title: Involvement of TRPV1 channels in the periaqueductal grey on the modulation of innate fear responses.
abstract: OBJECTIVE
  The transient receptor potential vanilloid type-1 channel (TRPV1) is expressed in the midbrain periaqueductal grey (PAG), a region of the brain related to aversive responses. TRPV1 antagonism in the dorsolateral PAG (dlPAG) induces anxiolytic-like effects in models based on conflict situations. No study, however, has investigated whether these receptors could contribute to fear responses to proximal threat. Thus, we tested the hypothesis that TRPV1 in the PAG could mediate fear response in rats exposed to a predator.
  
  
  METHODS
  We verified whether exposure to a live cat (a natural predator) would activate TRPV1-expressing neurons in the PAG. Double-staining immunohistochemistry was used as a technique to detect c-Fos, a marker of neuronal activation, and TRPV1 expression. We also investigated whether intra-dlPAG injections of the TRPV1 antagonist, capsazepine (CPZ), would attenuate the behavioural consequences of predator exposure.
  
  
  RESULTS
  Exposure to a cat increased c-Fos expression in TRPV1-positive neurons, mainly in the dorsal columns of the PAG, suggesting that TRPV1-expressing neurons are activated by threatening stimuli. Accordingly, local injection of CPZ inhibited the fear responses.
  
  
  CONCLUSIONS
  These data support the hypothesis that TRPV1 channels mediate fear reactions in the dlPAG. This may have an implication for the development of TRPV1-antagonists as potential drugs for the treatment of certain psychiatric disorders.
authors.affiliation: 1Department of Pharmacology,Institute of Biological Sciences,Universidade Federal de Minas Gerais,Belo Horizonte,MG,Brazil.
authors.forename: Daniele C
authors.initials: DC
authors.lastname: Aguiar
authors.affiliation: 1Department of Pharmacology,Institute of Biological Sciences,Universidade Federal de Minas Gerais,Belo Horizonte,MG,Brazil.
authors.forename: Ana F
authors.initials: AF
authors.lastname: Almeida-Santos
authors.affiliation: 1Department of Pharmacology,Institute of Biological Sciences,Universidade Federal de Minas Gerais,Belo Horizonte,MG,Brazil.
authors.forename: Fabricio A
authors.initials: FA
authors.lastname: Moreira
authors.affiliation: 2Department of Pharmacology,Ribeirao Preto School of Medicine,Universidade de São Paulo,Ribeirão Preto - SP,Brazil.
authors.forename: Francisco S
authors.initials: FS
authors.lastname: Guimarães
mesh_terms: D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D002211:Capsaicin / Q000031:analogs & derivatives / Q000494:pharmacology; D002415:Cats; D005239:Fear / Q000502:physiology*; D008297:Male; D010487:Periaqueductal Gray / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D000099169:Fos-Related Antigen 1
chemical_list: D014151:Anti-Anxiety Agents; D002211:Capsaicin; D016760:Proto-Oncogene Proteins c-fos; D050916:TRPV Cation Channels; D000099169:Fos-Related Antigen 1; C071423:capsazepine
keywords: vanilloid