Complementary and integrative health therapies in whole person resilience research.

Complementary and integrative health approaches can improve health and well-being, as well as play an important role in disease prevention. The concept of whole person health builds on these concepts by empowering individuals, families, communities, and populations to improve their health in multiple interconnected domains: biological, behavioural, social, and environmental. Research on whole person health involves studies of interconnected biological systems and complex approaches to prevention and treatment. Some of these approaches may involve methods of diagnosis and therapy that differ from those used in conventional Western medicine. Of growing interest is how complementary, integrative, and whole person health approaches contribute to resilience. This brief commentary describes an integrated framework for mapping the connections between various complementary and integrative health therapeutic inputs onto aspects of resilience, including the ability to resist, recover (partially or fully), adapt, and/or grow in response to a following a stressor. The authors present selected examples of research studies supported by the National Institutes of Health that test whether complementary and integrative health approaches can promote some aspect of resilience. We conclude with a discussion of the challenges and opportunities in incorporating the study of resilience in complementary, integrative, and whole person health research.

Biochemical and behavioral effects of decreasing dietary linoleic acid and increasing eicosapentaenoic acid and docosahexaenoic acid in a rat chronic monoarthrits model.

Clinical studies have demonstrated that decreasing linoleic acid (LA) while increasing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in diets evokes an analgesic effect in headache sufferers. We utilized a rat chronic monoarthritis model to determine if these analgesic effects can be reproduced in rats and to and further probe potential analgesic mechanisms. We fed 8 rats a control diet (with fatty acid levels similar to standard US diets) and 8 rats a low LA diet with added EPA and DHA (H3L6 diet) and after 10 weeks, performed a unilateral intraarticular injection of Complete's Freund Adjuvant (CFA). We evaluated thermal and mechanical sensitivity as well as hind paw weight bearing prior to and at 4 and 20 days post CFA injection. At 28 days post CFA injection rats were euthanized and tissue collected. H3L6 diet fed rats had higher concentrations of EPA and DHA, as well as higher concentrations of oxidized lipids derived from these fatty acids, in hind paw and plasma, compared to control fed rats. LA and oxidized LA metabolites were lower in the plasma and hind paw of H3L6 compared to control fed rats. Diet did not affect thermal or mechanical sensitivity, nor did it affect hind paw weight bearing. In conclusion, the H3L6 diet evoked biochemical changes in rats but did not impact pain related behavioral measures in this chronic monoarthritis model.

Pilot study assessing the effect of Fascial Manipulation on fascial densifications and associated pain.

We assessed effectiveness of Fascial Manipulation (FM) in reducing densification thickness and associated acute pain in normal humans. Fascial densifications were identified using palpation and measured with diagnostic ultrasound within self-reported painful somatic regions. Pain intensity ratings were obtained in response to deep palpation of the self-reported painful somatic region before and after a brief FM intervention. Brief FM resulted in reduced densification thickness as well pain intensity. Sex differences were found neither in densification thickness nor pain intensity at any time point. However, a statistically significant positive correlation between densification thickness and pain intensity was observed in females but not males at both pre-FM and post-FM time points. As such, FM may be an effective therapeutic approach for acute pain associated with fascial densifications. While males and females exhibited comparable densification thickness and pain intensity levels at both pre-FM and post-FM time points, only females showed a statistically significant relationship between pain and densification, suggesting that females may be better able to perceive subtle differences in the magnitude of noxious sensory input.

Imaging Modalities in Inflammatory Breast Cancer (IBC) Diagnosis: A Computer-Aided Diagnosis System Using Bilateral Mammography Images.

Inflammatory breast cancer (IBC) is an aggressive type of breast cancer. It leads to a significantly shorter survival than other types of breast cancer in the U.S. The American Joint Committee on Cancer (AJCC) defines the diagnosis based on specific criteria. However, the clinical presentation of IBC in North Africa (Egypt, Morocco, and Tunisia) does not agree, in many cases, with the AJCC criteria. Healthcare providers with expertise in IBC diagnosis are limited because of the rare nature of the disease. This paper reviewed current imaging modalities for IBC diagnosis and proposed a computer-aided diagnosis system using bilateral mammograms for early and improved diagnosis. The National Institute of Cancer in Egypt provided the image dataset consisting of IBC and non-IBC cancer cases. Type 1 and Type 2 fuzzy logic classifiers use the IBC markers that the expert team identified and extracted carefully. As this research is a pioneering work in its field, we focused on breast skin thickening, its percentage, the level of nipple retraction, bilateral breast density asymmetry, and the ratio of the breast density of both breasts in bilateral digital mammogram images. Granulomatous mastitis cases are not included in the dataset. The system's performance is evaluated according to the accuracy, recall, precision, F1 score, and area under the curve. The system achieved accuracy in the range of 92.3-100%.

Innocuous pressure sensation requires A-type afferents but not functional ΡΙΕΖΟ2 channels in humans.

The sensation of pressure allows us to feel sustained compression and body strain. While our understanding of cutaneous touch has grown significantly in recent years, how deep tissue sensations are detected remains less clear. Here, we use quantitative sensory evaluations of patients with rare sensory disorders, as well as nerve blocks in typical individuals, to probe the neural and genetic mechanisms for detecting non-painful pressure. We show that the ability to perceive innocuous pressures is lost when myelinated fiber function is experimentally blocked in healthy volunteers and that two patients lacking Aß fibers are strikingly unable to feel innocuous pressures at all. We find that seven individuals with inherited mutations in the mechanoreceptor PIEZO2 gene, who have major deficits in touch and proprioception, are nearly as good at sensing pressure as healthy control subjects. Together, these data support a role for Aß afferents in pressure sensation and suggest the existence of an unknown molecular pathway for its detection.

Persistent inflammatory pain alters sexually-motivated behavior in male rats.

Urine from pro-œstrus female rodents evokes increased levels of sexually-motivated behaviors in males, including sniffing and scent marking of the urine spot as well as activation of brain reward regions. Stressors such as social defeat can adversely impact urine scent marking behavior in male rodents, an effect that can be mitigated with anti-depressant drugs. Persistent pain is also known to be a potent stressor, producing elevated levels of plasma corticosterone as well as reduced sucrose preference and reduced social interaction. However, the effect of persistent pain on sexually-motivated behavior is unknown. Here, we compared urine scent marking behavior in male rats for up to 3 weeks following intra-articular injection of Complete Freund's Adjuvant (CFA) or sham injection. CFA-injected rats exhibited profound and ongoing deficits in static weight bearing capacity. CFA-induced persistent inflammatory pain increased plasma corticosterone levels and reduced urine scent marking behavior in male rats. Moreover, while the vast majority of injured rats showed decreased urine scent marking preference for the pro-œstrus female urine spot, male rats with higher baseline scent marking preference also exhibited higher post-injury scent marking preference, more sniffing behavior and lower levels of plasma corticosterone, compared to those with lower baseline scent marking preference. Overall, scent marking behavior may be an ethologically relevant behavioral predictor of persistent pain-induced stress in rats, representing a novel translational approach to understanding chronic pain comorbidities.

Prevalence and Profile of High-Impact Chronic Pain in the United States.

The multidimensional nature of chronic pain is not reflected by definitions based solely on pain duration, resulting in high prevalence estimates limiting effective policy development. The newly proposed concept of high-impact chronic pain (HICP) incorporates both disability and pain duration to identify a more severely impacted portion of the chronic pain population yet remains uncharacterized at the population level. As such, we used the 2011 National Health Interview Survey (N = 15,670) to 1) assess the likelihood of disability in the overall chronic pain population, 2) estimate the prevalence of HICP, and 3) characterize the disability, health status, and health care use profile of this population in the United States. Overall, chronic pain, defined as pain experienced on most days or every day in the previous 3 months, was strongly associated with an increased risk of disability after controlling for other chronic health conditions (odds ratio = 4.43; 95% confidence interval = 3.73-5.26), where disability was more likely in those with chronic pain than in those with stroke or kidney failure, among others. HICP affected 4.8% of the U.S. adult population, or approximately 10.6 million individuals, in 2011. The HICP population reported more severe pain and more mental health and cognitive impairments than persons with chronic pain without disability, and was also more likely to report worsening health, more difficulty with self-care, and greater health care use. HICP clearly represents a more severely impacted portion of the chronic pain population. Understanding this heterogeneity will contribute to developing more effective legislation promoting safe and cost-effective approaches to the prevention and treatment of chronic pain. PERSPECTIVE: HICP is a powerful new classification that differentiates those with debilitating chronic pain from those with less impactful chronic pain. By addressing the multidimensionality of chronic pain, this classification will improve clinical practice, research, and the development of effective health policy.

The Impact of Exercise in Rodent Models of Chronic Pain.

PURPOSE OF REVIEW: Physical activity is increasingly recommended for chronic pain. In this review, we briefly survey recent, high-quality meta-analyses on the effects of exercise in human chronic pain populations, followed by a critical discussion of the rodent literature. RECENT FINDINGS: Most meta-analytical studies on the effects of exercise in human chronic pain populations describe moderate improvements in various types of chronic pain, despite substantial variability in the outcomes reported in the primary literature. The most consistent findings suggest that while greater adherence to exercise programs produces better outcomes, there is minimal support for the superiority of one type of exercise over another. The rodent literature similarly suggests that while regular exercise reduces hypersensitivity in rodent models of chronic pain, exercise benefits do not appear to relate to either the type of injury or any particular facet of the exercise paradigm. Potential factors underlying these results are discussed, including the putative involvement of stress-induced analgesic effects associated with certain types of exercise paradigms. Exercise research using rodent models of chronic pain would benefit from increased attention to the role of stress in exercise-induced analgesia, as well as the incorporation of more clinically relevant exercise paradigms.

Chronic neuropathic pain reduces opioid receptor availability with associated anhedonia in rat.

The opioid system plays a critical role in both the experience and management of pain. Although acute activation of the opioid system can lead to pain relief, the effects of chronic pain on the opioid system remain opaque. Cross-sectional positron emission tomography (PET) studies show reduced availability of brain opioid receptors in patients with chronic pain but are unable to (1) determine whether these changes are due to the chronic pain itself or due to preexisting or medication-induced differences in the endogenous opioid system, and (2) identify the neurobiological substrate of reduced opioid receptor availability. We investigated these possibilities using a well-controlled longitudinal study design in rat. Using [F]-FDPN-PET in either sham rats (n = 17) or spared nerve injury rats (n = 17), we confirmed reduced opioid receptor availability in the insula, caudate-putamen, and motor cortex of nerve injured rats 3 months after surgery, indicating that painful neuropathy altered the endogenous opioid system. Immunohistochemistry showed reduced expression of the mu-opioid receptor, MOR1, in the caudate-putamen and insula. Neither the opioid peptide enkephalin nor the neuronal marker NeuN differed between groups. In nerve-injured animals, sucrose preference, a measure of anhedonia/depression-like behavior, positively correlated with PET opioid receptor availability and MOR1-immunoreactivity in the caudate-putamen. These findings provide new evidence that the altered supraspinal opioid receptor availability observed in human patients with chronic pain may be a direct result of chronic pain. Moreover, reduced opioid receptor availability seems to reflect decreased receptor expression, which may contribute to pain-induced depression.

Comment on "Molecular and neural basis of contagious itch behavior in mice".

Yu et al (Reports, 10 March 2017, p. 1072) state that contagious itch occurs in mice based on imitative scratching in normal mice observing excessive scratching in genetically modified demonstrator mice. However, despite employing multiple behavioral analysis approaches, we were unable to extend these findings to normal mice observing the well-established histamine model of acute itch in demonstrator mice.

Mild Social Stress in Mice Produces Opioid-Mediated Analgesia in Visceral but Not Somatic Pain States.

Visceral pain has a greater emotional component than somatic pain. To determine if the stress-induced analgesic response is differentially expressed in visceral versus somatic pain states, we studied the effects of a mild social stressor in either acute visceral or somatic pain states in mice. We show that the presence of an unfamiliar conspecific mouse (stranger) in an adjacent cubicle of a standard transparent observation box produced elevated plasma corticosterone levels compared with mice tested alone, suggesting that the mere presence of a stranger is stressful. We then observed noxious visceral or somatic stimulation-induced nociceptive behavior in mice tested alone or in mildly stressful conditions (ie, beside an unfamiliar stranger). Compared with mice tested alone, the presence of a stranger produced a dramatic opioid-dependent reduction in pain behavior associated with visceral but not somatic pain. This social stress-induced reduction of visceral pain behavior relied on visual but not auditory/olfactory cues. These findings suggest that visceral pain states may provoke heightened responsiveness to mild stressors, an effect that could interfere with testing outcomes during simultaneous behavioral testing of multiple rodents. PERSPECTIVE: In mice, mild social stress due to the presence of an unfamiliar conspecific mouse reduces pain behavior associated with noxious visceral but not somatic stimulation, suggesting that stress responsiveness may be enhanced in visceral pain versus somatic pain states.

Modest Amounts of Voluntary Exercise Reduce Pain- and Stress-Related Outcomes in a Rat Model of Persistent Hind Limb Inflammation.

Aerobic exercise improves outcomes in a variety of chronic health conditions, yet the support for exercise-induced effects on chronic pain in humans is mixed. Although many rodent studies have examined the effects of exercise on persistent hypersensitivity, the most used forced exercise paradigms that are known to be highly stressful. Because stress can also produce analgesic effects, we studied how voluntary exercise, known to reduce stress in healthy subjects, alters hypersensitivity, stress, and swelling in a rat model of persistent hind paw inflammation. Our data indicate that voluntary exercise rapidly and effectively reduces hypersensitivity as well as stress-related outcomes without altering swelling. Moreover, the level of exercise is unrelated to the analgesic and stress-reducing effects, suggesting that even modest amounts of exercise may impart significant benefit in persistent inflammatory pain states. PERSPECTIVE: Modest levels of voluntary exercise reduce pain- and stress-related outcomes in a rat model of persistent inflammatory pain, independently of the amount of exercise. As such, consistent, self-regulated activity levels may be more relevant to health improvement in persistent pain states than standardized exercise goals.

eIF2α phosphorylation controls thermal nociception.

A response to environmental stress is critical to alleviate cellular injury and maintain cellular homeostasis. Eukaryotic initiation factor 2 (eIF2) is a key integrator of cellular stress responses and an important regulator of mRNA translation. Diverse stress signals lead to the phosphorylation of the α subunit of eIF2 (Ser51), resulting in inhibition of global protein synthesis while promoting expression of proteins that mediate cell adaptation to stress. Here we report that eIF2α is instrumental in the control of noxious heat sensation. Mice with decreased eIF2α phosphorylation (eIF2α+/S51A) exhibit reduced responses to noxious heat. Pharmacological attenuation of eIF2α phosphorylation decreases thermal, but not mechanical, pain sensitivity, whereas increasing eIF2α phosphorylation has the opposite effect on thermal nociception. The impact of eIF2α phosphorylation (p-eIF2α) on thermal thresholds is dependent on the transient receptor potential vanilloid 1. Moreover, we show that induction of eIF2α phosphorylation in primary sensory neurons in a chronic inflammation pain model contributes to thermal hypersensitivity. Our results demonstrate that the cellular stress response pathway, mediated via p-eIF2α, represents a mechanism that could be used to alleviate pathological heat sensation.

Restraint training for awake functional brain scanning of rodents can cause long-lasting changes in pain and stress responses.

With the increased interest in longitudinal brain imaging of awake rodents, it is important to understand both the short-term and long-term effects of restraint on sensory and emotional processing in the brain. To understand the effects of repeated restraint on pain behaviors and stress responses, we modeled a restraint protocol similar to those used to habituate rodents for magnetic resonance imaging scanning, and studied sensory sensitivity and stress hormone responses over 5 days. To uncover lasting effects of training, we also looked at responses to the formalin pain test 2 weeks later. We found that while restraint causes acute increases in the stress hormone corticosterone, it can also cause lasting reductions in nociceptive behavior in the formalin test, coupled with heightened corticosterone levels and increased activation of the "nociceptive" central nucleus of the amygdala, as seen by Fos protein expression. These results suggest that short-term repeated restraint, similar to that used to habituate rats for awake functional brain scanning, could potentially cause long-lasting changes in physiological and brain responses to pain stimuli that are stress-related, and therefore could potentially confound the functional activation patterns seen in awake rodents in response to pain stimuli.

Translational control of nociception via 4E-binding protein 1.

Activation of the mechanistic/mammalian target of rapamycin (mTOR) kinase in models of acute and chronic pain is strongly implicated in mediating enhanced translation and hyperalgesia. However, the molecular mechanisms by which mTOR regulates nociception remain unclear. Here we show that deletion of the eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), a major mTOR downstream effector, which represses eIF4E activity and cap-dependent translation, leads to mechanical, but not thermal pain hypersensitivity. Mice lacking 4E-BP1 exhibit enhanced spinal cord expression of neuroligin 1, a cell-adhesion postsynaptic protein regulating excitatory synapse function, and show increased excitatory synaptic input into spinal neurons, and a lowered threshold for induction of synaptic potentiation. Pharmacological inhibition of eIF4E or genetic reduction of neuroligin 1 levels normalizes the increased excitatory synaptic activity and reverses mechanical hypersensitivity. Thus, translational control by 4E-BP1 downstream of mTOR effects the expression of neuroligin 1 and excitatory synaptic transmission in the spinal cord, and thereby contributes to enhanced mechanical nociception.

Stimulation of cutaneous low threshold mechanoreceptors in mice after intracolonic capsaicin increases spinal c-Fos labeling in an NKCC1-dependent fashion.

UNLABELLED: Stimulation of peripheral nociceptors results in increased c-Fos labeling in spinal cord regions associated with nociceptive processing. Accordingly, intracolonic capsaicin, which generates robust secondary (referred) allodynia on the abdomen of mice, also causes an increased spinal c-Fos labeling. In naïve rodents, low intensity innocuous stimulation does not affect c-Fos labeling in spinal nociceptive regions. However, after persistent noxious input, low intensity stimulation of the inflamed region further enhances c-Fos labeling, suggesting that low threshold mechanosensitive fibers gain access to the nociceptive channel after persistent inflammation. We have previously proposed that afferent activity in low threshold sensory fibers activates nociceptive sensory fibers through Na(+)-K(+)-Cl(-) cotransporter 1 (NKCC1) -mediated enhanced primary afferent depolarization. Here, we show that intracolonic capsaicin enhances spinal c-Fos labeling and secondary allodynia in an NKCC1-dependent manner. Furthermore, we demonstrate that gently brushing the abdomen, the region of secondary allodynia, further increased spinal c-Fos levels, an effect that can be prevented by spinal NKCC1 blockade. These findings provide evidence that increased NKCC1 activity contributes to secondary allodynia and that innocuous touch can access the nociceptive channel in part through enhanced NKCC1 activity. PERSPECTIVE: While touch normally soothes acute pain, we demonstrate that following peripheral inflammation, touch evokes pain (allodynia) through the switching of a normally inhibitory spinal pathway into an excitatory pathway. Activation of low threshold mechanoreceptors activates spinal nociceptive neurons following inflammation-induced enhancement of NKCC1 expression, as measured by spinal c-Fos labeling.

PKMζ is essential for spinal plasticity underlying the maintenance of persistent pain.

BACKGROUND: Chronic pain occurs when normally protective acute pain becomes pathologically persistent. We examined here whether an isoform of protein kinase C (PKC), PKMζ, that underlies long-term memory storage in various brain regions, also sustains nociceptive plasticity in spinal cord dorsal horn (SCDH) mediating persistent pain. RESULTS: Cutaneous injury or spinal stimulation produced persistent increases of PKMζ, but not other atypical PKCs in SCDH. Inhibiting spinal PKMζ, but not full-length PKCs, reversed plasticity-dependent persistent painful responses to hind paw formalin and secondary mechanical hypersensitivity and SCDH neuron sensitization after hind paw capsaicin, without affecting peripheral sensitization-dependent primary heat hypersensitivity after hind paw capsaicin. Inhibiting spinal PKMζ, but not full-length PKCs, also reversed mechanical hypersensitivity in the rat hind paw induced by spinal stimulation with intrathecal dihydroxyphenylglycine. Spinal PKMζ inhibition also alleviated allodynia 3 weeks after ischemic injury in rats with chronic post-ischemia pain (CPIP), at a point when allodynia depends on spinal changes. In contrast, spinal PKMζ inhibition did not affect allodynia in rats with chronic contriction injury (CCI) of the sciatic nerve, or CPIP rats early after ischemic injury, when allodynia depends on ongoing peripheral inputs. CONCLUSIONS: These results suggest spinal PKMζ is essential for the maintenance of persistent pain by sustaining spinal nociceptive plasticity.

Role of the NKCC1 co-transporter in sensitization of spinal nociceptive neurons.

The Na(+), K(+), 2Cl(-) co-transporter type 1 (NKCC1) plays a pivotal role in hyperalgesia associated with inflammatory stimuli. NKCC1 contributes to maintain high [Cl(-)](i) in dorsal root ganglia (DRG) neurons which cause primary afferent depolarization (PAD) when GABA(A) receptors are activated. Enhanced GABA-induced depolarization, through increased NKCC1 activity, has been hypothesized to produce orthodromic spike activity of sufficient intensity to account for touch-induced pain. In the present study, we investigate this hypothesis using in vivo electrophysiology on rat dorsal horn neurons; the effects of spinal blockade of NKCC1 on intraplantar capsaicin-induced sensitization of dorsal horn neurons were examined. Single wide dynamic range (WDR) and nociceptive specific (NS) neuron activity in the dorsal horn was recorded using glass microelectrodes in anesthetized rats. Dorsal horn neurons with a receptive field on the plantar surface of the hindpaw were studied. Neuronal responses to mechanical stimuli (brush, von Frey filaments) were recorded ten minutes before intraplantar injection of 0.3 ml 0.1% capsaicin (CAP), 40 min after CAP and 15 min after local application of the NKCC1 blocker bumetanide (BTD; 500 µM) on the spinal cord. After CAP, low and high threshold stimulation of the cutaneous receptive field produced a significant enhancement in spike frequency over pre-CAP values in both WDR and NS neurons. Spinal BTD application reduced the spike frequency to baseline levels as well as attenuated the CAP-induced increases in background activity. Our data support the hypothesis that NKCC1 plays an important role in the sensitization of dorsal horn neurons following a peripheral inflammatory insult.

Reliability of electromyographic and force measures during prone isometric back extension in subjects with and without low back pain.

Maximal voluntary isometric activations (MVIA) are frequently used as inputs for models attempting to predict muscle force and as normalization values in studies assessing muscle function. However, pain may adversely affect maximal muscle activation. The purpose of this study was to assess reliability of MVIA force and electromyographic (EMG) activity during prone isometric back extension in subjects with and without low back pain (LBP). A novel sub-maximal method using the percentages of the estimated mass of the head-arms-trunk (HAT) segment was also investigated. Repeated measures on 20 male volunteers divided into an LBP (n=10) and a control group (n=10) were made on 4 occasions. Force and EMG activity were recorded bilaterally from upper lumbar erector spinae (ULES), lower lumbar erector spinae (LLES), and biceps femoris (BF). Subjects exerted a maximal extension effort against a harness assembly that was attached to a force transducer. Submaximal exertions were also performed with an additional resistance of 100%, 110%, 120%, 130%, 140%, 150%, 160%, and 170% of HAT. Mean MVIA forces were significantly (p0.90), but were significantly less in LBP (R=0.36-0.80). EMG of BF demonstrated excellent reliability across both groups (R>0.90). The resistance at 100% HAT demonstrated the highest reliability for LBP patients, whereas higher percentages of HAT showed either similar or higher reliability for controls. Force output and back EMG activity are less reliable with LBP individuals and should be taken into consideration when testing.

Effects of inflammation on the ultrastructural localization of spinal cord dorsal horn group I metabotropic glutamate receptors.

Inflammatory pain is thought to induce functional plasticity of spinal dorsal horn neurons and may produce changes in glutamate receptor expression. Plasticity of group I metabotropic glutamate receptors (mGluR1 and mGluR5) is important in various neuronal systems, and these receptors are also known to modulate nociceptive neurotransmission in the spinal dorsal horn. The present study aimed at determining whether persistent inflammatory pain produces alterations in intracellular and plasma membrane-associated mGluR1alpha and mGluR5 in spinal cord dorsal horn. Persistent inflammation was induced in male Long Evans rats by a unilateral intraplantar injection of 100 muL of complete Freund's adjuvant (CFA). Three days after the CFA injection thermal withdrawal latencies were obtained prior to processing of transverse spinal cord sections for preembedding immunogold labeling after incubation in primary antibody for mGluR1alpha or mGluR5. Using electron microscopy, we quantified immunogold-labeled mGluR1alpha and mGluR5 profiles, located in lamina V and I-II, respectively, of both CFA-treated rats and untreated control rats. Compared to untreated rats, CFA-treated rats had a significant increase in the number of plasma membrane-associated mGluR5 immunogold-labeled particles in lamina I-II neurons of the spinal cord. Although no changes to mGluR1alpha expression were found in CFA-treated rats, plasma membrane-associated mGluR1alpha was significantly closer to the synapse. Therefore, in CFA-treated rats there was a specific increase in the ratio of plasma membrane-associated versus intracellular immunogold-labeled particles for mGluR5, and lateral movement of mGluR1alpha toward the synapse, indicating that peripheral inflammation-induced trafficking of group I mGluRs in spinal dorsal horn neurons may be an important factor in the development of plastic changes associated with inflammation-induced chronic pain.