• S Benson, V Kotsis, C Rosenberger, U Bingel, M Forsting, M Schedlowski, E R Gizewski, and S Elsenbruch.
• Institute of Medical Psychology & Behavioral Immunobiology, University Hospital of Essen, University of Duisburg-Essen, Essen, Germany.
• Eur J Pain. 2012 Mar 1;16(3):349-58.

IntroductionWe assessed sex differences in behavioural and neural responses to rectal pain stimuli in healthy subjects.MethodsIn age- and body mass index-matched healthy subjects (n = 15 men, 15 women), rectal sensory and pain thresholds were assessed with a pressure-controlled barostat device. The blood oxygen level-dependent response during cued anticipation and painful stimulation was measured using functional magnetic resonance imaging (fMRI). Retrospective pain evaluations were accomplished with visual analogue scales. For fMRI data, region-of-interest (ROI) analyses and additional whole-brain analyses were carried out.ResultsThere were no sex differences in rectal thresholds or pain ratings. ROI analyses revealed comparable distension-induced activation of the thalamus, somatosensory cortex, insula and dorsolateral prefrontal cortex (DLPFC). Only in additional whole-brain analyses did we find increased activation in women in DLPFC and middle temporal gyrus during pain anticipation and in the cerebellum and medial frontal gyrus during pain. A significant inverse association between rectal pain threshold and distension-induced activation in virtually all ROIs was found in women. In men, pain thresholds and insula activation were positively correlated, as were pain ratings and anterior cingulate cortex activation.ConclusionsHealthy men and women do not differ in behavioural measures of visceral pain sensitivity. The pattern of neural activation is comparable in the majority of pain-processing brain regions, although women may differ in the activation of DLPFC which could reflect sex differences in cognitive-emotional pain regulation. Women with lower pain thresholds showed greater neural responses, which may be relevant in the pathophysiology of visceral hyperalgesia.© 2011 European Federation of International Association for the Study of Pain Chapters.

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