Abstract
An in vitro electrophysiological study was performed to determine whether or not GABA receptor function changes in the medial vestibular nucleus (MVN) during vestibular compensation. The whole brains of rats were removed 4 and 48 h after unilateral labyrinthectomy (UL), and horizontal (coronal) slices of the dorsal brainstem (350–400 μm thickness) containing the MVN were prepared to allow for insertion of electrodes into the nuclei. The slices were transferred to an interface-type incubation chamber that was continuously perfused with artificial CSF. Single-unit extracellular recordings were made from tonically active MVN neurones using conventional glass micropipettes. The GABAA agonist muscimol at doses of 10 μM was applied to the slices in the chamber to examine the drug responsiveness in the MVN neurones of UL animals compared to intact animals. The mean resting discharge rate of MVN cells ipsilateral to UL showed a marked decrease in response to muscimol, while there was a significant increase in the responsiveness in the contralateral nucleus.By contrast, the small but significant decrease in the response of ipsi-lesional nucleus was still seen at 48 h post-UL although no significant change in response was obtained in MVN cells contralateral to UL compared to normal.These results suggest that the rapid adaptive down- and upregulation of GABA receptor efficacy on MVN neurones plays an important role in rectifying disparities in excitability of the vestibular nuclei to develop a vestibular compensation.
Published Version
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