title: GluA2-Containing AMPA Receptors Distinguish Ribbon-Associated from Ribbonless Afferent Contacts on Rat Cochlear Hair Cells.
abstract: Mechanosensory hair cells release glutamate at ribbon synapses to excite postsynaptic afferent neurons, via AMPA-type ionotropic glutamate receptors (AMPARs). However, type II afferent neurons contacting outer hair cells in the mammalian cochlea were thought to differ in this respect, failing to show GluA immunolabeling and with many "ribbonless" afferent contacts. Here it is shown that antibodies to the AMPAR subunit GluA2 labeled afferent contacts below inner and outer hair cells in the rat cochlea, and that synaptic currents in type II afferents had AMPAR-specific pharmacology. Only half the postsynaptic densities of type II afferents that labeled for PSD-95, Shank, or Homer were associated with GluA2 immunopuncta or presynaptic ribbons, the "empty slots" corresponding to ribbonless contacts described previously. These results extend the universality of AMPAergic transmission by hair cells, and support the existence of silent afferent contacts.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, the Center for Hearing and Balance.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Martinez-Monedero
authors.affiliation: Department of Neuroscience.
authors.forename: Chang
authors.identifier: 0000-0003-2544-7215
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Neuroscience.
authors.forename: Catherine
authors.identifier: 0000-0002-2595-835X
authors.initials: C
authors.lastname: Weisz
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, the Center for Hearing and Balance.
authors.forename: Pankhuri
authors.identifier: 0000-0003-3585-8851
authors.initials: P
authors.lastname: Vyas
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, the Center for Hearing and Balance; The Center for Sensory Biology, Institute for Basic Biomedical Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: Paul Albert
authors.identifier: 0000-0003-4627-4114
authors.initials: PA
authors.lastname: Fuchs
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, the Center for Hearing and Balance; The Center for Sensory Biology, Institute for Basic Biomedical Sciences, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Glowatzki
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D003051:Cochlea / Q000166:cytology; D000076122:Disks Large Homolog 4 Protein; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018683:Excitatory Amino Acid Agents / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D005136:Eye Proteins / Q000378:metabolism; D018698:Glutamic Acid / Q000494:pharmacology; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D000072233:Homer Scaffolding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009415:Nerve Net / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D017729:Presynaptic Terminals / Q000378:metabolism*; D011799:Quinazolines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism*; D014230:Triazoles / Q000494:pharmacology
chemical_list: C532253:2-(6,7-dimethoxyquinazolin-4-yl)-5-(pyridiin-2-yl)-2H-1,2,4-triazol-3-amine; C486016:Ctbp2 protein, rat; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D004791:Enzyme Inhibitors; D018683:Excitatory Amino Acid Agents; D005136:Eye Proteins; D000072233:Homer Scaffolding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D011799:Quinazolines; D018091:Receptors, AMPA; C120531:Shank1 protein, rat; D014230:Triazoles; D018698:Glutamic Acid; C104722:glutamate receptor ionotropic, AMPA 2; D002118:Calcium
keywords: AMPA receptors; cochlear afferents; outer hair cells; postsynaptic densities