59. Afferent immune-to-brain communication in human pain: A brain imaging study on experimental endotoxemia in a visceral pain model

Abstract

We previously showed that experimentally-induced endotoxemia leads to visceral hyperalgesia in healthy males (Benson et al., Pain 2012;153(4):794–9). However, it remains unclear whether and to what extent these effects are mirrored by altered pain processing within the brain. Hence, we designed a follow-up study to analyze behavioral and neural responses to visceral stimuli using functional magnetic resonance imaging (fMRI) and present preliminary analyses herein. Implementing a randomized, placebo-controlled design, healthy males received an intravenous injection of either lipopolysaccharide (LPS group; 0.4 ng/kg) or saline (control group). Visceral sensory and pain thresholds were assessed using pressure-controlled rectal distensions at baseline (prior to injection) and 3 h post injection. Additionally, subjective painfulness of rectal stimuli delivered during scanning was evaluated online using visual analogue scales. Blood samples were collected before and up to 6 h post injection to characterize changes in relevant immune parameters. LPS administration expectedly led to increases in circulating TNF-alpha, IL-6, and body temperature (all p