title: Characterization of primary sensory neurons mediating static and dynamic allodynia in rat chronic constriction injury model.
abstract: Mechanical allodynia, such as static and dynamic allodynia, is a prominent feature of neuropathic pain syndromes. The aim of this study is to characterize primary sensory neurons mediating the mechanical allodynia in a rat chronic constriction injury (CCI) model with a combination of pharmacological and histological investigations. N-(4-Tertiarybutylphenyl)-4-(3-chloropyridin-2-yl) tetrahydropyrazine-1(2H)-carbox-amide (BCTC), a selective and competitive antagonist of the vanilloid receptor 1 (TRPV1), and resiniferatoxin, which causes desensitization of TRPV1-expressing fibres, suppressed static allodynia but not dynamic allodynia in CCI rats. Immunohistochemical studies of TRPV1 and NF200, an A-fibre marker 200 kDa neurofilament, in dorsal root ganglion neurons demonstrated that each 48% of the positive-stained neurons were immunoreactive only for TRPV1 or NF200. The other 4% of stained neurons were double-positive for TRPV1 and NF200. Of the TRPV1positive neurons, more than 99% were small-(diameter <25 microm) and medium-(25-45 microm) sized. In contrast, 97% of NF200 single-labelled neurons were medium-and large-(>45 microm) sized. These findings suggest that two types of mechanical allodynia are transmitted by different primary sensory neurons: static allodynia is mediated by TRPV1 positive small-and medium-sized neurons and dynamic allodynia might be signalled by TRPV1-negative medium- and large-sized neurons.
authors.affiliation: Discovery Biology Research, Nagoya Laboratories, Pfizer Global Research and Development, Pfizer Inc., 5-2, Taketoyo, Aichi, 470-2393, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Yamamoto
authors.forename: Akemi
authors.initials: A
authors.lastname: Sugiura
authors.forename: Etsuko
authors.initials: E
authors.lastname: Nakazato-Imasato
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kita
mesh_terms: D000818:Animals; D048429:Cell Size; D003251:Constriction, Pathologic; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D008297:Male; D016900:Neurofilament Proteins / Q000378:metabolism*; D009475:Neurons, Afferent / Q000378:metabolism*; D010146:Pain / Q000209:etiology / Q000503:physiopathology*; D010147:Pain Measurement; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D050916:TRPV Cation Channels / Q000378:metabolism*
chemical_list: D016900:Neurofilament Proteins; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; C051774:neurofilament protein H