Regular physical activity (exercise) can reduce pain in people with chronic musculoskeletal pain;whereas, unaccustomed exercise can exacerbate pain. This apparent dichotomy in pain response to physical activity is poorly understood, making exercise prescription for individuals with pain challenging. In sedentary mice, a single bout of exercise enhances the nociceptive response to subthreshold muscle stimuli (pH 5.0 saline);this enhancement is prevented by 5 days of voluntary running wheel activity. Further, in mice the development of chronic muscle pain, induced by repeated intramuscular acid (pH 4.0) injections, is prevented by 8 weeks of voluntary running wheel activity. Regular exercise is believed to activate central inhibitory pathways that produce an opioid-mediated analgesia;the rostral ventromedial medulla (RVM) is a key central nucleus in opioid-induced analgesia. However, little data is available to support a role for central opioid mechanisms in exercise-induced analgesia, particularly in conditions of chronic pain. Our preliminary data show that the analgesic effect of 8 weeks of running wheel activity (i.e. regular exercise) is reversed by systemic blockade of opioid receptors, establishing that opioids are important in regular exercise-induced analgesia. Our preliminary data show that there is increased p-NR1 (NMDA receptor) in the RVM in sedentary animals after a single-bout of exercise or induction chronic muscle pain. These increases in p-NR1 in the RVM, however, are prevented by regular exercise, suggesting that p-NR1 is modulated by mechanisms activated by exercise. These data led to our central hypothesis that regular exercise enhances activation of central inhibitory pathways that utilize endogenous opioids to modulate p-NR1 in the RVM. We will address our central aim through the following specific aims.
Aim 1 will determine if regular physical activity (running wheel exercise) prevents the development of chronic muscle pain, and if such an effect is associated with motor and autonomic responses that might occur in response to exercise training and activation of the RVM.
Aim 2 will determine if regular physical activity prevents the development of hyperalgesia by activation of opioid receptors. We will test this by pharmacological and genetic manipulation of opioid receptors.
Aim 3 will explore the neural circuitry involved in the enhanced nociception to unaccustomed physical activity and the analgesia produced by regular physical activity. We will establish if NMDA receptors are located on and modulate pain facilitatory """"""""ON cells"""""""" through m- opioid receptors (MOR), and if these cells project to the spinal cord. These studies will be the first to evaluate the effects of regula exercise on hyperalgesia and the underlying mechanisms that mediate these effects. Understanding these interactions will give us a better understanding of the underlying neurobiology to improve the overall management of people with chronic musculoskeletal pain, and prevention of development of chronic pain.

Public Health Relevance

Regular physical activity (exercise) can reduce pain in people with chronic musculoskeletal pain;whereas, unaccustomed exercise can exacerbate pain. This proposal aims to examine the central mechanisms underlying the effects of exercise on pain using recently developed animal models of exercise-induced pain, and exercise-induced analgesia. Understanding these interactions will give us a better understanding of the underlying neurobiology to improve the overall management of people with chronic musculoskeletal pain, and prevention of development of chronic pain.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR061371-02
Application #
8456081
Study Section
Somatosensory and Chemosensory Systems Study Section (SCS)
Program Officer
Serrate-Sztein, Susana
Project Start
2012-04-06
Project End
2017-03-31
Budget Start
2013-04-01
Budget End
2014-03-31
Support Year
2
Fiscal Year
2013
Total Cost
$410,877
Indirect Cost
$138,773
Name
University of Iowa
Department
Other Health Professions
Type
Schools of Medicine
DUNS #
062761671
City
Iowa City
State
IA
Country
United States
Zip Code
52242
Sluka, Kathleen A; Frey-Law, Laura; Hoeger Bement, Marie (2018) Exercise-induced pain and analgesia? Underlying mechanisms and clinical translation. Pain 159 Suppl 1:S91-S97
Chimenti, Ruth L; Frey-Law, Laura A; Sluka, Kathleen A (2018) A Mechanism-Based Approach to Physical Therapist Management of Pain. Phys Ther 98:302-314
Bobinski, Franciane; Teixeira, Juliana Maia; Sluka, Kathleen Anne et al. (2018) Interleukin-4 mediates the analgesia produced by low-intensity exercise in mice with neuropathic pain. Pain 159:437-450
Teixeira, Juliana Maia; Bobinski, Franciane; Parada, Carlos Amílcar et al. (2017) P2X3 and P2X2/3 Receptors Play a Crucial Role in Articular Hyperalgesia Development Through Inflammatory Mechanisms in the Knee Joint Experimental Synovitis. Mol Neurobiol 54:6174-6186
Law, Laura Frey; Sluka, Kathleen A (2017) How does physical activity modulate pain? Pain 158:369-370
Lima, Lucas V; DeSantana, Josimari M; Rasmussen, Lynn A et al. (2017) Short-duration physical activity prevents the development of activity-induced hyperalgesia through opioid and serotoninergic mechanisms. Pain 158:1697-1710
Gong, Wei-Yi; Abdelhamid, Ramy E; Carvalho, Carolina S et al. (2016) Resident Macrophages in Muscle Contribute to Development of Hyperalgesia in a Mouse Model of Noninflammatory Muscle Pain. J Pain 17:1081-1094
Sabharwal, Rasna; Rasmussen, Lynn; Sluka, Kathleen A et al. (2016) Exercise prevents development of autonomic dysregulation and hyperalgesia in a mouse model of chronic muscle pain. Pain 157:387-98
Sluka, Kathleen A; Clauw, Daniel J (2016) Neurobiology of fibromyalgia and chronic widespread pain. Neuroscience 338:114-129
Leung, Audrey; Gregory, Nicholas S; Allen, Lee-Ann H et al. (2016) Regular physical activity prevents chronic pain by altering resident muscle macrophage phenotype and increasing interleukin-10 in mice. Pain 157:70-9

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