Maturation profile of inhibitory and excitatory postsynaptic currents in central vestibular neurons of rats

Abstract

In adult mammals, signal transmission within the vestibular nucleus is regulated by actions of inhibitory and excitatory synapses. Little is known about synaptic activities in the vestibular nucleus during postnatal development. Here we show the maturation profiles of synaptic connections within the spinal vestibular nucleus of Sprague-Dawley rats. Whole-cell patch-clamp recordings in brainstem slices revealed that GABAergic miniature inhibitory postsynaptic current (mIPSC) was observed from P1 onwards. The number and amplitude of mIPSC events increased while their decay time decreased with maturation. However, corresponding parameters of glutamatergic miniature excitatory postsynaptic current (mEPSC) did not change with development. These mEPSCs were equally contributed by AMPA and NMDA receptor-mediated currents before P9 but were dominated by the AMPA component at P21. While the rise and decay time of mEPSCs in both AMPA and NMDA components decreased from P5 to P7, no change was observed between P7 and P9. For EPSCs evoked by electrical stimulation of the vestibular nerve, predominance of the NMDA component was observed at P1. During the first two weeks of life, decline in NMDA receptor-mediated evoked-EPSCs is accompanied by increase in AMPA receptor-mediated evoked-EPSCs. Taken together, our findings document changes in inhibitory and excitatory synapses with regard to receptor utilization during the functional maturation of central vestibular neurons.