Functional identification of GABAergic medial vestibular neurons in VGAT-Venus transgenic mice

Abstract

The identification of neuronal subtype within the vestibular nucleus is fundamental to understanding the contribution of the central vestibular circuit in motor behavior. Here, brainstem slices of vesicular GABA transporter -Venus transgenic mice (VGAT-Venus mice) were used to identify GABAergic vestibular nuclear neurons under the fluorescent microscope. These transgenic mice were first verified for transgene expression with genotyping. Using whole-cell patch-clamp, the intrinsic membrane properties of VGAT neurons within the medial vestibular nucleus (MVN) were characterized. These VGAT neurons had higher input resistance, lower capacitance and action potentials of lower amplitude when compared to non-VGAT neurons. The GABAergic phenotype of these recorded neurons was confirmed with intracellular injection of biocytin after patch-recording. Dual-patch recording further confirmed that VGAT neuron could functionally release GABA to inhibit its receiving neuron. Using similar approach, we demonstrated that non-VGAT neurons were glutamatergic in nature. In both types of neurons, serotonin (5-hydroxytryptamine, 5-HT) could robustly facilitate spontaneous inhibitory and excitatory postsynaptic currents, suggesting that 5-HT functions to enhance inhibitory and excitatory synaptic inputs to MVN neurons. Taken together, our results indicate that VGAT and non-VGAT neurons in the MVN exhibit different electrical properties and their activities could be facilitated by 5-HT.