Effects of sleep deprivation on pain-related factors in the temporomandibular joint.

BACKGROUND: The objective of this study was to investigate the effects of experimental sleep deprivation (SD) on the temporomandibular joint (TMJ) in rats by examining pain-related factors and to determine the possible involvement of estrogen and NF (nuclear factor) kappaB signaling in the TMJ synovial membrane. METHODS: The influence of SD, conducted in rats using the modified multiple platform method, was estimated by observing behavioral manifestations and examining changes in serum hormone levels. The morphologic changes of synovial tissue were observed with light microscopy and the serum levels of estrogen were measured by radioimmunoassay. Activation of NF-kappaB in the synovial membrane was examined using an immunofluorescence technique, and the expression levels of interleukin (IL) 1beta, IL-6, tumor necrosis factor alpha, cyclooxygenase 2, and inducible nitric oxide synthase were measured with real-time polymerase chain reaction. RESULTS: The SD group showed evidence of elevated anxiety and stress, and increased plasma levels of estradiol compared with the control group. The activity of NF-kappaB was significantly enhanced and translocation of NF-kappaB p65 was evident in the synovial membrane after SD. The expression of pain-related factors IL-1beta, IL-6, cyclooxygenase-2, tumor necrosis factor alpha, and inducible nitric oxide synthase in the synovial membrane significantly increased after SD. CONCLUSIONS: These results indicate that SD increases serum levels of estrogen and induces alterations in pain-related factors in the TMJ. The NF-kappaB pathway has been associated with the regulation of these inflammatory cytokines and plays an important role in temporomandibular disorders.