Transient Ca2+-permeable AMPA receptors in postnatal rat primary auditory neurons

Michel Eybalin, Alejandro Caicedo, Nicole Renard, Jérôme Ruel, Jean Luc Puel

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


Fast excitatory transmission in the nervous system is mostly mediated by α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors whose subunit composition governs physiological characteristics such as ligand affinity and ion conductance properties. Here, we report that AMPA receptors at inner hair cell (IHC) synapses lack the GluR2 subunit and are transiently Ca2+-permeable before hearing onset as evidenced using agonist-induced Co2+ accumulation, Western blots and GluR2 confocal microscopy in the rat cochlea. AMPA (100 μM) induced Co2+ accumulation in primary auditory neurons until postnatal day (PND) 10. This accumulation was concentration-dependent, strengthened by cyclothiazide (50 μM) and blocked by GYKI 52466 (80 μM) and Joro spider toxin (1 μM). It was unaffected by D-AP5 (50 μM), and it could not be elicited by 56 mM K + or 1 mM NMDA + 10 μM glycine. Western blots showed that GluR1 immunoreactivity, present in homogenates of immature cochleas, had disappeared by PND12. GluR2 immunoreactivity was not detected until PND10 and GluR3 and GluR4 immunoreactivities were detected at all the ages examined. Confocal microscopy confirmed that the GluR2 immunofluorescence was not located postsynatically to IHCs before PND10. In conclusion, AMPA receptors on maturing primary auditory neurons differ from those on adult neurons. They are probably composed of GluR1, GluR3 and GluR4 subunits and have a high Ca2+ permeability. The postsynaptic expression of GluR2 subunits may be continuously regulated by the presynaptic activity allowing for variations in the Ca 2+ permeability and physiological properties of the receptor.

Original languageEnglish (US)
Pages (from-to)2981-2989
Number of pages9
JournalEuropean Journal of Neuroscience
Issue number11
StatePublished - Dec 2004


  • AMPA receptors
  • Cochlea
  • Inner hair cells
  • Maturation of hearing
  • Synaptic maturation

ASJC Scopus subject areas

  • Neuroscience(all)


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