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Background and Objectives： Studying the underlying mechanisms of opiate-induced hyperalgesia is fundamental to understanding and treating pain. Our previous study has proved that ephrinB/EphB signaling contributes to opiate-induced hyperagesia, but the manner in which ephrinB/EphB signaling acts on spinal nociceptive information networks to produce hyperalgesia remains unclear. Other studies have suggested that ephrinB/EphB signaling, NMDA receptor and COX-2 act together to participate in the modulation of nociceptive information processes at the spinal level. The objective of this research was to investigate the role of COX-2 in remifentanil-induced hyperalgesia and its relationship with ephrinB/EphB signaling. Methods： We characterized the remifentanil-induced pain behaviours by evaluating thermal hyperalgesia and mechanical allodynia in a mouse hind paw incisional model. Protein expression of COX-2 in spinal cord was assayed by western blotting and mRNA level of COX-2 was assayed by Real-time PCR (RT-PCR). Results： Continuing infusion of remifentanil produced thermal hyperalgesia and mechanical allodynia, which was accompanied by increased expression of spinal COX-2 protein and mRNA. This response was inhibited by pre-treatment with EphB2-Fc, an antagonist of ephrinB/EphB. SC58125 and NS398, inhibitors of COX-2, suppressed pain behaviours induced by remifentanil infusion and reversed the increased pain behaviours induced by intrathecal injection of ephrinB2-Fc, an agonist of ephrinB/EphB. Conclusions: Our findings confirmed that COX-2 is involved in remifentanil-induced hyperalgesia related to ephrinB/EphB signaling. EphrinB/EphB signaling might be the upstream of COX-2.
Learn More >Parental migraine in relation to migraine in offspring: Family linkage analyses from the HUNT Study.
Migraine is known to run in families. While some clinical studies have indicated that migraine is disproportionally transmitted through the maternal line, this has not been examined in a population-based setting.
Learn More >Two guidelines about opioid use in chronic pain management were published in 2017: the and the European Pain Federation position paper on appropriate opioid use in chronic pain management. Though the target populations for the guidelines are the same, their recommendations differ depending on their purpose. The intent of the Canadian guideline is to reduce the incidence of serious adverse effects. Its goal was therefore to set limits on the use of opioids. In contrast, the European Pain Federation position paper is meant to promote safe and appropriate opioid use for chronic pain. The content of the two guidelines could have unintentional consequences on other populations that receive opioid therapy for symptom management, such as patients with cancer. In this article, we present expert opinion about those chronic pain management guidelines and their impact on patients with cancer diagnoses, especially those with histories of substance use disorder and psychiatric conditions. Though some principles of chronic pain management can be extrapolated, we recommend that guidelines for cancer pain management should be developed using empirical data primarily from patients with cancer who are receiving opioid therapy.
Learn More >Intervertebral disc degeneration is a major cause of chronic low back pain, and excessive loading contributes to intervertebral disc degeneration. However, the lack of an effective bipedal in vivo animal model limits research about this condition.
Learn More >Calcitonin gene-related peptide (CGRP), is a peptide neurotransmitter with potent vasodilating properties. CGRP is believed to play a primary role in the pathogenesis of migraine. As such, CGRP and its receptors are obvious druggable targets for novel anti-migraine agents. While the development of small-molecule CGRP receptor antagonists started first, none of these agents is yet available in clinical practice. Conversely, both anti-CGRP and anti-CGRP receptor monoclonal antibodies (mABs) completed clinical development, and the first representatives of these 2 classes are available on the market. MABs are approved for prevention of migraine attacks in chronic or episodic migraine, involving long-term treatments. In light of the physiological role exerted by CGRP in the regulation of vascular tone, the potential risks of a long-term inhibition of CGRP functions raised diffuse concerns. These concerns were correctly addressed by the anti-CGRP receptor mABs erenumab with a 5-year open-label clinical trial; however, this study is currently ongoing and results are not yet available, leaving some uncertainty on the profile of erenumab long-term safety. Similar concerns can be raised with direct anti-CGRP mABs, which entrap the peptide preventing receptor activation. However, evidence exists that plasma CGRP is detectable in patients chronically treated with anti-CGRP mABs. Assuming that plasma CGRP is an indirect marker of peptide levels at the vascular receptor sites, such residual CGRP would maintain a physiological level of receptor stimulation, in spite of a well-established anti-migraine activity of the mABs. This might represent a potential advantage in the safety profile of anti-CGRP mABs, but it needs to be confirmed and expanded with data on free plasma CGRP.
Learn More >The increase in opioid-related deaths in the United States (and other countries) has prompted a national debate in medicine about the appropriateness of opioids for the treatment of acute and chronic pain, and specifically in children, if medical opioid use causes or increases the risk of opioid use disorder (OUD) later in life. Some in the medical community and in government advocate withholding opioids from children after an arbitrary number of days of treatment, regardless of diagnosis. Here, I argue that opioid experimentation and misuse is no more common in children and adolescents today than 2 or 3 decades ago, that there is no compelling evidence that appropriate medical use of opioids leads to OUD, and that the epidemic of inadequately treated pain in children remains the more compelling issue.
Learn More >Chronic itch is the most common skin-related condition, associated with a high psychosocial and economic burden. In recent years, increasing evidence of sex differences in the perception, clinical presentation and treatment requirements of itch points towards potential benefits when using sex-adapted therapies. It is well-known that body composition, absorption, metabolism, elimination and adverse drug reactions (ADRs) differ between sexes, but only little is known about the impact of sex in the pharmacology of itch treatments, which could help to rationalise sex-adapted treatment strategies.
Learn More >Cluster headache is by many regarded as a males' disorder that is often accompanied by an unhealthy lifestyle. We aimed to study the influence of sex and lifestyle factors on clinical presentation, the diagnostic process and management.
Learn More >Inflammation or injuries of the trigeminal nerve are often associated with persistent facial pain and its sequelae. A number of models have been described to study trigeminal pain in rodents, but the long-lasting behavioral consequences are unknown. The present study characterizes the impact of a distal infraorbital nerve injury, called DIONI, which consists of ligature and transection of distal fibers of the infraorbital nerve. We assessed nociception using a conflict paradigm and optogenetics, and a set of reward, aversion, spatial, temporal and competition tasks in the IntelliCage to study multiple aspects of cognition, circadian rhythms and social interactions in groups of mice in home cage environments. Mice with DIONI developed cold and mechanical allodynia, and hypersensitivity towards blue light stimulation. They maintained a long lasting memory of aversive stimuli (airpuff from above), but had no difficulty in learning appetitive tasks, which consisted of preference for a rewarding corner in the IntelliCage. Indeed, they were more strongly 'addicted' to sugar than sham mice but temporarily failed to re-learn the location of rewarding sites after corner switching (Reversal learning). They were mildly overactive in some tasks but without disruptions of circadian rhythms, or impact on social structure. They adopted a strategy to maintain licking with fewer nosepokes, presumably trying to avoid mechanical stimulation of the snout. The results suggest that mice with distal infraorbital nerve injury develop strong aversive memories and some cognitive inflexibility, but create adaptive strategies to cope with the persistent trigeminal hypersensitivity.
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