title: Descending facilitatory pain pathways mediate ongoing pain and tactile hypersensitivity in a rat model of trigeminal neuropathic pain.
abstract: The Chronic Constriction Injury of the Infraorbital Nerve (CCI-ION) is a well-established model to study facial sensory changes related to trigeminal neuropathic pain. CCI-ION induces heat hypersensitivity that resolves within 2-3 weeks and a delayed mechanical hypersensitivity that emerges during the second week post-injury. The role of descending facilitatory pain pathways from the rostro ventromedial medulla (RVM) in mediating the heat and tactile hypersensitivity was examined. CCI-ION induced heat hypersensitivity observed 5days post-surgery was reversed by systemic, but not RVM lidocaine. CCI-ION-induced tactile hypersensitivity observed 15days post-surgery was reversed by systemic lidocaine and attenuated by RVM lidocaine. CCI-ION-induced spontaneous pain was determined using conditioned place preference (CPP) to pain relief at each time-point. At day 5 post-CCI-ION, neither systemic nor RVM lidocaine induced CPP. However, at 15days post-CCI-ION, CPP was observed to the chamber paired with RVM lidocaine, but not systemic lidocaine. These data indicate that CCI-ION induced heat hypersensitivity is not dependent on descending facilitatory pain pathways 5-days post-injury whereas descending facilitatory pain pathways mediate tactile allodynia and spontaneous pain 15days post-CCI-ION. This suggests that CCI-ION induces early peripheral sensitization followed by development of central sensitization that mediates spontaneous pain and contributes to mechanical hypersensitivity.
authors.affiliation: Department of Pharmacology, Federal University of Parana, Curitiba, PR, Brazil.
authors.forename: C F M
authors.initials: CFM
authors.lastname: Nones
authors.affiliation: Department of Pharmacology, Federal University of Parana, Curitiba, PR, Brazil.
authors.forename: R F
authors.initials: RF
authors.lastname: Claudino
authors.affiliation: Department of Pharmacology, Federal University of Parana, Curitiba, PR, Brazil.
authors.forename: L E N
authors.initials: LEN
authors.lastname: Ferreira
authors.affiliation: Department of Pharmacology, Federal University of Parana, Curitiba, PR, Brazil.
authors.forename: R C
authors.initials: RC
authors.lastname: Dos Reis
authors.affiliation: Department of Biomedical Science, University of New England, Biddeford, ME, USA.
authors.forename: T
authors.initials: T
authors.lastname: King
authors.affiliation: Department of Pharmacology, Federal University of Parana, Curitiba, PR, Brazil. Electronic address: juliana.chichorro@ufpr.br.
authors.forename: J G
authors.initials: JG
authors.lastname: Chichorro
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D006358:Hot Temperature; D006930:Hyperalgesia / Q000503:physiopathology*; D008297:Male; D008526:Medulla Oblongata / Q000503:physiopathology*; D009434:Neural Pathways / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D014110:Touch; D014277:Trigeminal Neuralgia / Q000503:physiopathology*
keywords: Hypersensitivity; RVM; Spontaneous pain; Trigeminal neuropathic pain