Skip to main content
. 2023 Mar 15;18(11):2535–2542. doi: 10.4103/1673-5374.371373

Figure 8.

Figure 8

Exogenous RvE1 inhibits CPIP-induced nociception, neuroinflammation, and central sensitization.

(A–D) Intrathecal injection of RvE1 (10 ng) relieved bilateral punctate mechanical hyperalgesia and heat hyperalgesia on day 12 after CPIP model establishment (n = 6 mice/group). **P < 0.01, ***P < 0.001 and ****P < 0.0001, vs. CPIP RvE1 group. (E) Schematic of the CPP assay. (F) Schematic of the CPP protocol for CPIP mice. (G) Representative CPP traces from mice injected with vehicle, 10 ng of RvE1, or 20 ng of RvE1. CPIP mice activity was clearly increased in 20 ng of RvE1-paired chambers compared with vehicle- and 10 ng of RvE1-paired chambers. (H) Intrathecal injection of RvE1 (20 ng) induced CPP in CPIP mice (n = 5 mice/group). **P < 0.01, vs. vehicle. (I) Representative images of Iba1 (green, Alexa Fluor 488) immunofluorescence staining in the bilateral spinal dorsal horn of CPIP mice intrathecally injected with vehicle or RvE1 (10 ng). Iba1 fluorescence in CPIP mice was clearly reduced after RvE1 (10 ng) injection. The righthand images (bar: 100 μm) are high magnifications of the boxes in the lefthand images (bar: 200 μm). (J, K) Iba1 fluorescence intensity and numbers of Iba1-positive microglia (n = 3 mice/group). **P < 0.01, ***P < 0.001 and ****P < 0.0001, vs. CPIP vehicle group. (L, M) Intrathecal injection of RvE1 (10 ng) reduced the increase in mRNA levels of the proinflammatory cytokines IL-1β, IL-6, and TNF-α in the bilateral spinal lumbar enlargement induced by CPIP (n = 5 mice/group for TNF-α and n = 6 mice/group for the other cytokines). **P < 0.01 and ****P < 0.0001, vs. CPIP vehicle group. (N) Perfusion of the spinal cord with 10 ng of RvE1 but not 1 ng of RvE1 decreased the spontaneous firing rate of spinal cord WDR neurons in control mice (n = 3 mice/group, n = 11 cells). *P < 0.05, vs. baseline. (O) WDR neuron firing rate ratio to baseline in control mice injected with 1 ng and 10 ng of RvE1 respectisely. (P) Perfusion of the spinal cord with 1 ng or 10 ng of RvE1 decreased the spontaneous firing rate of spinal cord WDR neurons in CPIP mice (n = 3 mice/group, n = 11 cells). ***P < 0.001, vs. baseline. (Q) WDR neuron firing rate ratio to baseline in CPIP mice injected with 1 ng or 10 ng of RvE1 respectively. All data in A–D, H, J–M, O and Q are presented as the mean ± SEM, and the data in N and P are presented as the median ± IQR, and were analyzed by two-way analysis of variance followed by Bonferroni post hoc test (A-D), one-way analysis of variance followed by Bonferroni post hoc test (H), two-tailed unpaired Student’s t-test (J–M, O, Q), or Wilcoxon signed-rank test (N, P). Detailed statistical information is shown in Additional Table 2 (125.3KB, pdf) and Additional file 1 (136.8KB, pdf) . Contra: Contralateral; Control RvE1: the ankles of mice were surrounded by a cut-O-ring and were injected with RvE1; Control Vehicle: the ankles of mice were surrounded by a cut-O-ring and were injected with 1% ethanol; CPIP RvE1: mice were submitted to chronic postischemia pain and injected with RvE1; CPIP Vehicle: mice were submitted to chronic postischemia pain and injected with 1% ethanol; CPP: conditional place preference; Iba1: ionized calcium binding adaptor molecule 1; IOD: integrated optical density; IL: interleukin; Ipsi: ipsilateral; RvE1: Resolvin E1; TNF-α: tumor necrosis factor-α; WDR: wide dynamic range.