title: Intraganglionar resiniferatoxin prevents orofacial inflammatory and neuropathic hyperalgesia.
abstract: Trigeminal ganglion C-fiber neurons bearing transient receptor potential vanilloid-1 (TRPV1) channels are selectively destroyed by resiniferatoxin (RTX), a potent capsaicin analogue. The current study assessed the effect of an RTX injection (200 ng/4 μl) into the trigeminal ganglion in inflammatory and neuropathic rat models of orofacial thermal hyperalgesia. Intraganglionar RTX injection resulted in trigeminal ganglion C-fiber deletion, which was confirmed by the capsaicin eye wipes test, performed 6 days after the injection. The nociceptive responses induced by 2.5% formalin injected into the orofacial region were unchanged by a previous intraganglionar RTX injection. However, orofacial heat and cold hyperalgesia, induced by carrageenan injected into the upper lip (50 µg/50 μl), was abolished by previous intraganglionar RTX treatment. In addition, the development of orofacial heat and cold hyperalgesia after constriction of the infraorbital nerve was prevented by previous RTX treatment. Thus, trigeminal ganglion neurons expressing TRPV1 are crucial for the development of orofacial inflammatory and neuropathic thermal hyperalgesia.
authors.affiliation: Department of Pharmacology, Federal University of Parana, Curitiba, Parana, Brazil.
authors.forename: Lizane S
authors.initials: LS
authors.lastname: Cruz
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Kopruszinski
authors.forename: Juliana G
authors.initials: JG
authors.lastname: Chichorro
mesh_terms: D000818:Animals; D002211:Capsaicin / Q000031:analogs & derivatives; D002351:Carrageenan; D003080:Cold Temperature; D004195:Disease Models, Animal; D004224:Diterpenes / Q000008:administration & dosage / Q000494:pharmacology*; D005157:Facial Pain / Q000188:drug therapy* / Q000378:metabolism; D005557:Formaldehyde; D006358:Hot Temperature; D006930:Hyperalgesia / Q000188:drug therapy* / Q000378:metabolism; D008297:Male; D009437:Neuralgia / Q000188:drug therapy* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D059225:Nociception / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D018689:Sensory System Agents / Q000008:administration & dosage / Q000494:pharmacology*; D050916:TRPV Cation Channels / Q000378:metabolism; D012668:Trigeminal Ganglion / Q000187:drug effects* / Q000378:metabolism
chemical_list: D004224:Diterpenes; D018689:Sensory System Agents; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; D005557:Formaldehyde; D002351:Carrageenan; C024353:resiniferatoxin; D002211:Capsaicin