Neurovestibular Compensation following Ototoxic Lesion and Labyrinthectomy.

Introduction Unilateral labyrinthectomy and intra-tympanic gentamycin have been employed in the treatment of Ménière's disease, but the efficacy of these techniques has not been well established. Objective The objective of this study is to measure the time course of recovery from a unilateral labyrinthectomy either after ipsilateral topical treatment with gentamicin to the inner ear or without the previous insult. Methods Twenty-nine adult Mongolian gerbils were randomized into two experimental groups.

Effects of ciprofloxacin/dexamethasone and ofloxacin on tympanic membrane perforation healing.

Hypothesis: Exposure to ciprofloxacin/dexamethasone, but not ofloxacin, prolongs tympanic membrane (TM) healing.

Background: Exposure to hydrocortisone has been shown to delay TM wound healing. No published studies have compared the effects of ciprofloxacin/dexamethasone and ofloxacin on TM healing.

Effects of Ciprofloxacin/Dexamethasone and Ofloxacin on Tympanic Membrane Perforation Healing.

HYPOTHESIS:: Exposure to ciprofloxacin/dexamethasone, but not ofloxacin, prolongs tympanic membrane (TM) healing. BACKGROUND:: Exposure to hydrocortisone has been shown to delay TM wound healing. No published studies have compared the effects of ciprofloxacin/dexamethasone and ofloxacin on TM healing.

Asymmetric gene expression in the brain during acute compensation to unilateral vestibular labyrinthectomy in the Mongolian gerbil.

Commercial microarrays were used to identify transcriptome expression within vestibular related brain regions (vestibular brainstem and cerebellum, and caudotemporal cortical regions) during the acute period of recovery following unilateral surgical vestibular labyrinth ablation in the gerbil. As a representative model of vestibular compensation, vestibular lesions in the gerbil produced activation in a common set of genes related to vestibular compensation. The total RNA was prepared and amplified using Affymetrix Gene Chip probes from the Rat U34 Neurobiology and R230, and Mouse M430 gene sets, resulting in GCRMA summarized data from S+AA software.

Polysynaptic inputs to vestibular efferent neurons as revealed by viral transneuronal tracing.

The Bartha strain of the alpha-herpes pseudorabies virus (PrV) was used as a retrograde transneuronal tracer to map synaptic inputs to the vestibular efferent neurons of the Mongolian gerbil, Meriones unguiculatus. Although previous experiments have shown that vestibular efferent neurons respond to visual motion and somatosensory stimuli, the anatomic connections mediating those responses are unknown. PrV was injected unilaterally into the horizontal semicircular canal neuroepithelium of gerbils, where it was taken up by efferent axon terminals.

A rodent model for artificial gravity: VOR adaptation and Fos expression.

Vestibulo-ocular reflex (VOR) adaptation and brainstem Fos expression as a result of short radius cross-coupling stimuli were investigated to find neural correlates of the inherent Coriolis force asymmetry from an artificial gravity (AG) environment. Head-fixed gerbils (Meriones unguiculatus, N=79) were exposed, in the dark, to 60--90 minutes of cross-coupled rotations, combinations of pitch (or roll) and yaw rotation, while binocular horizontal, vertical, and torsional eye position were determined using infrared video-oculography. Centripetal acceleration in combination with angular cross-coupling was also studied.

Fos expression in the vestibular brainstem: what one marker can tell us about the network.

Fos inducible transcription factor expression in rodent brains (rats and gerbils) during manipulations of vestibular input is reviewed. Stimuli included centripetal hypergravity, unilateral labyrinth lesion or semicircular canal plugging, rotational axis cross-coupling (Coriolis forces), high and low rotational vestibulo-ocular reflex gain adaptation, translabyrinth galvanic stimulation, pharmacological manipulation, and combinations thereof. Each type of stimulation elicited unique but partially redundant response patterns in the vestibulo-olivo-cerebellar (VOC) network that reflect the origin and interaction of the labyrinth inputs.

Fos responses to short-term adaptation of the horizontal vestibuloocular reflex before and after vestibular compensation in the Mongolian gerbil.

Fos expression in vestibular brainstem and cerebellar regions was evaluated during vestibular adaptation in the Mongolian gerbil. In addition, vestibular adaptation was evaluated in both normal and compensated animals, as vestibular compensation reorganizes the vestibular pathway constraining adaptive processes. Behaviorally, discordant optokinetic and vestibular input induced appropriate high and low gain in horizontal angular vestibuloocular reflex responses.

VOR and Fos response during acute vestibular compensation in the Mongolian gerbil in darkness and in light.

We measured binocular horizontal eye movements in the gerbil following unilateral labyrinthectomy during the acute phase (1-24 h) of vestibular compensation. Regardless of whether the animals compensated in the light or the dark, VOR gain progressively reduced following the lesion, and normal oculomotor symmetry was disrupted. Initially, the VOR was comparable at 1 h post-lesion for both visual conditions.

Relationship of static and dynamic mechanisms in vestibuloocular reflex compensation.

Objectives/hypothesis: We tested the hypothesis that recovery of dynamic oculomotor behavior (specifically the vestibuloocular reflex [VOR]) after a unilateral labyrinthectomy (UL) is independent from static deficit recovery (e.g., spontaneous nystagmus).

Video-oculography in the gerbil.

Normative vestibulo-ocular and optokinetic reflexes (VOR and OKR) and pupil diameter were measured in young adult gerbils using infrared video-oculography with 60 Hz sampling during head-fixed binocular recordings. The pupillary light-sink technique was preferred over a single-beam retinal reflection method because its measurements were less affected by pupil size. Eye movements were generally conjugate with occasional independent saccadic movements, and independent drifting movements in the dark.