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Interneurons, GABA currents, and subunit composition of the GABA A receptor in type I and type II cortical dysplasia
Author(s) -
André Véronique M.,
Cepeda Carlos,
Vinters Harry V.,
Huynh My,
Mathern Gary W.,
Levine Michael S.
Publication year - 2010
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/j.1528-1167.2010.02634.x
Subject(s) - gabaergic , cortical dysplasia , inhibitory postsynaptic potential , glutamate decarboxylase , glutamate receptor , gabaa receptor , zolpidem , gamma aminobutyric acid , chemistry , cerebral cortex , neuroscience , medicine , endocrinology , receptor , biology , epilepsy , biochemistry , pharmacology , enzyme , insomnia
Summary Interneurons, γ‐aminobutyric acid (GABA) A receptor density, and subunit composition determine inhibitory function in pyramidal neurons and control excitability in cortex. Abnormalities in GABAergic cells or GABA A receptors could contribute to seizures in malformations of cortical development. Herein we review data obtained in resected cortex from pediatric epilepsy surgery patients with type I and type II cortical dysplasia (CD) and non‐CD pathologies. Our studies found fewer interneurons immunolabeled for glutamic acid decarboxylase (GAD) in type II CD, whereas there were no changes in tissue from type I CD. GAD‐labeled neurons had larger somata, and GABA transporter (VGAT and GAT1) staining showed a dense plexus surrounding cytomegalic neurons in type II CD. Functionally, neurons from type I CD tissue showed GABA currents with increased half maximal effective concentration compared to cells from the other groups. In type II CD, cytomegalic pyramidal neurons showed alterations in GABA currents, decreased sensitivity to zolpidem and zinc, and increased sensitivity to bretazenil. In addition, pyramidal neurons from type II CD displayed higher frequency of spontaneous inhibitory post synaptic currents. The GABAergic system is therefore, altered differently in cortex from type I and type II CD patients. Alterations in zolpidem, zinc, and bretazenil sensitivity and spontaneous inhibitory postsynaptic currents (IPSCs) suggest that type II CD neurons have altered GABA A receptor subunit composition and receive dense GABA inputs. These findings support the hypothesis that patients with type I and type II CD will respond differently to GABA receptor–mediated antiepileptic drugs and that cytomegalic neurons have features similar to immature neurons.