Pain
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Juvenile-onset fibromyalgia (JFM) is typically diagnosed in adolescence and characterized by widespread pain and marked functional impairment. The long-term impact of JFM into adulthood is poorly understood. The objectives of this study were to describe physical and psychosocial outcomes of youth diagnosed with JFM in early adulthood (∼8-year follow-up), examine longitudinal trajectories of pain and depressive symptoms from adolescence to young adulthood, and examine the impact of pain and depressive symptoms on physical functioning over time. ⋯ This study offers evidence that although JFM symptoms persist for most individuals, pain severity tends to decrease over time. However, depressive symptoms follow distinct trajectories that indicate subgroups of JFM. In particular, JFM patients with worsening depressive symptoms showed decreasing physical functioning and may require more intensive and consistent intervention to prevent long-term disability.
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The processing of pain in the central nervous system is now known to have an important immune component, including T cells of the adaptive immune system. T cells have been shown to release endogenous opioids, and although it is well known that opioids have effects on T-cell populations, very little attention has been given to the converse: how T cells may affect opioid regulation. We find here that, in addition to displaying significantly increased baseline pain sensitivity across various pain modalities, T-cell-deficient mice (CD-1 nude, Rag1 null mutant, and Cd4 null mutant) exhibit pronounced deficiencies in morphine inhibition of thermal or inflammatory pain. ⋯ As previously reported, we also observe a sex difference in CD-1 mice, with females requiring 2- to 3-fold more morphine than males to produce equal analgesia. Nude mice display no sex differences in morphine analgesia, and the sex difference is restored in nude mice of either sex receiving CD4 T cells from CD-1 donor male or female mice. These results suggest that CD4 T cells play an as yet unappreciated role in opioid analgesia and may be a driver of sex differences therein.
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Studies have shown that moderate alcohol consumption is strongly associated with reduced reporting of chronic widespread pain (CWP). The study designs used, however, are prone to confounding and are not able to establish the direction of causality. The current study overcomes these problems using the Mendelian randomisation design to determine the effect of alcohol consumption on the likelihood of reporting CWP. ⋯ Persons with "GG" genotype had an increased risk of CWP (odds ratio [OR] 1.17, 99% confidence interval 1.01-1.35) and were more likely to consume alcohol weekly (OR 1.76, 1.70-1.81) compared to those with "AA/AG" genotype. Weekly consumption of alcohol was associated with reduced risk of CWP (OR 0.33, 0.31-0.35), but instrumental variable analysis did not show a causal effect of alcohol consumption on reducing CWP (OR 1.29, 0.96-1.74). An interpretation of observational population studies as showing a protective effect of alcohol on CWP is not supported.
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Neuropathic pain represents a challenge to clinicians because it is resistant to commonly prescribed analgesics due to its largely unknown mechanisms. Here, we investigated a descending dopaminergic pathway-mediated modulation of trigeminal neuropathic pain. We performed chronic constriction injury of the infraorbital nerve from the maxillary branch of trigeminal nerve to induce trigeminal neuropathic pain in mice. ⋯ Specific excitation of dopaminergic neurons in the A11 nucleus attenuated the trigeminal neuropathic pain through the activation of D2 receptors in the spinal trigeminal nucleus caudalis. Conversely, specific ablation of the A11 dopaminergic neurons exacerbated such pain. Our results suggest that the descending A11-spinal trigeminal nucleus caudalis dopaminergic projection is critical for the modulation of trigeminal neuropathic pain and could be manipulated to treat such pain.
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Sensitization of the transient receptor potential ion channel vanilloid 1 (TRPV1) is critically involved in inflammatory pain. To date, manifold signaling cascades have been shown to converge onto TRPV1 and enhance its sensitization. However, many of them also play a role for nociceptive pain, which limits their utility as targets for therapeutic intervention. ⋯ Alongside, we identify numerous novel and pain state-dependent binding partners of native TRPV1 in dorsal root ganglia. These data represent a unique resource on the dynamics of the TRPV1 interactome and facilitate mechanistic insights into TRPV1 regulation. We propose that inflammation-related differences in the TRPV1 interactome identified here could be exploited to specifically target inflammatory pain in the future.