title: ACET is a highly potent and specific kainate receptor antagonist: characterisation and effects on hippocampal mossy fibre function.
abstract: Kainate receptors (KARs) are involved in both NMDA receptor-independent long-term potentiation (LTP) and synaptic facilitation at mossy fibre synapses in the CA3 region of the hippocampus. However, the identity of the KAR subtypes involved remains controversial. Here we used a highly potent and selective GluK1 (formerly GluR5) antagonist (ACET) to elucidate roles of GluK1-containing KARs in these synaptic processes. We confirmed that ACET is an extremely potent GluK1 antagonist, with a Kb value of 1.4+/-0.2 nM. In contrast, ACET was ineffective at GluK2 (formerly GluR6) receptors at all concentrations tested (up to 100 microM) and had no effect at GluK3 (formerly GluR7) when tested at 1 microM. The X-ray crystal structure of ACET bound to the ligand binding core of GluK1 was similar to the UBP310-GluK1 complex. In the CA1 region of hippocampal slices, ACET was effective at blocking the depression of both fEPSPs and monosynaptically evoked GABAergic transmission induced by ATPA, a GluK1 selective agonist. In the CA3 region of the hippocampus, ACET blocked the induction of NMDA receptor-independent mossy fibre LTP. To directly investigate the role of pre-synaptic GluK1-containing KARs we combined patch-clamp electrophysiology and 2-photon microscopy to image Ca2+ dynamics in individual giant mossy fibre boutons. ACET consistently reduced short-term facilitation of pre-synaptic calcium transients induced by 5 action potentials evoked at 20-25Hz. Taken together our data provide further evidence for a physiological role of GluK1-containing KARs in synaptic facilitation and LTP induction at mossy fibre-CA3 synapses.
authors.affiliation: MRC Centre for Synaptic Plasticity, University of Bristol, Bristol BS8 1TD, UK. sheila.dargan@bristol.ac.uk
authors.forename: Sheila L
authors.initials: SL
authors.lastname: Dargan
authors.forename: Vernon R J
authors.initials: VR
authors.lastname: Clarke
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Alushin
authors.forename: John L
authors.initials: JL
authors.lastname: Sherwood
authors.forename: Robert
authors.initials: R
authors.lastname: Nisticò
authors.forename: Zuner A
authors.initials: ZA
authors.lastname: Bortolotto
authors.forename: Ann M
authors.initials: AM
authors.lastname: Ogden
authors.forename: David
authors.initials: D
authors.lastname: Bleakman
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Doherty
authors.forename: David
authors.initials: D
authors.lastname: Lodge
authors.forename: Mark L
authors.initials: ML
authors.lastname: Mayer
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Fitzjohn
authors.forename: David E
authors.initials: DE
authors.lastname: Jane
authors.forename: Graham L
authors.initials: GL
authors.lastname: Collingridge
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000409:Alanine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002461:Cell Line, Transformed; D018360:Crystallography, X-Ray / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation / Q000379:methods; D018690:Excitatory Amino Acid Agonists / Q000737:chemistry* / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D066298:In Vitro Techniques; D008958:Models, Molecular; D019599:Mossy Fibers, Hippocampal / Q000187:drug effects*; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D051381:Rats; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors* / Q000235:genetics; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D014498:Uracil / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000409:Alanine; D002118:Calcium; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018092:Kainic Acid Receptors; D014498:Uracil; C519517:1-(2-amino-2-carboxyethyl)-3-(2-carboxy-5-phenylthiophene-3-ylmethyl)-5-methylpyrimidine-2,4-dione
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