Articles: hyperalgesia.
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The mechanism of pain in chronic pancreatitis (CP) has yet to be explored. Proteinase-activated receptor 2 (PAR2) plays a pronociceptive role in visceral pain. The study aimed to assess the expression of PAR2 in dorsal root ganglia (DRGs) and validate its role of thermal hyperalgesia in CP. ⋯ The thermal hyperalgesia in CP is associated with an up-regulation of the PAR2 in DRGs. Proteinase-activated receptor 2 was involved in the pain generation in rats with CP.
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Mechanical pain sensitivity is characteristic of many orofacial pain conditions; however, few models exist to quantify this pain. Here we evaluated a novel adaptation of our existing operant system to characterize orofacial pain following mechanical and thermal stimuli. We demonstrate that the operant system is able to detect painful and analgesic responses to mechanical stimuli. These findings allow comparison of both mechanical and thermal stimuli using the same outcome measures.
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Clin. Exp. Pharmacol. Physiol. · Mar 2011
Systematic evaluation of the nefopam-paracetamol combination in rodent models of antinociception.
1. The aim of the present study was to explore the concept of multimodal anaesthesia using a combination of two non-opioid analgesics, namely nefopam, a centrally acting non-opioid that inhibits monoamine reuptake, and paracetamol, an inhibitor of central cyclo-oxygenases. The antinociceptive characteristics of the combination were evaluated using four different animal models of pain. 2. ⋯ In a rat incision model of postoperative thermal hyperalgesia, coadministration of nefopam at a non-analgesic dose (3 mg/kg) with paracetamol at a low analgesic dose (300 mg/kg) showed the appearance of a strong antihyperalgesic effect, maintained for at least 3 h. In rat carrageenan-induced tactile allodynia, the combination of low analgesic doses of nefopam (10 or 30 mg/kg) with a non-analgesic dose of paracetamol (30 mg/kg), significantly blocked allodynia with a longer duration of efficacy. 4. In conclusion, coadministration of nefopam with paracetamol is worthy of clinical evaluation.
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The present study investigated the effects of intrathecal (i.t.) application of bovine adrenal medulla 22 (BAM22), an endogenous opioid peptide potently activating opioid receptors and sensory neuron-specific receptor (SNSR), on a model of complete Freund's adjuvant (CFA)-induced inflammatory pain. Unilateral, but not bilateral, inflammatory pain was induced by intraplantar (i.pl.) injection of CFA in one side, as indicated by the shortened paw withdrawal latency and the increased edema of paw. Paw withdrawal latency test, paw edema determination and immunohistochemistry were used in CFA-induced inflammatory pain model after i.t. administration of BAM22 or saline. ⋯ Furthermore, i.t. treatment of 10 nmol BAM22 evidently decreased the expressions of CFA-evoked neuronal nitric oxide synthase (nNOS)-positive cells and calcitonin gene-related peptide (CGRP)-immunoreactivity positive nerve fibers by 25.6% (P<0.01) and 25.2% (P<0.001) compared with saline group, respectively, at L3-L5 segments of the spinal cord. Small and medium CGRP-positive cells were 57.4% and 35.2% in dorsal root ganglion (DRG) in 10 nmol BAM22 group, respectively, which were remarkably lower than those in saline group (P<0.001). The present study suggests that BAM22 relieves CFA-induced thermal hyperalgesia in the early phase and resumes antinociceptive effects through down-regulation of nNOS and CGRP expressions in DRG and spinal cord, which is possibly mediated via SNSR.