15. No sex differences in endotoxin-mediated hyperalgesia

Abstract

Introduction: Growing evidence supports that immune mechanisms contribute to the pathophysiology of functional pain syndromes. Epidemiologic data demonstrate an increased prevalence of these pain syndromes in women. However, experimental evidence for sex differences in inflammation-mediated hyperalgesia is scarce. This study tested the hypothesis that women show more pronounced visceral and musculoskeletal pain sensitization during an experimentally-induced systemic immune activation. Methods: Healthy men ( n = 13) and women (n = 13) participated in this ongoing, randomized, double-blind crossover study. Subjects received an intravenous injection of 0.4 ng/kg bacterial endotoxin (lipopolysaccharide) or placebo on two separate study days. Pain sensitivity was assessed two hours post-injection with established visceral and musculoskeletal pain models (rectal pain thresholds; pressure pain thresholds). State anxiety (STAI-S) and plasma cytokines (TNF-α, IL-6, IL-8, IL-10) were measured at baseline, and 1, 2, 3, 4, and 6 h post-injection. Results: Endotoxin application led to significant, but comparable increases in plasma cytokines and state anxiety in men and women ( p p