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A novel GABAergic dysfunction in human Dravet syndrome
Author(s) -
Ruffolo Gabriele,
Cifelli Pierangelo,
Roseti Cristina,
Thom Maria,
van Vliet Erwin A.,
Limatola Cristina,
Aronica Eleonora,
Palma Eleonora
Publication year - 2018
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/epi.14574
Subject(s) - dravet syndrome , gabaergic , gabaa receptor , cannabidiol , epilepsy , vigabatrin , epilepsy syndromes , medicine , sodium channel , neuroscience , endocrinology , anesthesia , anticonvulsant , biology , receptor , chemistry , sodium , psychiatry , organic chemistry , cannabis
Summary Objective Dravet syndrome is a rare neurodevelopmental disease, characterized by general cognitive impairment and severe refractory seizures. The majority of patients carry the gene mutation SCN 1A , leading to a defective sodium channel that contributes to pathogenic brain excitability. A γ‐aminobutyric acid (GABAergic) impairment, as in other neurodevelopmental diseases, has been proposed as an additional mechanism, suggesting that seizures could be alleviated by GABA ergic therapies. However, up to now the physiological mechanisms underlying the GABA ergic dysfunction in Dravet syndrome are still unknown due to the scarce availability of this brain tissue. Here we studied, for the first time, human GABA A ‐evoked currents using cortical brain tissue from Dravet syndrome patients. Methods We transplanted in Xenopus oocytes cell membranes obtained from brain tissues of autopsies of Dravet syndrome patients, tuberous sclerosis complex patients as a pathological comparison, and age‐matched controls. Additionally, experiments were performed on oocytes expressing human α1β2γ2 and α1β2 GABA A receptors. GABA A currents were recorded using the two‐microelectrodes voltage‐clamp technique. Quantitative real‐time polymerase chain reaction, immunohistochemistry, and double‐labeling techniques were carried out on the same tissue samples. Results We found (1) a decrease in GABA sensitivity in Dravet syndrome compared to controls, which was related to an increase in α4‐ relative to α1‐containing GABA A receptors; (2) a shift of the GABA reversal potential toward more depolarizing values in Dravet syndrome, and a parallel increase of the chloride transporters NKCC 1/ KCC 2 expression ratio; (3) an increase of GABA A currents induced by low doses of cannabidiol both in Dravet syndrome and tuberous sclerosis complex comparable to that induced by a classical benzodiazepine, flunitrazepam, that still persists in γ‐less GABA A receptors. Significance Our study indicates that a dysfunction of the GABA ergic system, considered as a feature of brain immaturity, together with defective sodium channels, can contribute to a general reduction of inhibitory efficacy in Dravet brain, suggesting that GABA A receptors could be a target for new therapies.