Fischer Luana, Clemente Juliana T, Tambeli Cláudia H
Laboratory of Orofacial Pain, Department of Physiology, Faculty of Dentistry of Piracicaba, University of Campinas-Unicamp, São Paulo, Brazil.
J Pain. 2007 May;8(5):437-42. doi: 10.1016/j.jpain.2006.12.007. Epub 2007 Mar 13.
The lower prevalence of many pain conditions, including temporomandibular dysfunctions, in men than in women has not as yet been clarified. The aim of this study was to investigate the effect of testosterone on the risk of development of temporomandibular joint (TMJ) pain and on acute persistent TMJ pain. The TMJ formalin test was used as an experimental assay in the rat. Intra-TMJ 0.5% formalin induced a significant nociceptive behavior in naive female rats and gonadectomized male rats but not in naive male rats, suggesting that naive male rats have a lower risk for development of TMJ pain. The finding that the serum level of testosterone but not of estrogen and progesterone significantly decreased in gonadectomized male rats suggests that testosterone is the hormone underlying the decreased naive male rat's risk for development of TMJ pain. The magnitude of the nociceptive behaviors induced by intra-TMJ 1.5% formalin was similar in gonadectomized and naive male rats. Therefore, in contrast to the protective role of testosterone in TMJ pain development, testosterone, at physiological serum levels, does not appear to modulate acute persistent TMJ pain induced by the TMJ injection of 1.5% formalin. At a supraphysiological serum level, however, testosterone significantly attenuated 1.5% formalin-induced nociception in male rats but not in female rats. This antinociceptive effect was not mediated by estrogen derived from testosterone aromatization, because estrogen administration did not affect 1.5% formalin-induced TMJ nociception in gonadectomized male rats.
The present findings not only help to explain the lower prevalence of TMJ pain in males versus females but also show that testosterone reduces TMJ pain at supraphysiological serum levels.
包括颞下颌关节功能障碍在内的许多疼痛病症在男性中的患病率低于女性，其原因尚未明确。本研究的目的是调查睾酮对颞下颌关节（TMJ）疼痛发生风险以及急性持续性TMJ疼痛的影响。TMJ福尔马林试验被用作大鼠的实验测定方法。向TMJ内注射0.5%福尔马林会在未处理的雌性大鼠和去势雄性大鼠中诱发显著的伤害性反应行为，但在未处理的雄性大鼠中则不会，这表明未处理的雄性大鼠发生TMJ疼痛的风险较低。去势雄性大鼠血清中睾酮水平显著降低，而雌激素和孕酮水平未显著降低，这一发现表明睾酮是未处理雄性大鼠发生TMJ疼痛风险降低的基础激素。向TMJ内注射1.5%福尔马林诱发的伤害性反应行为程度在去势雄性大鼠和未处理雄性大鼠中相似。因此，与睾酮在TMJ疼痛发生中的保护作用相反，在生理血清水平下，睾酮似乎不会调节TMJ注射1.5%福尔马林诱发的急性持续性TMJ疼痛。然而，在超生理血清水平下，睾酮可显著减轻雄性大鼠中1.5%福尔马林诱发的伤害感受，但对雌性大鼠无效。这种抗伤害感受作用不是由睾酮芳香化衍生的雌激素介导的，因为给予雌激素对去势雄性大鼠中1.5%福尔马林诱发的TMJ伤害感受没有影响。
本研究结果不仅有助于解释男性与女性TMJ疼痛患病率较低的原因，还表明在超生理血清水平下睾酮可减轻TMJ疼痛。
