title: Inhibition of different GABA transporter systems is required to attenuate epileptiform activity in the CA3 region of the immature rat hippocampus.
abstract: GABA transporters (GATs) are an essential element of the GABAergic system, which regulate excitability in the central nervous system and are thus used as targets for anticonvulsive therapy. However, in the immature nervous system the functions of the GABAergic system and the expression profile of GATs are distinct from the adult situation, obscuring to predict how different GAT isoforms influence epileptiform activity. Therefore we analyzed the effects of subtype specific GAT inhibitors on repetitive epileptiform discharges using field potential and whole-cell patch-clamp recordings in the CA3 region of hippocampal slices of immature (postnatal days 4-7) rats. These experiments revealed that inhibition of GAT-1 with either tiagabine (30 μM) or NO-711 (10 μM) exhibited only a minor anticonvulsive effect on repetitive epileptiform discharges. Blockade of GAT-2/3 with SNAP-5114 (40 μM) had no anticonvulsive effect, but significantly prolonged the decay of spontaneous GABAergic postsynaptic currents. In contrast, the combined application of 10 μM NO-711 and 40 μM SNAP-5114 blocked epileptiform activity in 33% of all slices and reduced the occurrence of epileptiform discharges by 54% in the remaining slices. In addition, the input resistance decreased by 10.5 ± 1.0% under this condition. These results indicate that both GAT-1 and GAT-2/3 are functional in the immature hippocampus and that only the combined inhibition of GAT 1-3 is sufficient to promote a considerable anticonvulsive effect. We conclude from these results that both GAT-1 and GAT-2/3 act synergistically to regulate the excitability in the immature hippocampus.
authors.affiliation: Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany.
authors.forename: Salim
authors.initials: S
authors.lastname: Sharopov
authors.affiliation: Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany.
authors.forename: Rongqing
authors.initials: R
authors.lastname: Chen
authors.affiliation: Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Sun
authors.affiliation: Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany.
authors.forename: Sergei N
authors.initials: SN
authors.lastname: Kolbaev
authors.affiliation: Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany.
authors.forename: Sergei
authors.initials: S
authors.lastname: Kirischuk
authors.affiliation: Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany.
authors.forename: Heiko J
authors.initials: HJ
authors.lastname: Luhmann
authors.affiliation: Institute of Physiology, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, D-55120 Mainz, Germany. Electronic address: wkilb@uni-mainz.de.
authors.forename: Werner
authors.initials: W
authors.lastname: Kilb
mesh_terms: D015761:4-Aminopyridine / Q000008:administration & dosage / Q000633:toxicity*; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D056654:CA3 Region, Hippocampal / Q000187:drug effects / Q000254:growth & development* / Q000503:physiopathology*; D018756:GABA Antagonists / Q000494:pharmacology* / Q000627:therapeutic use; D050485:GABA Plasma Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D058805:GABA Uptake Inhibitors / Q000494:pharmacology*; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D012640:Seizures / Q000188:drug therapy / Q000503:physiopathology
chemical_list: D018756:GABA Antagonists; D050485:GABA Plasma Membrane Transport Proteins; D058805:GABA Uptake Inhibitors; C493415:Slc6a1 protein, rat; D015761:4-Aminopyridine
keywords: Development; Epilepsy; Field potential recording; Seizure; Tiagabine