Glutamate responsiveness of medial vestibular nucleus neurons in aged rats

Disequilibrium, dizziness, vertigo and falls are vestibular system-related problems which are very common especially in older people. In order to clarify these age-related disorders one must understand first the age-related changes in the properties of vestibular neurons that are responsible for equilibrium. The responsiveness of medial vestibular nucleus (MVN) neurons to the NMDA and AMPA/kainate receptor agonists was investigated in slices prepared from young and aged rats using extracellular single cell recording techniques. In both young and aged rats bath application of NMDA and AMPA caused a reversible, dose-dependant increase in the spontaneous discharge of the MVN neurons. The excitatory effects of both NMDA and AMPA on the spontaneous activity of aged MVN neurons were similar to those of young MVN neurons. The spontaneous firing rates of the MVN cells were also similar in young and aged rats. These results suggest that the responsiveness of the NMDA and AMPA/kainate receptors and the excitability of the MVN neurons do not change with age.