Articles: hyperalgesia.
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Neuroscience letters · Oct 2010
CC-chemokine MIP-1α in the spinal cord contributes to nerve injury-induced neuropathic pain.
We investigated the involvement of spinal macrophage inflammatory protein-1α (MIP-1α), an inflammatory chemokine, in partial sciatic nerve ligation (PSL)-induced neuropathic pain in mice. PSL increased MIP-1α mRNA levels as well as levels of the MIP-1α receptor, CCR1, but not CCR5 in the spinal dorsal horn. ⋯ Recombinant MIP-1α (10pmol, i.t.) elicited long-lasting tactile allodynia and thermal hyperalgesia in naïve mice. These results suggest that peripheral nerve injury elicits the up-regulation of spinal MIP-1α and CCR1 to participate in neuropathic pain.
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Noxious stimuli activate a complex cerebral network. During central sensitization to pain, activity in most of these areas is changed. One of these areas is the posterior parietal cortex (PPC). ⋯ Compared to sham stimulation, no significant effect of rTMS was observed on pain stimulus intensity and the area of allodynia. However, a reduction of the hyperalgesic area was observed for rTMS of the left PPC (P<0.05). We discuss the role of the PPC in central sensitization to pain, in spatial discrimination of pain stimuli and in spatial-attention to pain stimuli.
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Comparative Study
Involvement of peripheral opioid receptors in electroacupuncture analgesia for carrageenan-induced hyperalgesia.
Acupuncture is widely used to relieve pain; however, the mechanism underlying electroacupuncture analgesia (EAA) during inflammatory pain is unclear. We investigated whether endogenous peripheral opioid receptors participated in EAA during hyperalgesia elicited by carrageenan-induced inflammation. Moreover, we investigated which subtype of opioid receptor was involved in EAA. ⋯ NTI, nor-BNI and CTOP blocked EAA from immediately, 1h, and 3h after EA cessation, respectively. The EAA in the inflamed paw could not be blocked by i.v. injection of NTI, nor-BNI and CTOP. These findings suggest that peripheral μ, δ and κ receptors on peripheral nerve terminals are activated by EA, although there is a time difference among these activations.
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A chronic compressed dorsal root ganglion (CCD) in rat produces pain behavior and an enhanced excitability of neurons within the compressed ganglion. Kir2.1 is an inwardly rectifying potassium channel that acts to stabilize the resting potential of certain cell types. We hypothesized that an inducible expression of Kir2.1 channels in CCD neurons might suppress neuronal excitability in the dorsal root ganglion (DRG) and reduce the associated pain behavior. ⋯ We found that an inducible expression of Kir2.1 channels in chronically compressed DRG neurons can effectively suppress the neuronal excitability and, if induced at the beginning of CCD injury, prevent the development of hyperalgesia. We hypothesize that a higher level of neuronal hyperexcitability in the DRG is required to initiate than to maintain the hyperalgesia and that the hyperexcitability contributing to neuropathic pain is best inhibited as soon as possible after injury.
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Methods Find Exp Clin Pharmacol · Oct 2010
Comparative StudyValidation of the digital pressure application measurement (PAM) device for detection of primary mechanical hyperalgesia in rat and mouse antigen-induced knee joint arthritis.
Several tests have been developed to obtain mechanical nociceptive withdrawal thresholds for arthritis-associated pain research in preclinical animal models, which are routinely used for testing the efficacy of antinociceptive pharmaceutical candidates. Here, we aimed to validate a recently introduced and commercially available digital pressure application measurement (PAM) device for the detection of primary mechanical hyperalgesia in a model of antigen-induced knee joint arthritis (AIA) in rats and mice. Two particular advantages of the PAM device are visual feedback control of the force increase rate and the detection of the complete threshold range. ⋯ Inter-observer agreement was generally higher when using PAM instead of an analog dynamometer. In conclusion, the digital PAM device is a suitable apparatus to detect primary mechanical hyperalgesia in experimental knee joint arthritis in rats and mice. The use of this device allows visual feedback control of the stimulus rate, thus minimizing the chances of confounding factors arising from differences in ramp speed.