Objectives We aimed to study the role of vestibular input on spatial memory performance in mice that had undergone bilateral surgical labyrinthectomy, semicircular canal (SCC) occlusion and 4G hypergravity exposure.
Methods Twelve to 16 weeks old ICR mice (n=30) were used for the experiment. The experimental group divided into 3 groups. One group had undergone bilateral chemical labyrinthectomy, and the other group had performed SCC occlusion surgery, and the last group was exposed to 4G hypergravity for 2 weeks. The movement of mice was recorded using camera in Y maze which had 3 radial arms (35 cm long, 7 cm high, 10 cm wide). We counted the number of visiting arms and analyzed the information of arm selection using program we developed before and after procedure.
Results The bilateral labyrinthectomy group which semicircular canal and otolithic function was impaired showed low behavioral performance and spacial memory. The semicircular canal occlusion with CO2 laser group which only semicircular canal function was impaired showed no difference in performance activity and spatial memory. However the hypergravity exposure group in which only otolithic function impaired showed spatial memory function was affected but the behavioral performance was spared. The impairment of spatial memory recovered after a few days after exposure in hypergravity group.
Conclusions This spatial memory function was affected by bilateral vestibular loss. Space-related information processing seems to be determined by otolithic organ information rather than semicircular canals. Due to otolithic function impairment, spatial learning was impaired after exposure to gravity changes in animals and this impaired performance was compensated after normal gravity exposure.
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Galvanic Vestibular Stimulation Improves Spatial Cognition After Unilateral Labyrinthectomy in Mice Thanh Tin Nguyen, Gi-Sung Nam, Jin-Ju Kang, Gyu Cheol Han, Ji-Soo Kim, Marianne Dieterich, Sun-Young Oh Frontiers in Neurology.2021;[Epub] CrossRef
The Differential Effects of Acute Right- vs. Left-Sided Vestibular Deafferentation on Spatial Cognition in Unilateral Labyrinthectomized Mice Thanh Tin Nguyen, Gi-Sung Nam, Jin-Ju Kang, Gyu Cheol Han, Ji-Soo Kim, Marianne Dieterich, Sun-Young Oh Frontiers in Neurology.2021;[Epub] CrossRef
Background and Objectives: Altered environmental gravity, including both hypo- and hypergravity, may result in space adaptation syndrome. To explore the characteristics of this adaptive plasticity, the expression of immediate early gene c-fos mRNA in the vestibular system following an exposure to hypergravity stimulus was determined in rats.
Materials and Method: The animals were subjected to 2 G force (two-fold earth's gravity) stimulus for 3 hours, and were examined at post-stimulus hours 0, 2, 6, 12, and 24. Real time reverse transcription-polymerase chain reaction (RT-PCR) was adopted to analyze temporal changes in the expression of c-fos mRNA.
Results The hypergravity stimulation produced the expression of c-fos mRNA in the vestibular ganglion, medial vestibular nucleus, inferior vestibular nucleus, hippocampus, vestibulocerebellum, and vestibular cortex. The peak expression occurred at hour 6 in the animals hypergravity-stimulated for 3 hours. Bilateral labyrinthectomy significantly attenuated the degree of up-regulation in c-fos mRNA expression. MK-801, an NMDA receptor antagonist, also significantly attenuated the degree of up-regulation in c-fos mRNA expression.
Conclusion These results indicate that the adaptive neuroplasticity in response to an altered gravity occurs in the vestibular-related organs in the central nervous system, in which peripheral vestibular receptors and NMDA receptors play an important role.
Key Words : Hypergravity, Neuronal plasticity, Vestibule, c-fos gene