Articles: hyperalgesia.
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J. Pharmacol. Exp. Ther. · Aug 2012
Pharmacological characterization of (3S)-3-(hydroxymethyl)-4-(5-methylpyridin-2-yl)-N-[6-(2,2,2-trifluoroethoxy)pyridin-3-yl]-3,4-dihydro-2H-benzo[b][1,4]oxazine-8-carboxamide (JTS-653), a novel transient receptor potential vanilloid 1 antagonist.
Transient receptor potential vanilloid 1 (TRPV1) activation in peripheral sensory nerve is known to be associated with various pain-related diseases, thus TRPV1 has been the focus as a target for drug discovery. In this study, we characterized the pharmacological profiles of (3S)-3-(hydroxymethyl)-4-(5-methylpyridin-2-yl)-N-[6-(2,2,2-trifluoroethoxy)pyridin-3-yl]-3,4-dihydro-2H-benzo[b][1,4]oxazine-8-carboxamide (JTS-653), a novel TRPV1 antagonist. JTS-653 displaced [(3)H]resiniferatoxin binding to human and rat TRPV1. ⋯ JTS-653 showed a transient increase of body temperature at 0.3 mg/kg p.o. These results indicated that JTS-653 is a highly potent and selective TRPV1 antagonist in vitro and in vivo and suggested that JTS-653 is one of the most potent TRPV1 antagonists. The profiles of JTS-653, high potency in vivo and transient hyperthermia, seem to be associated with polymodal inhibition of TRPV1 activation.
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Lysophosphatidic acid (LPA), an initiator of neuropathic pain, causes allodynia. However, few studies have evaluated the pharmacological profile of LPA-induced pain. In this study, a LPA-induced pain model was developed and pharmacologically characterized with clinically relevant drugs used for neuropathic pain, including antiepileptics, non-steroidal anti-inflammatory agents, analgesics, local anaesthetics/antiarrhythmics and antidepressants. ⋯ In LPA-injected mice, expression of the α2δ1 subunit of the voltage-gated calcium channel (VGCC) was increased in the dorsal root ganglion (DRG) and spinal dorsal horn. Furthermore, the VGCC current was potentiated in both the DRG from LPA-injected mice and LPA (1 μM)-treated DRG from saline-injected mice, and the potentiated VGCC current was amended by treatment with gabapentin (100 μM). The LPA-induced pain model described here mimics aspects of the neuropathic pain state, including the sensitization of VGCC, and may be useful for the early assessment of drug candidates to treat neuropathic pain.
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Anesthesia and analgesia · Aug 2012
Antihyperalgesic effects of myrsinoic acid B in pain-like behavior induced by inflammatory and neuropathic pain models in mice.
Myrsinoic acid B (MAB) is a diprenylated benzoic acid widely found in the vegetal kingdom. Recent studies demonstrate that MAB has important antinociceptive effects in models of chemically or thermally induced nociception in mice. ⋯ MAB reduced mechanical and thermal hypersensitivity in mice submitted to models of inflammatory and neuropathic pain, showing excellent potential for treating persistent pain in humans.
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Randomized Controlled Trial
Analgesic tolerance without demonstrable opioid-induced hyperalgesia: a double-blinded, randomized, placebo-controlled trial of sustained-release morphine for treatment of chronic nonradicular low-back pain.
Although often successful in acute settings, long-term use of opioid pain medications may be accompanied by waning levels of analgesic response not readily attributable to advancing underlying disease, necessitating dose escalation to attain pain relief. Analgesic tolerance, and more recently opioid-induced hyperalgesia, have been invoked to explain such declines in opioid effectiveness over time. Because both phenomena result in inadequate analgesia, they are difficult to distinguish in a clinical setting. ⋯ The differences in visual analogue scale pain levels (P = .003) and self-reported disability (P = .03) between both treatment groups were statistically significant. After 1 month of oral morphine therapy, patients with chronic low-back pain developed tolerance but not opioid-induced hyperalgesia. Improvements in pain and functional ability were observed.
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Nerve growth factor (NGF) induces local hyperalgesia for a few days after intramuscular injection, but longer-lasting muscle pain upon systemic administration. As the muscle fascia is densely innervated by free nerve endings, we hypothesized a lasting sensitization of fascia nociceptors by NGF. We administered 1 μg NGF (dissolved in 100 μL saline) ultrasound-guided to the fascia of the Musculus erector spinae muscle at the lumbar level of 14 male volunteers and assessed hypersensitivity after 6 hours, and 1, 3, 7, 14, and 21 days. ⋯ Pain upon injected protons was significantly elevated (P<0.04) for 2 weeks. NGF induced a sensitization of the muscle fascia to mechanical and chemical stimuli lasting for up to 2 weeks. As nociceptors in the fascia appear to be particularly prone to sensitization, they may contribute to acute or chronic muscle pain.