2006 Fiscal Year Final Research Report Summary
Physiological and anatomical observations of the neural integrator in compensations of sensory organs
| Project/Area Number |
17591786
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Otorhinolaryngology
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| Research Institution | Clinical Research Center, Kyoto Medical Center |
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Principal Investigator |
TSUJI Jun Kyoto Medical Center, Clinical Research Center, Researcher, 政策医療企画研究部, 研究員 (30252448)
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| Co-Investigator(Kenkyū-buntansha) |
ITO Juichi Kyoto University, Dept Otolaryngology, Professor, 医学研究科, 教授 (90176339)
HIRAUMI Harukazu Kyoto University, Dept Otolaryngology, Assistant, 医学研究科, 助手 (10374167)
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| Project Period (FY) |
2005 – 2006
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| Keywords | vestibular compensation / vestibulo-ocular reflex / neural integrator / mouse / glutamate delta 2 receptor |
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| Research Abstract |
Vestibular compensation is attributed to functional and structural reorganization of neural networks in the central vestibular system, but its precise mechanism is still not clear. c-Fos protein is used as a marker of neuronal activation, because of its very limited expression in the normal state and rapid appearance after external stimulation. Previous reports, investigating c-Fos expression after unilateral labyrinthectomy were made in rats and guinea pigs, but not in the mouse brainstem. We elucidated, after unilateral labyrinthectomy in mice, the bilateral medial vestibular nucleus (MVe), bilateral spinal vestibular nucleus (SpVe), contralateral prepositus hypoglossal nucleus (PrH), and contralateral inferior olive nucleus (IO) were activated like in other species.
It is well known that the fixating mechanism of visual system suppress nystagmus of vestibular origin(visual suppression). And it is generally assumed that floccular Purkinje cells encodes retinal slip and controls the gain of the horizontal vestibulo-ocular reflex. Previous reports showed that lesions in the flocculus abolish visual suppression. However the precise mechanism of the visual suppression is not completely understood. We recorded the visual suppressions in mutant mice deficient in the delta 2 subunit of the ionotrphhic glutamate receptor (GluR delta-2) in Purkinje cells to investigate the role of glutaminergic system on the control of VOR. Eye movements were captured and analyzed by a computer. The pupil was fitted as an ellipse and the horizontal eye angular movement was calculated using the shape and direction of ellipse (Iwashita et al. 2001). In GluR delta-2 (-/-)mice the velocity was reduced very little (10 %), no change or even increased in light. These results suggest that the parallel fiber input to floccular Purkinje cells mediated by ionotrophic glutamate receptor play important roles in the visual suppression of the vestibular nystagmus.
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