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Pain Research and Treatment
Volume 2010, Article ID 949027, 7 pages
http://dx.doi.org/10.1155/2010/949027
Research Article

Relationships between Irritable Bowel Syndrome Pain, Skin Temperature Indices of Autonomic Dysregulation, and Sensitivity to Thermal Cutaneous Stimulation

1Department of Prosthodontics, College of Dentistry, University of Florida, 1600 SW Archer Rd, D11-006 Gainesville, FL 32610, USA
2Tufts University School of Medicine, Boston, MA 02111, USA
3Department of Community Dentistry and Behavioral Science, College of Dentistry, University of Florida, 1600 SW Archer Rd, D11-006 Gainesville, FL 32610, USA
4Community Health & Family Medicine, University of Florida, Gainesville, FL 32610, USA
5Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL 32610, USA

Received 17 February 2010; Accepted 3 June 2010

Academic Editor: Donald A. Simone

Copyright © 2010 Fong Wong et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This study evaluated relationships between irritable bowel syndrome (IBS) pain, sympathetic dysregulation, and thermal pain sensitivity. Eight female patients with diarrhea-predominant IBS and ten healthy female controls were tested for sensitivity to thermal stimulation of the left palm. A new method of response-dependent thermal stimulation was used to maintain pain intensity at a predetermined level (35%) by adjusting thermal stimulus intensity as a function of pain ratings. Clinical pain levels were assessed prior to each testing session. Skin temperatures were recorded before and after pain sensitivity testing. The temperature of palmar skin dropped (1.5 C ) when the corresponding location on the opposite hand of control subjects was subjected to prolonged thermal stimulation, but this response was absent for IBS pain patients. The patients also required significantly lower stimulus temperatures than controls to maintain a 35% pain rating. Baseline skin temperatures of patients were significantly correlated with thermode temperatures required to maintain 35% pain ratings. IBS pain intensity was not significantly correlated with skin temperature or pain sensitivity. The method of response-dependent stimulation revealed thermal hyperalgesia and increased sympathetic tone for chronic pain patients, relative to controls. Similarly, a significant correlation between resting skin temperatures and thermal pain sensitivity for IBS but not control subjects indicates that tonic sympathetic activation and a thermal hyperalgesia were generated by the chronic presence of visceral pain. However, lack of a significant relationship between sympathetic tone and ratings of IBS pain casts doubt on propositions that the magnitude of IBS pain is determined by psychological stress.