title: GABA(A) receptor-mediated excitation in dissociated neurons from human hypothalamic hamartomas.
abstract: The cellular mechanisms underlying intrinsic epileptogenesis in human hypothalamic hamartoma (HH) are unknown. We previously reported that HH tissue is composed predominantly of GABAergic neurons, but how GABAergic-neuron-rich HH tissue is intrinsically epileptogenic is unclear. Here, we tested the hypotheses that some HH neurons exhibit immature features and that GABA excites these neurons via activation of GABA(A) receptors (GABA(A)Rs). Gramicidin-perforated and cell-attached patch-clamp recordings were performed using freshly-dissociated HH neurons to evaluate GABA(A)R-mediated currents, Cl(-) equilibrium potentials, and intracellular Cl(-) concentrations. Single-cell RT-PCR and immunocytochemical techniques were used to examine cation-Cl(-) co-transporter (NKCC1 and KCC2) gene and KCC2 protein expression and molecular markers of maturation. From a total of 93 acutely-dissociated HH neurons from 34 patients, 76% were small (soma: 6-9 microm) and 24% were large (soma: >20 microm) in size. Under gramicidin-perforated patch recording conditions, GABA(A)R activation depolarized/excited large but hyperpolarized/inhibited small HH neurons in most cases. Compared to small HH neurons, large HH neurons exhibited more positive Cl(-) equilibrium potentials, higher intracellular Cl(-) concentrations, lower KCC2 expression, and an immature phenotype, consistent with GABA(A)R-mediated excitation. Taken collectively, we provide novel evidence for and mechanistic insights into HH epileptogenicity: GABA(A)R-mediated excitation.
authors.affiliation: Division of Neurology, NRC 445, Barrow Neurological Institute, St Joseph's Hospital and Medical Center, Phoenix, AZ 85013-4496, USA. Jie.Wu@chw.edu
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
authors.forename: Jamie
authors.initials: J
authors.lastname: DeChon
authors.forename: Fenqin
authors.initials: F
authors.lastname: Xue
authors.forename: Guohui
authors.initials: G
authors.lastname: Li
authors.forename: Kevin
authors.initials: K
authors.lastname: Ellsworth
authors.forename: Ming
authors.initials: M
authors.lastname: Gao
authors.forename: Qiang
authors.initials: Q
authors.lastname: Liu
authors.forename: Kechun
authors.initials: K
authors.lastname: Yang
authors.forename: Chao
authors.initials: C
authors.lastname: Zheng
authors.forename: Ping
authors.initials: P
authors.lastname: He
authors.forename: Jianglong
authors.initials: J
authors.lastname: Tu
authors.forename: Do Young
authors.initials: DY
authors.lastname: Kim
authors.forename: Jong M
authors.initials: JM
authors.lastname: Rho
authors.forename: Harold
authors.initials: H
authors.lastname: Rekate
authors.forename: John F
authors.initials: JF
authors.lastname: Kerrigan
authors.forename: Yongchang
authors.initials: Y
authors.lastname: Chang
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D005260:Female; D058785:GABA-A Receptor Agonists; D006222:Hamartoma / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D006801:Humans; D007027:Hypothalamic Diseases / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D066298:In Vitro Techniques; D007223:Infant; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D011963:Receptors, GABA-A / Q000502:physiology*
chemical_list: D058785:GABA-A Receptor Agonists; D011963:Receptors, GABA-A; D009118:Muscimol