title: Kv3.1/Kv3.2 channel positive modulators enable faster activating kinetics and increase firing frequency in fast-spiking GABAergic interneurons.
abstract: Due to their fast kinetic properties, Kv3.1 voltage gated potassium channels are important in setting and controlling firing frequency in neurons and pivotal in generating high frequency firing of interneurons. Pharmacological activation of Kv3.1 channels may possess therapeutic potential for treatment of epilepsy, hearing disorders, schizophrenia and cognitive impairments. Here we thoroughly investigate the selectivity and positive modulation of the two small molecules, EX15 and RE01, on Kv3 channels. Selectivity studies, conducted in Xenopus laevis oocytes confirmed a positive modulatory effect of the two compounds on Kv3.1 and to a minor extent on Kv3.2 channels. RE01 had no effect on the Kv3.3 and Kv3.4 channels, whereas EX15 had an inhibitory impact on the Kv3.4 mediated current. Voltage-clamp experiments in monoclonal hKv3.1b/HEK293 cells (34 °C) revealed that the two compounds indeed induced larger currents and faster activation kinetics. They also decrease the speed of deactivation and shifted the voltage dependence of activation, to a more negative activation threshold. Application of action potential clamping and repetitive stimulation protocols of hKv3.1b expressing HEK293 cells revealed that EX15 and RE01 significantly increased peak amplitude, half width and decay time of Kv3.1 mediated currents, even during high-frequency action potential clamping (250 Hz). In rat hippocampal slices, EX15 and RE01 increased neuronal excitability in fast-spiking interneurons in dentate gyrus. Action potential frequency was prominently increased at minor depolarizing steps, whereas more marginal effects of EX15 and RE01 were observed after stronger depolarizations. In conclusion, our results suggest that EX15 and RE01 positive modulation of Kv3.1 and Kv3.2 currents facilitate increased firing frequency in fast-spiking GABAergic interneurons.
authors.affiliation: Cardiac Physiology Laboratory, University of Copenhagen, Faculty of Health Sciences, Department of Biomedical Sciences, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark. Electronic address: kimboddum@sund.ku.dk.
authors.forename: Kim
authors.initials: K
authors.lastname: Boddum
authors.affiliation: Synaptic Transmission In vitro, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Hougaard
authors.affiliation: Cardiac Physiology Laboratory, University of Copenhagen, Faculty of Health Sciences, Department of Biomedical Sciences, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
authors.forename: Julie
authors.initials: J
authors.lastname: Xiao-Ying Lin
authors.affiliation: Cardiac Physiology Laboratory, University of Copenhagen, Faculty of Health Sciences, Department of Biomedical Sciences, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
authors.forename: Nadia Lybøl
authors.initials: NL
authors.lastname: von Schoubye
authors.affiliation: Synaptic Transmission In vitro, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark.
authors.forename: Henrik Sindal
authors.initials: HS
authors.lastname: Jensen
authors.affiliation: Synaptic Transmission In vitro, H. Lundbeck A/S, Ottiliavej 9, DK-2500 Valby, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Grunnet
authors.affiliation: Cardiac Physiology Laboratory, University of Copenhagen, Faculty of Health Sciences, Department of Biomedical Sciences, Blegdamsvej 3B, DK-2200 Copenhagen, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Jespersen
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D055592:Biophysical Phenomena / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000166:cytology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D059330:GABAergic Neurons / Q000187:drug effects / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D006827:Hydantoins / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009865:Oocytes; D011724:Pyridazines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012097:Repressor Proteins / Q000494:pharmacology; D029701:Saccharomyces cerevisiae Proteins / Q000494:pharmacology; D051670:Shaw Potassium Channels / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: C000606940:EX15 hydantoin compound; D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D006827:Hydantoins; D011724:Pyridazines; D011725:Pyridines; D011810:Quinoxalines; C083348:ROX1 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D051670:Shaw Potassium Channels; C056723:FG 9041; D015763:2-Amino-5-phosphonovalerate; C049853:gabazine
keywords: Fast-spiking interneuron; Hippocampus; K(v)3 channel; Positive modulator; Selectivity profile