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The synthetic cannabinoid WIN55,212-2 attenuates hyperalgesia and allodynia in a rat model of neuropathic pain.

ABSTRACT: The analgesic properties of the synthetic cannabinoid WIN55,212-2 were investigated in a model of neuropathic pain. In male Wistar rats, bilateral hind limb withdrawal thresholds to cold, mechanical and noxious thermal stimuli were measured. Following this, unilateral L5 spinal nerve ligation was performed. Seven days later, sensory thresholds were reassessed and the development of allodynia to cold and mechanical stimuli and hyperalgesia to a noxious thermal stimulus confirmed. The effect of WIN55,212-2 (0.1 - 5.0 mg kg(-1), i.p.) on the signs of neuropathy was then determined; there was a dose related reversal of all three signs of painful neuropathy at doses which did not generally alter sensory thresholds in the contralateral unligated limb. This effect was prevented by co-administration of the CB(1) receptor antagonist SR141716a, but not by co-administration of the CB(2) receptor antagonist SR144528, suggesting this action of WIN55,212-2 is mediated via the CB(1) receptor. Administration of SR141716a alone had no affect on the observed allodynia and hyperalgesia, which does not support the concept of an endogenous analgesic tone. These data indicate that cannabinoids may have therapeutic potential in neuropathic pain, and that this effect is mediated through the CB(1) receptor.

SUBMITTER: Bridges D

PROVIDER: S-EPMC1572814 | biostudies-other | 2001 Jun

REPOSITORIES: biostudies-other

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Project description:IntroductionThe aim of this study was to observe the effect of stress caused by neuropathic pain on serum cortisol concentration and expression of 11β-hydroxysteroid dehydrogenase type I enzyme (11βHSD1) in spinal cord and dorsal root ganglions (DRG) and investigate the role and mechanism of curcumin in the neuropathic pain of stressful rats. Neuropathic pain is a prevalent disease that greatly impairs the patients' quality of life. A lack of the understanding of its etiology, inadequate relief, development of tolerance and potential toxicity of classical antinociceptives warrant the investigation of the newer agents to relieve this pain. The aim of the present study was to explore the antinociceptive effect of curcumin and its effect on expression of 11β-hydroxysteroid dehydrogenase type I enzyme (11βHSD1) in spinal dorsal horn and DRG in chronic constriction injury (CCI) mode of neuropathic pain of rats.MethodsSeventy-two male Sprague-Dawley rats were randomized into four groups with 18 rats in each: sham operation group (Sham), chronic constrictive injury group (CCI), solvent contrast group (SC), and curcumin-treated group (Cur100). Curcumin, 100 mg/kg/day intraperitoneal, was given for 14 days starting from the first day after operation in the Cur100 group. Paw thermal withdrawal latency (PTWL) and paw mechanical withdrawal threshold (PMWT) of rats were measured 2 days pre-operative, and 1, 3, 5, 7, 10, and 14 days post-operative. The animals were deeply anesthetized and blood was taken from the heart, the lumbar segment (L4, 5) of the spinal cord and DRG were dissected out and homogenized. The change of cortisol was measured by enzyme-linked immunosorbent assay and the change of 11βHSD1 expression was determined by immunochemistry and Western blot.ResultsCompared with sham group, PTWL and PMWT significantly decrease after operation in the CCI group; serum cortisol concentration was significantly increased and the expression of 11βHSD1 was significantly increased in the CCI group. Comparing with CCI group, the PMWT and PTWL were increased and the serum cortisol concentration was decreased and the expression of 11βHSD1 was inhibited in Cur100 group.ConclusionStress caused by neuropathic pain triggers release of cortisol to the blood and expression of 11βHSD1 would increase at the same time. Curcumin could alleviate thermal and mechanical hyperalgesia induced by CCI and inhibit the serum cortisol concentration and expression of 11βHSD1 in the spinal cord and DRG.

Project description:Background:Reactive oxygen species (ROS) induced oxidative stress is linked to numerous neurological diseases, including neuropathic pain. Natural ROS scavenging enzymes like superoxide dismutase (SOD) and catalase have been found to be efficient in alleviating neuropathic pain. However, their sensitivity towards extreme pH and a short half-life limit their efficacy in vivo. Manganese oxide nanoparticles (MONPs) are recently known to possess ROS scavenging properties. In this study, MONPs were examined for their therapeutic effect on neuropathic pain. Methods:The MONPs were synthesized by a hydrothermal method. The synthesized MONPs were characterized by UV/Vis, TEM, SEM, FTIR, NTA and XRD. The biocompatibility of the nanoparticles is evaluated in neural cells using LDH assay. MONPs were evaluated for their antioxidant activity by DPPH assay. In addition, in vitro ROS scavenging properties were examined in bone marrow-derived macrophage (BMDM) cells using 2',7'-dichlorofluorescin diacetate (DCFDA) assay. To evaluate the in vivo efficacy of nanoparticles, neuropathic pain was induced in Wistar rats by partial sciatic nerve transection (PSNT). On post-transection days 14 to 18, rats were intrathecally injected with MONPs and paw withdrawal threshold was measured. The spinal cords were collected and processed for Western blotting and histological analysis. Results:The synthesized MONPs were biocompatible and showed effective antioxidant activity against DPPH free radical scavenging. Further, the nanoparticles scavenged ROS efficiently in vitro in BMDM and their intrathecal administration significantly reduced mechanical allodynia as well as the expression of cyclooxygenase-2 (COX-2), an important mediator of chronic and inflammatory pain in the spinal dorsal horns of PSNT rats. Conclusion:As ROS play a significant role in neuropathic pain, we expect that MONPs could be a promising tool for the treatment of various inflammatory diseases and might also serve as a potential nanocarrier for the delivery of analgesics.

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The synthetic cannabinoid WIN55,212-2 attenuates hyperalgesia and allodynia in a rat model of neuropathic pain.

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