In Vivo Recording of Ascorbate and Neural Excitability in Medial Vestibular Nucleus and Hippocampus Following Ice Water Vestibular Stimulation in Rats

Vertigo is a common clinical symptom; however, the chemical and electrophysiological processes involved in the pathological mechanism of vertigo remain to be fully understood. In this study, we used an online electrochemical system (OECS) and electrophysiological system to record the dynamics of ascorbate and the change in the neural excitability in medial vestibular nucleus (MVN) and hippocampus of rats following vertigo induced by vestibular ice water stimulation. The OECS employed for recording the dynamics of ascorbate consists of in vivo microdialysis and online selective electrochemical detection. We observed that the level of ascorbate in MVN increased to 155±14 % of the basal level after ice water vestibular stimulation. Whereas, the level of ascorbate in hippocampus decreased to 55±12 % of the basal level after ice water vestibular stimulation. To explore the neural excitability of MVN and hippocampus, we used an electrophysiological recording system and analyzed spontaneous firing rate (SFR) of the neuronal discharges in both nucleus. We found that, in MVN, the neural excitability began to increase during vestibular ice stimulation, remained to be elevated until 1 hour after stimulation. Whereas, in hippocampus, the neural excitability decreased soon after vestibular ice stimulation and recovered 1 hour after stimulation. Dynamics of ascorbate recorded with the OECS correlate with the change in the neural excitability, which may suggest the function of ascorbate as an antioxidant and possibly as a neuromodulator for glutamate‐mediated neurotransmission. The involvement of MVN and hippocampus for the dynamics of ascorbate observed here may be related to the vestibular compensation of vertigo.