摘要目的 研究米诺环素缓解大鼠甲醛溶液炎性痛的脊髓机制.方法 行为学实验:3～5周龄雄性SD大鼠随机分为4组:对照组、模型组、溶媒对照组及米诺环素组.模型组、溶媒对照组及米诺环素组大鼠于右后足背皮下注射10％中性甲醛溶液,对照组大鼠右后足背皮下注射生理盐水,其中溶媒对照组和米诺环素组在甲醛溶液注射前1h分别腹腔注射生理盐水和米诺环素,观察各组大鼠缩足和舔爪等炎性痛行为.电生理实验:选取同上SD大鼠,制作离体脊髓纵切片.采用全细胞膜片钳技术记录米诺环素对脊髓背角胶状质(SG)神经元的自发性抑制性突触后电流(sIPSCs)的作用.结果 与对照组相比,模型组缩足和舔爪时间显著增加;与溶媒对照组比较,米诺环素组缩足和舔爪时间显著减少.对照组和米诺环素组sIPSCs的频率分别为(2.5 ±0.3)Hz和(5.2 ±0.6)Hz,米诺环素可显著增加SG神经元sIPSCs的频率(t=9.32,P＜0.05),而对其幅度无明显影响(t=1.54,P＞0.05).去除细胞外液中的钙离子后,米诺环素用药前后sIPSCs的频率分别为(0.9±0.1)Hz与(0.9±0.1)Hz,振幅分别为(18.2 ±0.7)pA与(18.5±0.6)pA,差异均无统计学意义(t=0.32、0.82,均P＞0.05).在细胞外液中加入谷氨酸受体阻滞剂6-氰基-7-硝基喹喔啉2,3-二酮(CNQX)和D-α-氨基磷酸基戊酸(APV)后,米诺环素仍可增加sIPSCs的频率,分别为(2.0±0.1)Hz与(4.3±0.4) Hz,差异有统计学意义(t=13.51,P＜0.05).在细胞外液中加入电压门控钠通道阻滞剂河豚毒素(TTX)后,米诺环素仍可增加IPSCs的频率,分别为(2.2±0.2)Hz与(5.2±0.5)Hz,差异有统计学意义(t =8.67,P＜0.05).结论 米诺环素可缓解甲醛溶液诱导的炎性痛,这一效应与其增加脊髓背角SG神经元的抑制性突触传递有关.

abstractsObjective To investigate the spinal analgesic mechanism of minocycline in formalin-induced inflammatory pain.Methods Behavioral test:Male Sprague-Dawley rats (3-5-week old) were randomly assigned into four groups:control,model,vehicle-controlled and minocycline group.Ten percent neutral formalin was injected subcutaneously into the right hind paw dorsum of the rats in model,vehicle-controlled and minocycline group.Normal saline was injected subcutaneously into the right hind paw dorsum of the rats in control group.Before 1 h of formalin injection,the rats in vehicle-controlled and minocycline group received intraperitoneal injection of saline and minocycline,respectively.Licking and lifting time was observed as the behavior results of inflammatory pain.Electrophysiologic experiment:In vitro spinal cord parasagittal slices were prepared from the same rats as above.The effect of minocycline on spontaneous inhibitory postsynaptic currents(sIPSCs) of substantia gelatinosa (SG) neurons was observed using whole-cell patch-clamp technique.Results Compared with the control group,the licking and lifting time in the model group was significantly increased.Compared with the vehicle-controlled group,the licking and lifting time in the minocycline group was significantly decreased.Minocycline significantly increased the frequency (t =9.32,P ＜ 0.05) but not the amplitude(t =1.54,P ＞ 0.05) of sIPSCs of SG neurons,the frequency of sIPSCs of control and minocycline group were (2.5 ± 0.3) Hz and (5.2 ± 0.6) Hz,respectively.When calcium was removed from the extracellular solution,the frequency before and after minocycline perfusion were (0.9 ± 0.1)Hz and (0.9 ± 0.1)Hz,respectively,the amplitude before and after minocycline perfusion were (18.2 ± 0.7) pA and (18.5 ± 0.6) pA,respectively,the difference of frequency or amplitude was not statistically significant (t =0.32,0.82,all P ＞ 0.05).However,minocycline still increased the frequency of sIPSCs when glutamate receptor antagonists 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX) and D-(-)-2-Amino-5-phosphonopentanoic acid(APV) were included in extracellular solution(t =13.51,P ＜ 0.05),the frequency of sIPSCs were (2.0 ± 0.1) Hz and (4.3 ± 0.4) Hz,respectively.Minocycline still increased the frequency of IPSCs when voltage-gated sodium channel blocker tetrodotoxin (TTX) were included in extracellular solution (t =8.67,P ＜ 0.05),the frequency of IPSCs were (2.2 ± 0.2) Hz and (5.2 ± 0.5) Hz.Conclusion Minocycline can attenuate formalin-induced inflammatory pain which may be associated with its increase in the inhibitory synaptic transmission of SG neurons.