title: The influence of sex and ovarian hormones on temporomandibular joint nociception in rats.
abstract: The aim of this study was to investigate the influence of sex and ovarian hormones on formalin- and glutamate-induced temporomandibular joint (TMJ) nociception in rats. The influence of sex and ovarian hormones on the nociceptive behavior induced by formalin or glutamate was virtually the same. The nociceptive behavior of males was similar to that of females in the proestrus phase of the estrous cycle but was significantly lower than that in the diestrus phase. Since the serum level of estradiol but not of progesterone was significantly higher in the proestrus than in the diestrus phase, these data suggest that females with lower endogenous serum level of estradiol have an exacerbation of TMJ nociception. The nociceptive behavior of ovariectomized rats was similar to that of diestrus females and significantly greater than that of proestrus females. Although the administration of estradiol or progesterone in ovariectomized females significantly reduced TMJ nociception, the combination of both hormones did not increase the antinociceptive effect induced by each of them. These findings suggest that estradiol and progesterone decrease TMJ nociception in an independent way.
  
  
  CONCLUSIONS
  We report that ovarian hormones have an antinociceptive effect on the TMJ formalin and glutamate nociceptive behavior models. Therefore, the greater prevalence and severity of TMJ pain in women of reproductive age may be a consequence of hormonal fluctuation during the reproductive cycle, in that during low endogenous estradiol serum level TMJ pain sensitivity is increased, enhancing the risk of females experiencing TMJ pain.
authors.affiliation: Laboratory of Orofacial Pain, Department of Physiology, Faculty of Dentistry of Piracicaba, State University of Campinas-UNICAMP, São Paulo, Brazil.
authors.forename: Luana
authors.initials: L
authors.lastname: Fischer
authors.forename: Karla E
authors.initials: KE
authors.lastname: Torres-Chávez
authors.forename: Juliana T
authors.initials: JT
authors.lastname: Clemente-Napimoga
authors.forename: Dany
authors.initials: D
authors.lastname: Jorge
authors.forename: Franco
authors.initials: F
authors.lastname: Arsati
authors.forename: Maria Cecília F
authors.initials: MC
authors.lastname: de Arruda Veiga
authors.forename: Claudia H
authors.initials: CH
authors.lastname: Tambeli
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D004031:Diestrus / Q000502:physiology; D004958:Estradiol / Q000097:blood / Q000502:physiology*; D005260:Female; D005557:Formaldehyde / Q000008:administration & dosage / Q000633:toxicity; D018698:Glutamic Acid / Q000008:administration & dosage / Q000633:toxicity; D006801:Humans; D007270:Injections, Intra-Articular; D007274:Injections, Intraperitoneal; D008297:Male; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010052:Ovariectomy; D010146:Pain / Q000139:chemically induced / Q000503:physiopathology*; D010147:Pain Measurement / Q000379:methods; D011359:Proestrus / Q000502:physiology; D011374:Progesterone / Q000097:blood / Q000502:physiology*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D012737:Sex Factors; D013704:Temporomandibular Joint / Q000187:drug effects / Q000503:physiopathology; D013705:Temporomandibular Joint Disorders / Q000097:blood / Q000139:chemically induced / Q000503:physiopathology*
chemical_list: D005557:Formaldehyde; D018698:Glutamic Acid; D011374:Progesterone; D004958:Estradiol