Synaptic regulation of glutamate receptor subunit composition in central vestibular neurons during neonatal development

Abstract

To investigate the functional role of ionotropic glutamate receptor subunits (AMPA and NMDA) in the development of central vestibular system, whole-cell patch-clamp experiments were performed in neurons within the spinal vestibular nucleus of neonatal (P1-9) rats. In each brainstem slice preparation, the profiles of AMPA receptor- and NMDA receptor-mediated currents were recorded from spinal vestibular nuclear neurons in response to electrical stimulation of the vestibular nerve. At P1-3, around 85% of the evoked excitatory postsynaptic current (eEPSC) was identified as NMDA receptor-mediated current while the remaining was AMPA receptor-mediated current. From P5 to P9, the NMDA component decreased from 70% to 52% while the AMPA component increased from 30% to 48%. These indicate that the contribution of AMPA receptors to eEPSC increased with age. With selective blockade of NR2B receptor subunit, NMDA receptor-mediated eEPSC was largely blocked before P5, indicating the significant contribution of NR2B subunit in spinal vestibular nuclear neurons of neonatal rats. On the other hand, NMDA receptor-mediated eEPSC on or after P7 was dominated by NR2A subunit component. Taken together, our findings provide evidence that change in AMPA and NMDA receptor subunits within glutamatergic synapses is important to the functional maturation of central vestibular neurons in postnatal rats.