Mol Pain
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The occurrence of debilitating chronic persistent (24/7) headache after mild traumatic brain injury represents a central neuropathic pain state. Previous studies suggest that this chronic headache state can be attributed to altered supraspinal modulatory functional connectivity in both resting and evoked pain states. Abnormalities in the myelin sheaths along the supraspinal superior longitudinal fasciculus and anterior thalamic radiation are frequently associated with alteration in pain modulation related to functional connectivity deficit with the prefrontal cortex. This study assessed the correlated axonal injury-related white matter tract abnormality underlying these previously observed prefrontal functional connectivity deficits by comparing the fractional anisotropy, axial diffusivity, and radial diffusivity of brain white matter in patients with mild traumatic brain injury-related headache to healthy controls. ⋯ The identified white matter tract abnormalities may represent a state of Wallerian degeneration which correlates with the functional connectivity deficit in pain modulation and can contribute to the development of the chronic persistent headache in the patients with mild traumatic brain injury.
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Recent studies have shown that ethanol produces a widespread modulation of neuronal activity in the central nervous system. It is not fully understood, however, how ethanol changes nociceptive transmission. We investigated acute effects of ethanol on synaptic transmission in the substantia gelatinosa (lamina II of the spinal dorsal horn) and mechanical responses in the spinal dorsal horn. ⋯ In the presence of tetrodotoxin, such enhancement of spontaneous inhibitory postsynaptic currents was not detected. In addition, ethanol (20-100 mM) increased the frequency of spontaneous discharge of vesicular GABA transporter-Venus-labeled neurons and suppressed the mechanical nociceptive response in wide-dynamic range neurons in the spinal dorsal horn. The present results suggest that ethanol may reduce nociceptive information transfer in the spinal dorsal horn by enhancement of inhibitory GABAergic and glycinergic synaptic transmission.
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Complex regional pain syndrome (CRPS) is a highly enigmatic syndrome typically developing after injury or surgery to a limb. Severe pain and disability are common among those with chronic forms of this condition. Accumulating evidence suggests that CRPS may involve both autoinflammatory and autoimmune components. ⋯ More recently, autoimmune contributions have been suggested by the discovery of self-directed pain-promoting IgG and IgM antibodies in CRPS patients and model animals. Both the autoimmune and the autoinflammatory components of CRPS appear to be regulated by neuropeptide-containing peripheral nerve fibers and the sympathetic nervous system. While CRPS displays a complex neuroimmunological pathogenesis, therapeutic interventions could be designed targeting autoinflammation, autoimmunity, or the neural support for these phenomena.
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Bortezomib is a mainstay of therapy for multiple myeloma, frequently complicated by painful neuropathy. The objective of this study was to describe clinical, electrophysiological, and pathological changes of bortezomib-induced peripheral neuropathy (BiPN) in detail and to correlate pathological changes with pain descriptors. Clinical data, nerve conduction studies, and lower leg skin biopsies were collected from 22 BiPN patients. ⋯ Finally, significant correlations between UDNFD of PGP9.5 versus the evaluative Pain Rating Index (PRI) and number of words count (NWC) of the MPQ, and significant inverse correlations between SENFD/UDNFD of CGRP versus the sensory-discriminative MPQ PRI/NWC were found. BiPN is a sensory neuropathy, in which neuropathic pain is the most striking clinical finding. Bortezomib-induced neuropathic pain may be driven by sprouting of parasympathetic fibers in the upper dermis and impaired regeneration of CGRP fibers in the subepidermal layer.
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Objective To observe the analgesic effect of early hyperbaric oxygen (HBO) treatment in chronic constriction injury (CCI) rats, and to analyze the influence of HBO on the expression of neuronal nitric oxide synthase and inducible nitric oxide synthase and on the levels of inflammatory factors. Methods Rats were assigned into three groups randomly: sham, CCI, and HBO groups. The CCI rat model was established, and HBO treatment at 2.5 ATA (60 min) was given one day after surgery, lasting for five consecutive days. ⋯ The expressions of inducible nitric oxide synthase and neuronal nitric oxide synthase were decreased in the dorsal horn, and the release of inflammatory factor (TNF-α and IL-1β) was reduced. Conclusions Early HBO treatment significantly improves hyperalgesia in rats with neuropathic pain. The decreased expressions of inducible nitric oxide synthase and neuronal nitric oxide synthase and reduced levels of inflammatory factors are important mechanisms by which early HBO helps to alleviate neuropathic pain.