Developmental modulation of long-term plasticity at vestibular GABAergic synapses

Abstract

Determining the plastic properties of neurotransmission within the neonatal vestibular nucleus (VN) is essential to our understanding of how the central vestibular system undergoes maturation during development. Using whole-cell patch-clamp recording in brainstem slices, we found that most VN neurons of postnatal day (P) 3-5 rats exhibited long-term depression (LTD) of GABAA receptor-mediated evoked-postsynaptic currents. At this stage, these currents were excitatory in nature. By P14, LTD of these currents, which became inhibitory, was observed in only a small proportion of VN neurons. In contrast, long-term potentiation (LTP) of these currents was observed in about half of VN neurons. By P28, however, a sharp rebound of LTD in conjunction with a significant decrease in LTP occurred, such that the proportion of VN neurons showing LTD became higher than that showing LTP. These results indicate a postnatal period during which biphasic plastic feature of GABAergic VN synapses is observed. To further study the role of GABAergic transmission in the VN on developmental acquisition of vestibular behavior, we implanted above the VN of P1 rats with Elvax slice loaded with GABAA receptor antagonist bicuculline or agonist muscimol. These rats, when tested at adult stage, showed deficit in vestibular function, as indicated by impairment of performance in the rota-rod task, a vestibular-dependent behavior. Taken together, we have delineated the developmental profile of central vestibular plasticity in GABAergic transmission, which contributes to the establishment of mature vestibular function. (Supported by RGC 761812M)