• Junad Khan, Vanessa Benavent, Olga A Korczeniewska, Rafael Benoliel, and Eli Eliav.
• Center for Orofacial Pain, Department of Diagnostic Sciences, Rutgers School of Dental Medicine, Newark, New Jersey.
• J Pain. 2014 Nov 1;15(11):1179-89.

UnlabelledThe aim of this study was to investigate the predictive value of exercise-induced hypoalgesia (EIH) profile on pain intensity induced by nerve injury in a rat model. EIH was tested by evaluating the percentage of withdrawal responses to a train of 30 mechanical stimuli on the hind paw before and after 180 seconds of exercise on a rotating rod. The rats were grouped into low, medium, and high EIH based on their reduction in the percentage of withdrawal responses before and after exercise. Rats from each group then underwent left sciatic nerve constriction injury. Mechanical allodynia, mechanical hyperalgesia, and heat allodynia were assessed in the affected and contralateral hind paws prior to and 3 and 7 days following the procedure. The low EIH rats demonstrated increased hypersensitivity at baseline and developed significantly more severe heat allodynia, mechanical allodynia, and hyperalgesia 3 and 7 days following the injury compared to the medium and high EIH rats. Moreover, the low EIH rats developed contralateral heat allodynia following the injury. The EIH of habituated and nonhabituated rats was compared to study the role of stress on the hypoalgesic effect. No significant differences were found between the habituated and nonhabituated rats at baseline and 1 and 5 minutes after the exercise.PerspectiveEIH profile was found to be predictive of pain severity following nerve injury. It may suggest that selected patients with faulty pain modulation are at risk for developing chronic pain following injury or surgical procedures. EIH may represent a preoperative means to detect this predisposition and enable proactive management.Copyright © 2014 American Pain Society. Published by Elsevier Inc. All rights reserved.

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