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Objective To investigate the effects of spinal cannabinoid type 2 receptor (CB2R) and microglia activation on hyperalgesia in neuropathic pain mice. Methods Male C57/BL mice were randomly divided into six groups: sham, spinal nerve ligation (SNL), SNL＋CB2R agonist AM1241 (SNL＋AM1241), SNL＋microglia inhibitor minocycline (SNL＋minocycline), SNL＋small interfering RNA (siRNA) targeting CB2R (SNL＋siRNA), and SNL＋siRNA＋minocycline groups. A neuropathic pain mouse model was established by SNL. The expression levels of spinal CB2R and microglia-specific protein ionized calcium-binding adapter molecule 1 (IBA-1) were determined by Western blotting, mechanical pain thresholds were measured by Von Frey, spinal microglia activation was observed by IBA-1 immunofluorescence, and the expression levels of inflammatory factors in spinal cord dialysate were determined by quantitative real-time polymerase chain reaction (qRT-PCR). Electrophysiology was applied to observe the effect of CB2R agonist on spontaneous inhibitory postsynaptic current (sIPSC) in the spinal dorsal horn. Results Compared with the sham group, the expression of CB2R in spinal cord was significantly decreased in the SNL group (P＜0.012 5), the pain threshold was significantly reduced (P＜0.016 7), the fluorescence quantification and protein expression of IBA-1 were significantly increased (both P＜0.008 3), and the mRNA expression levels of tumor necrosis factor α (TNF-α), interleukin (IL)-1β and IL-6 were significantly increased (all P＜0.008 3). After intrathecal injection of CB2R agonist AM1241 or microglial inhibitor minocycline, compared with the SNL group, the pain thresholds of mice were significantly increased in the SNL＋AM1241 and SNL＋minocycline groups (both P＜0.008 3), the fluorescence quantification and protein expression of IBA-1 were significantly decreased (both P＜0.008 3), and the mRNA expression levels of TNF-α, IL-1β and IL-6 were significantly decreased (all P＜0.008 3). After targeted interfering CB2R expression by siRNA, compared with the SNL group, the pain threshold was significantly decreased in the SNL＋siRNA group (P＜0.008 3), the fluorescence quantification and protein expression of IBA-1 were significantly increased (both P＜0.008 3), and the mRNA expression levels of TNF-α, IL-1β and IL-6 were significantly increased (all P＜0.008 3); while intrathecal injection of minocycline significantly reversed the above changes (all P＜0.008 3). Intervention in vitro of AM1241 could significantly enhance the frequency and amplitude of sIPSC in the spinal dorsal horn (both P＜0.05), while continuous treatment with minocycline inhibited the enhancement effects of AM1241 on sIPSC. Conclusion CB2R can reduce the neuroinflammatory responses and enhance the inhibitory electrical activity in the spinal cord by inhibiting spinal microglia activation, thereby alleviating hyperalgesia of neuropathic pain in mice.
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Objective: To explore the effect and mechanism of intraoperative remifentanil (RF) on renal ischemia/reperfusion (I/R) injury. Methods: Fifty male C57/BL mice were randomly divided into 5 groups: sham group, I/R group, I/R+LY294002 (a phosphatidylinositol 3-kinase [PI3K] inhibitor) group, I/RRF group and I/R + RF+LY294002 group, with 10 mice in each group. Venous blood or renal tissue samples were collected from the mice of each group 6 h after I/R operation. The levels of blood urea nitrogen (BUN) and serum creatinine (SCr) were detected using automatic biochemical analyzer. The expression levels of PI3K/protein kinase B (Akt)/endothelial nitric oxide synthase (eNOS) pathway-related proteins in renal tissues of mice were detected using Western blotting. The aggregation of inflammatory cells was observed by H-E staining. The expression levels of tumor necrosis factor α (TNF-α), interleukin (IL)-1β, IL-6 and IL-10 in renal tissues of mice were detected by enzyme-linked immunosorbent assay. The mRNA expression levels of anti-apoptotic factor Bcl2 and apoptotic factor Caspase-3 in renal tissues were determined by real-time quantitative PCR. Results: Compared with the sham group, the BUN and SCr levels in venous blood were increased in the I/R group, the PI3K expression, phosphorylated-Akt (p-Akt)/Akt ratio and phosphorylated-eNOS (p-eNOS)/eNOS ratio in renal tissues were decreased, the release levels of inflammatory factors (TNF-α, IL-1β, IL-6 and IL-10) were increased, Bcl2 mRNA expression was decreased, and Caspase-3 mRNA expression was increased; and the differences were significant (all P < 0.05). The mice of the I/R group had increased inflammatory cell recruitment in renal tissues. After RF treatment, the mice of the I/R + RF group had decreased levels of BUN and SCr in venous blood, increased PI3K expression, p-Akt/Akt ratio and p-eNOS/eNOS ratio in renal tissues, decreased release levels of inflammatory factors (TNF-α, IL-1β, IL-6 and IL-10), increased Bcl2 mRNA expression, and decreased Caspase-3 mRNA expression; and the differences were significant compared with the mice of the I/R group (all P < 0.05). The inflammatory cell recruitment was decreased in the I/R RF group. Moreover, compared with the mice of the I/RRF group, the mice of the I/RRF LY294002 group had increased levels of BUN and SCr in venous blood, decreased p-eNOS/eNOS ratio in renal tissues, increased IL-1β and IL-6 release, and increased Caspase-3 mRNA expression; and the differences were significant (all P<0.05). The inflammatory cell recruitment was increased in the I/R + RF + LY294002 group. Conclusion: RF exerts protective effect on kidney with I/R injury by alleviating renal inflammation and cell apoptosis through activating PI3K/Akt/eNOS pathway.
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5-hydro xytryptamine (5-HT) receptors are widely distributed in the central and peripheral nervous systems, regulating and controlling various physiologic functions. 5-HT and its analogues can play both inhibitory or promoting roles in the pain signal conduction via interacting with various subtypes of 5-HT receptor at different locations. In the central nervous system, the descending serotonergic neurons exert analgesic effect by activating the inhibitory interneurons, and the analgesic efficiency depends on the quantity and subtype of the 5-HT receptors. In periphery, 5-HT receptors are involved in pain signal conduction and have a close relationship with hyperalgesia. In this review, we focusedon the different subtypes of 5-HT receptors locating in the central and peripheral nervous systems, and summarized the regulation mechanisms of 5-HT receptors in the pain signal, hoping to provide a theoretical basis and new target for the therapy and recovery of acute and chronic pain.