title: Nitric oxide in the flocculus works the inhibitory neural circuits after unilateral labyrinthectomy.
abstract: We previously reported that nitric oxide (NO) production in the unipolar brush (UB) cells is involved in vestibular compensation [T. Kitahara, N. Takeda, P.C. Emson, T. Kubo, H. Kiyama, Changes in nitric oxide synthase-like immunoreactivities in unipolar brush cells in the rat cerebellar flocculus after unilateral labyrinthectomy, Brain Res. 765 (1997) 1-6]. To further elucidate the role of NO-mediated signaling in flocculus after unilateral labyrinthectomy (UL), we examined UL-induced Fos expression, a marker of neural activity, in vestibular brainstem with continuous floccular infusions of Nomega-nitro-l-arginine methyl ester (l-NAME), an inhibitor of NO synthase (NOS). After UL with floccular l-NAME infusions, Fos expression appeared in bilateral medial vestibular (MVe) and prepositus hypoglossal (PrH) nuclei. After UL with floccular saline infusions, however, Fos expression was observed only in the ipsi-MVe and contra-PrH. Furthermore, it has been revealed that UL with l-NAME infusions caused more severe vestibulo-ocular disturbances than UL with saline infusions at the initial stage [Kitahara et al. Brain Res. 765 (1997) 1-6]. Therefore, it is suggested that UL with floccular l-NAME infusions activates the contra-MVe and ipsi-PrH neurons and causes more severe imbalance between intervestibular nuclear activities at the initial stage. NO-mediated signaling in flocculus could be a possible driving force of the flocculus-mediated inhibition on the contra-MVe and ipsi-PrH at the initial stage of vestibular compensation.
authors.affiliation: Department of Otolaryngology, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan. kitahara@ent.med.osaka-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Kitahara
authors.forename: N
authors.initials: N
authors.lastname: Takeda
authors.forename: T
authors.initials: T
authors.lastname: Kubo
authors.forename: H
authors.initials: H
authors.lastname: Kiyama
mesh_terms: D000818:Animals; D001931:Brain Mapping; D002531:Cerebellum / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D007758:Ear, Inner / Q000502:physiology*; D007839:Functional Laterality; D007263:Infusions, Parenteral; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage; D009434:Neural Pathways / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D014726:Vestibular Nuclei / Q000187:drug effects / Q000502:physiology
chemical_list: D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester