fenoglio Kristina A, Simeone Timothy A, Coons Stephen W, Wu Jie, Chang Yongchang, Kerrigan John F, Rho Jong M
Division of Pediatric Neurology, Barrow Neurological Institute, St. Joseph's Hospital & Medical Center, Phoenix, AZ 85013, USA.
Epilepsia. 2008 May;49(5):861-71. doi: 10.1111/j.1528-1167.2007.01455.x. Epub 2007 Dec 10.
The human hypothalamic hamartoma (HH) is a rare, intrinsically epileptogenic lesion associated with gelastic seizures, but the underlying mechanisms remain unclear. Here, we examined the role of GABAA receptors in surgically resected HH tissue.
HH tissue slices (350 microm) were studied using cellular electrophysiological, calcium imaging, and immunocytochemical techniques.
Two neuronal cell types were seen: small (10-16 microm) spontaneously firing GABAergic neurons and large (20-28 microm) quiescent neurons. In gramicidin-perforated patch recordings, muscimol (30 microM) induced membrane depolarization in 70% of large (but not small) neurons and a concomitant rise in intracellular calcium. These responses were blocked by bicuculline methiodide (50 microM). Depolarizing neurons also exhibited more positive reversal potentials (Emuscimol) and significantly higher intracellular chloride concentrations compared to those that hyperpolarized. The cation chloride co-transporters NKCC1 and KCC2 were coexpressed in the majority of large neurons, but fluorometric measurements revealed that 84% of large HH neurons expressed solely or relatively more NKCC1. Bumetanide (20 microM), a NKCC1 antagonist, partially suppressed muscimol-induced excitation in large neurons. Concordant with robust expression of CaV1.2 and CaV1.3 subunits in HH neurons, the L-type calcium channel blocker nifedipine (100 microM) prevented muscimol-induced neuronal excitation.
GABAA receptor-mediated excitation, due in part to differential expression of NKCC1 and KCC2 and subsequent activation of L-type calcium channels, may contribute to seizure genesis in HH tissue. Given the ready availability of L-type calcium channel blockers, our results have clinical ramifications for the treatment of seizures associated with HH lesions.
人类下丘脑错构瘤（HH）是一种罕见的、具有内在致痫性的病变，与痴笑性癫痫发作相关，但其潜在机制仍不清楚。在此，我们研究了GABAA受体在手术切除的HH组织中的作用。
使用细胞电生理、钙成像和免疫细胞化学技术研究HH组织切片（350微米）。
观察到两种神经元细胞类型：小型（10 - 16微米）自发放电的GABA能神经元和大型（20 - 28微米）静止神经元。在短杆菌肽穿孔膜片钳记录中，蝇蕈醇（30微摩尔）在70%的大型（而非小型）神经元中诱导膜去极化，并伴随细胞内钙升高。这些反应被甲磺酸荷包牡丹碱（50微摩尔）阻断。与超极化的神经元相比，去极化的神经元还表现出更正的反转电位（E蝇蕈醇）和显著更高的细胞内氯离子浓度。阳离子氯离子共转运体NKCC1和KCC2在大多数大型神经元中共表达，但荧光测量显示，84%的大型HH神经元仅表达或相对更多地表达NKCC1。NKCC1拮抗剂布美他尼（20微摩尔）部分抑制了蝇蕈醇诱导的大型神经元兴奋。与HH神经元中CaV1.2和CaV1.3亚基的强烈表达一致，L型钙通道阻滞剂硝苯地平（100微摩尔）可防止蝇蕈醇诱导的神经元兴奋。
GABAA受体介导的兴奋，部分归因于NKCC1和KCC2的差异表达以及随后L型钙通道的激活，可能导致HH组织中的癫痫发作。鉴于L型钙通道阻滞剂容易获得，我们的结果对治疗与HH病变相关的癫痫发作具有临床意义。
