title: Blockade of β₁-, β₂- and β₃-adrenoceptors in the temporomandibular joint induces antinociception especially in female rats.
abstract: BACKGROUND
  Temporomandibular joint (TMJ) receives rich sympathetic innervations that may contribute to TMJ pain through the local release of sympathomimetic amines. The aim of this study was to determine whether blockade of β-adrenoceptors in the TMJ of male and female rats reduces formalin-induced TMJ nociceptive behaviour.
  
  
  METHODS
  We co-administrated each one of the selective β(1) -, β(2) - and β(3) -adrenoceptors antagonists, atenolol, ICI 118.551 and SR59230A, respectively, with formalin in the TMJ of male and proestrus and dioestrus female rats. Because intra-temporomandibular joint formalin induces significantly different concentration-dependent responses among the three groups, with dioestrus females showing greater responses than males or proestrus females, equi-nociceptive formalin concentrations were used to test the effects of the β-adrenoceptor antagonists.
  
  
  RESULTS
  We found that atenolol, ICI 118.551 and SR59230A significantly reduced formalin-induced TMJ nociception in a dose response fashion in both males and females. However, a lower dose of each β-adrenoceptor antagonist was sufficient to significantly reduce nociceptive responses in females than in males. Administration of the highest doses of each β-adrenoceptor antagonist in the TMJ contralateral to that receiving formalin did not affect formalin-induced nociception in males and females, confirming the local action of the β-adrenoceptor antagonists.
  
  
  CONCLUSIONS
  We conclude that blockade of β-adrenoceptors in the temporomandibular joint suppresses formalin-induced TMJ nociceptive behaviour in both males and females but females are more responsive. These findings suggest that the use of β-blockers in the treatment of TMJ pain might be of benefit, especially in females.
authors.affiliation: Department of Physiological Sciences, Laboratory of Orofacial Pain, Piracicaba Dental School, State University of Campinas, Piracicaba, Brazil.
authors.forename: N C
authors.initials: NC
authors.lastname: Fávaro-Moreira
authors.forename: C A
authors.initials: CA
authors.lastname: Parada
authors.forename: C H
authors.initials: CH
authors.lastname: Tambeli
mesh_terms: D058671:Adrenergic beta-1 Receptor Antagonists / Q000494:pharmacology*; D058672:Adrenergic beta-2 Receptor Antagonists / Q000494:pharmacology*; D058673:Adrenergic beta-3 Receptor Antagonists / Q000494:pharmacology*; D000818:Animals; D001262:Atenolol / Q000494:pharmacology*; D005260:Female; D007270:Injections, Intra-Articular; D008297:Male; D059225:Nociception / Q000187:drug effects*; D010147:Pain Measurement / Q000187:drug effects; D011412:Propanolamines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012737:Sex Factors; D013704:Temporomandibular Joint
chemical_list: C097869:3-(2-ethylphenoxy)-1-(1,2,3,4-tetrahydronaphth-1-ylamino)-2-propanol oxalate; D058671:Adrenergic beta-1 Receptor Antagonists; D058672:Adrenergic beta-2 Receptor Antagonists; D058673:Adrenergic beta-3 Receptor Antagonists; D011412:Propanolamines; C026777:ICI 118551; D001262:Atenolol