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Objective To evaluate the role of transient receptor potential ankyrin 1 (TRPA1) in the dorsal root ganglion neurons in the development of diabetic neuropathic pain (DNP) in rats.Methods Twenty-four Sprague-Dawley rats with DNP were randomly divided into 3 groups (n-=8 each) using a random number table:DNP group,TRPA1-specific siRNA group (siRNA group) and TRPA1-negative siRNA group (NC group).Another 8 Sprague-Dawley rats with normal blood glucose served as control group (C group).In siRNA group,TRPA1-specific siRNA 45 μl was injected intrathecally.In NC group,TRPA1-negative siRNA 45 μl was injected intrathecally.In DNP and C groups,normal saline 45 μl was injected intrathecally.On 2nd day after intrathecal administration,the lumbar segment (L4-6) of the dorsal root ganglions was removed for determination of the expression of TRPA1 mRNA.On 7,14,21 and 28 days after intrathecal administration (T1-4),MWT was measured.Results Compared with DNP group,TRPA1 mRNA expression was down-regulated in siRNA and C groups.Compared with DNP group,and MWT was significantly decreased at T1.2 in siRNA group,MWT was decreased at T1-3 in NC group,MWT was increased at T1-4 in group C.Compared with siRNA group,MWT was significantly increased at T1-4 in group C.MWT was significantly higher at T1~ in group C than in NC group.Conclusion TRPA1 in the dorsal root ganglion neurons is involved in the development of DNP in rats.
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Objective To evaluate the role of transient receptor potential ion channel 1 (TRPA1) in the spinal dorsal horn neurons in maintenance of neuropathic pain in rats.Methods Fifty-six adult male SpragueDawley rats,weighing 200-250 g,were randomly divided into 4 groups (n =14 each):sham operation group (group S); chronic compression of dorsal root ganglia (CCD) group; CCD + dimethyl sulfoxide group (group D); and CCD + TRPA1 blocker HC-030031 group (group H).CCD was produced by infiltrating the L5 intervertebral foramen with 50 μl of a hemostatic matrix (SURGIFLO) in anesthetized rats in CCD,D and H groups.In D and H groups,10％ dimethyl sulfoxide 20 μl and HC-030031 50 μg were injected intrathecally at 7 days after CCD operation,respectively.Paw withdrawal threshold to mechanical stimulation (PWMT) was measured at 1 day before operation (T0),at 1 h before intrathecal administration (T1),and at 1,2,4,6,8,and 24 h after intrathecal administration (T2-7).Six rats in each group were sacrificed at T4 and T7,the L3-5 segments of the spinal cord were obtained for determination of TRPA1 expression in the spinal cord by Western blot.Results Compared with group S,PWMT was significantly decreased at T1-7,the expression of TRPA1 in the spinal cord was up-regulated at T4 and T7 in CCD and D groups,and the PWMT was decreased at T1 and T5-7 and the expression of TRPA1 was up-regulated at T7 in H group (P ＜ 0.05).Compared with CCD group,the PWMT was significantly increased at T2-5 and the expression of TRPA1 was down-regulated at T4 in H group (P ＜ 0.05).Conclusion TRPA1 in the spinal dorsal horn neurons is involved in the maintenance of neuropathic pain in rats.
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Objective To evaluate the role of phosphatidylinositol 3-kinase (PI3K) p110β in spinal dorsal horn neurons in the development of arthritic pain (AP) in rats and the relationship with transient receptor potential vanilloid 1 (TRPV1) and acid-sensing ion channel (ASIC)1 a.Methods Forty adult female Sprague-Dawley rats in which intrathecal catheters were successfully placed,aged 3 months,weighing 250-300 g,were randomly divided into 4 groups (n =10 each):control group (group C),group AP,AP + PI3K p110β missense oligo-deoxynucleotide group (group MS) and AP + PI3K p110β antisense oligo-deoxynucleotide group (group AS).AP was induced by injecting complete Freund's adjuvant into the ankle joint cavity of right hindpaw.Normal saline 20 μl,missense oligo-deoxynucleotide 15 μg (20μl) and antisense oligo-deoxynucleotide 15 μg (20 μl) were administered intrathecally once a day for 6 consecutive days starting from the time immediately after arthritis was induced in groups AP,MS and AS,respectively.Mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured 1 day before operation (T0) and on days 4,7,10 after operation (T1-3).The rats were then sacrificed after the last measurement of pain threshold at T3.L4-6 segment of the spinal cord was removed for detection of expression of PI3K p110β (by Western blot),and TRPV1 and ASICla (by immunohistochemistry)in spinal dorsal horn neurons.Results Compared with group C,MWT and TWL were significantly decreased atT1-3,and the expression of PI3K p110β,TRPV1 and ASIC1a was up-regulated in the other 3 groups(P＜ 0.01).MWT and TWL were significantly higher at T1-3,and the expression of PI3K p110β,TRPV1 and ASIC1a was lower in group AS than in groups AP and MS (P ＜ 0.01).Conclusion PI3K p110β in spinal dorsal horn neurons is involved in the development of AP in rats,and the mechanism is related to up-regulation of TRPV1 and ASIC1a expression in spinal dorsal horn neurons.
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Objective To investigate the changes in the number of microglias and astrocytes in the spinal dorsal born in a rat model of phantom limb pain.Methods Eleven healthy adult SD rats of both sexes weighing 290-300 g were randomly divided into 2 groups:sham operation group (group S,n =5 ) and unilateral sciatic nerve transection group (group SNT,n =6).Phantom limb pain model was induced by resection of a 0.5 cm segment of unilateral sciatic nerve in group SNT.In group S unilateral sciatic nerve was exposed but not transected.The animals were observed for autotomy and scored (0 =no autotomy,13 =the worst autotomy) after operation and were sacrificed on the 28th day after operation.The L5 segment of the spinal cord was removed for determination of the number of microglials (by iba-1 immuno-histochemistry) and astrocytes (by GFAP immuno-histochemistry).Results In group S no animal developed autotomy.In group SNT autotomy started from the 2nd day after operation and the score reached 9-11.Compared with group S,the number of the microglias and astrocytes in the spinal dorsal horn was significantly decreased in the operated side in group SNT ( P ＜ 0.05 ).Conclusion The number of microglias and astrocytes in the spinal dorsal horn is decreased in animals with phantom limb pain.
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Objective To investigate the effects of dexmedetomidine (Dex) on the neuronal apoptosis in spinal dorsal horn in a rat model of chronic neuropathic pain.Methods Seventy-two adult male SD rats weighing 180-220 g were randomly divided into 3 groups ( n =24 each):sham operation group (group S) ; chronic constrictive injury (CCI) group; Dex + CCI group (group D).Two ligatures were placed on right sciatic nerve at 1 mm intervals with 4-0 silk thread in groups CCI and D.In group D Dex 50 μg/kg was injected intraperitoneally once a day starting from the end of operation until the animals were sacrificed.Paw withdrawal threshold to mechanical stimulation with yon Frey filament (PWT) and paw withdrawal latency to thermal stimulation (PWL) were measured at one day before (T0,baseline) and on the 3rd,7th and 14th day after operation (T1,2,3).Six animals were sacrificed at each time points (T1,2,3) after the measurement of PWT and PWL.Their lumbar segments (L4,5)were removed for examination with transmission electron microscope and detection of Bcl-2 and caspase-3 expression (by immune-histochemistry).Results CCI significantly decreased PWT and PWL,increased Bcl-2 and caspase-3 expression at T1,2,3 and induced apoptosis in spinal dorsal horn neurons in group CCI as compared with group S.Intraperitoneal Dex significantly attenuated CCI-induced mechanical and thermal hyperalgesia and neuronal apoptosis in group D as compared with group CCI.Dex injected intraperitoneally further increased Bcl-2 expression but decreased caspase-3 expression in group D as compared with group CCI.Conclusion Reduction in neuronal apoptosis in spinal dorsal horn is involved in the attenuation of neuropathic pain by Dex.
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Objective To investigate the changes in the number of synapses and neurons in the spinal dorsal horn in a rat model of phantom limb pain. Methods Eleven healthy adult SD rats of both sexes weighing 209-300 g were randomly divided into 2 groups: sham operation group (group S, n = 5) and phantom limb pain group (group P, n = 6). Phantom limb pain was induced by resection of a 0.5 cm segment of unilateral sciatic nerve in group P. In group S unilateral sciatic nerve was exposed but not transected. The animals were observed for autotomy and scored (0 = no autotomy, 13 = the worst autotomy) after operation and were sacrificed on the 28th day after operation. The L3-6 segment of the spinal cord was removed for determination of the number of neurons (by Nissl's staining) and synapses (by synaptophysin immuno-histochemistry).Results In group S no animal developed autotomy. In group P autotomy started from the 2nd day after operation and the score reached 9-11. The number of the neurons in the spinal dorsal horn in all 4 segments and the number of synapses in L3 and 16 segments were comparable between the two sides and the 2 groups. The number of synapses in the spinal dorsal horn of L4and L5 segment was significantly larger in the operated side than in the contralateral side in group P. Conclusion The number of synapses in the spinal dorsal horn significantly increases in animals with plantom limb pain which induces no increase in the number of neurons in the spinal dorsal horn.