General Pathways of Pain Sensation and the Major Neurotransmitters Involved in Pain Regulation

Sub-acute toxicity, antinociceptive and anti-inflammatory effects of Mucuna pruriens L. leaves in experimental rodents

ETHNOPHARMACOLOGICAL RELEVANCE

Mucuna pruriens L is a wild and cultivated leguminous plant which have been used as an aphrodisiac, diuretic, nerve tonic, and antiarthritic agent.

AIM

To evaluate the toxicity, antinociceptive, and anti-inflammatory activities of M. pruriens (EEMP) ethanol extract in experimental models.

METHODS

M. pruriens dried leaves were extracted using aqueous ethanol (30:70). Tests for acute and subacute toxicity were conducted on rats and mice. Mice were used in hotplate, acetic acid, and formalin models to test the antinociceptive activity of EEMP. The anti-inflammatory properties of EEMP (25, 100, and 400 mg/kg) were assessed egg albumin, carrageenan, and formalin-induced oedema models. The study examined the anti-inflammatory mechanism of EEMP (25-400 mg/kg) in rats with an air pouch caused by carrageenan. Air pouch exudates were tested for total leucocytes and differential cell counts, TNF-α, IL-6, myeloperoxidase activity, malondialdehyde, nitrites, and reduced glutathione (GSH).

RESULTS

The acute oral toxic dose of EEMP is greater than 2000 mg/kg. There were no significant behavioral, hematological or biochemical alterations seen after 14-days repeated administration of EEMP (200, 400 and 800 mg/kg) in mice. The EEMP demonstrated significant antinociceptive activity in hotplate, acetic acid and formalin-induced nociception in mice. The EEMP significantly and dose dependently reduced paw oedema at 2, 4 and 96 h in the egg-albumin, carrageenan- and formalin-induced paw oedema, respectively. Exudates volume, inflammatory cell counts, TNF-α, IL-6, myeloperoxidase, malondialdehyde and nitrites were significantly reduced, while GSH increased in carrageenan-air pouch of EEMP-treated rats.

CONCLUSION

Mucuna pruriens leaves ethanol extract demonstrated good safety profile as well as antinociceptive and anti-inflammatory activity through mechanisms related to inhibition of oxidative stress and pro-inflammatory cytokines as well as lysosomal membrane stability.

Targeting the soluble epoxide hydrolase pathway as a novel therapeutic approach for the treatment of pain

Chronic pain is a major burden and the complexities of chronic pain pathophysiology, including both peripheral and central sensitisation mechanisms, involves multiple cell types (neuronal, immune, neuroimmune, and vascular) which substantially complicates the development of new effective analgesic treatments. The epoxy fatty acids (EpFAs), including the epoxyeicosatrienoic acids (EETs), are derived from the metabolism of polyunsaturated fatty acids (PUFAs) via the cytochrome P450 enzymatic pathway and act to shut-down inflammatory signalling and provide analgesia. The EpFAs are rapidly metabolised by the enzyme soluble epoxide hydrolase (sEH) into their corresponding diol metabolites, which recent studies suggest are pro-inflammatory and pro-nociceptive. This review discusses clinical and mechanistic evidence for targeting the sEH pathway for the treatment of pain.

The impact of opioids on the hallmarks of ageing

Opioids rank among the most hazardous substances of abuse, leading to opioid use disorders (which greatly diminish life quality) and contributing to the highest drug-related mortality rates. Nonetheless, both the therapeutic and recreational use of opioids is escalating globally. Interestingly, chronic opioid users often exhibit signs consistent with accelerated ageing, suggesting that they likely interfere with well-characterized ageing mechanisms (e.g., telomere shortening, epigenetic changes, mitochondrial dysfunction, cellular senescence). Here, we review the most recent advances regarding the impact of opioids on well-characterized hallmarks of ageing, to ascertain a potential association between opioid use and accelerated ageing. Our findings indicate that there is accumulating evidence supporting a close association between the use of opioids and the early onset of some ageing hallmarks, namely mitochondrial dysfunction, genomic instability, or telomere shortening. However, there is still limited data available regarding how opioids specifically impact other ageing hallmarks, like nutrient sensing, cellular senescence, or loss of proteostasis. Taking into consideration the high prevalence of opioid use, strengthening the understanding of the mechanisms underlying opioids' impact on ageing assumes utmost relevance, both in terms of improving risk assessment, as well as to help researchers and clinicians prevent or mitigate these effects in clinical settings.

Anatomical and functional basis of facial expressions and their relationship with emotions in horses

An emotion is defined as the affective response to a stimulus that leads to specific bodily changes, enabling individuals to react to positive or negative environmental conditions. In the absence of speech, emotions in animals are primarily studied by observing expressive components, such as facial expressions. This review aims to analyze the available literature on the influence of environmental stimuli on measurable behaviors in horses, describing the anatomical components involved in perception at the central nervous system level and the efferent pathways that trigger facial muscle contraction or relaxation, thus altering facial expressions. Additionally, articles addressing the function of facial expressions in communication are discussed, emphasizing their role in social interactions in this species. While there is limited research on equine neurophysiology, considering the common structure of the limbic system in most mammals, studies conducted on canines and primates were taken into account. In conclusion, the article underscores the importance of understanding equine facial expressions to assess their emotional states and, by extension, their welfare.

Chronic pain in the elderly: Exploring cellular and molecular mechanisms and therapeutic perspectives

Chronic pain is a debilitating condition frequently observed in the elderly, involving numerous pathological mechanisms within the nervous system. Diminished local blood flow, nerve degeneration, variations in fiber composition, alterations in ion channels and receptors, accompanied by the sustained activation of immune cells and release of pro-inflammatory cytokines, lead to overactivation of the peripheral nervous system. In the central nervous system, chronic pain is strongly associated with the activation of glial cells, which results in central sensitization and increased pain perception. Moreover, age-related alterations in neural plasticity and disruptions in pain inhibitory pathways can exacerbate chronic pain in older adults. Finally, the environmental influences on the development of chronic pain in the elderly must be considered. An understanding of these mechanisms is essential for developing novel treatments for chronic pain, which can significantly improve the quality of life for this vulnerable population.

Pulp Sensitivity Testing in Multiple Sclerosis: Disease Duration and Sensory/Motor Associations-A Cross-Sectional Study

Introduction: This study explores a relatively unexplored aspect of multiple sclerosis (MS) by examining the sensitivity threshold of dental pulp as a potential indicator of neuropathy in MS patients. Building upon earlier research that focused on assessing the response to electrical pulp testing in MS patients who did not have a history of trigeminal neuralgia, this survey is aimed at delving into the relationship between MS duration and the threshold for stimulation in response to pulp sensitivity tests. Materials and Methods: This study encompassed a total of 124 maxillary central incisors from patients diagnosed with relapsing-remitting multiple sclerosis (RRMS). The participants were uniform in terms of age, falling within the 18-50 years range, and all had RRMS with no history of trigeminal neuralgia. The electric pulp sensitivity test was conducted on all samples, and the results of the electric pulp testing (EPT) were recorded according to the grade of the pulp tester that elicited a response. The threshold was considered reached when the patient first experienced a burning sensation after EPT application and the use of 1,1,1,2-tetrafluoroethane spray. Data analysis employed paired t-tests, Fisher's exact test, and Spearman correlation, with a significance level set at p < 0.05. Results: Based on the study's findings, the average response value to EPT was 2.69 ± 1.17, while the response time to the cold test was 2.61 ± 1.03 s. There was no statistically significant difference in the response to the cold test based on age (p = 0.45). However, it was observed that the mean response time to the cold test was significantly longer among male participants (p = 0.001). No significant differences were identified in the pulpal response to EPT or the cold test between patients with and without sensory-motor involvement (p > 0.05). Furthermore, Spearman's analysis revealed a noteworthy positive correlation between the electrical pulp threshold and the time taken to respond to the cold test (p = 0.025, r = 0.2). Conclusions: The utilization of the pulpal sensitivity test in MS patients holds promise for practical clinical use. Notably, individuals with a more extended duration of the disease exhibited a notably elevated threshold for both the EPT and the cold test conducted on their maxillary central incisors.

Fecal Microbiota Transplantation Improves Clinical Symptoms of Fibromyalgia: An Open-Label, Randomized, Nonplacebo-Controlled Study

Fibromyalgia (FM) is a complex and poorly understood disorder characterized by chronic and widespread musculoskeletal pain, of which the etiology remains unknown. Now, the disorder of the gut microbiome is considered as one of the main causes of FM. This study aimed to investigate the potential benefits of fecal microbiota transplantation (FMT) in patients with FM. A total of 45 patients completed this open-label, randomized, nonplacebo-controlled clinical study. The numerical rating scale scores in the FMT group were slightly lower than the control group at 1 month (P > .05), and they decreased significantly at 2, 3, 6, and 12 months after treatment (P < .001). Besides, compared with the control group, the Widespread Pain Index, Symptom Severity, Hospital Anxiety and Depression Scale, and Pittsburgh Sleep Quality Index scores were significantly lower in the FMT group at different time points (P < .001). After 6 months of treatment, there was a significant increase in serotonin (5-hydroxytryptamine) and gamma-aminobutyric acid levels (P < .001), while glutamate levels significantly decreased in the FMT group (P < .001). The total effective rate was higher in the FMT group (90.9%) compared to the control group (56.5%) after 6 months of treatment (P < .05). FMT can effectively improve the clinical symptoms of FM. With the close relations between the changes in neurotransmitters and FM, certain neurotransmitters may serve as a diagnostic marker or potential target for FM patients. PERSPECTIVE: FMT is a novel therapy that aims to restore the gut microbial balance and modulate the gut-brain axis. It is valuable to further explore the therapeutic effect of FMT on FM. Furthermore, certain neurotransmitters may become a diagnostic marker or a new therapeutic target for FM patients.

A Pathophysiological Approach for Selecting Medications to Treat Nociceptive and Neuropathic Pain in Servicemembers

INTRODUCTION

The prevalence of chronic pain of service members (SMs) in the U.S. is estimated to be higher (roughly 31-44%) compared to that of civilian population (26%). This higher prevalence is likely due to the high physical demands related combat and training injuries that are not immediately resolved and worsen over time. Mental Health America reports that chronic pain can lead to other mental health conditions such as severe anxiety, depression, bipolar disorder, and post-traumatic stress disorder. Such mental health conditions can negatively affect job performance, reduce readiness for military duties, and often lead to patterns of misuse of opioid after SMs entering civilian life. The primary objective of this narrative review is to present a summarized guideline for the treatment of two types of pain that likely affect SMs, namely nociceptive somatic pain and neuropathic pain. This review focused on a stepwise approach starting with nonopioid interventions prior to opioid therapy. The secondary objective of this review is to elucidate the primary mechanisms of action and pathways associated with these two types of pain.

METHODS

We followed the Scale for Assessment of Narrative Review Articles when transcribing this narrative review article to enhance the quality and brevity of this review. This Scale has 0.77% an intra-class coefficient of correlation, 95% confidence interval and 0.88 inter-rater reliability. We searched PubMed, Google Scholar, WorldCAT, and the Cochrane Library for the primary and secondary articles that targeted mechanisms of action, pathways, and pharmacological modalities for nociceptive somatic and neuropathic pain that were published from 2011 to 2022. We excluded articles related to pediatric, some specific pain conditions such as cancer-related pain, palliative care, end-of-life care, and articles that were not written in English language. For pharmacologic selection, we adopted the guidelines from the Policy for Implementation of a Comprehensive Policy on Pain Management by the Military Health Care system for the Fiscal Year 2021; the Clinical Practice Guidance for Opioid Therapy for Chronic Pain by the Department of Defense/Veterans Health Administration (2022); the (2021) Implementation of a Comprehensive Policy on Pain Management by the Military Health Care System; and the (2022) Guideline for Prescribing Opioids for Chronic Painby the Centers for Disease Control.

DISCUSSION

From the knowledge of the mechanisms of action and pathways, we can be more likely to identify the causative origins of pain. As a result, we can correctly diagnose the type of pain, properly develop an efficient and personalized treatment plan, minimize adverse effects, and optimize clinical outcomes. The guideline, however, does not serve as a substitute for clinical judgment in patient-centered decision-making. Medication choices should be individualized judiciously based on the patient's comorbid conditions, available social and economic resources, and the patient's preferences to balance the benefits and risks associated with various pain medications and to achieve optimal pain relief and improve the patient's quality of life.

Molecular Sex Differences and Clinical Gender Efficacy in Opioid Use Disorders: From Pain Management to Addiction

Opioids have been utilized for both medical and recreational purposes since their discovery. Primarily recognized for their analgesic properties, they are also associated with the development of tolerance and dependence, contributing to a significant public health concern worldwide. Sex differences in opioid use disorder reveal that while men historically exhibit higher rates of abuse, women may develop dependence more quickly and are more susceptible to the addictive nature of opioids. This narrative review explores sex differences in opioid response in both clinical and experimental models, focusing on opioid receptor mechanisms, pain modulation, and hormonal influences. Additionally, it discusses the complexities of opioid addiction and withdrawal, highlighting sex-specific responses and the role of opioid replacement therapies. Diverse experimental outcomes, together with observational data, underscore the need for further research into sex-specific opioid biological mechanisms in a wider context, including demographic, cultural, and health-related factors. A comprehensive understanding of these complexities holds the potential to enhance personalized opioid therapies.

Epigenetic Regulation and Molecular Mechanisms of Burn Injury-Induced Nociception in the Spinal Cord of Mice

Epigenetic mechanisms, including histone post-translational modifications (PTMs), play a critical role in regulating pain perception and the pathophysiology of burn injury. However, the epigenetic regulation and molecular mechanisms underlying burn injury-induced pain remain insufficiently explored. Spinal dynorphinergic (Pdyn) neurons contribute to heat hyperalgesia induced by severe scalding-type burn injury through p-S10H3-dependent signaling. Beyond p-S10H3, burn injury may impact various other histone H3 PTMs. Double immunofluorescent staining and histone H3 protein analyses demonstrated significant hypermethylation at H3K4me1 and H3K4me3 sites and hyperphosphorylation at S10H3 within the spinal cord. By analyzing Pdyn neurons in the spinal dorsal horn, we found evidence of chromatin activation with a significant elevation in p-S10H3 immunoreactivity. We used RNA-seq analysis to compare the effects of burn injury and formalin-induced inflammatory pain on spinal cord transcriptomic profiles. We identified 98 DEGs for burn injury and 86 DEGs for formalin-induced inflammatory pain. A limited number of shared differentially expressed genes (DEGs) suggest distinct central pain processing mechanisms between burn injury and formalin models. KEGG pathway analysis supported this divergence, with burn injury activating Wnt signaling. This study enhances our understanding of burn injury mechanisms and uncovers converging and diverging pathways in pain models with different origins.

D2-like dopamine receptors blockade within the dentate gyrus shows a greater effect on stress-induced analgesia in the tail-flick test compared to D1-like dopamine receptors

INTRODUCTION

Acute stress, as a protective mechanism to respond to an aversive stimulus, can often be accompanied by suppressing pain perception via promoting consistent burst firing of dopamine neurons. Besides, sensitive and advanced research techniques led to the recognition of the mesohippocampal dopaminergic terminals, particularly in the hippocampal dentate gyrus (DG). Moreover, previous studies have shown that dopamine receptors within the hippocampal DG play a critical role in induced antinociceptive responses by forced swim stress (FSS) in the presence of inflammatory pain. Since different pain states can trigger various mechanisms and transmitter systems, the present experiments aimed to investigate whether dopaminergic receptors within the DG have the same role in the presence of acute thermal pain.

METHODS

Ninety-seven adult male albino Wistar rats underwent stereotaxic surgery, and a stainless steel guide cannula was unilaterally implanted 1 mm above the DG. Different doses of SCH23390 or sulpiride as D1- and D2-like dopamine receptor antagonists were microinjected into the DG 5-10 min before exposure to FSS, and 5 min after FSS exposure, the tail-flick test evaluated the effect of stress on the nociceptive response at the time-set intervals.

RESULTS

The results demonstrated that exposure to FSS could significantly increase the acute pain perception threshold, while intra-DG administration of SCH23390 and sulpiride reduced the antinociceptive effect of FSS in the tail-flick test.

DISCUSSION

Additionally, it seems the D2-like dopamine receptor within the DG plays a more prominent role in FSS-induced analgesia in the acute pain model.

Intervertebral disc injury triggers neurogenic inflammation of adjacent healthy discs

BACKGROUND CONTEXT

Intervertebral disc degeneration is common and may play an important role in low back pain, but it is not well-understood. Previous studies have shown that the outer layer of the annulus fibrosus of a healthy disc is innervated by nociceptive nerve fibers. In the process of disc degeneration, it can grow into the inner annulus fibrosus or nucleus pulposus and release neuropeptides. Disc degeneration is associated with inflammation that produces inflammatory factors and potentiates nociceptor sensitization. Subsequently neurogenic inflammation is induced by neuropeptide release from activated primary afferent terminals. Because the innervation of a lumbar disc comes from multisegmental dorsal root ganglion neurons, does neurogenic inflammation in a degenerative disc initiate neurogenic inflammation in neighboring healthy discs by antidromic activity?

PURPOSE

This study was based on animal experiments in Sprague-Dawley rats to investigate the role of neurogenic inflammation in adjacent healthy disc degeneration induced by disc injury.

STUDY DESIGN

This was an experimental study.

METHODS

Seventy-five 12-week-old, male Sprague-Dawley rats were allocated to 3 groups (sham group, disc injury group and disc injury+TrkA antagonist group). The disc injury group was punctured in the tail disc between the eighth and ninth coccygeal vertebrae (Co8-9) to establish an animal model of tail intervertebral disc degeneration. The sham group underwent only skin puncture and the disc injury+TrkA antagonist group was intraperitoneally injected with GW441756 two days before disc puncture. The outcome measure included quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

Disc injury induced an increase in aggrecan, NGF, TrkA, CGRP, SP, IL-1β, and IL-6 mRNA levels in the injured (Co8-9) and adjacent discs (Co7-8), which reached a peak on day 1, then gradually decreased, and returned to normal on day 14. After intraperitoneal injection of GW441756 prior to puncture, the mRNA levels of the above indicators were down-regulated in Co7-8 and Co8-9 intervertebral discs on the 1st and 7th days. The protein content of the above indicators in Co7-8 and Co8-9 intervertebral discs showed roughly the same trend as mRNA levels.

CONCLUSIONS

Degeneration of one disc can induce neurogenic inflammation of adjacent healthy discs in a rat model.

CLINICAL SIGNIFICANCE

This model supports a key role of neurogenic inflammation in disc degeneration, and may play a role in the experience of low back pain.

Advances in gut-brain organ chips

The brain and gut are sensory organs responsible for sensing, transmitting, integrating, and responding to signals from the internal and external environment. In-depth analysis of brain-gut axis interactions is important for human health and disease prevention. Current research on the brain-gut axis primarily relies on animal models. However, animal models make it difficult to study disease mechanisms due to inherent species differences, and the reproducibility of experiments is poor because of individual animal variations, which leads to a significant limitation of real-time sensory responses. Organ-on-a-chip platforms provide an innovative approach for disease treatment and personalized research by replicating brain and gut ecosystems in vitro. This enables a precise understanding of their biological functions and physiological responses. In this article, we examine the history and most current developments in brain, gut, and gut-brain chips. The importance of these systems for understanding pathophysiology and developing new drugs is emphasized throughout the review. This article also addresses future directions and present issues with the advancement and application of gut-brain-on-a-chip technologies.

Therapeutic Implication of miRNAs as an Active Regulatory Player in the Management of Pain: A Review

Chronic pain is frequently associated with neuropathy, inflammation, or the malfunctioning of nerves. Chronic pain is associated with a significant burden of morbidity due to opioid use, associated with addiction and tolerance, and disability. MicroRNAs (miRs) are emerging therapeutic targets to treat chronic pain through the regulation of genes associated with inflammation, neuronal excitability, survival, or de-differentiation. In this review, we discuss the possible involvement of miRs in pain-related molecular pathways. miRs are known to regulate high-conviction pain genes, supporting their potential as therapeutic targets.

Closed-Loop Infraslow Brain-Computer Interface can Modulate Cortical Activity and Connectivity in Individuals With Chronic Painful Knee Osteoarthritis: A Secondary Analysis of a Randomized Placebo-Controlled Clinical Trial

Introduction. Chronic pain is a percept due to an imbalance in the activity between sensory-discriminative, motivational-affective, and descending pain-inhibitory brain regions. Evidence suggests that electroencephalography (EEG) infraslow fluctuation neurofeedback (ISF-NF) training can improve clinical outcomes. It is unknown whether such training can induce EEG activity and functional connectivity (FC) changes. A secondary data analysis of a feasibility clinical trial was conducted to determine whether EEG ISF-NF training can significantly alter EEG activity and FC between the targeted cortical regions in people with chronic painful knee osteoarthritis (OA). Methods. A parallel, two-arm, double-blind, randomized, sham-controlled clinical trial was conducted. People with chronic knee pain associated with OA were randomized to receive sham NF training or source-localized ratio ISF-NF training protocol to down-train ISF bands at the somatosensory (SSC), dorsal anterior cingulate (dACC), and uptrain pregenual anterior cingulate cortices (pgACC). Resting state EEG was recorded at baseline and immediate post-training. Results. The source localization mapping demonstrated a reduction (P = .04) in the ISF band activity at the left dorsolateral prefrontal cortex (LdlPFC) in the active NF group. Region of interest analysis yielded significant differences for ISF (P = .008), slow (P = .007), beta (P = .043), and gamma (P = .012) band activities at LdlPFC, dACC, and bilateral SSC. The FC between pgACC and left SSC in the delta band was negatively correlated with pain bothersomeness in the ISF-NF group. Conclusion. The EEG ISF-NF training can modulate EEG activity and connectivity in individuals with chronic painful knee osteoarthritis, and the observed EEG changes correlate with clinical pain measures.

TRPA1, TRPV1, and Caffeine: Pain and Analgesia

Caffeine (1,3,7-trimethylxanthine) is a naturally occurring methylxanthine that acts as a potent central nervous system stimulant found in more than 60 different plants and fruits. Although caffeinated beverages are widely and casually consumed, the application of caffeine beyond dietary levels as pharmacologic therapy has been recognized since the beginning of its recorded use. The analgesic and vasoactive properties of caffeine are well known, but the extent of their molecular basis remains an area of active research. There is existing evidence in the literature as to caffeine's effect on TRP channels, the role of caffeine in pain management and analgesia, as well as the role of TRP in pain and analgesia; however, there has yet to be a review focused on the interaction between caffeine and TRP channels. Although the influence of caffeine on TRP has been demonstrated in the lab and in animal models, there is a scarcity of data collected on a large scale as to the clinical utility of caffeine as a regulator of TRP. This review aims to prompt further molecular research to elucidate the specific ligand-host interaction between caffeine and TRP by validating caffeine as a regulator of transient receptor potential (TRP) channels-focusing on the transient receptor potential vanilloid 1 (TRPV1) receptor and transient receptor potential ankyrin 1 (TRPA1) receptor subtypes-and its application in areas of pain.

The problem of residual pain in the assessment of rheumatoid arthritis activity

Residual pain is a major unmet medical need observed in patients suffering from rheumatoid arthritis (RA), which decreases their quality of life, even after achieving remission or low disease activity. The article has two aims: 1) to present mechanisms involved in the pathophysiology of residual pain, both inflammatory and non-inflammatory, i.e. neuropathic and nociplastic pain, as well as secondary pain syndromes, i.e. osteoarthritis and fibromyalgia, which can contribute to residual pain; 2) to show the limitations of current disease activity measures recommended by European Alliance of Associations for Rheumatology (EULAR) and American College of Rheumatology (ACR), which raise the need for a separate assessment of pain, and examples of methods that could be used by medical professionals to assess the pain and make a differential diagnosis. In conclusion, establishing a valid method to assess pain is essential to identify the pathomechanism of residual pain and to create treatments tailored specifically to individual RA patients.

Communicating pain: emerging axonal signaling in peripheral neuropathic pain

Peripheral nerve damage often leads to the onset of neuropathic pain (NeuP). This condition afflicts millions of people, significantly burdening healthcare systems and putting strain on families' financial well-being. Here, we will focus on the role of peripheral sensory neurons, specifically the Dorsal Root Ganglia neurons (DRG neurons) in the development of NeuP. After axotomy, DRG neurons activate regenerative signals of axons-soma communication to promote a gene program that activates an axonal branching and elongation processes. The results of a neuronal morphological cytoskeleton change are not always associated with functional recovery. Moreover, any axonal miss-targeting may contribute to NeuP development. In this review, we will explore the epidemiology of NeuP and its molecular causes at the level of the peripheral nervous system and the target organs, with major focus on the neuronal cross-talk between intrinsic and extrinsic factors. Specifically, we will describe how failures in the neuronal regenerative program can exacerbate NeuP.

Assessment of antinociceptive property of Cynara scolymus L. and possible mechanism of action in the formalin and writhing models of nociception in mice

Background

Cynara scolymus has bioactive constituents and has been used for therapeutic actions. The present study was undertaken to investigate the mechanisms underlying pain-relieving effects of the hydroethanolic extract of C. scolymus (HECS).

Methods

The antinociceptive activity of HECS was assessed through formalin and acetic acid-induced writhing tests at doses of 50, 100 and 200 mg/kg intraperitoneally. Additionally, naloxone (non-selective opioid receptors antagonist, 2 mg/kg), atropine (non-selective muscarinic receptors antagonist, 1 mg/kg), chlorpheniramine (histamine HH1-receptor antagonist, 20 mg/kg), cimetidine (histamine H2-receptor antagonist, 12.5 mg/kg), flumazenil (GABAA/BDZ receptor antagonist, 5 mg/kg) and cyproheptadine (serotonin receptor antagonist, 4 mg/kg) were used to determine the systis implicated in HECS-induced analgesia. Impact of HECS on locomotor activity was executed by open-field test. Determination of total phenolic content (TPC) and total flavonoid content (TFC) was done. Evaluation of antioxidant activity was conducted iploying 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay.

Results

HECS (50, 100 and 200 mg/kg) significantly indicated dose dependent antinociceptive activity against pain-related behavior induced by formalin and acetic acid (P < 0.001). Pretreatment with naloxone, atropine and flumazenil significantly reversed HECS-induced analgesia. Antinociceptive effect of HECS riained unaffected by chlorpheniramine, cimetidine and cyproheptadine. Locomotor activity was not affected by HECS. TPC and TFC of HECS were 59.49 ± 5.57 mgGAE/g dry extract and 93.39 ± 17.16 mgRE/g dry extract, respectively. DPPH free radical scavenging activity (IC50) of HECS was 161.32 ± 0.03 μg/mL.

Conclusions

HECS possesses antinociceptive activity which is mediated via opioidergic, cholinergic and GABAergic pathways.

Withanicandrin Isolated from Datura Ferox Promotes Antinociception by Modulating the Asics and TRPS Channels and Anti-Inflammation in Adult Zebrafish

This is the first study to analyze the anti-inflammatory and antinociceptive effect of withanicandrin, isolated from Datura Ferox leaves, and the possible mechanism of action involved in adult zebrafish (ZFa). To this end, the animals were treated intraperitoneally (i. p.) with withanicandrin (4; 20 and 40 mg/kg; 20 μL) and subjected to locomotor activity and acute toxicity. Nociception tests were also carried out with chemical agents, in addition to tests to evaluate inflammatory processes induced by κ-Carrageenan 1.5 % and a Molecular Docking study. As a result, withanicandrin reduced nociceptive behavior by capsaicin at a dose of 40 mg/kg and by acid saline at doses of 4 and 40 mg/kg, through neuromodulation of TRPV1 channels and ASICs, identified through blocking the antinociceptive effect of withanicandrin by the antagonists capsazepine and naloxone. Furthermore, withanicandrin caused an anti-inflammatory effect through the reduction of abdominal edema, absence of leukocyte infiltrate in the liver tissue and reduction of ROS in thel liver tissue and presented better affinity energy compared to control morphine (TRPV1) and ibuprofen (COX-1 and COX-2).

Pain Relief Interventions in Australian Livestock Husbandry: A Review of Animal Welfare and Pain Duration

In veterinary medicine and livestock production, ensuring good animal husbandry is vital for the physical and emotional wellbeing of animals under our care. Pain poses challenges for assessment and mitigation, especially in species unable to express pain overtly. This review examines current pain mitigation interventions in routine husbandry, focuses on the duration of pain after procedures and implications for animal welfare. Pain behaviours have been observed for days or weeks after regular husbandry procedures, and many studies have noted pain-related behaviour persisting until study finalisation, suggesting potential undocumented pain beyond study completion. Current products registered in Australia for pain mitigation in livestock primarily target immediate pain associated with procedures. The future of pain relief in livestock demands longer-acting solutions to address post-procedural pain adequately. Providing pain relief for at least 72 h post surgery is recommended, but current products require retreatment intervals to achieve this, posing practical challenges, especially in livestock. Methods of pain relief provision, such as voluntary consumption of medicated feed, transdermal medication delivery and long-acting formulations offer potential solutions for prolonged pain relief, with research ongoing in these areas. There is a need for further research and development of longer-acting pain relief to ensure optimal welfare of livestock.

New Insight into Neuropathic Pain: The Relationship between α7nAChR, Ferroptosis, and Neuroinflammation

Neuropathic pain, which refers to pain caused by a lesion or disease of the somatosensory system, represents a wide variety of peripheral or central disorders. Treating neuropathic pain is quite demanding, primarily because of its intricate underlying etiological mechanisms. The central nervous system relies on microglia to maintain balance, as they are associated with serving primary immune responses in the brain next to cell communication. Ferroptosis, driven by phospholipid peroxidation and regulated by iron, is a vital mechanism of cell death regulation. Neuroinflammation can be triggered by ferroptosis in microglia, which contributes to the release of inflammatory cytokines. Conversely, neuroinflammation can induce iron accumulation in microglia, resulting in microglial ferroptosis. Accumulating evidence suggests that neuroinflammation, characterized by glial cell activation and the release of inflammatory substances, significantly exacerbates the development of neuropathic pain. By inhibiting microglial ferroptosis, it may be possible to prevent neuroinflammation and subsequently alleviate neuropathic pain. The activation of the homopentameric α7 subtype of the neuronal nicotinic acetylcholine receptor (α7nAChR) has the potential to suppress microglial activation, transitioning M1 microglia to an M2 phenotype, facilitating the release of anti-inflammatory factors, and ultimately reducing neuropathic pain. Recent years have witnessed a growing recognition of the regulatory role of α7nAChR in ferroptosis, which could be a potential target for treating neuropathic pain. This review summarizes the mechanisms related to α7nAChR and the progress of ferroptosis in neuropathic pain according to recent research. Such an exploration will help to elucidate the relationship between α7nAChR, ferroptosis, and neuroinflammation and provide new insights into neuropathic pain management.

Heterogeneous Integration of Memristive and Piezoresistive MDMO-PPV-Based Copolymers in Nociceptive Transmission with Fast and Slow Pain for an Artificial Pain-Perceptual System

Nociceptive pain perception is a remarkable capability of organisms to be aware of environmental changes and avoid injury, which can be accomplished by specialized pain receptors known as nociceptors with 4 vital properties including threshold, no adaptation, relaxation, and sensitization. Bioinspired systems designed using artificial devices are investigated to imitate the efficacy and functionality of nociceptive transmission. Here, an artificial pain-perceptual system (APPS) with a homogeneous material and heterogeneous integration is proposed to emulate the behavior of fast and slow pain in nociceptive transmission. Retention-differentiated poly[2-methoxy-5-(3,7-dimethyoctyoxyl)-1,4-phenylenevinylene] (MDMO-PPV) memristors with film thicknesses of 160 and 80 nm are manufactured and adopted as A-δ and C nerve fibers of nociceptor conduits, respectively. Additionally, a nociceptor mimic, the ruthenium nanoparticles (Ru-NPs)-doped MDMO-PPV piezoresistive pressure sensor, is fabricated with a noxiously stimulated threshold of 150 kPa. Under the application of pricking and dull noxious stimuli, the current flows predominantly through the memristor to mimic the behavior of fast and slow pain, respectively, in nociceptive transmission with postsynaptic potentiation properties, which is analogous to biological pain perception. The proposed APPS can provide potential advancements in establishing the nervous system, thus enabling the successful development of next-generation neurorobotics, neuroprosthetics, and precision medicine.

Lumbar Sympathetic Block Leading to Increased Arterial Diameter and Blood Flow: A Mechanism of Therapeutic Benefit

Lumbar sympathetic blocks (LSBs) have long been used for the treatment of chronic lower extremity pain and for conditions such as complex regional pain syndrome (CRPS). With a better understanding of the autonomic nervous system and its function, these blocks have grown in their utility. Through this growth, however, our understanding of sympathetic-mediated pain is still vaguely understood. Here, we present a case of a patient who underwent a point-of-care ultrasound (POCUS) before and after an LSB, and we were able to show significant dilation of the posterior tibial artery (PTA) following the block. We propose that this arterial dilation plays a mechanistic role in providing pain relief to patients who undergo LSB. This increased blood flow can not only enhance healing properties to surrounding tissues but also allow for nitric oxide to play potential regulatory roles in pain pathways. Here, we also review potential mechanisms of the amelioration of sympathetic-mediated pain as well as the potential utilization of LSBs and neuromodulation in treating visceral pathologies through a better understanding of visceral somatic relationships.

Comparison of Thermal and Mechanical Pain Testing Modalities in Sprague Dawley and Fischer 344 Rats (Rattus norvegicus)

While rodents are used extensively for studying pain, there is a lack of reported direct comparisons of thermal and mechanical pain testing methods in rats of different genetic backgrounds. Understanding the range of interindividual variability of withdrawal thresholds and thermal latencies based on these testing methods and/or genetic background is important for appropriate experimental design. Testing was performed in two common rat genetic backgrounds: outbred Sprague-Dawley (SD) and inbred Fischer 344 (F344). Male and female, 10- to 14-wk-old F344 and SD rats were used to assess withdrawal thresholds in 3 different modalities: the Randall-Selitto test (RST), Hargreaves test (HT), and tail flick test (TFT). The RST was performed by using an operator-controlled handheld instrument to generate a noxious pressure stimulus to the left hind paw. The HT and the TFT used an electronically controlled light source to deliver a noxious thermal stimulus to the left hind paw or tail tip, respectively. Rats of each sex and genetic background underwent one type of test on day 0 and day 7. Withdrawal thresholds and thermal latencies were compared among tests. No significant differences were observed. Our findings can serve as a guide for researchers considering these nociceptive tests for their experiments.

Lessons from short chest drain management for primary spontaneous pneumothorax

OBJECTIVES

Video-assisted thoracic surgery (VATS) bullectomy is the mainstay treatment for primary spontaneous pneumothorax (PSP) but we encounter patients with pain due to chest tube. This study investigated the postoperative outcomes of shortened silicone drain as a chest tube after VATS bullectomy to reduce pain.

METHODS

The current study included patients aged < 30 years who underwent VATS bullectomy for PSP. Patients with normal intrathoracic lengths of the silicone drain placed in a loop at the apex toward the diaphragm were categorized as Group L, whereas those with the silicone drain shortened to approximately 10 cm and placed toward the apex were classified as Group S. Postoperative pain evaluated using a numerical rating scale (NRS) and other perioperative outcomes were compared between the groups.

RESULTS

Altogether, 43 patients were included, with 22 in Group L and 21 in Group S, respectively. The NRS before chest tube removal was significantly lower in Group S (mean, 2.1) than in Group L (4.4; p = 0.001). In Group L, 4 patients (p = 0.017) required early chest tube removal than expected due to severe pain whereas none in Group S required this intervention; additionally, more patients needed additional analgesics than in Group S (p = 0.003).

CONCLUSION

In VATS bullectomy for PSP, the pain intensity could be reduced by shortening the intrathoracic length of the silicone drain, compared to a longer intrathoracic length of the silicon drain. Our findings contribute to the establishment of optimal postoperative management of general thoracic surgery.

The psychophysiology of music-based interventions and the experience of pain

In modern times there is increasing acceptance that music-based interventions are useful aids in the clinical treatment of a range of neurological and psychiatric conditions, including helping to reduce the perception of pain. Indeed, the belief that music, whether listening or performing, can alter human pain experiences has a long history, dating back to the ancient Greeks, and its potential healing properties have long been appreciated by indigenous cultures around the world. The subjective experience of acute or chronic pain is complex, influenced by many intersecting physiological and psychological factors, and it is therefore to be expected that the impact of music therapy on the pain experience may vary from one situation to another, and from one person to another. Where pain persists and becomes chronic, aberrant central processing is a key feature associated with the ongoing pain experience. Nonetheless, beneficial effects of exposure to music on pain relief have been reported across a wide range of acute and chronic conditions, and it has been shown to be effective in neonates, children and adults. In this comprehensive review we examine the various neurochemical, physiological and psychological factors that underpin the impact of music on the pain experience, factors that potentially operate at many levels - the periphery, spinal cord, brainstem, limbic system and multiple areas of cerebral cortex. We discuss the extent to which these factors, individually or in combination, influence how music affects both the quality and intensity of pain, noting that there remains controversy about the respective roles that diverse central and peripheral processes play in this experience. Better understanding of the mechanisms that underlie music's impact on pain perception together with insights into central processing of pain should aid in developing more effective synergistic approaches when music therapy is combined with clinical treatments. The ubiquitous nature of music also facilitates application from the therapeutic environment into daily life, for ongoing individual and social benefit.

Anatomo-physiological basis and applied techniques of electrical neuromodulation in chronic pain

Chronic pain, a complex and debilitating condition, poses a significant challenge to both patients and healthcare providers worldwide. Conventional pharmacological interventions often prove inadequate in delivering satisfactory relief while carrying the risks of addiction and adverse reactions. In recent years, electric neuromodulation emerged as a promising alternative in chronic pain management. This method entails the precise administration of electrical stimulation to specific nerves or regions within the central nervous system to regulate pain signals. Through mechanisms that include the alteration of neural activity and the release of endogenous pain-relieving substances, electric neuromodulation can effectively alleviate pain and improve patients' quality of life. Several modalities of electric neuromodulation, with a different grade of invasiveness, provide tailored strategies to tackle various forms and origins of chronic pain. Through an exploration of the anatomical and physiological pathways of chronic pain, encompassing neurotransmitter involvement, this narrative review offers insights into electrical therapies' mechanisms of action, clinical utility, and future perspectives in chronic pain management.

A rare case of upper lip schwannoma: A case report with analysis of the histological, immunohistochemical and pathogenesis aspects

INTRODUCTION AND IMPORTANCE

Schwannoma, a benign tumor originating from Schwann cells, is a rare case found intraorally. The tongue, palate and buccal mucosa are the most common sites of intraoral Schwannoma while it is very rarely found on the lips. Previous studies reported only twelve cases of Schwannoma on the upper lip. The etiology of Schwannoma is unknown, but in some literature, Schwannoma occurs due to a defect in the NF2 gene. Management of Schwannoma is excision of the capsule. The prognosis is good, and the recurrency is low. This article reports a rare case of upper lip Schwannoma in adolescent and its management with its histological, immunohistochemical and pathogenesis aspects.

CASE PRESENTATION

A 16-years old female presented a painless, semi-solid, mobile lump on the upper lip measuring of approximately 1.5 × 3 cm that had similar color with the surrounding tissue. The lump appeared 7 years ago.

CLINICAL DISCUSSION

Excision of the capsule and margins of the tumor. Histopathological examination showed a unique feature of Schwannoma, the Verocay bodies. Subsequent immunohistochemical examination of S100 protein showed a classic type of Schwannoma.

CONCLUSION

Upper lip schwannoma is a very rare tumor, and this type of tumor cannot be distinguished from other benign soft tissue tumors based on clinical findings. Immunohistochemical results are in accordance with the Histopathological results for the final diagnosis of Schwannoma. Schwannoma can be used as a differential diagnosis in cases of lumps on the lips with sessile, similar color like surrounding tissue, painless, and movable features.

An in silico analysis of neuromodulation for pain relief: Determining the role of classical electrodynamics

There has been ongoing debate about the efficacy and mechanism of action of neuromodulation devices in pain relief applications. It has recently been suggested that both issues may be resolved if electromagnetic theory is incorporated into the understanding and application of this technology, and we therefore undertook an in silico analysis to further explore this idea. We created a CAD replication of a standard neuromodulation electrode array with a generic linear 3/6 mm 8-contact lead, developed a parameterized algorithmic model for the pulse delivered by the device and assigned material properties to biologic media to accurately reflect their electromagnetic properties. We then created a physical simulation of the device's output both in air and in the biophysical environment. The simulations confirmed the presence of an electromagnetic field (EM field). Variations in programming of the device affected the strength of the EM field by orders of magnitude. The biologic media all absorbed the EM field, an effect which was particularly pronounced in cerebrospinal fluid and muscle. We discuss the implications of all these findings in relation to the literature. We suggest that knowledge of electromagnetic theory and its application within the biophysical space is required for the optimal use of neuromodulation devices in pain relief applications.

Assessing the Knowledge, Attitude, and Practice of Orthopedicians for Pain Management by Multimodal Approach: A Prospective, Cross-Sectional, and Observational Survey

BACKGROUND

The routine use of multimodal analgesic modality results in lower pain scores with minimum side effects and opioid utilization.

MATERIALS AND METHODS

 A prospective, cross-sectional, observational study was conducted among orthopedicians practicing across India to assess the professional opinions on using analgesics to manage orthopedic pain effectively.

RESULTS

 A total of 530 orthopedicians participated in this survey. Over 50% of the participants responded that tramadol with or without paracetamol was the choice of therapy for acute pain. Nearly 50% of the participants mentioned that multimodal interventions can sometimes help to manage pain. A total of 55.6% of participants mentioned that using Non-steroidal anti-inflammatory drugs was the most common in their clinical practice, while 25.7% of participants mentioned that they used tramadol more commonly in their clinical practice. As per clinical efficacy ranking, the combination of tramadol plus paracetamol (44.3%) was ranked first among analgesic combinations, followed by aceclofenac plus paracetamol (40.0%). The severity of pain (62.6%) followed by age (60.6%) and duration of therapy (52.6%) were the most common factors that should be considered while prescribing tramadol plus paracetamol combination. Gastrointestinal and renal are reported as the most common safety concerns encountered with analgesics.

CONCLUSION

 The combination of tramadol and paracetamol was identified as the most preferred choice of analgesics for prolonged orthopedic pain management.

Managing Severe Cancer Pain with Oxycodone/Naloxone Treatment: A Literature Review Update

Severe cancer pain substantially affects patients' quality of life, increasing the burden of the disease and reducing the disability-adjusted life years. Although opioid analgesics are effective, they may induce opioid-induced bowel dysfunction (OIBD). Oxycodone/naloxone combination therapy has emerged as a promising approach to mitigate opioid-induced constipation (OIC) while providing effective pain relief. This review provides an updated analysis of the literature of the last decade regarding the use of oxycodone/naloxone in the management of severe cancer pain. Through a comprehensive search of databases, studies focusing on the efficacy, safety, and patient experience of oxycodone/naloxone's prolonged release in severe cancer pain management were identified. Furthermore, the literature discusses the mechanism of action of naloxone in mitigating OIC without compromising opioid analgesia. Overall, the evidence suggests that oxycodone/naloxone combination therapy offers a valuable option for effectively managing severe cancer pain while minimizing opioid-induced constipation, thereby improving patients' quality of life. However, further research is needed to optimize dosing regimens, evaluate long-term safety, and assess patient outcomes in diverse cancer populations.

Advancing Postoperative Pain Management in Oral Cancer Patients: A Systematic Review

The goal of this review is to shed light on the management of orofacial discomfort after a cancer diagnosis in the head and neck region. A search was conducted on PubMed, Scopus, and Web of Science to identify studies on postoperative pain control in oral cancer. The review included open-access research, investigations into pain management, randomized clinical trials, retrospective studies, case-control studies, prospective studies, English-written studies, and full-text publications. Exclusion criteria included animal studies; in vitro studies; off-topic studies; reviews, case reports, letters, or comments; and non-English language. Three reviewers independently accessed databases and assigned a quality rating to the chosen articles. The review explores postoperative pain management in oral cancer patients; highlighting persistent opioid use; the efficacy of adjuvant drugs, such as gabapentin; and a multimodal approach. It emphasizes the need for personalized pain management, recognizing individual pain perception and tailoring interventions. Integrating pharmacological and non-pharmacological strategies is crucial for comprehensive pain management. The review also serves as a guide for future research, emphasizing the need for standardized methodologies and diverse participant populations.

Dexmedetomidine Prolongs Lidocaine Intravenous Regional Anesthesia in Rats by Blocking the Hyperpolarization-Activated Cation Current

Purpose

Intravenous regional anesthesia (IVRA) using lidocaine provides effective localized analgesia but its duration is limited. The mechanism by which dexmedetomidine enhances lidocaine IVRA is unclear but may involve modulation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels.

Materials and Methods

Lidocaine IVRA with varying dexmedetomidine concentrations was performed in the tails of Sprague-Dawley rats. Tail-flick and tail-clamping tests assessed IVRA analgesia and anesthesia efficacy and duration. Contributions of α2 adrenergic receptors and HCN channels were evaluated by incorporating an α adrenergic receptor antagonist, the HCN channel inhibitor ZD7288, and the HCN channel agonist forskolin. Furthermore, whole-cell patch clamp electrophysiology quantified the effects of dexmedetomidine on HCN channels mediating hyperpolarization-activated cation current (Ih) in isolated dorsal root ganglion neurons.

Results

Dexmedetomidine dose-dependently extended lidocaine IVRA duration and analgesia, unaffected by α2 receptor blockade. The HCN channel inhibitor ZD7288 also prolonged lidocaine IVRA effects, while the HCN channel activator forskolin shortened effects. In dorsal root ganglion neurons, dexmedetomidine concentration-dependently inhibited Ih amplitude and shifted the voltage-dependence of HCN channel activation.

Conclusion

Dexmedetomidine prolongs lidocaine IVRA duration by directly inhibiting HCN channel activity, independent of α2 adrenergic receptor activation. This HCN channel inhibition represents a novel mechanism underlying the anesthetic and analgesic adjuvant effects of dexmedetomidine in IVRA.

Analgesic Peptides: From Natural Diversity to Rational Design

Pain affects one-third of the global population and is a significant public health issue. The use of opioid drugs, which are the strongest painkillers, is associated with several side effects, such as tolerance, addiction, overdose, and even death. An increasing demand for novel, safer analgesic agents is a driving force for exploring natural sources of bioactive peptides with antinociceptive activity. Since the G protein-coupled receptors (GPCRs) play a crucial role in pain modulation, the discovery of new peptide ligands for GPCRs is a significant challenge for novel drug development. The aim of this review is to present peptides of human and animal origin with antinociceptive potential and to show the possibilities of their modification, as well as the design of novel structures. The study presents the current knowledge on structure-activity relationship in the design of peptide-based biomimetic compounds, the modification strategies directed at increasing the antinociceptive activity, and improvement of metabolic stability and pharmacodynamic profile. The procedures employed in prolonged drug delivery of emerging compounds are also discussed. The work summarizes the conditions leading to the development of potential morphine replacements.

Pregabalin versus Gabapentin Efficacy in the Management of Neuropathic Pain Associated with Failed Back Surgery Syndrome

OBJECTIVE

Failed back surgery syndrome (FBSS) is a common long-term complication following spine surgeries characterized by chronic persistent pain; different strategies of management were employed to deal with it. This clinical trial aims to compare the efficacy of Pregabalin and Gabapentin in the management of this condition.

METHODS

A double-blind, randomized, comparative study (clinical trial registry NCT05324761 on 11th April 2022) with two parallel arms with Pregabalin and Gabapentin were used in arms one and two, respectively. Visual analog scale was used for basal and endpoint assessment of pain. T-test and analysis of covariance were used to deal with different variables. A pairwise test was used to compare pairs of means.

RESULTS

Of 66 patients referred to the trial, 64 were eligible, with 60 patients completing the 30 days trial. Both pregabalin and gabapentin effectively reduce pain, with significant p-values of 0.001 for each group. However, the pregabalin group was superior to gabapentin in pain reduction (p=0.001). Gender was an insignificant factor (p=0.574 and p=0.445 for the pregabalin and gabapentin groups, respectively, with a non-significant reduction (p=0.393) for both groups in total. Location of stenosis before surgery and type of surgery performed show non-significant effect on pain reduction for both groups.

CONCLUSION

Both pregabalin and gabapentin effectively and safely relieve neuropathic pain associated with FBSS; pregabalin was significantly more effective irrespective of the patients' gender.

Evaluation of the anti-nociceptive profile of essential oil from Melissa officinalis L. (lemon balm) in acute and chronic pain models

ETHNOPHARMACOLOGICAL RELEVANCE

Melissa officinalis L. (Lamiaceae) is a medicinal plant native to Mediterranean regions and found in other parts of the world. Extracts and essential oil from this widely cultivated culinary medicinal herb are used in traditional medicine to manage a variety of disorders that include epilepsy and pain.

AIM OF THE STUDY

To assess the anti-nociceptive potentials of Melissa officinalis essential oil (MO) and probe the involvement of adrenergic, opioidergic, serotonergic and potassium adenosine triphosphate (KATP) mechanisms in its anti-nociceptive effects.

MATERIAL AND METHODS

We employed formalin-, acetic acid and hot plate-induced nociception to study the acute anti-nociceptive effects of MO. The sciatic nerve injury (CCI) model of neuropathic pain was utilized to study the anti-nociceptive effects of MO on chronic pain. Effects of MO on anxiety, cognitive deficits, oxidative stress and inflammation in the CCI rats were evaluated on elevated plus maze, open field test, novel object recognition, oxidative stress parameters and pro-inflammatory cytokines, respectively. The possible mechanism(s) of MO's anti-nociceptive effects were elucidated using prazosin, yohimbine, propranolol, glibenclimide, naloxone and metergoline, which are acknowledged antagonists for α1-, α2- and β-adrenergic, potassium adenosine triphosphate (KATP), opioidergic and serotonergic systems, respectively.

RESULTS

MO significantly attenuated acetic acid- and formalin-induced nociception; prolonged the mean reaction time of rats on hot plate before and following sciatic nerve chronic injury (CCI). MO ameliorated anxiety, cognitive deficits and oxidative stress, reduced pro-inflammatory cytokine levels and produced a near total restoration of injured sciatic nerves in CCI rats. Naloxone, metergoline and glibenclimide significantly blocked, while prazosin, yohimbine and popranolol failed to block the anti-nociceptive effects of MO in formalin-induced nociception.

CONCLUSIONS

MO contains biologically active compounds with potential anti-nociceptive properties that modulate KATP, opioidergic and serotonergic pathways. These support the development of bioactive compounds from MO as anti-nociceptive agents.

Dorsal root ganglion stimulation provides significant functional improvement from acute debilitating Crohn's disease: A novel use

Crohn's disease is a chronic inflammatory bowel condition causing symptoms, notably pain, due to ongoing intestinal inflammation or complications like abscesses, strictures, and fistulas, which are common in IBD patients. Abdominal pain affects up to 60 % of IBD patients, irrespective of disease severity, prompting medical attention. Various medications like NSAIDs, antidepressants, antispasmodics, anticonvulsants, and opioids are used to manage pain, but they have limited effectiveness and potential side effects, even during remission. In this case, a 20-year-old Caucasian female college student [height 5'4″, weight 120lbs (54.4 kg)] with juvenile idiopathic arthritis and Crohn's disease experienced severe daily abdominal pain, negatively impacting her life. Despite a multimodal regimen, including gabapentin, nortriptyline, duloxetine, and acetaminophen, her pain persisted, significantly affecting her appetite, sleep, mood, activity level, and overall quality of life (QOL). To address this, dorsal root ganglion (DRG) stimulation was considered. The patient aimed for a 20 % pain reduction and improved QOL. Trial leads were placed along the T10 and T12 DRG, resulting in a 25 % pain reduction (8-6 out of 10) and substantial QOL improvement. She could eat, sleep without interruptions, walk longer distances, and be more active. The T12 lead was more effective than the T10, targeting upper abdomen stimulation. The patient and her mother were highly satisfied and opted for permanent implantation for the T11 and T12 DRG. While DRG stimulation was approved in 2016 for chronic pain, to our knowledge, this is the first reported case of its use in a patient with debilitating Crohn's disease.

Role of bradykinin and prostaglandin EP4 receptors in regulating TRPV1 channel sensitization in rat dorsal root ganglion neurons

Transient receptor potential vanilloid type-1 (TRPV1) channels play key roles in chronic pain conditions and are modulated by different inflammatory mediators to elicit heat sensitisation. Bradykinin is a 9-amino acid peptide chain that promotes inflammation. The aim of present study is to investigate how bradykinin and prostaglandin receptors (EP3 and EP4 ) modulate the sensitisation of TRPV1-mediated responses. Calcium imaging studies of rat dorsal root ganglion (DRG) neurons were employed to investigate the desensitizing responses of TRPV1 ion channels by capsaicin, and the re-sensitization of TRPV1 by bradykinin, then to explore the role EP3 and EP4 receptors in mediating these bradykinin-dependent effects. Immunocytochemistry was used to study the co-expression and distribution of EP4, TRPV1, COX-1 and B2 in rat DRG neurons. Desensitization was seen upon repeated capsaicin application, we show that bradykinin-mediated sensitization of capsaicin-evoked calcium responses in rat DRG neurons occurs is dependent on COX-1 activity and utilizes a pathway that involves EP4 but not EP3 receptors. Immunocytochemical techniques revealed that EP4, TRPV1, COX-1 and B2 proteins are expressed mainly in small diameter (<1000 μm2 ) cell bodies of rat DRG neurons which are typically nociceptors. The present study provides suggestive evidence for a potential signalling pathway through which bradykinin may regulate TRPV1 ion channel function via EP4 receptors. In addition to confirming existing knowledge, the anatomical distribution and colocalization of these proteins in DRG neurons as revealed by this study offer valuable insight.

Whole Body Cryostimulation: A New Adjuvant Treatment in Central Sensitization Syndromes? An Expert Opinion

Central sensitisation is defined as a multifactorial etiopathogenetic condition involving an increase in the reactivity of nociceptive neurons and alterations in pain transmission and perception in the central nervous system. Patients may present with widespread chronic pain, fatigue, sleep disturbance, dizziness, psychological (e.g., depression, anxiety, and anger) and social impairment. Pain can be spontaneous in onset and persistence, characterised by an exaggerated response and spread beyond the site of origin, and sometimes triggered by a non-painful stimulus. Whole-body cryostimulation (WBC) could be an adjuvant therapy in the management of this type of pain because of its global anti-inflammatory effect, changes in cytokines and hormone secretion, reduction in nerve conduction velocity, autonomic modulation, and release of neurotransmitters involved in the pain pathway. In several conditions (e.g., fibromyalgia, rheumatoid arthritis, and chronic musculoskeletal pain), WBC affects physical performance, pain perception, and psychological aspects. Given its multiple targets and effects at different organs and levels, WBC appears to be a versatile adjuvant treatment for a wide range of conditions of rehabilitation interest. Further research is needed to fully understand the mechanisms of analgesic effect and potential actions on pain pathways, as well as to study long-term effects and potential uses in other chronic pain conditions.

Effects and mechanisms of acupuncture analgesia mediated by afferent nerves in acupoint microenvironments

In the past few decades, the use of acupuncture analgesia in clinical practice has increased worldwide. This is due to its various benefits, including natural alleviation of pain without causing various adverse effects associated with non-steroidal anti-inflammatory drugs (NSAID) and opioids. The acupoint represents the initial site of acupuncture stimulation, where diverse types of nerve fibers located at the acupoint hold significant roles in the generation and transmission of acupuncture-related information. In this study, we analyzed the patterns and mechanisms of acupuncture analgesic mediated by acupoint afferent fibers, and found that acupuncture stimulates acupoints which rapidly and directly induces activation of high-density primary afferent fibers under the acupoints, including myelinated A fibers and unmyelinated C fibers. During acupuncture stimulation at the muscle layer, the analgesic effects can be induced by stimulation of A fiber threshold intensity. At the skin layer, the analgesic effects can only be produced by stimulation of C fiber threshold intensity. Electroacupuncture (EA) activates A fibers, while manual acupuncture (MA) activates both A and C fibers. Furthermore, acupuncture alters acupoint microenvironments, which positively modulates afferent fibers, enhancing the transmission of analgesic signals. In addition to local activation and conduction at acupoints, nerve fibers mediate the transmission of acupuncture information to pain centers. In the spinal cord, acupuncture activates neurons by inducing afferent fiber depolarization, modulating pain gating, inhibiting long-term potentiation (LTP) of the spinal dorsal horn and wide dynamic range (WDR) neuronal activities. At higher nerve centers, acupuncture inhibits neuronal activation in pain-related brain regions. In summary, acupuncture inhibits pain signal transmission at peripheral and central systems by activating different patterns of afferent fibers located on various layers of acupoints. This study provides ideas for enhancing the precise application and clinical translation of acupuncture.

Chemogenetics Modulation of Electroacupuncture Analgesia in Mice Spared Nerve Injury-Induced Neuropathic Pain through TRPV1 Signaling Pathway

Neuropathic pain, which is initiated by a malfunction of the somatosensory cortex system, elicits inflammation and simultaneously activates glial cells that initiate neuroinflammation. Electroacupuncture (EA) has been shown to have therapeutic effects for neuropathic pain, although with uncertain mechanisms. We suggest that EA can reliably cure neuropathic disease through anti-inflammation and transient receptor potential V1 (TRPV1) signaling pathways from the peripheral to the central nervous system. To explore this, we used EA to treat the mice spared nerve injury (SNI) model and explore the underlying molecular mechanisms through novel chemogenetics techniques. Both mechanical and thermal pain were found in SNI mice at four weeks (mechanical: 3.23 ± 0.29 g; thermal: 4.9 ± 0.14 s). Mechanical hyperalgesia was partially attenuated by 2 Hz EA (mechanical: 4.05 ± 0.19 g), and thermal hyperalgesia was fully reduced (thermal: 6.22 ± 0.26 s) but not with sham EA (mechanical: 3.13 ± 0.23 g; thermal: 4.58 ± 0.37 s), suggesting EA's specificity. In addition, animals with Trpv1 deletion showed partial mechanical hyperalgesia and no significant induction of thermal hyperalgesia in neuropathic pain mice (mechanical: 4.43 ± 0.26 g; thermal: 6.24 ± 0.09 s). Moreover, we found increased levels of inflammatory factors such as interleukin-1 beta (IL1-β), IL-3, IL-6, IL-12, IL-17, tumor necrosis factor alpha, and interferon gamma after SNI modeling, which decreased in the EA and Trpv1-/- groups rather than the sham group. Western blot and immunofluorescence analysis showed similar tendencies in the dorsal root ganglion, spinal cord dorsal horn, somatosensory cortex (SSC), and anterior cingulate cortex (ACC). In addition, a novel chemogenetics method was used to precisely inhibit SSC to ACC activity, which showed an analgesic effect through the TRPV1 pathway. In summary, our findings indicate a novel mechanism underlying neuropathic pain as a beneficial target for neuropathic pain.

Snake and arthropod venoms: Search for inflammatory activity in human cells involved in joint diseases

Most anti-inflammatory drugs currently adopted to treat chronic inflammatory joint diseases can alleviate symptoms but they do not lead to remission. Therefore, new and more efficient drugs are needed to block the course of joint inflammatory diseases. Animal venoms, rich in bioactive compounds, can contribute as valuable tools in this field of research. In this study, we first demonstrate the direct action of venoms on cells that constitute the articular joints. We established a platform consisting of cell-based assays to evaluate the release of cytokines (IL-6, IL-8, TNFα, IL-1β, and IL-10) by human chondrocytes, synoviocytes and THP1 macrophages, as well as the release of neuropeptides (substance-P and β-endorphin) by differentiated sensory neuron-like cells, 24 h after stimulation of cells with 21 animal venoms from snake and arthropod species, sourced from different taxonomic families and geographic origins. Results demonstrated that at non-cytotoxic concentrations, the venoms activate at varying degrees the secretion of inflammatory mediators involved in the pathology of articular diseases, such as IL-6, IL-8, and TNF-α by chondrocytes, synoviocytes, and macrophages and of substance P by neuron-like cells. Venoms of the Viperidae snake family were more inflammatory than those of the Elapidae family, while venoms of Arthropods were less inflammatory than snake venoms. Notably, some venoms also induced the release of the anti-inflammatory IL-10 by macrophages. However, the scorpion Buthus occitanus venom induced the release of IL-10 without increasing the release of inflammatory cytokines by macrophages. Since the cell types used in the experiments are crucial elements in joint inflammatory processes, the results of this work may guide future research on the activation of receptors and inflammatory signaling pathways by selected venoms in these particular cells, aiming at discovering new targets for therapeutic intervention.

Based on spinal central sensitization creating analgesic screening approach to excavate anti-neuropathic pain ingredients of Corydalis yanhusuo W.T.Wang

ETHNOPHARMACOLOGICAL RELEVANCE

Corydalis Rhizome (RC) as a traditional analgesic Chinese medicine is the dried tuber of Corydalis yanhusuo W.T.Wang. Many efforts have revealed that RC could effectively alleviate neuropathic pain, while its active ingredients in neuropathic pain are still not clear.

AIM OF THE STUDY

Spinal central sensitization contributes greatly to neuropathic pain, and neuron, astrocyte and microglia play important roles in spinal central sensitization. The aim of the present study is to excavate active compounds in RC regulating spinal central sensitization to inhibit neuropathic pain.

MATERIALS AND METHODS

Immunofluorescence and western blotting were used to determine protein expression levels. Gene expression levels were detected by RT-PCR. PC12 neuronal cells, C6 astrocyte cells, and BV2 microglia cells were cultured for in vitro studies. Targeting multi types of cells extraction combined with HPLC-Q-TOF-MS/MS was established to identify components binding to above cells. Animal studies were used to verify the analgesic activities of components.

RESULTS

Total alkaloids of RC (RC-TA) significantly relieved neuropathic pain in chronic constriction injury (CCI) rats and repressed spinal central sensitization. Eight components of RC-TA were found to bind to PC12, C6, or BV2 cells. They could respectively suppress the activation of cells in vitro and alleviate CCI-induced neuropathic pain, among which glaucine and dehydrocorydaline induced antinociception was stronger than l-THP. Meanwhile, glaucine had no effect on acute or chronic inflammatory pain, and its antinociception in neuropathic pain could be abolished by dopamine D1 receptor agonist.

CONCLUSIONS

Employing multi types of cells based on spinal central sensitization rather than single cell may allow for more thorough excavation of active substances. Glaucine was firstly found could attenuate neuropathic pain but not other types of pain which indicated that different alkaloids in RC exert distinct analgesic effects on different pain models, and gluacine has the potential to be developed as an analgesic drug specifically for neuropathic pain relieving.

Cardiorespiratory fitness mediates cortisol and lactate responses to winter and summer marches

Background

The influence of homeostatically regulated physiological processes, including cardiorespiratory fitness (VO2max), on the response to physical stressors such as acclimatisation and marching, remains understudied. We aimed to investigate the effects of summer and winter acclimatisation and marching on cortisol levels and blood lactate, to gain insight into the role of these physiological processes in the stress response.

Methods

Two groups of young Europeans, classified as poor (PCF; n=9) and good physical condition (GCF; n=21), based on a VO2MAX threshold of 40 mL O2/ kg/min, underwent 2-h March (6-7 km/h) in winter (5˚C) and summer (32˚C). Commercial tests, UniCel DxI Access Cortisol assay and EKF Biosen Clinic/GP assay were used for cortisol and lactate blood measurements (morning samples and those taken immediately after marches), respectively.

Exploring the Mechanism of Immediate Analgesia Induced by Tuina Intervention on Minor Chronic Constriction Injury in Rats Using LC-MS

Purpose

This study aimed to investigate changes in metabolomic expression in the spinal dorsal horn (SDH) and thalamus during a Tuina session, aiming to elucidate the mechanism of immediate analgesia.

Methods

The rats were randomly divided into three groups: the Sham group, the Model group, and the Tuina group. A minor chronic constriction injury (minor CCI) model was established in both the Model group and the Tuina group. The therapeutic effect of Tuina was determined using the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) tests. Differential metabolites of the SDH and thalamus were detected using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Bioinformatic analysis was performed using CV, PCA, Venn, and KEGG.

Results

The therapeutic effect of MWT and TWL after instant Tuina intervention was significant. The therapeutic effect of Tuina instant was significantly better compared to the Model group. In the Veen analysis, it was found that Tuina instantly regulates 10 differential metabolites in the SDH and 5 differential metabolites in the thalamus. In the KEGG enrichment analysis, we found that differential metabolites were enriched in 43 pathways in the thalamus and 70 pathways in the SDH.

Conclusion

Tuina therapy may have analgesic effects by metabolizing neurotransmitters such as 2-Picolinic Acid, 5-Hydroxy-Tryptophan Glutathione Betaine-aldehyde-chloride Leucine Lysine Methionine Sarcosine Succinic Acid Histidine Acetylcholine and 5-Hydroxyindoleacetic Acid through the cAMP pathway. It also affects pathways of neurodegeneration-multiple diseases, butanoate metabolism, tyrosine metabolism.

Investigation of Cox-2 inhibition of Laportea decumana (Roxb). Wedd extract to support its analgesic potential

ETHNOPHARMACOLOGICAL RELEVANCE

Itchy leaves Laportea decumana (Roxb). Wedd is an indigenous plant in Maluku, Indonesia, and is used traditionally to treat complaints such as fatigue and joint and muscle pains.

AIM OF THE STUDY

To provide scientific proof of the analgesic effect of L. decumana ethanolic extract tested in in vivo assays while investigating its bioactive phytochemicals using liquid chromatography tandem high-resolution mass spectrometry (LC-HRMS) profiling and Cox-2 inhibition assay.

MATERIALS AND METHODS

To investigate the analgesic activity of the ethanolic extract, assays were conducted on male mice Balb/c strain by chemical induction using acetic acid (i.p.) and heat induction (hotplate). Mice were divided into six groups consisting of six mice, i.e., the baseline group; positive control group (paracetamol 80 mg/kg BW); groups treated with extracts in dosages of 100, 200, and 400 mg/kg bodyweight (BW); and negative control group (acetic acid 0.6%, i. p.). The crude extract was partitioned with liquid-liquid fractionation to yield hexane, ethyl acetate, and water fractions. The extract and fraction were assayed for Cox-2 enzyme inhibition, and the chemical profiles were analyzed using untargeted LC-HRMS.

RESULTS

The analgesic assays revealed the dose-dependent effect of the extracts, of the effect of treatment with 400 mg/kg BW was not significantly different with that of paracetamol (p < 0.05). The ethyl acetate fraction showed IC50 of 19.25 μg/mL on Cox-2 inhibition (IC50 celexocib 18.48 μg/mL). LC-HRMS showed a distinctive profile of the ethyl acetate fraction compared with those in the extract and other fractions.

CONCLUSIONS

This study presents scientific evidence of the analgesic activity of the L. decumana ethanol extract given orally to experimental animals. Inflammatory inhibition plays a role in the overall analgesic mechanism by Cox-2 inhibition of the extract and all fractions. This finding is also supported by the phytochemical profiles of the extract and fractions, showing the presence of compounds reported elsewhere as anti-inflammatory activity.

Standardized Centella asiatica extract ECa 233 alleviates pain hypersensitivity by modulating P2X3 in trigeminal neuropathic pain

OBJECTIVE

During oral surgery and temporomandibular joint repositioning, pain hypersensitivity often occurs due to irritation or inflammation of the nerve endings in the orofacial region. This study aimed to investigate the effects of ECa 233, a Centella asiatica-standardized extract, on the development of mechanical hyperalgesia and allodynia induced by chronic constriction injury of the infraorbital nerve in mice.

METHODOLOGY

The right infraorbital nerves of the mice were ligated. Oral carbamazepine (20 mg/kg) or ECa 233 (30, 100, or 300 mg/kg) was administered daily for 21 days. Von Frey and air-puff tests were performed on both sides of the whisker pad on days 0, 7, 14, and 21. Thereafter, the expression of purinergic receptor subtype 3 (P2X3) and voltage-gated sodium channel 1.7 (NaV1.7), a transmembrane protein, in the trigeminal ganglion and c-fos immunoreactivity-positive neurons in the trigeminal nucleus caudalis was assessed.

RESULTS

After 21 days of infraorbital nerve ligation, the mice showed allodynia- and hyperalgesia-like behavior, P2X3 and NaV1.7 were upregulated in the trigeminal ganglion, and nociceptive activity increased in the trigeminal nucleus caudalis. However, the oral administration of carbamazepine (20 mg/kg), ECa 233 (100 mg/kg), or ECa 233 (300 mg/kg) mitigated these effects. Nevertheless, ECa 233 failed to affect NaV1.7 protein expression.

CONCLUSION

Carbamazepine and ECa 233 can prevent pain hypersensitivity in mice. Considering the side effects of the long-term use of carbamazepine, ECa 233 monotherapy or combined ECa 233 and carbamazepine therapy can be used as an alternative for regulating the development of hypersensitivity in trigeminal pain. However, further detailed clinical studies should be conducted to provide comprehensive information on the use of ECa 233.

Systematic Review on Herbal Preparations for Controlling Visceral Hypersensitivity in Functional Gastrointestinal Disorders

BACKGROUND

Visceral hypersensitivity (VH) is an overreaction of the gastrointestinal (GI) tract to various stimuli and is characterized by hyperalgesia and/or allodynia. VH contributes to the etiology of many GI dysfunctions, particularly irritable bowel syndrome (IBS). Although the exact mechanisms underlying VH are yet to be found, inflammation and oxidative stress, psychosocial factors, and sensorimotor alterations may play significant roles in it.

OBJECTIVE

In this review, we provide an overview of VH and its pathophysiological function in GI disorders. Adverse effects of synthetic drugs may make herbal agents a good candidate for pain management. Therefore, in this review, we will discuss the efficacy of herbal agents in the management of VH with a focus on their anti-inflammatory and antioxidant potentials.

METHODS

Data were extracted from clinical and animal studies published in English between 2004 and June, 2020, which were collected from PubMed, Google Scholar, Scopus, and Cochrane Library.

RESULTS

Overall, Radix, Melissia, Glycyrrhizae, Mentha, and Liquorice were the most efficient herbals for VH management in IBS and dyspepsia, predominantly through modulation of the mRNA expression of transient receptor potential vanilloid type-1 (TRPV1) and suppression of 5- hydroxytryptamine 3 (5-HT3) or the serotonin receptors.

CONCLUSION

Considering the positive effects of herbal formulations in VH management, further research on novel herbal and/or herbal/chemical preparations is warranted.