• The Korean Journal of Physiology and Pharmacology
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• 제21권4호
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• pp.423-428
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• 2017

Vestibular compensation is a recovery process from vestibular symptoms over time after unilateral loss of peripheral vestibular end organs. The aim of the present study was to observe time-dependent changes in long-term potentiation (LTP) at Schaffer collateral-CA1 synapses in the CA1 area of the hippocampus during vestibular compensation. The input-output (I/O) relationships of fEPSP amplitudes and LTP induced by theta burst stimulation to Schaffer's collateral commissural fibers were evaluated from the CA1 area of hippocampal slices at 1 day, 1 week, and 1 month after unilateral labyrinthectomy (UL). The I/O relationships of fEPSPs in the CA1 area was significantly reduced within 1 week post-op and then showed a non-significant reduction at 1 month after UL. Compared with sham-operated animals, there was a significant reduction of LTP induction in the hippocampus at 1 day and 1 week after UL. However, LTP induction levels in the CA1 area of the hippocampus also returned to those of sham-operated animals 1 month following UL. These data suggest that unilateral injury of the peripheral vestibular end organs results in a transient deficit in synaptic plasticity in the CA1 hippocampal area at acute stages of vestibular compensation.

• The Korean Journal of Physiology and Pharmacology
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• 제7권2호
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• pp.73-77
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• 2003

The effects of nitric oxide on the vestibular function recovery following unilateral labyrinthectomy (UL) were studied. Sprague-Dawley male rats, treated with nitric oxide liberating agent sodium nitroprusside (SNP) and NOS inhibitor $N^G$-nitro-L-arginine methyl ester (L-NAME), were subjected to destruction of the unilateral vestibular apparatus, and then spontaneous nystagmus was observed in the rat. To explore the effects of nitric oxide on the neuronal excitability, whole cell patch clamp technique was applied on isolated medial vestibular nuclear neurons. The frequency of spontaneous nystagmus in SNP treated rats was lesser than that of spontaneous nystagmus in control animals. In contrast, pre-UL treatment with L-NAME resulted in a significant increase in spontaneous nystagmus frequency. In addition, SNP increased the frequency of spontaneous action potential in isolated medial vestibular nuclear neurons. Potassium currents of the vestibular nuclear neurons were inhibited by SNP. After blockade of calcium dependent potassium currents by high EGTA (11 mM) in a pipette solution, SNP did not inhibit outward potassium currents. 1H-[1,2,4] oxadiazolo [4,3-a] quinozalin-1-one (ODQ), a specific inhibitor of soluble guanylyl cyclase, inhibited the effects of SNP on the spontaneous firing and the potassium current. These results suggest that nitric oxide after unilateral labyrinthectomy would help to facilitate vestibular compensation by inhibiting calcium-dependent potassium currents through increasing intracellular cGMP, and consequently would increase excitability in ipsilateral vestibular nuclear neurons.

• 대한한의학회지
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• 제20권3호
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• pp.66-76
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• 1999

The purpose of this study was to asses the etlect of Uncaria rhynchophylla (UR). one of the oriental herbs having a capability to block calcium channels, on affecting vestibular compensation (VC) in Sprague - Dawley rats. Animals were divided into a drug treatment group receiving, UR per oral for 10 days preceding unilateral labyrinthectomy (ULX) and a control group with saline ingestion, To evaluate behavioral changes. horizontal spontaneous nystagmus (SN) and roll head tilt (RHT) were recorded by a video camem with zoom lens in the course of vestibular compensation (VC). Immunohistochemical staining was performed by conventional ABC method to visualize cFos-like immunoreactive (cFLI) neurons in the medial vestibular nuclei (MVN) and cFLI cells were counted by image analyzer. Bodyweight was increased significantly, about 35g, by UR treatment for 10 clays before ULX. Compared with the control group, the drug group showed significant reduction of RHT 6 hrs after ULX as well as fast disappearance of SN at early stages of vestibular compensation. Also, recovery of the spatial and temporal cFLI expressions in the bilateral MVN was accelerated 24 hrs after ULX. These results suggest that Uncaria rhynchophyila has a beneficial effect to ameliorate vestibular compensation in unilateral labryinthectomized rats.

• 대한간호학회지
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• 제46권5호
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• pp.710-719
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• 2016

Purpose: In this study an examination was done of the effect of self-efficacy promoting vestibular rehabilitation (S-VR) on dizziness, exercise self-efficacy, adherence to vestibular rehabilitation (VR), subjective and objective vestibular function, vestibular compensation and the recurrence of dizziness in patients with vestibular hypofunction. Methods: This was a randomized controlled study. Data were collected 3 times at baseline, 4 and 8 weeks after beginning the intervention. Outcome measures were level of dizziness, exercise self-efficacy, and level of adherence to VR. Subjective and objective vestibular function, vestibular compensation and the recurrence of dizziness were also obtained. Data were analyzed using Windows SPSS 21.0 program. Results: After 4 weeks of S-VR, there was no difference between the groups for dizziness, subjective and objective vestibular functions. However, exercise self-efficacy and adherence to VR were higher in the experimental group than in the control group. After 8 weeks of S-VR, dizziness (p =.018) exercise self-efficacy (p <.001), adherence to VR (p <.001), total-dizziness handicap inventory (DHI) (p =.012), vision analysis ratio (p =.046) in the experimental group differ significantly from that of the control group. The number of patients with recurring dizziness were higher in the control group than in the experimental group (p <.001). Conclusion: The results indicate that continuous 8 weeks of S-VR is effective in reducing dizziness, and improving exercise self-efficacy, subjective vestibular function and adherence to VR. Objective vestibular function and vestibular compensation were also improved in the experimental group at the end of 8 weeks of S-VR.

• The Korean Journal of Physiology and Pharmacology
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• 제1권3호
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• pp.275-284
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• 1997

Unilateral labyrinthectorny (ULX) causes autonomic symptoms, ocular and postural asymmetries, which disappear over tune in the process of equilibrium recovery known as vestibular compensation. In the present study in order to elucidate mechanisms responsible for the effects of electrical stimulation on vestibular compensation and investigate the relationship between vestibular compensation and c-Fos expression in the medial vestibular nuclei following ULX, we measured spontaneous nystagmus, eye movement induced by sinusoidal rotation and c-Fos expression or to 72 hs after ULX in Sprague-Dawley rats. Experimental animals were divided into two groups: ULX group with ULX only, and electrical stimulation (ES) group with electrical stimulation of $-2{\sim}-5V$, 1.0ms, 100 Hz to the lesioned vestibular system for 4 hs/day. Spontaneous nystagmus following ULX disappeared by 72 hs in ULX group and 36 hs in ES group. In eye movement induced by sinusoidal rotation, normal pattern of eye movement by rotation toward the lesioned side was recovered 24 hs after ULX at rotation of 0.1 Hz and 6 hs after at 0.2 Hz, 0.5 Hz in ULX group. In ES group, the eye movement recovered after 12 hs at 0.1 Hz, 6 hs at 0.2 Hz, and 4 hs at 0.5 Hz. Directional Preponderance which represents the symmetry of bilateral vestibular functions showed significantly early recovery in ES group compared with that of ULX group. Expression or c-Fos immunoreactive cells in the bilateral medial vestibular nuclei was severely asymmetrical till 36 hs in ULX group, and then it became a symmetry and disappeared after 72 hs. However, ES group showed the symmetry of c-Fos expression after 6 hs, which was significantly early recovery in 25 group. All these findings suggest that electrical stimulation ameliorates recovery of vestibuloocular reflex following ULX by the restoration of the balance of the resting activity between bilateral medial vestibular nuclei. In addition, c-Fos expression in the medial vestibular nuclei could be used as a marker of vestibular compensation since c-Fos expression is closely related to the course of recovery following ULX.

• The Korean Journal of Physiology and Pharmacology
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• 제6권6호
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• pp.287-291
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• 2002

Intrinsic excitabilities of acutely isolated medial vestibular nucleus (MVN) neurons of rats with normal labyrinth and with undergoing vestibular compensation from 30 min to 24 h after unilateral vestibular deafferentation (UVD) were compared. In control rats, proportions of type A and B cells were 30 and 70%, respectively, however, the proportion of type A cells increased following UVD. Bursting discharge and irregular firing patterns were recorded from 2 to 12 h post UVD. The spontaneous discharge rate of neurons in the ipsilesional MVN increased significantly at 2 h post-UVD and remained high until 12 h post-UVD in both type A and type B cells. After-hyperpolarization (AHP) of the MVN neurons decreased significantly from 2 h post-UVD in both types of cells. These results suggest that the early stage of vestibular compensation after peripheral neurectomy is associated with an increase in intrinsic excitability due to reduction of AHP in MVN neurons.

• The Korean Journal of Physiology and Pharmacology
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• 제1권5호
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• pp.505-513
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• 1997

To search the correlations between electrical activity and c-Fos expression in the process of vestibular compensation, we examined the changes of those two parameters in the medial vestibular nuclei (MVN) of unilaterally labyrinthectomized (ULX) rats. Spontaneous nystagmus with fast component toward the intact side disappeared gradually within 48 hours. Fourty eight hours after ULX, directional preponderance of the eye movement induced by sinusoidal rotation of the whole body which represents the symmetry of bilateral vestibular functions showed less than 20% by rotation of 0.1, 0.2, and 0.5 Hz, indicating the recovery of symmetry in bilateral vestibular functions. Six hours after ULX, spontaneous electrical activity of type I neurons resulted in asymmetry between bilateral MVN, however, the asymmetry of the electrical activity was decreased 48 hours after ULX. Immunocytochemical staining revealed that ULX produced dramatic induction of c-Fos positive cells in the MVN bilaterally. The number of c-Fos immunoreactive cells in the contralateral MVN was significantly higher than those in the ipsilateral MVN (p＜0.0001) 2 hours after ULX. Thereafter, the number of c-Fos positive cells decreased bilaterally and was slightly, but not significantly higher in the ipsilateral MVN at 48 hours after ULX. The present results suggest that both electrical activity of type I neurons and c-Fos expression in MVN following ULX will reflect underlying mechanisms of recovery process of vestibular compensation.

• The Korean Journal of Physiology and Pharmacology
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• 제1권3호
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• pp.263-273
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• 1997

The purpose of this study was to evaluate the effects of electrical stimulation on vestibular compensation following ULX in rats. Electrical stimulation (ES) with square pulse ($100{\sim}300uA$, 1.0 ms, 100 Hz) was applied to ampullary portion bilaterally for 6 and 24 hours in rats receiving ULX. After ES, animals that showed the recovery of vestibular symptoms by counting and comparing the number of spontaneous nystagmus were selected for recording resting activity of type I, II neurons in the medial vestibular nuclei (MVN) of the lesioned side. And then the dynamic neuronal activities were recorded during sinusoidal rotation at a frequency of 0.1 Hz and 0.2 Hz. The number of spontaneous nystagmus was significantly different 24 hours (p<0.01, n=10), but not 6 hours after ULX+ES. As reported by others, the great reduction of resting activity only in the type I neurons ipsilateral to lesioned side was observed 6, 24 hours after ULX compared to that of intact labyrinthine animal. However, the significant elevation (p<0.01) of type I and reduction (p<0.01) of type II neuronal activity were seen 24 hours after ULX+ES. Interestingly, gain, expressed as maximum neuronal activity(spikes/sec)/maximum rotational velocity(deg/sec), was increased in type I cells and decreased in type II cells 24 hours after ULX+ES in response to sinusoidal rotation at frequencies of both 0.1 Hz and 0.2 Hz. This result suggests that accompanying the behavioral recovery, the electrical stimulation after ULX has beneficial effects on vestibular compensation, especially static symptoms (spontaneous nystagmus), by enhancing resting activity of type I neurons and reducing that of type II neurons.

• The Korean Journal of Physiology and Pharmacology
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• 제5권2호
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• pp.123-131
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• 2001

To investigate the effects of electrical stimulation on vestibular compensation, which is the recovery of vestibular symptoms following unilateral labyrinthectomy (UL), intermittent electrical stimulation was applied to the injured vestibular portion in Sprague-Dawley rats. Vestibuloocular and vestibulospinal reflexes, electrical activity and expression of c-Fos protein in medial vestibular nuclei (MVN) were measured with time following UL. Spontaneous nystagmus occurred with frequency of $2.9{\pm}0.2$ beats/sec at 2 hours after UL and disappeared after 72 hours. Electrical stimulation decreased the frequency of nystagmus significantly till 24 hours after UL. Roll head deviation was $107{\pm}9.7^{\circ}$ at 2 hours after UL and the deviation was maintained till 72 hours, but electrical stimulation decreased the deviation significantly 6 hours after UL. Resting activity of type I neurons in ipsilateral MVN to the injured vestibular side decreased significantly compared with control at 6 and 24 hours after UL, but the activity of type I neurons was recovered to control level by electrical stimulation at 24 hours after UL. Gain of type I neurons induced by sinusoidal rotation of 0.1 Hz decreased significantly till 24 hours after UL, but electrical stimulation restored the activity at 24 hours. The gain of type II neurons decreased significantly at 6 hours after UL, but electrical stimulation restored the activity. Expression of c-Fos protein was asymmetric between bilateral MVN till 24 hours after UL, but the asymmetry disappeared by electrical stimulation 6 hours after UL. These results suggest that electrical stimulation to the injured vestibular portion facilitates vestibular compensation following UL by restoration of symmetry of neuronal activity between bilateral vestibular nuclei resulting from increased activity in ipsilateral vestibular nuclei to the injured side.

• 대한청각학회지
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• 제25권1호
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• pp.36-42
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• 2021

Background and Objectives: Globally, the human immunodeficiency virus (HIV) is responsible for one of the most serious pandemics to date. The vulnerability of the vestibular system in individuals with HIV has been confirmed, and central vestibular impairments have been frequently reported. However, there are disagreements on the impact of HIV on peripheral vestibular function. Thus, the current study aimed to determine the prevalence of peripheral vestibular impairment, specifically related to the semi-circular canals (SCCs), in HIV-positive individuals receiving antiretroviral (ARV) treatment. Subjects and Methods: A total of 92 adults between the ages of 18 and 50 years (divided into two groups) participated in the study. The first group comprised HIV-positive individuals receiving ARV treatment (n₁=60), and the second group comprised HIV-negative participants (n₂=32). The video head impulse test was used to conduct the head impulse paradigm (HIMP). Results: Bilateral normal HIMP results were obtained in 95% of the HIV-positive participants and all HIV-negative participants. The gain of the left posterior SCCs was significantly lower in the HIV-positive group, while the gains of all other canals between the two groups were comparable. Conclusions: The prevalence of peripheral vestibular impairment in the HIV-positive group was not significantly different from that of the HIV-negative group. The reduced prevalence in the current study may be attributed to participant characteristics, the test battery employed, and the central compensation of the vestibular dysfunctions at the later stages of infection.