Social stress, epigenetic changes and pain.

Aims Bullying is a prevalent issue in society, with adverse effects ranging from psychological symptoms to somatic ailments like chronic pain. The purpose of this study was to generate new knowledge about the underlying mechanisms behind this association. Using an animal model, we investigated the changes in microRNA expression in plasma, in the pituitary gland and the adrenal gland following social stress. Methods A resident-intruder paradigm where male Sprague Dawley rats (intruders) were exposed to male Long Evans rats (resident) 1 h daily for a week was used. Bodyweight was measured and blood samples were collected throughout the experiment. Changes in plasma microRNA expression was determined by qPCR. Results Rats exposed to social stress showed reduced weight gain compared to controls. Preliminary results suggested that social stress increased the plasma expression of miR-146a-5p, miR-30c- 5p and miR-223-3p. Conclusions The data showed that social stress gives reduced weight gain and increased expression of several circulating microRNAs. How this affects the development of persistent pain remains to be investigated.