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BioRxiv : the Preprint Server For... Jun 2024Chronic pain is a wide-spread condition that is debilitating and expensive to manage, costing the United States alone around $600 billion in 2010. In a common type of...
UNLABELLED
Chronic pain is a wide-spread condition that is debilitating and expensive to manage, costing the United States alone around $600 billion in 2010. In a common type of chronic pain called allodynia, non-painful stimuli produce painful responses with highly variable presentations across individuals. While the specific mechanisms remain unclear, allodynia is hypothesized to be caused by the dysregulation of excitatory-inhibitory (E-I) balance in pain-processing neural circuitry in the dorsal horn of the spinal cord. In this work, we analyze biophysically-motivated subcircuit structures that represent common motifs in neural circuits in layers I-II of the dorsal horn. These circuits are hypothesized to be part of the neural pathways that mediate two different types of allodynia: static and dynamic. We use neural firing rate models to describe the activity of populations of excitatory and inhibitory interneurons within each subcircuit. By accounting for experimentally-observed responses under healthy conditions, we specify model parameters defining populations of subcircuits that yield typical behavior under normal conditions. Then, we implement a sensitivity analysis approach to identify the mechanisms most likely to cause allodynia-producing dysregulation of the subcircuit's E-I signaling. We find that disruption of E-I balance generally occurs either due to downregulation of inhibitory signaling so that excitatory neurons are "released" from inhibitory control, or due to upregulation of excitatory neuron responses so that excitatory neurons "escape" their inhibitory control. Which of these mechanisms is most likely to occur, the subcircuit components involved in the mechanism, and the proportion of subcircuits exhibiting the mechanism can vary depending on the subcircuit structure. These results suggest specific hypotheses about diverse mechanisms that may be most likely responsible for allodynia, thus offering predictions for the high interindividual variability observed in allodynia and identifying targets for further experimental studies on the underlying mechanisms of this chronic pain condition.
AUTHOR SUMMARY
While chronic pain affects roughly 20% of the US adult population [1], symptoms and presentations of the condition are highly variable across individuals and its causes remain largely unknown. A prevailing hypothesis for the cause of a type of chronic pain called allodynia is that the balance between excitatory and inhibitory signaling pathways between neuron populations in the spinal cord dorsal horn may be disrupted. To help better understand neural mechanisms underlying allodynia, we analyze biologically-motivated mathematical models of subcircuits of neuron populations that are part of the pain processing signaling pathway in the dorsal horn of the spinal cord. We use a novel sensitivity analysis approach to identify mechanisms of subcircuit dysregulation that may contribute to two different types of allodynia. The model results identify specific subcircuit components that are most likely to contribute to each type of allodynia. These mechanisms suggest targets for further experimental study, as well as for pharmacological intervention for better pain treatments.
PubMed: 38915505
DOI: 10.1101/2024.06.10.598179 -
Journal of Rehabilitation Medicine Jun 2024To explore and characterize somatosensory dysfunction in patients with post-polio syndrome and chronic pain, by conducting examinations with Quantitative Sensory Testing.
OBJECTIVE
To explore and characterize somatosensory dysfunction in patients with post-polio syndrome and chronic pain, by conducting examinations with Quantitative Sensory Testing.
DESIGN
A cross-sectional, descriptive, pilot study conducted during 1 month.
SUBJECTS/PATIENTS
Six patients with previously established post-polio syndrome and related chronic pain.
METHODS
All subjects underwent a neurological examination including neuromuscular function, bedside sensory testing, a thorough pain anamnesis, and pain drawing. Screening for neuropathic pain was done with 2 questionnaires. A comprehensive Quantitative Sensory Testing battery was conducted with z-score transformation of obtained data, enabling comparison with published reference values and the creation of sensory profiles, as well as comparison between the study site (more polio affected extremity) and internal control site (less affected extremity) for each patient.
RESULTS
Derived sensory profiles showed signs of increased prevalence of sensory aberrations compared with reference values, especially Mechanical Pain Thresholds, with significant deviation from reference data in 5 out of 6 patients. No obvious differences in sensory functions were seen between study sites and internal control sites.
CONCLUSION
Post-polio syndrome may be correlated with a mechanical hyperalgesia/allodynia and might be correlated to a somatosensory dysfunction. With lack of evident side-to-side differences, the possibility of a generalized dysfunction in the somatosensory system might be considered.
Topics: Humans; Postpoliomyelitis Syndrome; Pilot Projects; Cross-Sectional Studies; Female; Male; Middle Aged; Aged; Pain Measurement; Pain Threshold; Chronic Pain; Somatosensory Disorders; Adult; Neurologic Examination; Hyperalgesia; Neuralgia
PubMed: 38915293
DOI: 10.2340/jrm.v56.26192 -
Pain Reports Aug 2024In 85% of patients with chronic low back pain (CLBP), no specific pathoanatomical cause can be identified. Besides primary peripheral drivers within the lower back,...
INTRODUCTION
In 85% of patients with chronic low back pain (CLBP), no specific pathoanatomical cause can be identified. Besides primary peripheral drivers within the lower back, spinal or supraspinal sensitization processes might contribute to the patients' pain.
OBJECTIVES
The present study conceptualized the most painful area (MP) of patients with nonspecific CLBP as primarily affected area and assessed signs of peripheral, spinal, and supraspinal sensitization using quantitative sensory testing (QST) in MP, a pain-free area adjacent to MP (AD), and a remote, pain-free control area (CON).
METHODS
Fifty-nine patients with CLBP (51 years, SD = 16.6, 22 female patients) and 35 pain-free control participants individually matched for age, sex, and testing areas (49 years, SD = 17.5, 19 female participants) underwent a full QST protocol in MP and a reduced QST protocol assessing sensory gain in AD and CON. Quantitative sensory testing measures, except paradoxical heat sensations and dynamic mechanical allodynia (DMA), were -transformed to the matched control participants and tested for significance using -tests (α = 0.001). Paradoxical heat sensations and DMA occurrence were compared between cohorts using Fisher's exact tests (α = 0.05). The same analyses were performed with a high-pain and a low-pain CLBP subsample (50% quantile).
RESULTS
Patients showed cold and vibration hypoesthesia in MP (all s < 0.001) and mechanical hyperalgesia ( < 0.001) and more frequent DMA ( = 0.044) in AD. The results were mainly driven by the high-pain CLBP subsample. In CON, no sensory alterations were observed.
CONCLUSION
Mechanical hyperalgesia and DMA adjacent to but not within MP, the supposedly primarily affected area, might reflect secondary hyperalgesia originating from spinal sensitization in patients with CLBP.
PubMed: 38910867
DOI: 10.1097/PR9.0000000000001166 -
Redox Biology Jun 2024Morphine, a typical opiate, is widely used for controlling pain but can lead to various side effects with long-term use, including addiction, analgesic tolerance, and...
Morphine, a typical opiate, is widely used for controlling pain but can lead to various side effects with long-term use, including addiction, analgesic tolerance, and hyperalgesia. At present, however, the mechanisms underlying the development of morphine analgesic tolerance are not fully understood. This tolerance is influenced by various opioid receptor and kinase protein modifications, such as phosphorylation and ubiquitination. Here, we established a murine morphine tolerance model to investigate whether and how S-nitrosoglutathione reductase (GSNOR) is involved in morphine tolerance. Repeated administration of morphine resulted in the down-regulation of GSNOR, which increased excessive total protein S-nitrosation in the prefrontal cortex. Knockout or chemical inhibition of GSNOR promoted the development of morphine analgesic tolerance and neuron-specific overexpression of GSNOR alleviated morphine analgesic tolerance. Mechanistically, GSNOR deficiency enhanced S-nitrosation of cellular protein kinase alpha (PKCα) at the Cys78 and Cys132 sites, leading to inhibition of PKCα kinase activity, which ultimately promoted the development of morphine analgesic tolerance. Our study highlighted the significant role of GSNOR as a key regulator of PKCα S-nitrosation and its involvement in morphine analgesic tolerance, thus providing a potential therapeutic target for morphine tolerance.
PubMed: 38901102
DOI: 10.1016/j.redox.2024.103239 -
Seminars in Oncology Nursing Jun 2024Duloxetine, the only American Society of Clinical Oncology (ASCO) treatment recommended for chemotherapy-induced peripheral neuropathy (CIPN) in cancer survivors, is not...
OBJECTIVES
Duloxetine, the only American Society of Clinical Oncology (ASCO) treatment recommended for chemotherapy-induced peripheral neuropathy (CIPN) in cancer survivors, is not effective for 40% of survivors. This study examined the ability of a duloxetine-prazosin combination to prevent the development of allodynia and hyperalgesia in a rat model of oxaliplatin-induced peripheral neuropathy (OPIN).
METHODS
Female (n = 24) and male (n = 41) rats were started on duloxetine (15 mg), prazosin (2 mg), or a duloxetine-prazosin combination one week prior to administration of the chemotherapy drug, oxaliplatin, and continued the duloxetine-prazosin combination for 32 days. Behavioral testing for mechanical allodynia and mechanical hyperalgesia was done with selected von Frey filaments over the course of the study.
RESULTS
Overall percent paw withdrawal for rats that received the duloxetine-prazosin combination was significantly lower in female (p < .001 for both conditions) and male (p = .029 for allodynia; p < .001 for hyperalgesia) than those that received water. No significant posttreatment differences were found for allodynia or hyperalgesia between rats treated with duloxetine and rats that received the duloxetine-prazosin combination in either sex.
CONCLUSIONS
These finding provide preliminary evidence that a duloxetine-prazosin combination can prevent the posttreatment development of allodynia and hyperalgesia in both male and female rats; however, the results suggest that the duloxetine-prazosin combination is no more efficacious than duloxetine alone in preventing chronic OIPN.
IMPLICATIONS FOR NURSING PRACTICE
The profession of nursing is built on clinical practice supported by scientific research. The current study addressed the clinical practice problem of prevention and management of painful OIPN, which is a priority area in oncology nursing.
PubMed: 38897856
DOI: 10.1016/j.soncn.2024.151686 -
International Journal of Molecular... May 2024Paclitaxel, a microtubule-stabilizing chemotherapy drug, can cause severe paclitaxel-induced peripheral neuropathic pain (PIPNP). The roles of transient receptor...
Paclitaxel, a microtubule-stabilizing chemotherapy drug, can cause severe paclitaxel-induced peripheral neuropathic pain (PIPNP). The roles of transient receptor potential (TRP) ion channel vanilloid 1 (TRPV1, a nociceptor and heat sensor) and melastatin 8 (TRPM8, a cold sensor) in PIPNP remain controversial. In this study, Western blotting, immunofluorescence staining, and calcium imaging revealed that the expression and functional activity of TRPV1 were upregulated in rat dorsal root ganglion (DRG) neurons in PIPNP. Behavioral assessments using the von Frey and brush tests demonstrated that mechanical hyperalgesia in PIPNP was significantly inhibited by intraperitoneal or intrathecal administration of the TRPV1 antagonist capsazepine, indicating that TRPV1 played a key role in PIPNP. Conversely, the expression of TRPM8 protein decreased and its channel activity was reduced in DRG neurons. Furthermore, activation of TRPM8 via topical application of menthol or intrathecal injection of WS-12 attenuated the mechanical pain. Mechanistically, the TRPV1 activity triggered by capsaicin (a TRPV1 agonist) was reduced after menthol application in cultured DRG neurons, especially in the paclitaxel-treated group. These findings showed that upregulation of TRPV1 and inhibition of TRPM8 are involved in the generation of PIPNP, and they suggested that inhibition of TRPV1 function in DRG neurons via activation of TRPM8 might underlie the analgesic effects of menthol.
Topics: Animals; Paclitaxel; TRPM Cation Channels; TRPV Cation Channels; Ganglia, Spinal; Rats; Neuralgia; Male; Rats, Sprague-Dawley; Hyperalgesia; Capsaicin; Neurons
PubMed: 38892000
DOI: 10.3390/ijms25115813 -
BMJ Open Jun 2024An endogenous pain modulation profile, reflecting antinociceptive and pronociceptive mechanisms, may help to direct management by targeting the involved pain mechanism....
BACKGROUND
An endogenous pain modulation profile, reflecting antinociceptive and pronociceptive mechanisms, may help to direct management by targeting the involved pain mechanism. For individuals with cervicogenic headache (CeH), the characteristics of such profiles were never investigated. However, the individual nature of experiencing pain demands profiling within a multidimensional framework including psychosocial lifestyle characteristics. The objective of the current protocol is to assess the pain modulation profile, which includes psychosocial lifestyle characteristics among people with CeH.
METHODS AND ANALYSIS
A protocol is described to map pain modulation profiles in people with CeH. A cross-sectional non-randomised experimental design will be used to assess feasibility of mapping these profiles. The pain modulation profile is composed based on results on the Depression, Anxiety, Stress Scale, Pittsburgh Sleep Quality Index, Headache Impact Test and on responses to temporal summation of pain (pinprick), conditioned pain modulation and widespread hyperalgesia (mechanical pressure pain threshold and cuff algometry). Primary analyses will report results relating to outcomes on feasibility. Secondary analyses will involve an analysis of proportions (%) of the different psychosocial lifestyle profiles and pain profiles.
ETHICS AND DISSEMINATION
Ethical approval was granted by the Ethics Committee Research UZ/KU Leuven (Registration number B3222024001434) on 30 May 2024. Results will be published in peer-reviewed journals, at scientific conferences and, through press releases. Protocol V.3. protocol date: 3 June 2024.
Topics: Humans; Post-Traumatic Headache; Feasibility Studies; Cross-Sectional Studies; Pain Measurement; Adult; Pain Threshold; Male; Female; Life Style
PubMed: 38890144
DOI: 10.1136/bmjopen-2023-074743 -
Biomedicine & Pharmacotherapy =... Jun 2024The aim of this study was to determine the anti-hypersensitivity activity of novel non-hallucinogenic compounds derived from iboga alkaloids (i.e., ibogalogs), including...
The aim of this study was to determine the anti-hypersensitivity activity of novel non-hallucinogenic compounds derived from iboga alkaloids (i.e., ibogalogs), including tabernanthalog (TBG), ibogainalog (IBG), and ibogaminalog (DM506), using mouse models of neuropathic (Chronic Constriction Injury; CCI) and visceral pain (dextrane sulfate sodium; DSS). Ibogalogs decreased mechanical hyperalgesia and allodynia induced by CCI in a dose- and timeframe-dependent manner, where IBG showed the longest anti-hyperalgesic activity at a comparatively lower dose, whereas DM506 displayed the quickest response. These compounds also decreased hypersensitivity induced by colitis, where DM506 showed the longest activity. To understand the mechanisms involved in these effects, two approaches were utilized: ibogalogs were challenged with the 5-HT receptor antagonist ketanserin and the pharmacological activity of these compounds was assessed at the respective 5-HT 5-HT, and 5-HT receptor subtypes. The behavioral results clearly demonstrated that ketanserin abolishes the pain-relieving activity of ibogalogs without inducing any effect per se, supporting the concept that 5-HT receptor activation, but not inhibition, is involved in this process. The functional results showed that ibogalogs potently activate the 5-HT and 5-HT receptor subtypes, whereas they behave as inverse agonists (except TBG) at the 5-HT receptor. Considering previous studies showing that 5-HT receptor inhibition, but not activation, and 5-HT receptor activation, but not inhibition, relieved chronic pain, we can discard these two receptor subtypes as participating in the pain-relieving activity of ibogalogs. The potential involvement of 5-HT receptor subtypes was also ruled out. In conclusion, the anti-hypersensitivity activity of ibogalogs in mice is mediated by a mechanism involving 5-HT receptor activation.
PubMed: 38889634
DOI: 10.1016/j.biopha.2024.116867 -
The Journal of Clinical Investigation Jun 2024We report that diazepam binding inhibitor (DBI) is a glial messenger mediating satellite glia-sensory neuron crosstalk in the dorsal root ganglion (DRG). DBI is highly...
We report that diazepam binding inhibitor (DBI) is a glial messenger mediating satellite glia-sensory neuron crosstalk in the dorsal root ganglion (DRG). DBI is highly expressed in satellite glia cells (SGCs) of mice, rat and human, but not in sensory neurons or most other DRG-resident cells. Knockdown of DBI results in a robust mechanical hypersensitivity without major effects on other sensory modalities. In vivo overexpression of DBI in SGCs reduces sensitivity to mechanical stimulation and alleviates mechanical allodynia in neuropathic and inflammatory pain models. We further show that DBI acts as an unconventional agonist and positive allosteric modulator at the neuronal GABAA receptors, particularly strongly effecting those with a high-affinity benzodiazepine binding site. Such receptors are selectively expressed by a subpopulation of mechanosensitive DRG neurons and these are also more enwrapped with DBI-expressing glia, as compared to other DRG neurons, suggesting a mechanism for specific effect of DBI on mechanosensation. These findings identified a new, peripheral neuron-glia communication mechanism modulating pain signalling, which can be targeted therapeutically.
PubMed: 38888973
DOI: 10.1172/JCI176227 -
The role of spinal neurons targeted by corticospinal neurons in central poststroke neuropathic pain.CNS Neuroscience & Therapeutics Jun 2024Central poststroke pain (CPSP) is one of the primary sequelae following stroke, yet its underlying mechanisms are poorly understood.
BACKGROUND
Central poststroke pain (CPSP) is one of the primary sequelae following stroke, yet its underlying mechanisms are poorly understood.
METHODS
By lesioning the lateral thalamic nuclei, we first established a CPSP model that exhibits mechanical and thermal hypersensitivity. Innocuous mechanical stimuli following the thalamic lesion evoked robust neural activation in somatosensory corticospinal neurons (CSNs), as well as in the deep dorsal horn, where low threshold mechanosensory afferents terminate. In this study, we used viral-based mapping and intersectional functional manipulations to decipher the role of somatosensory CSNs and their spinal targets in the CPSP pathophysiology.
RESULTS
We first mapped the post-synaptic spinal targets of lumbar innervating CSNs using an anterograde trans-synaptic AAV1-based strategy and showed these spinal interneurons were activated by innocuous tactile stimuli post-thalamic lesion. Functionally, tetanus toxin-based chronic inactivation of spinal neurons targeted by CSNs prevented the development of CPSP. Consistently, transient chemogenetic silencing of these neurons alleviated established mechanical pain hypersensitivity and innocuous tactile stimuli evoked aversion linked to the CPSP. In contrast, chemogenetic activation of these neurons was insufficient to induce robust mechanical allodynia typically observed in the CPSP.
CONCLUSION
The CSNs and their spinal targets are required but insufficient for the establishment of CPSP hypersensitivity. Our study provided novel insights into the neural mechanisms underlying CPSP and potential therapeutic interventions to treat refractory central neuropathic pain conditions.
Topics: Animals; Neuralgia; Pyramidal Tracts; Male; Stroke; Neurons; Hyperalgesia; Rats, Sprague-Dawley; Rats; Disease Models, Animal; Spinal Cord
PubMed: 38887838
DOI: 10.1111/cns.14813