Chronic Sleep Disturbance Enhances Inflammation and Collagen Production in Neural- and Myofascial Tissues in Uninjured Rats.

Chronic sleep disturbance is postulated to enhance pain and inflammatory responses, although systemic inflammation has been primarily investigated to date. We sought to examine the effects of chronic intermittent sleep disturbance on pain-related behaviors and peripheral forelimb neural- and myofascial tissues in the context of aging. Uninjured young adult and mature female rats (3 mo. and 9-10 mo. of age) were exposed to either normal or disturbed sleep for 9 h/day on 4 d/week (using in-cage environmental stimulation), for 6 weeks. Compared to rats with normal sleep, sleep disturbed rats of both ages displayed: (1) mild declines in grip strength; (2) low-grade elevations in immune cells and collagen in forepaw neural- and myofascial tissues; and (3) higher protein expression of collagen type I, CTGF, and phosphorylated AKT in forearm flexor muscles. Young adult sleep disturbed also showed increased TGF-beta. Mature sleep disturbed rats also displayed low-grade yet greatest forepaw mechanical sensitivity, muscle and serum TNF-α, and peripheral immune cell numbers. These data suggest that chronic intermittent sleep disruption can enhance pain-related behaviors, inflammation, and fibrosis-related changes in peripheral neural- and myofascial tissues in uninjured rats. These effects occurred in both age groups, yet were more pronounced in the older rats.