Articles: hyperalgesia.
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The pathogenesis of visceral hypersensitivity, a characteristic pathophysiological feature of irritable bowel syndrome (IBS), remains elusive. Recent studies suggest a role for hydrogen sulfide (H2S) in pain signaling but this has not been well studied in visceral models of hyperalgesia. We therefore determined the role for the endogenous H2S producing enzyme cystathionine-beta-synthetase (CBS) in a validated rat model of IBS-like chronic visceral hyperalgesia (CVH). CVH was induced by colonic injection of 0.5% acetic acid (AA) in 10-day-old rats and experiments were performed at 8-10 weeks of age. Dorsal root ganglion (DRG) neurons innervating the colon were labeled by injection of DiI (1,1'-dioleyl-3,3,3',3-tetramethylindocarbocyanine methanesulfonate) into the colon wall. ⋯ Our results suggest that upregulation of CBS expression in colonic DRG neurons and H2S signaling may play an important role in developing CVH, thus identifying a specific neurobiological target for the treatment of CVH in functional bowel syndromes.
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Bmc Musculoskel Dis · Jan 2009
Electric toothbrush application is a reliable and valid test for differentiating temporomandibular disorders pain patients from controls.
Current methods for identifying patients with pain hypersensitivity are sufficiently complex to limit their widespread application in clinical settings. We assessed the reliability and validity of a simple multi-modal vibrotactile stimulus, applied using an electric toothbrush, to evaluate its potential as a screening tool for central sensitization. ⋯ The electric toothbrush stimulus had excellent test-retest reliability. Validity of the scores was demonstrated with modest sensitivity and good specificity for differentiating TMD pain patients from controls, which are acceptable properties for a screening test.
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Lidocaine produces analgesia by inhibiting excitation of nerve endings or blocking impulse conduction in peripheral nerves. This study was performed to determine whether intrathecal or intravesical administration of lidocaine prior, or subsequent, to induction of chemical cystitis in rats would block referred mechanical hyperalgesia. ⋯ These results indicate that pre-treatment with lidocaine attenuates referred hyperalgesia associated with cystitis. Lidocaine treatment 4 hr after induction of cystitis failed to prevent referred hyperalgesia despite a similar decrease in bladder NGF. Neurourol. Urodynam. (c) 2009 Wiley-Liss, Inc.
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Activation of P2X3,2/3 receptors by endogenous ATP contributes to the development of inflammatory hyperalgesia. Given the clinical importance of mechanical hyperalgesia in inflammatory states, we hypothesized that the activation of P2X3,2/3 receptors by endogenous ATP contributes to carrageenan-induced mechanical hyperalgesia and that this contribution is mediated by an indirect and/or a direct sensitization of the primary afferent nociceptors. Co-administration of the selective P2X3,2/3 receptors antagonist A-317491, or the non-selective P2X3 receptor antagonist, TNP-ATP, with carrageenan blocked the mechanical hyperalgesia induced by carrageenan, and significantly reduced the increased concentration of tumor necrosis factor alpha (TNF-alpha) and chemokine-induced chemoattractant-1 (CINC-1) but not of interleukin-1 beta (IL-1 beta) induced by carrageenan. ⋯ Intrathecal administration of oligonucleotides antisense against P2X3 receptors for seven days significantly reduced the expression of P2X3 receptors in the saphenous nerve and significantly reduced the mechanical hyperalgesia induced by carrageenan. We concluded that the activation of P2X3,2/3 receptors by endogenous ATP is essential to the development of the mechanical hyperalgesia induced by carrageenan. Furthermore, we showed that this essential role of P2X3,2/3 receptors in the development of carrageenan-induced mechanical hyperalgesia is mediated by an indirect sensitization of the primary afferent nociceptors dependent on the previous release of TNF-alpha and by a direct sensitization of the primary afferent nociceptors.
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TrpV1, the receptor for capsaicin, contributes to nociception in animals but appears to be much more important for signaling increased behavioral sensitivity in the injured state. The current study examined the relationship between the marked reduction in heat hyperalgesia after incision in TrpV1 knockout (KO) mice and the activity of the nociceptors in these same mice. Also, the role of TrpV1 in spontaneous activity (SA) of afferents after incision was examined. ⋯ We conclude that a distinct class of afferents outside the mechano-heat-sensitive afferent population likely contributes to heat hypersensitivity after plantar incision. KO of TrpV1 influences SA in these unclassified afferents in incised skin. SA in these afferents is perhaps a manifestation of heat sensitization.