Pain
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Patients receiving opioids for pain may experience decreased effectiveness of the drug and even abnormal pain sensitivity-hyperalgesia and/or allodynia. We hypothesized that peripheral nociceptor hyperexcitability contributes to opioid-induced hyperalgesia and tested this using an in vitro mouse glabrous skin-nerve preparation. Mice were injected intraperitoneally with escalating doses of morphine (5, 8, 10, 15 mg/kg) or saline every 12 hours for 48 hours and killed approximately 12 hours after the last injection. ⋯ In morphine-treated mice, aberrant activity and hyperexcitability of nociceptors could contribute to increased pain sensitivity. Importantly, this activity is likely driving central sensitization, a phenomenon contributing to abnormal sensory processing and chronic pain. If similar changes occur in human patients, aberrant nociceptor activity is likely to be interpreted as pain and could contribute to opioid-induced hyperalgesia.
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The objectives of the current study were to describe fibromyalgia patient-spouse incongruence regarding patient pain, fatigue, and physical function; and to examine the associations of individual and interpersonal factors with patient-spouse incongruence. Two hundred four fibromyalgia patients and their coresiding partners rated the patient's symptoms and function. Multilevel modeling revealed that spouses, on average, rated patient fatigue significantly lower than patients. ⋯ An important within-couple interaction was found for pain interference, suggesting that couples who are similar on level of communication problems experience low incongruence; those with disparate ratings of communication problems experience high incongruence. Findings suggest the important roles of spouse response and the patient's perception of how well the couple is communicating. Couple-level interventions targeting communication or other interpersonal factors may help to decrease incongruence and lead to better patient outcomes.
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Oxidized linoleic acid metabolites (OLAMs) are a class of endogenous transient receptor potential vanilloid 1 (TRPV1) channel agonists released on exposure of tissue to transient noxious temperatures. These lipid compounds also contribute to inflammatory and heat allodynia. Because persistent pain after a burn injury represents a significant clinical challenge for treatment, we developed an in vivo rat model of partial-thickness cutaneous thermal injury and examined whether TRPV1 and specific OLAM metabolites play a role in mediating postburn pain injury. ⋯ Additional studies of the metabolism of [C(14)]-linoleic acid in skin biopsies revealed the role of the cytochrome P450 (CYP) system in mediating the metabolism of linoleic acid after thermal injury. Finally, we demonstrated that direct inhibition of OLAMs using OLAM antibodies and indirect inhibition using the CYP inhibitor ketoconazole significantly reduced postburn thermal allodynia. Collectively, these findings point to a novel role of the OLAMs and CYP-related enzymes in generating postburn allodynia via activation of peripheral TRPV1.
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The clinical effects of motor cortex stimulation (MCS) for neuropathic pain (NP) is thought to be mediated primarily by the secretion of endogenous opioids in humans and in animal models. Because opioid receptor density is itself decreased in patients with NP, we investigated whether the magnitude and distribution of the remaining opioid receptors in patients with NP could be biological predictors of the pain-relieving effects of MCS. Using (11)C-diprenorphine positron emission tomography scans, opioid receptor availability was assessed in 15 patients suffering refractory NP, who subsequently received chronically implanted MCS. ⋯ The levels of preoperative opioid-binding in the insula, thalamus, periaqueductal gray, anterior cingulate, and orbitofrontal cortex were significantly and positively correlated with postoperative pain relief at 7mo. Patients with receptor density values below the lower limits in age-matched controls in the thalamus, periaqueductal gray and contralateral insula were the least likely to benefit from MCS. Opioid-receptor availability as shown in preoperative positron emission tomography scans appears to be related to the efficacy of MCS in NP and may help clinicians to select the candidates most likely to benefit from this procedure.
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Triathletes and ironman triathletes engage in an extremely intense sport that involves hours of considerable pain, as well as physical and psychological stress, every day. The basic pain modulation properties of these athletes has not been established and therefore it is not clear whether they present with unique features that enable them to engage in such efforts. The aim was to investigate the existence of possible alterations in pain perception and modulation of triathletes, as well as possible underlying factors. ⋯ The magnitude of CPM was significantly greater in triathletes (P<.05), and negatively correlated with fear of pain (P<.05) and with perceived mental stress during training and competition (P<.05). The results suggest that triathletes exhibit greater pain tolerance and more efficient pain modulation than controls, which may underlie their perseverance in extreme physical efforts and pain during training/competitions. This capability may be enhanced or mediated by psychological factors, enabling better coping with fear of pain and mental stress.