Developmental profile of inhibitory synaptic transmission in medial vestibular neurons of rats

Abstract

Inhibitory synaptic transmission is known to play a key regulatory role in the coordination of the central vestibular pathways. While GABA(A) receptor is expressed in vestibular nuclear neurons of newborn rodents, the functional efficacy of the GABAergic inhibitory network in the developing vestibular nucleus remains to be addressed. Inhibitory postsynaptic currents (IPSCs) evoked by electrical stimulation of the ipsilateral vestibular afferents were recorded in medial vestibular nucleus of rats using whole-cell patch-clamp technique. Evoked-IPSCs of medial vestibular neurons were found in brainstem slices of P1 rats, indicating that inhibitory connection between the vestibular afferents and ipsilateral vestibular nuclear neurons have been established at newborns. Evoked-IPSCs of P1 neurons were mediated by both GABA(A) and glycine receptors. Such phenomenon was only observed in about half of the neurons in P3-21 preparations. These IPSCs were dominated by GABA(A) receptor-mediated current. The remaining neurons in P3-21 rats showed evoked-IPSCs that were mediated by GABAA receptor only. The duration and decay time of evoked-IPSCs mediated by GABA(A) receptor decreased after P3. These results demonstrate that (1) vestibular nuclear neurons of rodents are modulated by inhibitory inputs arising from ipsilateral vestibular afferents and (2) GABAergic and glycinergic inputs may play differential roles during the maturation of vestibular neural network.