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AMPA type glutamate receptor mediates neurotransmission at turtle vestibular calyx synapse
Author(s) -
Bonsacquet Jérémie,
Brugeaud Aurore,
Compan Vincent,
Desmadryl Gilles,
Chabbert Christian
Publication year - 2006
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2006.116467
Subject(s) - ampa receptor , neurotransmission , neuroscience , synapse , silent synapse , glutamate receptor , hair cell , biology , long term depression , nmda receptor , chemistry , receptor , inner ear , biochemistry
Glutamate is thought to be the main neurotransmitter at the synapse between the type I vestibular hair cell and its cognate calyx afferent. The present study was designed to identify the type of glutamate receptors involved in neurotransmission at this unusual synapse. Immunocytochemistry showed that AMPA GluR2, NMDA NR1 and NR2A/B subunits of the glutamate receptors were confined to the synaptic contact. We then examined the electrical activity at calyx terminals using direct electrophysiological recordings from intact dendritic terminals in explanted turtle posterior crista. We found that sodium‐based action potentials support a background discharge that could be modulated by the mechanical stimulation of the hair bundle of the sensory cells. These activities were prevented by blocking both the mechano‐electrical transduction channels and L‐type voltage‐gated Ca 2+ channels involved in synaptic transmission. Although pharmacological analysis revealed that NMDA receptors could operate, our results show that AMPA receptors are mainly involved in synaptic neurotransmission. We conclude that although both AMPA and NMDA glutamate receptor subunits are present at the calyx synapse, only AMPA receptors appear to be involved in the synaptic transmission between the type I vestibular hair cell and the calyx afferent.