Articles: hyperalgesia.
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Low-dose naloxone-precipitated withdrawal hyperalgesia is a reliable indicator of physical dependence after chronic morphine treatment. A remarkably similar long-lasting (>3-4 h) hyperalgesia is evoked by injection of a low dose of naloxone (10 microg/kg, s.c.) in naïve mice after acute pretreatment with the glycolipid, GM1 ganglioside (1 mg/kg) (measured by warm-water-immersion tail-flick assays). GM1 treatment markedly increases the efficacy of excitatory Gs-coupled opioid receptor signaling in nociceptive neurons. ⋯ Co-treatment with kelatorphan stabilizes putative endogenous opioid peptide agonists released by naloxone in GM1-treated mice, so that analgesia is evoked rather than hyperalgesia. Acute treatment of chronic morphine-dependent mice with ultra-low-dose naltrexone (0.1 ng/kg) results in remarkably similar rapid blocking of naloxone (10 microg/kg)-precipitated withdrawal hyperalgesia and unmasking of prominent opioid analgesia. These studies may clarify complex mechanisms underlying opioid physical dependence and opioid addiction.
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To evaluate in patients with different types of facial pain the association between muscle tenderness and a set of characteristics, 649 consecutive outpatients with facial myogenous pain (MP), TMJ disorder, neuropathic pain (NP) and facial pain disorder (FPD) (DSM-IV) were enrolled. For each patient a psychological assessment on the Axis 1 of the DSM-IV and standardized palpation of pericranial and cervical muscles were carried out. A pericranial muscle tenderness score (PTS), a cervical muscle tenderness score (CTS) and a cumulative tenderness score (CUM, range 0-6) were calculated. ⋯ To assess associations between CUM score and patients' demographic and clinical characteristics an ordered logit model was fit and interactions between psychiatric disorders and diagnostic groups were tested. The analysis showed that, regardless of the diagnostic group, anxiety and depression independently increase the likelihood of having one point higher muscle tenderness score (OR=1.55, 95% CI: 1.13-2.12 and OR=1.56, 95% CI: 1.10-2.21, respectively). A careful screening for the presence of an underlying psychiatric disorder, either anxiety or depression, should be part of the clinical evaluation in patients suffering from facial pain.
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In humans, the acute inflammatory reaction caused by ultraviolet (UV) radiation is well studied and the sensory changes that are found have been used as a model of cutaneous hyperalgesia. Similar paradigms are now emerging as rodent models of inflammatory pain. Using a narrowband UVB source, we irradiated the plantar surface of rat hind paws. ⋯ Sequestration of NGF, starting at the time of UVB irradiation, significantly reduced sensory changes. We conclude that UVB inflammation produces a dose-dependent hyperalgesic state sensitive to established analgesics. This suggests that UVB inflammation in the rat may represent a useful translational tool in the study of pain and the testing of analgesic agents.
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At-level neuropathic pain is a frequent symptom following spinal cord injury, but the underlying pathophysiology is not completely understood. We report a patient suffering from treatment-resistant at-level pain characterized by ongoing pain and mechanical allodynia for three years after an incomplete spinal lesion. Quantitative sensory testing revealed severe thermosensory deficits in the neuropathic pain area. ⋯ Treatment with topical lidocaine patches (5%) led to considerable pain relief. These results indicate a functional connection between peripheral, spinal and supraspinal nociceptive pathways and that peripheral afferents may contribute to at-level neuropathic pain after spinal cord injury in this patient. Lesioned peripheral afferents in combination with central neuronal hyperexcitability are discussed as a likely underlying pain mechanism.
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The aim of this study was to evaluate the use of computerized cuff pressure algometry (CPA) in fibromyalgia (FM) and to correlate deep-tissue sensitivity assessed by CPA with other disease markers of FM. Forty-eight women with FM and 16 healthy age-matched women were included. A computer-controlled, pneumatic tourniquet cuff was placed over the gastrocnemius muscle. ⋯ CPA-parameters were significantly correlated to isokinetic muscle strength where more hypersensitivity resulted in lower strength. Pressure-pain threshold and pressure-pain tolerance assessed by CPA were significantly lower in patients with FM indicating muscle hyperalgesia. CPA was associated with knee muscle strength but not with measures thought to be influenced by psychological distress and mood.