title: Nigrostriatal dopaminergic depletion increases static orofacial allodynia.
abstract: BACKGROUND
  This study investigated mesencephalic dopamine depletion effects on static mechanical allodynia (SMA) elicited by chronic constriction of the infraorbitary nerve (CCI-IoN).
  
  
  METHODS
  Dopamine depletion (6-OHDA administration into the medial forebrain bundle) effects on CCI-IoN-induced SMA were explored using behavioral (nocifensive behavior score upon non-noxious stimuli using von Frey filament), pharmacological (bromocriptine injections) and immunohistochemical (PKCγ and pERK1/2) techniques.
  
  
  RESULTS
  The central dopamine depletion increased significantly the SMA score. Intraperitoneal and intracisternal injections of bromocriptine alleviated the allodynic behavior observed in both CCI-IoN and CCI-IoN + 6-OHDA animal groups. At the cellular level, dopamine depletion induced a significant increase in PKCγ expression in the medullary dorsal horn (MDH) in rat with CCI-IoN + 6-OHDA when compared to sham animals (CCI-IoN only). Similarly, after static non-noxious stimuli, the expression of pain marker proteins pERK1/2 within the MDH revealed significantly a higher number of positive cells in CCI-IoN + 6-OHDA rats when compared to the CCI-IoN group.
  
  
  CONCLUSIONS
  This study demonstrates that nigrostriatal dopamine depletion exacerbates the neuropathic pain resulting from CCI-IoN. This effect is probably due to an action through descending pain inhibitory systems which increased pain sensitization at the MDH level. It demonstrates also an analgesic effect elicited by D2R activation at the segmental level.
authors.affiliation: UFR Odontologie, Université Paris Diderot, Paris, France. wisamdieb@yahoo.com.|Centre de Psychiatrie et Neurosciences, INSERM U894, Paris, France. wisamdieb@yahoo.com.|Clermont Université, Université d'Auvergne, EA7280, Clermont-Ferrand, France. wisamdieb@yahoo.com.
authors.forename: Wisam
authors.initials: W
authors.lastname: Dieb
authors.affiliation: Clermont Université, Université d'Auvergne, EA7280, Clermont-Ferrand, France. ouachikh1@yahoo.fr.
authors.forename: Omar
authors.initials: O
authors.lastname: Ouachikh
authors.affiliation: Clermont Université, Université d'Auvergne, EA7280, Clermont-Ferrand, France. alves.sofia@hotmail.fr.
authors.forename: Sofia
authors.initials: S
authors.lastname: Alves
authors.affiliation: UFR Odontologie, Université Paris Diderot, Paris, France. yves.boucher@univ-paris-diderot.fr.|Centre de Psychiatrie et Neurosciences, INSERM U894, Paris, France. yves.boucher@univ-paris-diderot.fr.
authors.forename: Yves
authors.initials: Y
authors.lastname: Boucher
authors.affiliation: Clermont Université, Université d'Auvergne, EA7280, Clermont-Ferrand, France. Franck.DURIF@udamail.fr.|CHU Clermont-Ferrand, Service de Neurologie, 63000, Clermont-Ferrand, France. Franck.DURIF@udamail.fr.
authors.forename: Franck
authors.initials: F
authors.lastname: Durif
authors.affiliation: Clermont Université, Université d'Auvergne, EA7280, Clermont-Ferrand, France. azhafidi@univ-bpclermont.fr.
authors.forename: Aziz
authors.initials: A
authors.lastname: Hafidi
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D003251:Constriction, Pathologic / Q000150:complications; D004195:Disease Models, Animal; D004298:Dopamine / Q000378:metabolism*; D005157:Facial Pain / Q000209:etiology / Q000378:metabolism*; D006930:Hyperalgesia / Q000209:etiology / Q000378:metabolism*; D008297:Male; D009437:Neuralgia / Q000209:etiology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013378:Substantia Nigra / Q000378:metabolism*
chemical_list: D004298:Dopamine
keywords: Chronic constriction injury; Dopamine; Infraorbitary nerve; Neuropathic pain; Pain; Parkinson disease; Substantia nigra