1985 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Pharmacological Role of Tryptamine in Pain @ University of Minnesota Twin Cities
Our experiments suggest that, not only does the distribution of tryptamine-immunoreactivity differ from that of serotonin, but the injection of tryptamine intrathecally or i.c.v. in rats causes hyperalgesia, rather than analgesia. Inconsistences in the role of serotonin in analgesia, as determined by pharmacologic studies, may result from simultaneous alterations in the activities of both indolemines. The proposed experiments will test the hypothesis that, in spite of their structural similarity, endogenously formed tryptamine and serotonin play opposite roles in the modulation of pain. Changes in tryptaminergic activity may participate in the development of tolerance to narcotic analgesics or in hyperalgesia during withdrawal from opiates. The long-term objective is to determine whether tryptamine in the CNS plays a role in pain or in any action of narcotic analgesics, and not to prove or disprove a transmitter role of tryptamine. The first specific objective is to characterize the distribution of tryptamine-immunoreactivity using immunohistofluorescence and its relation to the concentration and turnover of tryptamine in brain extracts, as measured using high pressure liquid chromatography (HPLC) with fluorometric detection, focusing on areas of known pain-pathways in the CNS. The second specific objective is to differentially manipulate the metabolisms of tryptamine and serotonin (using precursor loading and enzyme inhibitors) in order to correlate changes produced in the concentration or distribution of tryptamine, relative so that of serotonin, with changes in pain-thresholds. The tail-flick, hot plate and flinch jump assays will be used to reflect changes in pain-thresholds in rats. The third specific objective is to determine whether the concentrations or distributions of tryptamine and serotonin in the CNS are differentially affected by manipulations known to affect the activity along pain-pathways, such as acute vs. chronic treatment with narcotics, naloxone-precipitated withdrawal, acute pain produced by electric shock, and chronic pain produced by a polyarthritic condition. This research will provide a better understanding of pain-mechanisms, a necessary prerequisite in the long term development of pain-therapy as well as in the control of tolerance to and withdrawal from narcotics.
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1986 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Excitatory Amino Acids--Role in Pain &Opiod Activity @ University of Minnesota Twin Cities
Electrophysiological studies of cultured dorsal root ganglion (DRG) cells suggest that approximately 80% of DRG neurons utilize excitatory amino acids (EAA) as neurotransmitters. Recently our laboratory has raised a monoclonal antibody specific for fixative-modified glutamate. Using this antibody, immunoreactivity was observed within the spinal trigeminal nucleus (STN), spinal cord dorsal horn and dorsal root ganglia neurons, areas known to be involved in nociception. Based on these preliminary immunohistochemical data and other results from our laboratory showing apparent glutamatergic projections from the STN to the thalamus, we hypothesize that neurons in pathways involved in nociception utilize EAAs as neurotransmitters. Furthermore, their activity may be affected by substances which are known to alter nociception, such as opioids. Our long term goal is to determine whether EAAs play a role in primary afferent and/or centrally projecting fibers involved in pain transmission and whether these EAA pathways are specifically affected by opioid and non-opioid compounds. This goal is defined by the following specific objectives: 1) to characterize the distribution of glutamate- and aspartate-like immunostaining in the DRG and spinal cord, to analyze the relationship between opioid axon terminals and EAA-containing neurons, and to ascertain if spinal EAA-containing neurons project to the thalamus; 2) to compare using HPLC analysis as well as immunostaining, the concentrations of glutamate, aspartate and other EAAs in specific areas of the spinal cord before and after dorsal rhizotomy; 3) to measure the release of EAAs from spinal tissue into CSF following peripheral nerve stimulation and injection of opioid and non-opiate compounds which are known to alter either sensory-perception or EAA activity; 4) to determine the effect of a variety of recently developed EAA-analogs on nociception, as measured by methods which selectively elicit nociception using thermal, mechanical or chemical stimuli. These studies will provide important and novel data on the role of EAAs in the spinal cord and the involvement of sigma opioid agonists in antinociception, perhaps involving blockade of EAA action.
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1987 — 1988 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Excitatory Amino Acids: Role in Pain &Opioid Activity @ University of Minnesota Twin Cities
Electrophysiological studies of cultured dorsal root ganglion (DRG) cells suggest that approximately 80% of DRG neurons utilize excitatory amino acids (EAA) as neurotransmitters. Recently our laboratory has raised a monoclonal antibody specific for fixative-modified glutamate. Using this antibody, immunoreactivity was observed within the spinal trigeminal nucleus (STN), spinal cord dorsal horn and dorsal root ganglia neurons, areas known to be involved in nociception. Based on these preliminary immunohistochemical data and other results from our laboratory showing apparent glutamatergic projections from the STN to the thalamus, we hypothesize that neurons in pathways involved in nociception utilize EAAs as neurotransmitters. Furthermore, their activity may be affected by substances which are known to alter nociception, such as opioids. Our long term goal is to determine whether EAAs play a role in primary afferent and/or centrally projecting fibers involved in pain transmission and whether these EAA pathways are specifically affected by opioid and non-opioid compounds. This goal is defined by the following specific objectives: 1) to characterize the distribution of glutamate- and aspartate-like immunostaining in the DRG and spinal cord, to analyze the relationship between opioid axon terminals and EAA-containing neurons, and to ascertain if spinal EAA-containing neurons project to the thalamus; 2) to compare using HPLC analysis as well as immunostaining, the concentrations of glutamate, aspartate and other EAAs in specific areas of the spinal cord before and after dorsal rhizotomy; 3) to measure the release of EAAs from spinal tissue into CSF following peripheral nerve stimulation and injection of opioid and non-opiate compounds which are known to alter either sensory-perception or EAA activity; 4) to determine the effect of a variety of recently developed EAA-analogs on nociception, as measured by methods which selectively elicit nociception using thermal, mechanical or chemical stimuli. These studies will provide important and novel data on the role of EAAs in the spinal cord and the involvement of sigma opioid agonists in antinociception, perhaps involving blockade of EAA action.
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1987 — 1989 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Opoids &Desensitization to Substance P in the Spinal @ University of Minnesota Twin Cities
pain threshold; neuropharmacology; spinal cord; analgesics; opiate alkaloid; behavioral medicine; biotransformation; drug interactions; naloxone; drug metabolism; drug administration routes; drug addiction antagonist; protease inhibitor; radiotracer; autoradiography; high performance liquid chromatography;
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1988 — 1992 |
Larson, Alice A |
K02Activity Code Description: Undocumented code - click on the grant title for more information. |
Nociceptive Transmission in the Spinal Cord @ University of Minnesota Twin Cities
The long term goal of this plan is to clarify, in discrete areas of the spinal cord, the interrelationships of transmitter candidates that appear to be involved in pain and analgesia. Substance P (SP) and excitatory amino acids (EAA) appear to participate in pain- transmission and endogenous analgesia. We are currently using a combination of biochemical, anatomical and behavioral approaches to focus on the roles of these compounds in pain and analgesia. The goal of our present work on SP is to determine the mechanism of desensitization to SP. Analgesic drugs may then be designed which mimic or exploit such desensitization. The specific objectives are to correlate changes in desensitization to SP with changes in the concentration of specific SP metabolites and in SP binding. The goals of our EAA studies are to elucidate the role that EAAs play in transmission along primary afferent and/or centrally projecting fibers involved in pain-transmission and to determine whether such EAA neurotransmission is specifically affected by opioid and non-opioid compounds. The specific objectives are to characterize the distribution (immunostaining), concentration (HPLC) and release (potassium-evoked changes in extracellular fluid) of EAAs in areas of the CNS presumed to be involved in pain transmission and their relation to endogenously occurring antinociceptive mechanisms. Our long term plans are to extend our present research examining transmitter release during nociceptive and antinoceptive processing in discrete areas of the spinal cord. The system currently in use in our laboratory involves the implantation of a semipermeable dialysis tubing through the spinal cord and provides us with an excellent method of examining extracellular fluid as a reflection of transmitter release. Compounds or mainpulations presumed to alter pain or transmitter release can then be tested in vivo. While our present studies focus on EAA release in the rat spinal cord, our long term goal is to use larger species, such as cat, to examine the release of not only EAAs but also that of SP, SP metabolites and serotonin from even more discrete regions and from any two distinct areas simultaneously. The experiments described will integrate our current research programs and expand their scope. This research will contribute to our understanding of neurotransmission by SP and EAAs.
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1989 — 1991 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Excitatory Amino Acids--Role in Pain &Opioid Activity @ University of Minnesota Twin Cities
The long term goal is to compare nociceptive processing by excitatory amino acids (EAAs) and substance P (SP) in the spinal cord. The proposed experiments will test the hypothesis that EAAs & SP in the spinal cord are contained in and released from distinct groups of primary afferents, cause distinct nociceptive characteristics which are inhibited by compounds acting at unique receptor subtypes. Sp. Aim 1. Anatomical double labeling procedures will be utilized to determine whether anterogradely labeled primary afferent terminal contain glutamate (glu)- like immunoreactivity, whether these terminal are surrounded by astrocytic processes containing glu dehydrogenase or glutamine synthetase, and whether glu immunoreactive fibers and terminal co-contain CGRP or SP. Sp. Aim 2. We will use in vivo microdialysis in the spinal cords of conscious, freely moving rats to study the release of presumably nociceptive [EEA & SP] and antinociceptive [5HT & NE] transmitters released in response to formalin-injection and in response to specific opioid receptor activity. We will then administer fluorogold, a retrograde tracer, directly into the cannula for combined retrograde tracing-immunocytochemical procedures to identify neurons that may contribute to release. Sp. Aim 3. Microdialysis will be used in anesthetized rats to compare release of EAAs & SP after electrical stimulation of primary afferents at intensities that activate large and large plus small diameter fibers. Sp. Aim 4. Using in vivo microdialysis in spinal cords of freely moving animals together with pharmacologic manipulation of NE, 5HT, SP and EAA activity, we will determine whether EAAs & SP differentially activate distinct descending pathways and whether activity at specific monoamine receptor subtypes differentially alters SP or EAA release. Sp. Aim 5. We will measure autonomic and nociceptive responses in acute and chronic models of allodynia to examine the involvement of EAAs, SP and glycine (gly) in this model of pain. We will compare transmitter release in rats with allodynia to release after formalin-injection (Aim 2). Sp. Aim 6. EAAs, gly & strychnine will be iontophoresed onto antidromically identified nociceptive dorsal horn neurons and determine the effect of gly on NMDA- and SP-induced depolarization in control rats and in formalin & allodynia-models of chronic pain to determine whether gly potentiates NMDA in nociceptive pathways and whether the interaction between gly & NMDA is different in these 2 models of chronic pain.
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1990 — 1992 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Opioids &Desensitization to Substance P Inspinal Cord @ University of Minnesota Twin Cities
Repeated intrathecal (i.t.) injections of SP in mice leads to a "desensitization" or decreased behavioral response to SP. Our research suggests that desensitization to the behavioral effects of SP is dependent on an accumulation of N-terminal metabolic fragments of SP and excitatory amino acid (EAA) activity. The experiments proposed will further test the hypothesis that N-terminal metabolites of SP regulate pain perception by inhibiting the release as well as the effect of nociceptive transmitters in the spinal cord, in part, by a direct interaction with mu-type opioid receptors. Objective 1: We will raise monoclonal antibodies to N-terminal fragments of SP and use them in RIAs and as potential pharmacologic antagonists in vivo to examine the role of SP fragments in the spinal cord. Objective 2: We will assess the ability of SP fragments to regulate the release of SP in the spinal cork by using in vivo microdialysis in the conscious, freely-moving rat to monitor the effects of N- and C-terminal fragments of SP on KCI- or nociception-induced changes in the concentrations of SP and EAAs. We will establish the role of opiate receptors in this regulation using selective opiate antagonists. Objective 3: We will continue to characterize the binding site(s) on N-terminal SP fragment in the CNS by determining whether SP metabolites interact exclusively with mu1-type opioid binding sites or whether they also interact with distinct site(s), unique from that of either mu1 or SP. Binding will then be examined in mice after an intraplantar injection of Freund's adjuvant to determine whether pain result from a change in SP N- terminal binding. Objective 4: We will examine N-terminal SP binding using autoradiographic techniques to see if binding is differentially localized within the brain and spinal cord and to quantify the density of binding sites, especially in areas thought to be involved in pain-transmission and areas known to contain SP(1-11)-like immunoreactivity. Objective 5: We will determine whether desensitization to the behavioral effects of i.t. SP or N-methyl-D-aspartate (NMDA) or sensitization to kainate or quisqualate alters nociception using the hot plate and writhing assays. Opiate antagonists will be used to determine whether opioids of their receptor are involved in any changes detected.
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1992 — 1993 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Excitatory Amino Acids: Role in Pain and Opioid Activity @ University of Minnesota Twin Cities
Several lines of evidence suggest that substance P (SP) and excitatory amino acids (EAAs) mediate pain transmission at the spinal cord level. Our past studies provide evidence that kainic acid evokes the release of SP from the dorsal spinal cord and this release is, in turn, potentiated by the N-terminal portion of SP. This interaction may reflect a possible mechanism underlying pain transmission and be related to the "wind up" phenomenon observed electrophysiologically. We will test the hypothesis that (1) pain is mediated by the release of both SP and EAAs, and (2) that these two systems interact synergistically. EAAs cause the release of SP from primary afferent C-fibers. SP in turn potentiates the effect of EAAs via the N-terminal portion of SP at a receptor that is unique from that of the neurokinin receptor. The accumulation of SP of N- terminal metabolites during chronic pain alters SP and EAA activity along nociceptive pathways. On the other hand, decreased SP released during chronic opioid administration may lead to changes in SP- and EAA- mediated nociceptive activity that are reflected in opioid withdrawal symptoms. [1] We will use electronmicroscopic techniques together with immunocytochemistry and anterograde labelling to determine whether EAA receptors are located on SP-containing primary afferents. [2} We shall construct dose-response curves for the ability of [D-Pro(2), D- Phr(7)]SP(1-7) (D-SP(1-7)), a SP N-terminal analog that inhibits (3)H- SP(1-7) binding, to inhibit the effects of SP(1-7) on SP- and EAA- induced behavior and on opioid-induced antinociception. [3] We will determine the effect of SP(1-7) on "wind up" and on EAA-induced firing of antidromically identified nociceptive dorsal horn neurons that project to the thalamus. [4] Using in vivo microdialysis of the spinal cord of freely moving rats, we will determine (a) the role of SP(1-7) in EAA-induced release of SP-like immunoreactivity from primary afferent C- fibers, and (b) the role of EAAs and SP(1-7) in noxious stimulation- induced SP release using NMDA, non-NMDA and SP(1-7) antagonists. [5] We will determine whether nociceptive involves a synergistic interaction between SP and EAA receptors by measuring the antinociceptive effects of EAA and SP antagonists.
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1994 — 1996 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Excitatory Amino Acids--Role in Pain and Opioid Activity @ University of Minnesota Twin Cities |
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1999 — 2003 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Neurotrophins and An Animal Model of Fibromyalgia @ University of Minnesota Twin Cities
DESCRIPTION (taken from the application): Fibromyalgia syndrome (FMS) is characterized by pain throughout the body (multifocal) with specific areas that are particularly sensitive to pressure. Primary afferent C-fibers are believed to be important in pain transmission. Some C-fibers contain substance P (SP) and are regulated by nerve growth factor (NGF), while others are characterized by the enzyme thiamine monophosphatase (TMPase) and are supported by glial derived neurotrophic factor (GDNF). Consistent with the hypothesis that C-fibers are involved in FMS, the concentrations of SP and NGF in the CSF of these patients are elevated. What initiates this is not known. C-fibers are depolarized by kainic acid, an excitatory amino acid analog. A single i.p. injection of kainic acid increases TMPase stain in the dorsal spinal cord, suggesting sprouting, and produces a persistent (> 12 weeks) decrease in the intensity of mechanical stimulation required to evoke withdrawal responses in rats similar to the lowered threshold of pressure required to produce pain in patients with FMS. Whether kainic acid produces these effects by increasing GDNF or NGF activity along nociceptive pathways is not known. We will test the hypotheses that the mechanical hyperalgesia produced by kainic acid is caused by enhancement of neurotrophic activity that supports C-fibers (NGF and GDNF) which, in turn, enhances proteins associated with these nociceptive pathways. To accomplish this, we will use a rat model (1) to characterize the effect of kainic acid on mechanical nociception using von Frey fibers and grip force; (2) determine whether the content of NGF and GDNF (immunoreactivity) or its receptors (binding) are affected by treatment with kainic acid; (3) to determine whether the application of exogenous NGF or GDNF is sufficient to increase mechanical nociception; (4) to determine whether there is a change in the density of SP- or NkiR immunoreactivity and/or the density of TMPase in the spinal cord or DRG after injection of NGF or GDNF; and (5) to determine whether injection of kainic acid alters either the density of SP- or NKiR-immunoreactivity in the spinal cord or DRG, in a fashion that correlates with its ability to induce mechanical hyperalgesia. These studies will determine whether kainic acid alters neurotrophic activity and nociceptive responses in the rat in a fashion that is consistent with the biochemical and sensory characteristics of FMS. If kainic acid activity proves to be a useful model of FMS, therapeutic options may be more readily developed for this disease.
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2009 — 2011 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Urocortin &Musculoskeletal Hyperalgesia @ University of Minnesota
DESCRIPTION (provided by applicant): There is a high degree of co-morbidity between painful musculoskeletal disorders, such as fibromyalgia, and various painful abdominal disorders, such as irritable bowel syndrome and interstitial cystitis. These conditions are exacerbated by stress, and, like stress, gastrointestinal disorders are associated with increases in corticotropin-releasing factor (CRF) and urocortins. Many of urocortins'effects match symptoms of fibromyalgia syndrome in particular. First, the literature indicates that urocortins attenuate abdominal nociception and our preliminary data suggest that urocortins simultaneously induce musculoskeletal hyperalgesia. Second, urocortins inhibit circulating glucocorticoids, consistent with a diminished diurnal rhythm and attenuated cortisol response to stress in patients with fibromyalgia. Third, there are sex differences in the regulation of urocortin's synthesis in rodents, consistent with the higher incidence of fibromyalgia in females than males. Finally, our preliminary data suggest that tolerance does not develop to the hyperalgesic effect of urocortins, thus, repeated surges in their release may persistently induce hyperalgesia, consistent with the chronic nature of fibromyalgia. Because urocortins recapitulate many characteristics of fibromyalgia and are elevated in abdominal disorders, we hypothesize that increased activity of urocortins produces musculoskeletal mechanical hyperalgesia. To test this, we will determine whether urocortin II in mice models chronically painful conditions in humans in terms of gender sensitivity, duration, and pharmacologic sensitivity. We will 1) characterize the receptor population responsible for the hyperalgesic effects of urocortins, 2) assess the sensitivity of urocortin-induced hyperalgesia to antinociceptive compounds, and 3) investigate whether mice develop tolerance to urocortins or are capable of long-term hyperalgesic activity. Our studies will provide important information about a new biochemical mechanism of hyperalgesia, and they will be translational in the following ways: if urocortins produce widespread mechanical hyperalgesia, similar to symptoms of fibromyalgia: 1) this will justify studies in patients, 2), these data will define a possible causal relationship between stress, chronic widespread musculoskeletal pain, and painful abdominal disorders, and 3) these studies will provide a model to test clinical interventions that relieve widespread musculoskeletal pain in humans. PUBLIC HEALTH RELEVANCE Our studies will provide important mechanistic information about the role of urocortins in chronic musculoskeletal pain and potentially the role of urocortins in the pain associated with fibromyalgia. Our results will have three broad benefits to translational research in the area of pain: first, if urocortin II recapitulates the symptoms of fibromyalgia, this will support the possibility that urocortins contribute to symptoms of fibromyalgia and will justify studies in patients with this disorder;second, these data will deepen our understanding of the relationship between painful abdominal disorders and chronic musculoskeletal pain;and third, the effects of urocortin II in mice will provide a model that can be used to test potential therapies and clinical interventions that relieve widespread musculoskeletal pain in humans.
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2012 — 2013 |
Larson, Alice A |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Urocortin & Musculoskeletal Hyperalgesia @ University of Minnesota
DESCRIPTION (provided by applicant): There is a high degree of co-morbidity between painful musculoskeletal disorders, such as fibromyalgia, and various painful abdominal disorders, such as irritable bowel syndrome and interstitial cystitis. These conditions are exacerbated by stress, and, like stress, gastrointestinal disorders are associated with increases in corticotropin-releasing factor (CRF) and urocortins. Many of urocortins' effects match symptoms of fibromyalgia syndrome in particular. First, the literature indicates that urocortins attenuate abdominal nociception and our preliminary data suggest that urocortins simultaneously induce musculoskeletal hyperalgesia. Second, urocortins inhibit circulating glucocorticoids, consistent with a diminished diurnal rhythm and attenuated cortisol response to stress in patients with fibromyalgia. Third, there are sex differences in the regulation of urocortin's synthesis in rodents, consistent with the higher incidence of fibromyalgia in females than males. Finally, our preliminary data suggest that tolerance does not develop to the hyperalgesic effect of urocortins, thus, repeated surges in their release may persistently induce hyperalgesia, consistent with the chronic nature of fibromyalgia. Because urocortins recapitulate many characteristics of fibromyalgia and are elevated in abdominal disorders, we hypothesize that increased activity of urocortins produces musculoskeletal mechanical hyperalgesia. To test this, we will determine whether urocortin II in mice models chronically painful conditions in humans in terms of gender sensitivity, duration, and pharmacologic sensitivity. We will 1) characterize the receptor population responsible for the hyperalgesic effects of urocortins, 2) assess the sensitivity of urocortin-induced hyperalgesia to antinociceptive compounds, and 3) investigate whether mice develop tolerance to urocortins or are capable of long-term hyperalgesic activity. Our studies will provide important information about a new biochemical mechanism of hyperalgesia, and they will be translational in the following ways: if urocortins produce widespread mechanical hyperalgesia, similar to symptoms of fibromyalgia: 1) this will justify studies in patients, 2), these data will define a possible causal relationship between stress, chronic widespread musculoskeletal pain, and painful abdominal disorders, and 3) these studies will provide a model to test clinical interventions that relieve widespread musculoskeletal pain in humans. PUBLIC HEALTH RELEVANCE Our studies will provide important mechanistic information about the role of urocortins in chronic musculoskeletal pain and potentially the role of urocortins in the pain associated with fibromyalgia. Our results will have three broad benefits to translational research in the area of pain: first, if urocortin II recapitulates the symptoms of fibromyalgia, this will support the possibility that urocortins contribute to symptoms of fibromyalgia and will justify studies in patients with this disorder; second, these data will deepen our understanding of the relationship between painful abdominal disorders and chronic musculoskeletal pain; and third, the effects of urocortin II in mice will provide a model that can be used to test potential therapies and clinical interventions that relieve widespread musculoskeletal pain in humans.
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