Modulation of temporomandibular joint nociception and inflammation in male rats after administering a physiological concentration of 17β-oestradiol
Article first published online: 19 JUN 2012
© 2012 European Federation of International Association for the Study of Pain Chapters
European Journal of Pain
Volume 17, Issue 2, pages 174–184, February 2013
How to Cite
Kramer, P.R. and Bellinger, L.L. (2013), Modulation of temporomandibular joint nociception and inflammation in male rats after administering a physiological concentration of 17β-oestradiol. European Journal of Pain, 17: 174–184. doi: 10.1002/j.1532-2149.2012.00183.x
This study was funded through NIH/NIDCR grants DE016059 to LLB and DE15372 to PRK.
Conflicts of interest
- Issue published online: 9 JAN 2013
- Article first published online: 19 JUN 2012
- Manuscript Accepted: 17 MAY 2012
- NIH/NIDCR. Grant Numbers: DE016059, DE15372
Previous studies have shown 17β-estradiol will reduce temporomandibular joint (TMJ) inflammation and hypersensitivity in female rats. Although male rats contain significant amounts of oestradiol, it was unknown whether a physiological concentration of 17β-estradiol would attenuate male TMJ inflammation and nociception.
Intact and castrated rats were given a physiological concentration of oestradiol to examine first, if oestradiol will affect male TMJ nociception/inflammation and, second, if administration of oestradiol would act synergistically with endogenous male hormones to attenuate TMJ nociception. The hormonally treated rats were given TMJ injections of complete Freund's adjuvant (CFA) and then nociception was measured using a validated method in which a lengthening in meal duration is directly correlated to the intensity of deep TMJ nociception. Inflammation was assayed by quantitating pro-inflammatory gene expression.
Meal duration was significantly lengthened after TMJ CFA injection and this lengthening was significantly attenuated in the castrated but not intact males after administering a physiological concentration of oestradiol. A physiological concentration of 17β-estradiol also significantly increased IL-6 expression in the inflamed TMJ of castrated males while 17β-estradiol did not alter IL-1β, CXCL2 and CCL20 expression. Castration increased pro-inflammatory mediators IL-6, IL-1β and CXCL2 suggesting male sex hormones were anti-inflammatory. Calcitonin gene-related peptide in the trigeminal ganglia was unchanged.
Similar to females, male rats with TMJ inflammation showed a reduced nociceptive response after treatment with a physiological concentration of oestradiol suggesting the effects of oestradiol treatment were not constrained by organizational processes in the males.