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Analgesia induced by stressful and painful stimuli is an adaptive response during life-threatening situations. There is no evidence linking the mechanisms underlying them, while the former depends on the activation of stress-related brain pathways, the second depends on opioidergic mechanisms in the nucleus accumbens and on nicotinic cholinergic mechanisms in the rostral ventromedial medulla. In this study, we hypothesized that stress-induced analgesia is also dependent on opioidergic mechanisms in the nucleus accumbens and on nicotinic cholinergic mechanisms in the rostral ventromedial medulla. We used immobilization, a classical procedure to induce acute stress, and evaluated its ability to decrease the nociceptive responses induced either by carrageenan or by formalin in rats. Immobilization stress significantly decreased either carrageenan-induced hyperalgesia or formalin-induced tonic nociception in a time-dependent manner. This stress-induced analgesia is similar to pain-induced analgesia, as revealed by contrasting the antinociceptive effect induced by immobilization and by a forepaw injection of capsaicin. The administration of a µ-opioid receptor antagonist (CTOP, 0.5 µg) into the nucleus accumbens, as well as that of a nicotinic cholinergic receptor antagonist (mecamylamine, 0.6 µg) into the rostral ventromedial medulla, blocked immobilization stress-induced analgesia in both pain models. These results demonstrate that supraspinal mechanisms which are known to mediate pain-induced analgesia also mediate stress-induced analgesia. Therefore both forms of analgesia have overlapping mechanisms, probably recruited in response to the perception of danger.
Learn More >The opioid-related behaviours in treatment (ORBIT) scale are a measure of recent indicators of potential extra-medical opioid use. Indicators of potential extra-medical opioid use are divergent practices among people prescribed opioids that may place them at risk of harm. This study aimed to examine the correlates of indicators of potential extra-medical opioid use in people prescribed opioids for chronic non-cancer pain (CNCP).
Learn More >The purpose of this research is to explore the philosophy regarding understanding the complex experience of living with chronic pain. As well, this article addresses a person's suffering as an evolving process of learning to not only manage pain but to learn how to live well through exploring their suffering narrative. A hermeneutical interpretive approach was used to engage participants in this research and to offer a philosophical reinterpretation of living with chronic pain from a humanistic and tacit perspective. This work is offered to invite and extend our discussions about the complexity of living with chronic pain. It can also be understood as a process of rewriting oneself from a lived chaotic state of pain into a new affective historical consciousness. This transition from acute to chronic pain explored through a philosophical context can provide insight into the ways in which patients learn to live well with their condition.
Learn More >Endometriosis is an estrogen-dependent chronic progressive gynecological disease that affects around 10% of women of reproductive age. A recent study shows that brain-derived neurotrophic factor (BDNF) has the potential as a clinical marker in the diagnosis of endometriosis. We aimed to determine whether BDNF levels are correlated with pain scores associated with endometriosis.
Learn More >Little is still known about the underlying mechanisms that drive and maintain neuropathic pain (NeuP). Recently, lipids have been implicated as endogenous proalgesic ligands affecting onset and maintenance of pain; however, in the case of NeuP, the relationship is largely unexplored.
Learn More >Hind paw-directed assays are commonly used to study the analgesic effects of opioids in mice. However, opioid-induced hyperlocomotion can obscure results of such assays.
Learn More >Some evidence indicates endometriosis and migraine have a common genetic predisposition in sex-hormone genes, which could have important implications for the treatment of these two heterogenous conditions. To date, the genes responsibility remains unknown. Based on the biological hypothesis that polymorphisms of genes involved in sex-hormone pathways may influence estrogen levels and phenotypes of both disorders, we did a literature search for candidate sex-hormone genes and genes involved in the metabolism of estradiol. The aim was to review the evidence for shared sex-hormone-related polymorphisms between endometriosis and migraine and provide an exhaustive overview of the current literature. We included case-control studies investigating associations between candidate sex-hormone-related genes and the disorders endometriosis and migraine, respectively. Results showed three overlapping sex-hormone-associated polymorphisms in estrogen receptor genes that are associated with both conditions. To confirm possible associations with other sex-hormone genes, larger studies are needed.
Learn More >Bladder pain syndrome/interstitial cystitis (BPS/IC) is a persistent pain perceived in the urinary bladder region, accompanied by at least one symptom, such as pain worsening with bladder filling and daytime or nighttime urinary frequency without any proven infection or obvious pathology. The aim of this study is to evaluate the efficacy and safety of pentosan polysulfate (PPS) in patients with BPS/IC.
Learn More >Pulsed radiofrequency (PRF) therapy is one of the most common treatment options for neuropathic pain, albeit the underlying mechanism has not been hitherto elucidated. In this study, we investigated the efficacy and mechanism of PRF therapy on resiniferatoxin (RTX)-induced mechanical allodynia, which has been used as a model of postherpetic neuralgia (PHN). Adult male rats were intraperitoneally injected with a vehicle or RTX. Furthermore, PRF current was applied on a unilateral sciatic nerve in all RTX-treated rats. On both ipsilateral and contralateral sides, the paw mechanical withdrawal thresholds were examined and L4-6 dorsal root ganglia (DRG) were harvested. In the DRG of rats with RTX-induced mechanical allodynia, Na1.7, a voltage-gated Na channel, was upregulated following the enhancement of extracellular signal-regulated kinase phosphorylation. Early PRF therapy, which was applied 1 week after RTX exposure, suppressed this Na1.7 upregulation and showed an anti-allodynic effect; however, late PRF therapy, which was applied after 5 weeks of RTX exposure, failed to inhibit allodynia. Interestingly, late PRF therapy became effective after daily tramadol administration for 7 days, starting from 2 weeks after RTX exposure. Both early PRF therapy and late PRF therapy combined with early tramadol treatment suppressed Na1.7 upregulation in the DRG of rats with RTX-induced mechanical allodynia. Therefore, Na1.7 upregulation in DRG is related to the development of RTX-induced neuropathic pain; moreover, PRF therapy may be effective in the clinical management of patients with PHN via Na1.7 upregulation inhibition.
Learn More >Chronic pain conditions are common and have a considerable impact on health and wellbeing. This impact can be reduced by cognitive behavioral therapy (CBT), the most commonly applied psychological approach to chronic pain. At the same time, CBT continues to develop, and now includes what is sometimes called "third wave" CBT. In this review, we examine the evidence for application of acceptance and commitment therapy (ACT), a principal example of this new wave or latest generation of treatment approaches, in people with chronic pain. We identified 25 randomized controlled trials of ACT for adults with chronic pain. Across the included trials, small to large effect sizes favoring ACT were reported for key outcomes including pain interference, disability, depression, and quality of life. Evidence from three studies provided some support for the cost effectiveness of ACT for chronic pain. Evidence also supported the mediating role of theoretically consistent processes of change (psychological flexibility) in relation to treatment outcomes. Investigation of moderators and predictors of outcomes was limited and inconsistent. In future, a greater focus on process based treatments is recommended. This should include continued identification of evidence based processes of change, and research methods more suited to understanding the experience and needs of individual people.
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