Pain
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Randomized Controlled Trial
Safety, Tolerability, Pharmacokinetics, and Effects on Human Experimental Pain of the Selective Ionotropic Glutamate Receptor 5 (iGluR5) Antagonist LY545694 in Healthy Volunteers.
The objective of this study was to establish in healthy volunteers the maximally tolerated multiple dose (MTMD) of the ionotropic glutamate receptor 5 antagonist LY545694 (part A), and to investigate whether that dose had analgesic or antihyperalgesic effects in the brief thermal stimulation (BTS) pain model (Part B). Part A was a double-blind, placebo-controlled study in 3 groups of 10 healthy men. To simulate an extended-release formulation, study drug was administered orally over 6hours (12 equally divided aliquots at 30-minute intervals). ⋯ Neither gabapentin nor LY545694 reduced the painfulness of skin heating during BTS model induction. The most common treatment-emergent adverse event was dizziness. The results of this study suggest that LY545694 should be explored further as a potential treatment for chronic pain involving neuronal sensitization.
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Patient characteristics associated with the course and severity of low back pain (LBP) and disability have been the focus of extensive research, however, known characteristics do not explain much of the variance in outcomes. The relationship between anterior trunk pain (ATP) and LBP has not been explored, though mechanisms for visceral referred pain have been described. Study objectives were: (1) determine prevalence of ATP in chronic LBP patients, (2) determine whether ATP is associated with increased pain and disability in these patients, and (3) evaluate whether ATP predicts the course of pain and disability in these patients. ⋯ The presence of ATP did not affect the clinical course of LBP outcomes. The results of this study suggest that patients who present with LBP and ATP have higher pain and disability levels than patients with localised LBP. Visceral referred pain mechanisms may help to explain some of this difference.
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Comparative Study
Heritability of Nociception IV: Neuropathic pain assays are genetically distinct across methods of peripheral nerve injury.
Prior genetic correlation analysis of 22 heritable behavioral measures of nociception and hypersensitivity in the mouse identified 5 genetically distinct pain types. In the present study, we reanalyzed that dataset and included the results of an additional 9 assays of nociception and hypersensitivity, with the following goals: to replicate the previously identified 5 pain types; to test whether any of the newly added pain assays represent novel genetically distinct pain types; and to test the level of genetic relatedness among 9 commonly used neuropathic pain assays. Multivariate analysis of pairwise correlations between assays shows that the newly added zymosan-induced heat hypersensitivity assay does not conform to the 2 previously identified groups of heat hypersensitivity assays and cyclophosphamide-induced cystitis, the first organ-specific visceral pain model examined, is genetically distinct from other inflammatory assays. ⋯ In addition, 2 itch assays and Comt genotype were compared to the expanded set of nociception and hypersensitivity assays. Comt genotype was strongly related only to spontaneous inflammatory nociception assays. These results indicate the priority for continued investigation of genetic mechanisms in several assays newly identified to represent genetically distinct pain types.