The development of animal models of persistent pain has advanced our knowledge of the initiation of pain hypersensitivity due to sensitization of peripheral nociceptors and neurons in the medullary and spinal dorsal horns as well as other sites in the central nervous system (CNS). It is now commonly proposed that the initiation of this plasticity and resultant pain amplification is dependent upon activation of peripheral nociceptors. It is assumed that peripheral mechanisms are also responsible for the maintenance of the pain hypersensitivity, though the findings in this area are less compelling. Recent findings suggest that behavioral hyperalgesia following injury persists despite a reduction in peripheral neuronal activity suggesting that peripheral drive may be necessary but not sufficient for the maintenance of pain hypersensitivity after injury. The primary aim of this proposal is to study the mechanisms that underlie the maintenance of pain amplification after injury and to determine whether there are CNS mechanisms that participate in pain chronicity and how persistent pain emerges from the more acute stage after injury. Current animal models are not entirely adequate for the study of the chronicity and maintenance of pain hypersensitivity. We have developed two new models in the trigeminal system: a tendomyositis model of the masseter muscle and a neuropathic pain model of the infraorbital nerve. Both models exhibit long-term hyperalgesia/allodynia that is constant and lasts for months, and the inflammation due to the surgical procedure can be separated with the use of long-duration local anesthetics. Our major hypothesis is that tissue and nerve injury in the orofacial region can lead to the maintenance of secondary hyperalgesia that involves the activation CNS descending mechanisms and is less dependent on the peripheral drive associated with the injured target. The following Specific Aims will test these hypotheses using multidisciplinary approaches. #1: Test the hypothesis that the maintenance of long-term hyperalgesia after injury involves an attenuation of peripheral afferent drive and a transition to central mechanisms. #2: Test the hypothesis that the maintenance of long-term hyperalgesia is dependent upon an enhancement of descending facilitatory or a reduction of descending inhibitory inputs. #3: Test the hypothesis that the maintenance of long-term hyperalgesia is dependent upon an enhancement of descending facilitatory drive involving activation of trigeminal non-neural glial cells and their release of cytokines. #4: Test the hypothesis that the maintenance of long-term hyperalgesia is dependent upon an enhancement of descending facilitatory drive that involves shifts in the anionic reversal potential of trigeminal GABA-responsive neurons and a reduction in GABAA-induced inhibitory tone. #5: Test the hypothesis that the maintenance of long-term mechanical hyperalgesia is dependent upon rostral ventromedial medulla activation of a trigeminal brain stem interactive signaling cascade of 5-HT3, GABAA and NMDA receptors as well as glia and cytokines.

Public Health Relevance

The major goal of the proposed research is to study the central nervous system mechanisms that account for the chronicity of persistent orofacial pain after tissue or nerve injury. Although it is now commonly proposed that the initiation of injury-induced neural plasticity and resultant pain amplification is dependent upon activation of peripheral nociceptors, it is unclear whether peripheral mechanisms are also responsible for the maintenance and chronicity of pain hypersensitivity and how persistent pain emerges from the more acute stage after injury. Our findings will lead to a transformative shift in the search for unique treatment approaches for persistent pain.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Research Project (R01)
Project #
5R01DE021804-03
Application #
8420543
Study Section
Special Emphasis Panel (ZDE1-VH (02))
Program Officer
Kusiak, John W
Project Start
2011-04-04
Project End
2016-02-28
Budget Start
2013-03-01
Budget End
2014-02-28
Support Year
3
Fiscal Year
2013
Total Cost
$614,001
Indirect Cost
$204,667
Name
University of Maryland Baltimore
Department
Other Basic Sciences
Type
Schools of Dentistry
DUNS #
188435911
City
Baltimore
State
MD
Country
United States
Zip Code
21201
Guo, Wei; Imai, Satoshi; Yang, Jia-Le et al. (2018) NF-KappaB Pathway Is Involved in Bone Marrow Stromal Cell-Produced Pain Relief. Front Integr Neurosci 12:49
Guo, Wei; Imai, Satoshi; Yang, Jia-Le et al. (2017) In vivo immune interactions of multipotent stromal cells underlie their long-lasting pain-relieving effect. Sci Rep 7:10107
Castro, Alberto; Li, Ying; Raver, Charles et al. (2017) Neuropathic pain after chronic nerve constriction may not correlate with chloride dysregulation in mouse trigeminal nucleus caudalis neurons. Pain 158:1366-1372
Guo, Wei; Chu, Yu-Xia; Imai, Satoshi et al. (2016) Further observations on the behavioral and neural effects of bone marrow stromal cells in rodent pain models. Mol Pain 12:
Bai, Guang; Ren, Ke; Dubner, Ronald (2015) Epigenetic regulation of persistent pain. Transl Res 165:177-99
Guo, Wei; Imai, Satoshi; Dubner, Ronald et al. (2014) Multipotent stromal cells for arthritic joint pain therapy and beyond. Pain Manag 4:153-62
Guo, Wei; Miyoshi, Kan; Dubner, Ronald et al. (2014) Spinal 5-HT3 receptors mediate descending facilitation and contribute to behavioral hypersensitivity via a reciprocal neuron-glial signaling cascade. Mol Pain 10:35
Kim, Yu Shin; Chu, Yuxia; Han, Liang et al. (2014) Central terminal sensitization of TRPV1 by descending serotonergic facilitation modulates chronic pain. Neuron 81:873-887
Zhang, R-X; Ren, K; Dubner, R (2013) Osteoarthritis pain mechanisms: basic studies in animal models. Osteoarthritis Cartilage 21:1308-15
Okubo, Masamichi; Castro, Alberto; Guo, Wei et al. (2013) Transition to persistent orofacial pain after nerve injury involves supraspinal serotonin mechanisms. J Neurosci 33:5152-61

Showing the most recent 10 out of 12 publications