Episodic vestibular disruption following ablation of the inferior olive in rats: behavioral correlates.

Dale W Saxon, Gary White

Index: Behav. Brain Res. 175(1) , 128-38, (2006)

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Abstract

The experiments herein investigate whether the behavioral responses to transient and episodic vestibular disruption and permanent ablation are distinct in the absence of climbing fiber input. Subjects in group 1 received an IP injection of PBS followed by an IP injection of niacinamide. Seven days later these rats received the first of 3 serial transtympanic injections of TTX on the same side with 7 days between each injection. Following each TTX injection rats displayed unilateral vestibular symptoms that persisted beyond 48h. Spontaneous barrel rolling behavior was not observed. Group 2 subjects received an IP injection of 3-acetylpyridine (3-AP)+niacinamide followed by the same TTX regimen as group 1. Following each TTX injection vestibular symptoms (severe body twisting and persistent spontaneous barrel rolling) emerged rapidly (<15min) and resolved by 72h. Group 3 subjects received an IP injection of 3-AP+niacinamide and 7 days later a single unilateral transtympanic injection of sodium arsanilate. Rats in group 3 developed vestibular symptoms similar to those observed in group 2 although there was no resolution of these symptoms. The results indicate that TTX has a rapid rate of infiltration and blockade of the VIIIth nerve that persists for >48h and then completely resolves. The contrast in vestibular symptoms between groups 1 and 2 suggest that climbing fibers are recruited soon after onset of vestibular disruption and play a role in attenuating the severity of vestibular symptoms associated with transient/episodic vestibular disruption.