Differential expression of capsaicin-, menthol-, and mustard oil-sensitive receptors in naive rat geniculate ganglion neurons.
The roles of capsaicin, menthol, and mustard oils and their receptors in geniculate ganglion (GG) neurons still remain to be elucidated. These receptors belong to the transient receptor potential (TRP) family. Capsaicin-, menthol-, and mustard oil-sensitive receptors are TRPV1, TRPM8, and TRPA1, respectively. The present study aimed to investigate the expression of TRPV1, TRPM8, and TRPA1 in naive rat GG neurons. Furthermore, we examined whether these TRP-expressing GG neurons are myelinated A-fiber or unmyelinated C-fiber neurons. Firstly, using reverse transcription-polymerase chain reaction, TRPV1 mRNA and TRPA1 mRNA were distinctly detected in the naive GG. TRPM8 mRNA was faintly detected. Secondly, using in situ hybridization, TRPV1 mRNA- or TRPA1 mRNA-labeled neurons (signal/noise ratio >or= 10) were observed in 15-20% of GG neurons. Few neurons were labeled by TRPM8 mRNA. Thirdly, neurofilament 200 (NF200) protein, a marker of mylinated A-fiber neurons, was detected in 57% of naive GG neurons. Coexpression of TRPV1 mRNA or TRPA1 mRNA with NF200 was detected in 10% of GG neurons. The present study confirmed the expression of the TRP receptors in the naive GG. The possible roles of TRP receptors in naive GG neurons in somatosensory or gustatory function were suggested.
Katsura
Hirokazu
H
Department of Otolaryngology, Hyogo College of Medicine, 1-1 Mukogawa, Nishinomiya, Hyogo 663-8501, Japan. kasturahirokazu@yahoo.co.jp
Tsuzuki
Kenzo
K
Noguchi
Koichi
K
Sakagami
Masafumi
M
D000818:Animals; D017487:Ankyrins; D015220:Calcium Channels / Q000096:biosynthesis* / Q000187:drug effects / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology; D005830:Geniculate Ganglion / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008610:Menthol / Q000494:pharmacology; D009149:Mustard Plant; D009413:Nerve Fibers, Myelinated / Q000378:metabolism; D036421:Nerve Fibers, Unmyelinated / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010938:Plant Oils / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; D050053:TRPM Cation Channels / Q000096:biosynthesis* / Q000187:drug effects / Q000502:physiology; D050916:TRPV Cation Channels / Q000096:biosynthesis* / Q000187:drug effects / Q000502:physiology
D017487:Ankyrins; D015220:Calcium Channels; D010938:Plant Oils; D012333:RNA, Messenger; D000074025:TRPA1 Cation Channel; D050052:TRPC Cation Channels; D050053:TRPM Cation Channels; D050916:TRPV Cation Channels; C480976:Trpa1 protein, rat; C498947:Trpm8 protein, rat; C493922:Trpv1 protein, rat; D008610:Menthol; D002211:Capsaicin; C027793:mustard oil