Glutamatergic and GABAergic neurons represent the main component of the medial vestibular nuclei. We assessed the functional role of glutamatergic and GABAergic neuronal pathways arising from the vestibular nuclei in the maintenance of gate and balance, by optogenetically stimulating the vestibular nuclei of VGluT2-cre and GAD2-cre mice. We demonstrated the VN glutamatergic, but not GABAergic subpopulation are responsible for immediate and strong posturo-locomotor deficits, comparable to unilateral vestibular deafferentation models. During optogenetic stimulation, the support surface is also dramatically increased for VN-VGluT2+ animals, and rapidly come back to baseline level after stimulation, whilst it remained unchanged during all the experiment for VN-GAD2+ animals. This effect persists in condition where vestibular compensation is removed. Finally, posturolocomotor parameters such as support surface, immobility and velocity revealed the effect for VN-VGLuT2+ animals was still present immediately after stimulation, while it disappears 1h after. Overall, these results indicate a fundamental role for VN-VGluT2+ neurons in balance and posturo-locomotor functions, but not for VN-GAD2+ neurons, at least at short term. This new optogenetic approach offers to better characterize the role of glutamatergic and gabaergic functions in vestibular compensation.
bioRxiv Subject Collection: Neuroscience