Influência dos hormônios sexuais na analgesia induzida pelo estresse / Influence of sex hormones in stress-induced analgesia
AUTOR(ES)
Carlos Eduardo da Silva Nossa Tuma
FONTE
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia
DATA DE PUBLICAÇÃO
25/07/2011
RESUMO
Temporomandibular disorders comprehend a variable group of conditions which result in joint and/or muscle pain and contribute to the development of acute pains, being more prevalent in women than men, especially during the reproductive period. They involve the muscles of mastication and temporomandibular joint (ATM), being usually associated with inflammatory processes, ocurring the participation of gonadal hormones in these dysfunctions. The formalin test in the ATM is a valid animal model to study Temporomandibular dysfuntions. The aims of this research were to evaluate 1) the effect of acute stress of 15 minutes, 30 minutes and 1 hour over the nonciceptive behavioral responses after the formalin test in the ATM of female rats in estrus (low levels of estrogen) and proestrus (high levels of estrogen) phase and castrated female and male rats with or without hormonal manipulation (17ß-estradiol), 2) to evaluate the role of opioid system in the possible nonciceptive alterations induced by stressful situations, and 3) the evaluation of the blood levels of corticosterone and anxiety after acute stress. The rats were were castrated 60 days after birth, being the hormonal replacement (17ß-estradiol sigma® - E0756 - 5 mg in mineral oil; s.c.; 50µg/Kg/day; at nine AM) or the administration of the vehicle (mineral oil), initiated 21 days after the surgical procedure, for seven days. After the seventh day of hormonal treatment or administration of the vehicle, the animals were sumitted to a session of acute stress by restraint during one hour and afterwards: (1) were immediately killed for collection of blood and hormonal measurement by radioimmunoassay; or (2) were submitted to the elevated plus-maze for anxiety evaluation; or (3) submitted to the formalin test in the ATM for nociception evaluation. It was also evaluated the role of opioid system in nociceptive changes induced by stress, through the administration of nor-BNI- 200 µg/25µL (antagonist of the receptors kappa opioids) before the nociceptive evaluation. For statistical analysis, it was used the analysis of variance (ANOVA) followed by specific tests for the comparison of final results, the level of significance was set at p?0.05. All groups submitted to acute stress showed a significant increase in the plasma corticosterone. The acute stress induced the decrease of nociceptive responses in intact females, an effect that was not expressed in orquidectomized and ovariectomized rats. The strees-induced analgesia (SIA) was partially mediated by opioid system, once the administration of nor-BNI changed the antinociception in the females, being more effective on female rats in proestrus phase. Orquidectomized male rats presented an increase of nociceptive responses (hyperalgesia), and the administration of estradiol restored the stress-induced analgesia in ovariectomized rats, not affecting the nociceptive behavioral responses in orquidectomized male rats. It has been concluded that: 1) acute stress caused analgesia in female intact rats in the proestrus phase and ovariectomized with estrogen treatment; 2) acute stress induced an increase in the levels of anxiety in ovariectomized female rats; 3) The gonadal hormones considerably influence the nociception of ATM
ASSUNTO(S)
estresse articulação temporomandibular estradiol dor analgesia stress temporomandibular joint estradiol pain analgesia
