Articles: hyperalgesia.
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Alcohol. Clin. Exp. Res. · Jul 2016
Randomized Controlled TrialEffect of Intravenous Ethanol on Capsaicin-Induced Hyperalgesia in Human Subjects.
The objective of this study was to assess ethanol's (EtOH's) effects on capsaicin-induced hyperalgesia in healthy participants. Specifically, we investigated the change in area of capsaicin-induced hyperalgesia following 3 interventions: intravenous EtOH at 2 targeted breath alcohol concentrations (BrAC), or placebo. ⋯ In a human model examining pain phenomena related to central sensitization, this study is the first to demonstrate that capsaicin-induced hyperalgesia is markedly attenuated by EtOH. The capsaicin experimental pain paradigm employed provides a novel approach to evaluate EtOH's effects on pain processing. The antihyperalgesic effects of EtOH observed have important clinical implications for the converging fields of substance abuse and pain medicine and may inform why patients with chronic pain often report alcohol use as a form of self-medication.
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The sympathetic nervous system may play an important role in certain forms of chronic pain. The main aim of this study was to determine whether functional blockade of α1 -adrenoceptors would alter sensitivity to cutaneous stimulation in patients with complex regional pain syndrome (CRPS). ⋯ Prazosin cream inhibited adrenergic axon reflex vasodilatation in healthy volunteers, and also inhibited dynamic allodynia and punctate hyperalgesia in the CRPS-affected limb of some patients. Further studies are required to assess the potential benefits of topically applied prazosin for CRPS.
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Glucose-6-phosphate isomerase and collagen type II antibody-induced arthritis models (K/BxN and CAIA, respectively) have an inflammatory and a post-inflammatory phase. Both phases display robust tactile allodynia. In previous work, inflammatory phase allodynia was reversed by gabapentin and ketorolac, whereas in late phase only gabapentin was effective. Here, we sought to determine if the effects of these two drugs during the early and late phases of the two arthritis models were observed in the conditioned place preference (CPP) paradigm, indicating a differential drug effect on the aversive state. ⋯ CPP validated the aversive state in the inflammatory and post-inflammatory phases of the K/BxN and CAIA arthritis models and correspondence between the anti-hyperpathic pharmacology as defined by thresholds and CPP.
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Despite a fundamental interest in the relationship between structure and function, the relationships between measures of white matter microstructural coherence and functional brain responses to pain are poorly understood. We investigated whether fractional anisotropy (FA) in 2 white matter regions in pathways associated with pain is related to the functional magnetic resonance imaging (fMRI) blood oxygen level-dependent (BOLD) response to thermal stimulation. BOLD fMRI was measured from 16 healthy male subjects during painful thermal stimulation of the right arm. Diffusion-weighted images were acquired for each subject and FA estimates were extracted from the posterior internal capsule and the cingulum (cingulate gyrus). These values were then included as covariates in the fMRI data analysis. We found BOLD response in the midcingulate cortex (MCC) to be positively related to FA in the posterior internal capsule and negatively related to FA in the cingulum. Our results suggest that the MCC's involvement in processing pain can be further delineated by considering how the magnitude of the BOLD response is related to white matter microstructural coherence and to subjective perception of pain. Considering relationships to white matter microstructural coherence in tracts involved in transmitting information to different parts of the pain network can help interpretation of MCC BOLD activation. ⋯ Relationships between functional brain responses, white matter microstructural coherence, and subjective ratings are crucial for understanding the role of the MCC in pain. These findings provide a basis for investigating the effect of the reduced white matter microstructural coherence observed in some pain disorders on the functional responses to pain.
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Chronic opioid treatment is complicated by the development of tolerance and hyperalgesia. Social environment alters both opioid-induced behaviours and nociceptive mechanisms. Our previous studies demonstrated that, in adolescent rodents, the susceptibility to acquire opioid dependence and reward is dependent on the nature of social housing conditions. Specifically, our previous studies demonstrate that housing morphine-treated mice with drug-naïve animals mitigates the abuse liability of opioids. Thus, this study tested the effect of social housing conditions on the development of adaptive processes to morphine antinociception. ⋯ This study demonstrates that housing morphine-treated mice with drug-naïve animals mitigates the development of opioid-induced hyperalgesia and antinociceptive tolerance. Thus, this study indicates that social environment influences the effectiveness of opioid pain management.