Pain
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The basal ganglia modulate somatosensory pain pathways, but it is unclear whether a common circuit exists to mitigate hyperalgesia in pain states induced by peripheral nociceptive stimuli. As a key output nucleus of the basal ganglia, the substantia nigra pars reticulata (SNr) may be a candidate for this role. To test this possibility, we optogenetically modulated SNr GABAergic neurons and examined pain thresholds in freely behaving male mice in inflammatory and neuropathic pain states as well as comorbid depression in chronic pain. ⋯ However, SNr modulation did not affect baseline pain thresholds. We also found that SNr-STN GABAergic projection was attenuated in pain states, resulting in disinhibition of STN neurons. Thus, impairment of the SNr-STN GABAergic circuit may be a common pathophysiology for the maintenance of hyperalgesia in both inflammatory and neuropathic pain states and the comorbid depression in chronic pain; compensating this circuit has potential to effectively treat pain related conditions.
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Randomized Controlled Trial
Effects of Hypnosis vs Mindfulness Meditation vs Education on Chronic Pain Intensity and Secondary Outcomes in Veterans: A Randomized Clinical Trial.
Effective, rigorously evaluated nonpharmacological treatments for chronic pain are needed. This study compared the effectiveness of training in hypnosis (HYP) and mindfulness meditation (MM) with an active education control (ED). Veterans (N = 328) were randomly assigned to 8 manualized, group-based, in-person sessions of HYP (n = 110), MM (n = 108), or ED (n = 110). ⋯ No significant differences on outcomes between HYP and MM were detected at any time point. This study suggests that all 3 interventions provide posttreatment benefits on a range of outcomes, but the benefits of HYP and MM continue beyond the end of treatment, while the improvements associated with ED dissipate over time. Future research is needed to determine whether the between-group differences that emerged posttreatment are reliable, whether there are benefits of combining treatments, and to explore moderating and mediating factors.
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Data are equivocal on the consequences of COVID-19 pandemic on pain and well-being for individuals with chronic pain. Furthermore, little is known regarding its impact on the health of young adults with chronic pain. We conducted a longitudinal study to compare pain, psychological functioning, and substance use before and during the pandemic of 196 young adults with chronic pain. ⋯ Mixed linear models revealed that COVID-19 exposure and impact were not associated with changes in pain intensity or interference, with female sex associated with increased pain intensity (β = 0.86, P = 0.02) and pain interference (β = 0.87, P = 0.02). Our findings indicated relative stability of pain symptoms experienced by young adults with chronic pain. However, the increases in anxiety highlight the need to facilitate treatment access for mental health services to mitigate downstream impact.
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Despite being involved in a number of functions, such as nociception and locomotion, spinal lamina X remains one of the least studied central nervous system regions. Here, we show that Aδ- and C-afferent inputs to lamina X neurons are presynaptically inhibited by homo- and heterosegmental afferents as well as by descending fibers from the corticospinal tract, dorsolateral funiculus, and anterior funiculus. Activation of descending tracts suppresses primary afferent-evoked action potentials and also elicits excitatory (mono- and polysynaptic) and inhibitory postsynaptic responses in lamina X neurons. Thus, primary afferent input to lamina X is subject to both spinal and supraspinal control being regulated by at least 5 distinct pathways.
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Meta Analysis
Pain mechanisms in carpal tunnel syndrome: a systematic review and meta-analysis of quantitative sensory testing outcomes.
Carpal tunnel syndrome (CTS) is the most common nerve compression in the arm. A mix of peripheral and central contributions on quantitative sensory testing (QST) has been reported in the literature. Thus, this systematic review or meta-analysis aimed to identify the dominant sensory phenotype and draw conclusive evidence about the presence of central sensitization (CS) in CTS. ⋯ Furthermore, there was a significant increase in mechanical pain sensitivity in median nerve territories and remotely in the forearm ( P < 0.05) and a significant gain in pressure and heat pain thresholds in the carpal area ( P < 0.05). Conditioned pain modulation was impaired in CTS. Hypoesthesia and increased thermal and mechanical pain ratings are the dominant sensory phenotype with inconclusive evidence about CS in CTS due to the heterogenous results of thermal and mechanical pain thresholds.