Articles: hyperalgesia.
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Comparative Study
Ankle joint mobilization decreases hypersensitivity by activation of peripheral opioid receptors in a mouse model of postoperative pain.
Investigate whether ankle joint mobilization (AJM) decreases hypersensitivity in the mouse plantar incision (PI) model of postoperative pain as well as to analyze the possible mechanisms involved in this effect. ⋯ Our results indicate that joint mobilization reduces postoperative pain by activation of the peripheral opioid pathway. However, antihypersensitivity induced by AJM is apparently not limited by the number of opioid-containing leukocytes but by opioid receptors availability in sensory neurons. A better understanding of the peripheral mechanisms of AJM could stimulate therapists to integrate joint mobilization with strategies also known to influence endogenous pain control, such as exercise, acupuncture, and transcutaneous electrical nerve stimulation to potentiate endogenous analgesia.
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To clarify the mechanism of tenderness after bone injury, we investigated changes in the withdrawal threshold to mechanical stimuli, nerve distribution and nerve growth factor (NGF)-expression in a rat model of bone injury without immobilization for bone injury healing. Rats were divided into three groups as follows: (1) rats incised in the skin and periosteum, followed by drilling a hole in the tibia [bone lesion group (BLG)]; (2) those incised in the skin and periosteum without bone drilling [periosteum lesion group (PLG)]; and (3) those incised in the skin [skin lesion group (SLG)]. Mechanical hyperalgesia continued for 28 days at a lesion in the BLG, 21 days in PLG and 5 days in SLG after treatments, respectively. ⋯ Anti-NGF and trk inhibitor K252a inhibited hyperalgesia in the different time course. This study shows that localized tenderness coincides with the bone healing and involves NGF expression and nerve sprouting after bone injury. The findings present underlying mechanisms and provide pathophysiological relevance of local tenderness to determination of bone fracture and its healing.
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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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P2X3 and P2X2/3 receptors are selectively expressed on primary afferent nociceptors and have been implicated in modulating nociception in different models of pathological pain, including inflammatory pain. In an effort to delineate further the role of P2X3 receptors (homomeric and heteromeric) in the modulation of nociceptive transmission after a chronic inflammation injury, A-317491, a potent and selective P2X3-P2X2/3 antagonist, was administered to CFA-inflamed rats in order to examine its effects on responses of spinal dorsal horn neurons to mechanical and thermal stimulation. Systemic injection of A-317491 (30 μmol/kg, i.v.) reduced the responses of wide-dynamic-range (WDR) and nociceptive specific (NS) neurons to both high-intensity mechanical (pinch) and heat (49°C) stimulation. ⋯ By using immunohistochemistry, P2X3 receptors were demonstrated to be enhanced in lamina II of the spinal dorsal horn after inflammation. In summary, blockade of P2X3 and P2X2/3 receptors dampens mechanical- and heat-related signaling, as well as nonevoked activity of key classes of spinal nociceptive neurons in inflamed animals. These data suggest that P2X3 and/or P2X2/3 receptors have a broad contribution to somatosensory/nociceptive transmission in rats with a chronic inflammatory injury and are consistent with previous behavioral data demonstrating antiallodynic and antihyperalgesic effects of receptor antagonists.