Neuroscience
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Clinical Trial
The role of sex in sleep deprivation related changes of nociception and conditioned pain modulation.
Sex matters both in the clinical field of pain and sleep medicine. Sleep disturbances are highly prevalent in chronic pain patients and have been shown to deteriorate the pain condition. The pathomechanisms by which insomnia aggravates pain are currently unknown. ⋯ While TSD-induced cold and mechanical hyperalgesia were independent of sex, heat pain thresholds did only significantly decrease in sleep deprived females (p = 0.041). Our results point to a sex specific impact of TSD on descending pain inhibition. In the future, therapeutic strategies for pain patients with co-morbid insomnia may need to more explicitly respect the specific role of sex.
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Comparative Study
Human vs. Mouse Nociceptors - Similarities and Differences.
The somatosensory system allows us to detect a diverse range of physical and chemical stimuli including noxious ones, which can initiate protective reflexes to prevent tissue damage. However, the sensation of pain can - under pathological circumstances - outlive its usefulness and perpetrate ongoing suffering. Rodent model systems have been tremendously useful to help understand basic mechanisms of pain perception. ⋯ Additionally, co-expression of Ret and TrkA was also found to be more abundant in human neurons. Moreover, the neurofilament heavy polypeptide was detected in all human sensory DRG neurons compared to a more selective expression pattern observed in rodents. To our knowledge, this is the first time that such detailed comparative analysis has been performed and we believe that our findings will direct future experimentation geared to understand the difficulties we face in translating findings from rodent models to humans.
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This study aimed to investigate the relation of GABA and glutamate levels in the posterior insula and mechanical pain sensitivity in healthy subjects. Nineteen healthy female individuals underwent single voxel magnetic resonance spectroscopy (MRS) at 3 T. Metabolites were measured in the right posterior insula using MEGA-PRESS spectral editing. ⋯ No significant correlation for pinprick stimuli of lower forces than 256 mN was observed. The results of our study support the hypothesis that excitatory and inhibitory neurotransmitter levels and/or the ratio of glutamate/GABA levels in the posterior insula are related to individual differences in pain sensitivity. These results are in line with chronic pain studies, where elevated glutamate/GABA ratios in the insular cortex of patients with chronic pain syndromes were observed.
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Chronic low back pain (CLBP) is challenging to treat. Minimal invasive neurostimulation therapies, such as subcutaneous peripheral nerve field stimulation (SPNS), improve pain relief and quality of life. The goal of the present study was to assess the usefulness, safety, and efficacy of SPNS in patients with CLBP. ⋯ The complication rate was 23% (3/13 patients). In non-responders, VAS and ODI at 24 months dropped significantly as well but the decrease was less pronounced compared to responders and had not led to a decrease in pain medication. SPNS is a novel, safe, and effective treatment for CLBP and may have advantages over interventional treatments including intrathecal therapy and spinal cord stimulation.
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Although bone is continually being remodeled and ultimately declines with aging, little is known whether similar changes occur in the sensory and sympathetic nerve fibers that innervate bone. Here, immunohistochemistry and confocal microscopy were used to examine changes in the sensory and sympathetic nerve fibers that innervate the young (10 days post-partum), adult (3 months) and aging (24 months) C57Bl/6 mouse femur. In all three ages examined, the periosteum was the most densely innervated bone compartment. ⋯ In cortical bone, sensory and sympathetic nerve fibers are largely confined to vascularized Haversian canals and while there is no significant decline in the density of sensory fibers, there was a 75% reduction in sympathetic nerve fibers in the aging vs. adult cortical bone. In contrast, in the bone marrow the overall density/unit area of both sensory and sympathetic nerve fibers appeared to remain largely unchanged across the lifespan. The preferential preservation of sensory nerve fibers suggests that even as bone itself undergoes a marked decline with age, the nociceptors that detect injury and signal skeletal pain remain relatively intact.