Kazunori Matsuda1, Tadashi Kitahara2, Taeko Ito2, Munehisa Fukushima3, Junya Fukuda1, Go Sato1, Yoshiaki Kitamura1, Koji Abe1, Atsuhiko Uno4, Koichi Tomita5, Hiromi Sakata-Haga6, Yoshihiro Fukui7, Noriaki Takeda1. 1. a Department of Otolaryngology , Institute of Biomedical Sciences, Tokushima University Graduate School , Tokushima , Japan. 2. b Department of Otolaryngology , Nara Medical University , Kashihara , Japan. 3. c Department of Otolaryngology - Head and Neck Surgery , Kansai Rosai Hospital , Amagasaki , Japan. 4. d Department of Otorhinolaryngology - Head and Neck Surgery , Osaka General Medical Center , Osaka , Japan. 5. e Department of Anatomy and Developmental Neurobiology , Institute of Biomedical Sciences, Tokushima University Graduate School , Tokushima , Japan. 6. f Department of Anatomy , Kanazawa Medical University , Kahoku , Japan. 7. g School of Nutritional Science , Nagoya University of Arts and Sciences Graduate School of Nutritional Science , Nagoya , Japan.
Abstract
BACKGROUND: Unilateral labyrinthectomy (UL) causes the disappearance of ipsilateral medial vestibular nuclear (ipsi-MVe) activity and induces spontaneous nystagmus (SN), which disappears during the initial process of vestibular compensation (VC). Ipsi-MVe-activity restores in the late process of VC. OBJECTIVE: We evaluated the late process of VC after UL in rats and examined the effects of thioperamide (H3 antagonist) on VC. MATERIALS AND METHODS: MK801 (NMDA antagonist)-induced Fos-like immunoreactive (-LIR) neurons in contra-MVe, which had been suppressed by NMDA-mediated cerebellar inhibition in UL rats was used as an index. RESULTS: The number of MK801-induced Fos-LIR neurons in contra-MVe gradually decreased to the same level as that of sham-operated rats 14 days after UL. Thioperamide moved the disappearance of the MK801-induced Fos-LIR neurons 2 days earlier. The number of MK801-induced Fos-LIR neurons in thioperamide-treated rats was significantly decreased, compared with that of vehicle rats on days 7 and 12 after UL. But, thioperamide did not influence the decline of SN frequency in UL rats. CONCLUSION: These findings suggested that the number of MK801-induced Fos-LIR neurons in contra-MVe was decreased in concordance with the restoration of ipsi-MVe-activity during the late process of VC after UL and that thioperamide accelerated the late, but not the initial process of VC.
BACKGROUND: Unilateral labyrinthectomy (UL) causes the disappearance of ipsilateral medial vestibular nuclear (ipsi-MVe) activity and induces spontaneous nystagmus (SN), which disappears during the initial process of vestibular compensation (VC). Ipsi-MVe-activity restores in the late process of VC. OBJECTIVE: We evaluated the late process of VC after UL in rats and examined the effects of thioperamide (H3 antagonist) on VC. MATERIALS AND METHODS:MK801 (NMDA antagonist)-induced Fos-like immunoreactive (-LIR) neurons in contra-MVe, which had been suppressed by NMDA-mediated cerebellar inhibition in UL rats was used as an index. RESULTS: The number of MK801-induced Fos-LIR neurons in contra-MVe gradually decreased to the same level as that of sham-operated rats 14 days after UL. Thioperamide moved the disappearance of the MK801-induced Fos-LIR neurons 2 days earlier. The number of MK801-induced Fos-LIR neurons in thioperamide-treated rats was significantly decreased, compared with that of vehicle rats on days 7 and 12 after UL. But, thioperamide did not influence the decline of SN frequency in UL rats. CONCLUSION: These findings suggested that the number of MK801-induced Fos-LIR neurons in contra-MVe was decreased in concordance with the restoration of ipsi-MVe-activity during the late process of VC after UL and that thioperamide accelerated the late, but not the initial process of VC.