Maturation profile of ionotropic glutamate receptors in central vestibular neurons of rats

Abstract

To investigate the role of ionotropic glutamate receptors (AMPAR and NMDAR) in the development of central vestibular neurons, whole-cell patch-clamp experiments were performed in spinal vestibular neurons of postnatal (P1 16) Sprague Dawley rats. The profiles of AMPAR- and NMDARmediated EPSCs evoked by electrical stimulation of the ipsilateral vestibular nerve were also studied. From P1 to P3, glutamatergic transmission is primarily mediated by NMDARs. The relative contribution of AMPARs versus NMDARs at vestibular afferent synapses increased during the first two weeks of life. Using minimal stimulation paradigm, we found that silent NMDAR-only synapses were present only up to P5. From P5 to P7, there was a significant increase in the quantal amplitude of AMPAR-mediated eEPSCs, as confirmed with the use of extracellular strontium instead of calcium, thereby increasing the AMPAR/NMDAR ratio. These age-dependent increase of AMPARs towards the end of the first postnatal week coincides with the disappearance of NMDAR-only synapses. Taken together, our findings provide evidence on the developmental shift in AMPAR and NMDAR of glutamatergic synapses, contributing to functional maturation of central vestibular neurons in postnatal rats. Acknowledgment: Supported by HKRGC.