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Objective To evaluate the role of monocyte chemotactic factor-1 (MCP-1)∕chemokine C-C receptor 2 ( CCR2) in amygdala in neuropathic pain ( NP) in rats. Methods Clean-grade healthy male Sprague-Dawley rats, weighing 200-260 g, aged 2 months, in which NP model was established by ligating the left L5,6spinal nerve, were used in this study. The experiment was performed in two parts. Ex-periment Ⅰ Thirty-two rats were divided into 2 groups using a random number table method: control group (C group, n＝8) and NP group (n＝24). Rats were sacrificed at 7, 14 and 21 days after establis-hing NP model in group NP or at the corresponding time points before establishing NP model in group C, and the amygdala was removed for determination of the expression of MCP-1 and CCR2 mRNA and positive cell count using quantitative real-time polymerase chain reaction and immunohistochemistry. Experiment ⅡThirty-two rats were divided into 4 groups ( n＝8 each) using a random number table method: control group (C group), NP group, MCP-1 group and specific CCR2 antagonist RS102895 group (RS group). MCP-1 (50 pmol for each side) or RS102895 (100 pmol for each side) was injected into the bilateral a-mygdala at days 3, 6, 13 and 20 after establishing NP model in MCP-1 and RS groups, respectively. The thermal paw withdrawal latency (TWL) and mechanical paw withdrawal threshold (MWT) were measured at days 4, 7, 14 and 21 after establishing NP model (T1-4). Rats were sacrificed at T4and the L5segment of the spinal cord was removed for determination of interleukin-1beta (IL-1β), IL-6 and tumor necrosis fac-tor-alpha ( TNF-α) contents by enzyme-linked immunosorbent assay. Results Experiment Ⅰ Compared with group C, the expression of MCP-1 and CCR2 mRNA in amygdala was significantly up-regulated, and the number of MCP-1 and CCR2 positive cells was increased in group NP ( P＜0. 05). Experiment ⅡCompared with group C, the MWT was significantly decreased and TWL was shortened at T1-4, and the contents of IL-1β, IL-6 and TNF-α were increased in the other three groups ( P＜0. 05). Compared with group NP, the MWT was significantly decreased and TWL was shortened at T1, and the contents of IL-1β, IL-6 and TNF-α were increased in group MCP-1, and the MWT was significantly increased and TWL was prolonged at T1-4, and the contents of IL-1β, IL-6 and TNF-α were decreased in group RS ( P＜0. 05 or 0. 01). Conclusion Enhanced function of MCP-1∕CCR2 in amygdala may be involved in the pathophysio-logical process of NP in rats.
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Objective To evaluate the relationship between neuropeptide S (NPS) in the amygdala and 5-hydroxytryptamine (5-HT) and GABA in spinal dorsal horns of rats with neuropathic pain.Methods Eighty pathogen-free healthy male Sprague-Dawley rats,weighing 200-260 g,aged 2 months,were divided into 4 groups (n =20 each) using a random number table:sham operation group (group Sham),neuropathic pain group (group NP),low dose NPS group (group L-NPS) and high dose NPS group (group H-NPS).The neuropathic pain model was established by left L5,6 spinal nerve ligation (SNL) in anesthetized rats.NPS was injected into the bilateral amygdala at 3,6,9,12,15 and 18 days after SNL in LNPS group (10 pmol per side) and H-NPS group (100 pmol per side).The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 2 days before SNL and 1,4,7,11,14,17 and 21 days after SNL.Five rats were selected at 7,14 and 21 days after SNL and sacrificed,and the lumbar segment (L5) of the spinal cord was removed for detection of the expression of 5-HT and GABA in spinal dorsal horns by immunofluorescence histochemistry.Results Compared with group Sham,the MWT was significantly decreased,the TWL was shortened,and the expression of 5-HT and GABA in spinal dorsal horns was down-regulated in NP,L-NPS and H-NPS groups (P＜0.05).Compared with group NP,the MWT was significantly increased,the TWL was prolonged,and the expression of 5-HT and GABA in spinal dorsal horns was up-regulated in L-NPS and H-NPS groups (P＜0.05).Compared with group L-NPS,the MWT was significantly increased,the TWL was prolonged,and the expression of 5-HT and GABA in spinal dorsal horns was up-regulated in group H-NPS (P＜0.05).Conclusion The spinal mechanism of endogenous analgesia induced by NPS in the amygdala may be related to up-regulation of the expression of 5-HT and GABA in spinal dorsal horns of rats with neuropathic pain.
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Objective To investigate the analgesic effects of intraperitoneal lithium chloride injection on radicular pain behaviors in rats.Methods Using rat model of radicular pain induced by chronic compression of dorsal root ganglion(CCD) ,40 male SD rats were randomly divided into model group and Sham-operation group (group S, n= 12) of radicular pain were established.The rats in the model group were subdivided randomly into Control group(group C, n= 12) ,Early treatment group(group E, n=8) and Later treatment group(group L, n= 8 ).Rats in group E were intraperitoneal injected with lithium chloride once daily on day 2 ～ 4 after CCD respectively,while rats in L,group C and S treated with Vehicle(0.9% NaCl).Rats in L group were intraperitoneal treated with lithium chloride on day 12 ～ 14 after CCD respectively,while rats in E,group C and S received Vehicle.The pain ethology indexes such as paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were tested on day 1 before operation and day 1,4,7,10, 14, 17 and 21 after operation.Results Compared to S group and preoperative level, PWMT and PWTL decreased at Day 1 postoperative in group C (P＜0.05).At day 4 after the operation,compared with group C(7.712 ±0.237)g and (8.190 ±0.382) s,PWMT and PWTL of E group increased to ( 14.607 ± 0,280) g and ( 19.940 ± 0.933 ) s (P ＜ 0.05 ) after intraperitoneal injected lithium chloride.At day 14, compared with group C ( 6.788 ± 0.331 ) g and ( 7.301 ± 0.481 ) s, PWMT and PWTL of group L increased to ( 11.700 ± 0.379) 8 and ( 18.524 ± 1.060) s (P ＜ 0.05 ).This analgesic effect of lithium chloride continued to exist at day 21.However, there was still a significant difference between S group and E,group L(P＜0.05).Conclusion Intraperitoneal lithium chloride injection alleviates pain behavior on radicular pain in rats.
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Objective To investigate the effects of intrathecally coadministered dexamethasone and spironolactone in trathecally on radicular pain behaviors.Methods Using rat model of radicular pain induced by chronic compression of dorsal root ganglion (CCD) ,48 male SD rats successfully received intrathecal catheter implantation and without motor dysfunction were randomly divided into Sham-operation group (Sham group, n= 12),Control group ( C group, n = 12 ), Dexamethasone group ( D group, n = 8 ), Spironolactone group ( S group, n = 8 )and Dexamethasone plus spironolactone group (DS group, n=8).Rats in D group,S group or DS group were intrathecally treated with dexamethasone 4 μg, spironolactone 3 μg or dexamethasone 4 μg plus spironolactone 3 μg twice daily on day 2 ～4 after CCD respectively,while rats in C and Sham group received 10μl 10% alcohol.Paw withdrawal mechanical threshold(PWMT) and paw withdrawal thermal latency (PWTL) were tested on day 1 before CCD and day 1,4,7,10,14,17 and 21 after CCD.Results Compared with Sham group, both PWMT and PWTL were significantly decreased after CCD surgery on the ipsilateral side(P＜0.01 ＝.Intrathecally administrated with dexamethasone significantly improved pain behaviors (P＜0.01 ＝ and these therapeutic effects lasted up to 10 days after CCD surgery.As with dexamethasone,intrathecal spironolactone also significantly attenuated PWMT (P＜0.01 ＝ and PWTL (P＜0.01 ＝ and the change lasted up to 7 days after CCD surgery.Coadministration spironolactone and dexamethasone exhibited significant synergies( PWMT: ( 13.52 ± 0.72) g vs ( 11.58 ± 1.38 ) g, P ＜0.01; PWTL: ( 19.63 ± 1.68) s vs ( 14.14 ± 1.52) s, P ＜ 0.01 ＝.These effects lasted up to at least 10 days.Conclusion Both dexamethasone and spironolactone intrathecally have therapeutic effects on radicular pain behaviors, combination injection of these two drugs could generate significant synergies.
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Objective To investigate the role of Ca2+/calmodulin-dependent protein kinase Ⅱ on pain behavior in a mouse model of bone cancer pain. Methods 40 male C3H/HeN mice were divided randomly into 5 groups:sham group (S group, n=8) ,control group (C group, n=8) and KN93 treat group (T1, n=8;T2, n=8;T3, n = 8 ). Group C and T were induced mouse models of bone cancer pain by intra-left-femur inoculations of osteolytic NCTC2472 cells while group S were injected only α-MEM. On the 14 d after inoculations,group S and C received intrathecal injection of 20% DMSO 5 μl . While group T1, T2, T3 received intrathecal injection of KN93 15nmol,30nmol,60nmol which dissolved in 5 μl 20% DMSO respectively. Mice received pain behavior tests including quantification of spontaneous flinches, paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) before and at 0.5 h,2 h,4 h,8 h after administration. Results Treatment with KN93(15 nmol) have no effect on bone cancer pain,while treatment with KN93(30 nmol,60 nmol) can dose-dependently reverse quantification of spontaneous flinches, mechanical allodynia and thermal hyperalgesia which were induced by bone cancer pain, At 0. 5h after administration, the quantification of spontaneous flinches of the two groups ( (7.25 + 1.49 ), (4. 12 + 1.36 ) ) were decreased when compared with control group ( 11.62 + 1.92 ),PWMT((1.28 +0.14)g;(1.75 +0.46)g),PWTL((14.64 +2.12) s; (16.85 + 1.61)s)were increased when compared with control group ( (0.47 + 0. 16) g, ( 11.32 + 1.68 ) s) (P ＜ 0.05 ＝. The effect lasts for at least 4 h and disappears at 8 h. Conclusion CaMK Ⅱ may play an important role in the mechanism of bone cancer pain. Intrathecal KN93 injection can effectively attenuated bone cancer pain.