Effect of labyrinthectomy on the spike generator of vestibular neurons in the guinea pig

In the guinea pig, in the absence of any stimulation, all the neurons of the vestibular nuclei are tonically firing. After an ipsilateral labyrinthectomy, these neurons first cease to fire but recover their previous discharge in 7 days. Here, we tested whether a modification of the spike generator, the process transforming synaptic currents into spike patterns, could be a factor underlying this restoration. For this purpose, we studied the firing rate responses of neurons of the medial vestibular nucleus in brain stem slices to intracellularly injected currents. We conclude that although labyrinthectomy induces some plastic changes in the excitability of the neurons of the medial vestibular nucleus, these changes do not underlie the restoration of activity which occurs in these neurons when they are deprived of their labyrinthine input.