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The goal of this research is the identification of new treatments for neuropathic pain. We characterized the GABAergic system of immortalized mouse and human microglia using electrophysiology and qRT-PCR. Cells from both species exhibited membrane current changes in response to γ-aminobutyric acid, with an EC50 of 260 nM and 1940 nM, respectively. Human microglia expressed high levels of the γ-aminobutyric acid type A receptor (GABAAR) α3 subunit, which can assemble with β1 and γ2/δ subunits to form functional GABAARs. Mouse microglia contained α2, α3 and α5, in addition to β1-3, γ1-2 and δ, mRNA, enabling a more diverse array of GABAARs than human microglia. Benzodiazepines are well-established modulators of GABAAR activity, prompting a screen of a library of diverse benzodiazepines in microglia for cellular effects. Several active compounds were identified by reduction of nitric oxide (NO) in interferon gamma and lipopolysaccharide activated microglia. However, further investigation with GABAAR antagonists flumazenil, picrotoxin, and bicuculline demonstrated that GABAARs were not linked to the NO response. A screen of 48 receptors identified the κ-opioid receptor and to a lesser extent the µ-opioid receptor as molecular targets, with opioid receptor antagonist norbinaltorphimine reversing benzodiazepine induced reduction of microglial NO. Functional assays identified the downregulation of inducible NO synthase as the mode of action of imidazodiazepines MP-IV-010 and GL-IV-03. Like other κ-opioid receptor agonists, GL-IV-03 reduced the agitation response in both phases of the formalin nociception test. However, unlike other κ-opioid receptor agonists, MP-IV-010 and GL-IV-03 did not impair sensorimotor coordination in mice. Thus, MP-IV-010 and GL-IV-03 represent a new class of non-sedative drug candidates for inflammatory pain.
Learn More >The role of voltage-gated sodium (Na) channels in pain perception is indisputable. Of particular interest as targets for the development of pain therapeutics are the tetrodotoxin-resistant isoforms Na1.8 and Na1.9, based on animal as well as human genetic studies linking these ion channel subtypes to the pathogenesis of pain. However, only a limited number of inhibitors selectively targeting these channels have been reported. HSTX-I is a peptide toxin identified from saliva of the leech Haemadipsa sylvestris. The native 23-residue peptide, stabilised by two disulfide bonds, has been reported to inhibit rat Na1.8 and mouse Na1.9 with low micromolar activity, and may therefore represent a scaffold for development of novel modulators with activity at human tetrodotoxin-resistant Na isoforms. We synthetically produced this hydrophobic peptide in high yield using a one-pot oxidation and single step purification and determined the three-dimensional solution structure of HSTX-I using NMR solution spectroscopy. However, in our hands, the synthetic HSTX-I displayed only very modest activity at human Na1.8 and Na1.9, and lacked analgesic efficacy in a murine model of inflammatory pain.
Learn More >To examine whether sleep disturbance modifies the association between physical activity and incident pain.
Learn More >The aetiology of painful diabetic neuropathy is unclear. We have evaluated vitamin D levels in diabetic patients with and without painful neuropathy. Forty-three patients with type 1 diabetes and painless (DPN) (n = 20) or painful (PDN) (n = 23) neuropathy and 14 non-diabetic healthy control subjects (C) underwent assessment of neurologic deficits, quantitative sensory testing (QST), electrophysiology, skin biopsy, corneal confocal microscopy (CCM) and measurement of serum 25(OH)D. There were no significant differences for age, BMI, HbA1c, lipids, neurological deficits, QST, electrophysiology, intra-epidermal nerve fibre density (IENFD) and corneal nerve morphology between patients with DPN and PDN. Both positive (hyperalgesia and allodynia) and negative symptoms (paraesthesia and numbness) of diabetic neuropathy were greater in PDN compared to DPN (P = 0.009 and P = 0.02 respectively). Serum 25(OH)D level were significantly lower in PDN (24.0 ± 14.1 ng/mL) compared to DPN (34.6 ± 15.0 ng/mL, P = 0.01) and controls (34.1 ± 8.6 ng/mL, P = 0.03). The odds ratio in favour of painful diabetic neuropathy was 9.8 (P = 0.003 (95% CI 2.2-76.4) for vitamin D deficiency (<20 ng/mL) and 4.4 (P = 0.03 [95% CI 1.1-19.8]) for vitamin D insufficiency (<30 ng/mL). This study suggests that vitamin D deficiency and insufficiency are associated with painful diabetic neuropathy. This article is protected by copyright. All rights reserved.
Learn More >Opioid use has increased to epidemic levels over the past decade within the United States, particularly among vulnerable populations. This retrospective study aimed to evaluate rates of prolonged opioid use in the Veteran population after thoracic surgery and identify specific risk clusters.
Learn More >Differences in fibromyalgia impact on functioning exist and appear to be influenced by numerous factors, including symptomatology severity, as well as the cognitive profile of the individual. The contribution of these elements, however, tends to be explored in a fragmented manner. To address this issue, we tested a comprehensive structural equation model in which associations of cognitive fusion and pain catastrophizing with function limitations are investigated through fibromyalgia symptomatology (i.e., fatigue, pain severity, and depression) in 231 women with fibromyalgia. In the model, cognitive fusion and two catastrophizing components (magnification and helplessness) were associated with poorer functioning indirectly through fibromyalgia symptomatology. Only the rumination component of catastrophizing had a direct association with functional limitations. All fibromyalgia symptoms were linked to increased functional limitations. A parsimonious model with significant associations only obtained an excellent fit (S-B = 774.191, df = 543, < 0.001; CFI = 0.943; RMSEA = 0.043; CAIC = -2724.04) and accounted for 50% of the variance of functional limitations. These results suggest that the relationship between psychological cognitive processes, fibromyalgia symptomatology, and functional limitations is complex and support the need for comprehensive models such as the present. The findings are discussed in the context of personalized psychological treatments (i.e., the need to address certain cognitive processes according to the problematic symptomatology or outcome).
Learn More >The purpose of this review is to provide a comprehensive update of the different known components of the endogenous cannabinoid system and the mechanisms of action, as it applies to analgesia.
Learn More >Neurofeedback provides real-time feedback about neurophysiological signals to patients, thereby encouraging modulation of pain-associated brain activity. This review aims to evaluate the effectiveness and safety of neurofeedback in alleviating pain and pain-associated symptoms in chronic pain patients.
Learn More >Chronic pain among adolescents is common but effective interventions applicable in a school setting are rare. Person-centred care (PCC) is a key factor in improving health by engaging people as partners in their own care.
Learn More >An increasing number of studies are focusing on secondary hyperalgesia to better understand central sensitization, as this phenomenon may play an important role in persistent pain. Recent studies have shown that, compared to the classical high frequency stimulation protocol (HFS) at 100 Hz, a protocol using 42 Hz stimulation induces a more intense and a larger area of secondary hyperalgesia (SH).
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