title: Functional expression of TRPV1 and TRPA1 in rat vestibular ganglia.
abstract: Both TRPV1 and TRPA1 are non-selective cation channels. They are co-expressed, and interact in sensory neurons such as dorsal root ganglia (DRG) and trigeminal ganglia (TG), and are involved in nociception, being activated by nociceptive stimuli. Immunohistological localization of TRPV1 in vestibular ganglion (VG) neurons has been reported. Although TRPA1 is co-expressed with TRPV1 in DRG and TG neurons, it is unclear whether TRPA1 channels are expressed in VG neurons. Moreover, it is unknown whether TRPV1 and TRPA1 channels are functional in VG neurons. We investigated the expression of TRPV1 and TRPA1 in rat VG neurons by RT-PCR, in situ hybridization, immunohistochemistry, and Ca(2+) imaging experiments. Both TRPV1 and TRPA1 RT-PCR products were amplified from the mRNA of rat VG neurons. In situ hybridization experiments showed TRPV1 and TRPA1 mRNA expression in the majority of VG neurons. Immunohistochemistry experiments confirmed TRPV1 protein expression. In Ca(2+) imaging experiments, capsaicin, a TRPV1 agonist, induced a significant increase in intracellular calcium ion concentration ([Ca(2+)]i) in rat primary cultured VG neurons, which was almost completely blocked by capsazepine, a TRPV1-specific antagonist. Cinnamaldehyde, a TRPA1 agonist, also caused an increase in [Ca(2+)]i, which was completely inhibited by HC030031, a TRPA1-specific antagonist. Moreover, in some VG neurons, a [Ca(2+)]i increase was evoked by both capsaicin and cinnamaldehyde in the same neuron. In summary, our histological and physiological studies reveal that TRPV1 and TRPA1 are expressed in VG neurons. It is suggested that TRPV1 and TRPA1 in VG neurons might participate in vestibular function and/or dysfunction such as vertigo.
authors.affiliation: Department of Otorhinolaryngology - Head and Neck Surgery, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; Department of Neuroscience and Cell Biology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Takefumi
authors.initials: T
authors.lastname: Kamakura
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ishida
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamada
authors.forename: Tadashi
authors.initials: T
authors.lastname: Kitahara
authors.forename: Yasumitsu
authors.initials: Y
authors.lastname: Takimoto
authors.forename: Arata
authors.initials: A
authors.lastname: Horii
authors.forename: Atsuhiko
authors.initials: A
authors.lastname: Uno
authors.forename: Takao
authors.initials: T
authors.lastname: Imai
authors.forename: Suzuyo
authors.initials: S
authors.lastname: Okazaki
authors.forename: Hidenori
authors.initials: H
authors.lastname: Inohara
authors.forename: Shoichi
authors.initials: S
authors.lastname: Shimada
mesh_terms: D000083:Acetanilides / Q000494:pharmacology; D000171:Acrolein / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002211:Capsaicin / Q000031:analogs & derivatives / Q000494:pharmacology; D057054:Molecular Imaging; D061251:Primary Cell Culture; D011687:Purines / Q000494:pharmacology; D051381:Rats; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels / Q000819:agonists / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D050916:TRPV Cation Channels / Q000819:agonists / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000502:physiology*; D014725:Vestibular Nerve / Q000187:drug effects / Q000378:metabolism*
chemical_list: C552888:2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4-isopropylphenyl)acetamide; D000083:Acetanilides; D011687:Purines; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; D050916:TRPV Cation Channels; C480976:Trpa1 protein, rat; C493922:Trpv1 protein, rat; D000171:Acrolein; C071423:capsazepine; D002211:Capsaicin; C012843:cinnamaldehyde; D002118:Calcium
keywords: Ca(2+) imaging experiment; In situ hybridization; TRPA1; TRPV1; Vestibular ganglia