Preoperative inflammatory pain exacerbates postoperative pain and neurocognitive impairment.

AIMS: Many studies have shown that postoperative pain aggravates perioperative neurocognitive disorder (PND). In this study we aimed to clarify the effect of preoperative inflammatory pain on postoperative pain and cognitive function. METHODS: We established the inflammatory pain model by injected complete freund adjuvant (CFA) and the PND model by tibial fracture surgery in 14- month-old C57BL/6 mice. The paw withdrawal threshold and body weight of the mice were measured 7 days before surgery and 3 days after surgery. On the third postoperative day, mice were subjected to behavioral testing or sacrificed to collect brain tissue. RESULTS: The result shows that CFA exacerbated postoperative pain and cognitive dysfunction in mice, enhanced surgery-induced activation of microglia and astrocytes in the hippocampus, and increased surgery-induced the overexpression of IL-1β, IL-6, and TNF-α, as well as aggravated the decreased expression of α7nAChR and the overexpression of HMGB1 in the hippocampus induced by surgery. CONCLUSION: Our study shows that preoperative inflammatory pain further aggravates postoperative pain and neurocognitive dysfunction in aged rats, and the mechanism may be related to neuroinflammation caused by α7nAChR-mediated CAP dysfunction and high release of HMGB1.