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Sex and Gender Differences in Pain and Inflammation

Testosterone and estrogen have opposing actions on inflammation-induced plasma extravasation in the rat temporomandibular joint

¹Department of Biomedical Sciences, University of Maryland Dental School; ²Department of Anatomy and Neurobiology and ³Program in Neuroscience, University of Maryland School of Medicine, University of Maryland, Baltimore, Baltimore, Maryland

Submitted 30 November 2005 ; accepted in final form 7 February 2006

The present study was designed to test the hypothesis that estrogen exacerbates inflammation of the temporomandibular joint (TMJ). Evans blue dye was used to quantify plasma extravasation (PE) around the rat TMJ. In an initial set of experiments, TMJ PE was compared in naïve intact male and female rats, as well as in both groups after complete Freund’s adjuvant (CFA)-induced inflammation of the TMJ. In contrast to our hypothesis, TMJ PE was significantly greater in both naïve and CFA-inflamed male rats than in females. To determine whether these differences were due to gonadal hormones, four additional groups of rats were studied: gonadectomized (Gx) males and females, Gx males with chronic testosterone (T) replacement, and Gx females with chronic estrogen (E) replacement. The sex difference in baseline TMJ PE appeared to reflect the actions of T. However, in the presence of TMJ inflammation, T augmented TMJ PE in males, while E attenuated TMJ PE in females. Changes in PE were also assessed in the contralateral TMJ. Results from this analysis indicated that there is a transient contralateral increase in TMJ PE in females but not males. Given that there is an inverse relationship between PE and joint damage, our results suggest that testosterone may mitigate, but estrogen may exacerbate, TMJ damage, particularly in the presence of overt inflammation. Importantly, our results may help explain both the higher prevalence and severity of temporomandibular disorder pain in females than males.

temporomandibular disorder; craniofacial pain; sex difference

This article has been cited by other articles:

				K. J. Berkley, S. S. Zalcman, and V. R. Simon Sex and gender differences in pain and inflammation: a rapidly maturing field Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2006; 291(2): R241 - R244. [Full Text] [PDF]