右美托咪定上调海马脑源性神经营养因子-酪氨酸激酶受体B的表达及改善完全费氏佐剂所致小鼠焦虑样和抑郁样行为

Dexmedetomidine improving complete Freund’s adjuvant-induced anxiety-like and depression-like behaviour by promoting the expression of brain-derived neurotrophic factor-tyrosin kinase receptor B in mice hippocampus

目的探讨α2-肾上腺素受体激动剂右美托咪定(DEX)对完全弗氏佐剂(CFA)诱导疼痛模型小鼠焦虑样和抑郁样行为的影响及其可能的机制。方法36只ICR雌鼠随机分成生理盐水(NS)组、CFA组和DEX+CFA组,每组n=12。向小鼠右后肢足底皮下注射10μl CFA建立慢性炎性疼痛模型,DEX+CFA组小鼠在痛阈检测前30 min腹腔注射0.025 mg/kg DEX,1次/1 d,持续7 d。实验采用von-frey纤维丝评价3组小鼠机械性痛阈值;采用旷场实验检测小鼠焦虑样行为;采用糖水偏好、悬尾实验和强迫游泳检测3组小鼠抑郁样行为;采用Western blotting检测3组小鼠海马肾上腺素能受体β2(ADRB2)、脑源性神经营养因子(BDNF)、酪氨酸激酶B受体(TrkB)及突触相关蛋白谷氨酸受体1(GluR1)和GluR2的表达,每组n=8;采用免疫组织化学染色方法检测各组小鼠海马新生神经元标记物双肾上腺皮质激素(DCX)的表达情况,每组n=4。结果痛阈检测结果显示,与NS组相比,CFA注射后的第1天、3天、7天小鼠机械痛阈值均显著降低(P<0.05);与CFA组相比,DEX+CFA组小鼠机械疼痛阈值差异无显著性(P>0.05)。旷场结果显示,与NS组相比,CFA组小鼠进入中央格区域的时间(P<0.01)、次数(P<0.01)和中央格运动距离(P<0.01)均明显减少,而DEX+CFA组小鼠进入中央格区域的时间(P<0.01)、次数(P<0.05)和距离(P<0.05)明显多于CFA组。抑郁样行为检测结果显示,CFA组小鼠糖水偏好百分比(P<0.05)与NS组相比明显减少,悬尾不动时间(P<0.01)和强迫游泳不动时间(P<0.001)与NS组相比均显著增加;而DEX干预能明显增加小鼠糖水偏好百分比(P<0.05),降低小鼠悬尾不动时间(P<0.05)和强迫游泳不动时间(P<0.05)。Western blotting结果显示,与NS组相比,CFA组小鼠海马ADRB2(P<0.001)、BDNF(P<0.001)、TrkB(P<0.01)、GluR1(P<0.001)和GluR2(P<0.001)明显减少;DEX干预能明显增加ADRB2(P<0.05)、BDNF(P<0.001)、TrkB(P<0.001)、GluR1(P<0.001)和GluR2(P<0.001)的表达。免疫组织化学结果显示,与NS组相比,CFA组小鼠海马DCX平均吸光度显著降低(P<0.05);与CFA组相比,DEX+CFA组小鼠海马DCX平均吸光度显著升高(P<0.05)。结论右美托咪定可能通过上调BDNF-TrkB的表达促进海马神经发生,从而改善CFA所致小鼠焦虑样和抑郁样行为。

Objective To study the effect of dexmedetomidine(DEX),anα2-adrenoceptor agonist,on the painrelated anxiety-like and depression-like behaviour induced by complete Freund’s adjuvant(CFA)injection and its possible regulatory mechanism.Methods Thirty-six ICR female mice were randomly divided into normal saline(NS)group,CFA group and DEX+CFA group,n=12 for each group.Chronic inflammatory pain model was established by subcutaneous injection of 10μl CFA into the right hind limb of mice.DEX+CFA group mice were injected intraperitoneally with 0.025 mg/kg DEX 30 minutes before nociceptive behavior test,and once a day for 7 days.Von-frey fiber was used to evaluate the threshold of mechanical pain in mice,n=12 for each group.The anxiety-like behavior of mice were detected by open field test,n=12 for each group.Sucrose preference,tail suspension test and forced swimming test were used to detected the depression-like behavior of mice,n=12 for each group.The expression of adrenergic receptorβ2(ADRB2),Brain-derived neurotrophic factor(BDNF),tyrosine kinase B receptor(TrkB),and glutamate receptors 1(GluR1)and GluR2 were detected by Western blotting,n=8 for each group.Immunohistochemical staining was used to detect the expression of recombinant doublecortin(DCX),which is a marker of newborn neurons in the hippocampus,n=4 for each group.Results Compared with the NS group,the mechanical threshold of mice on the 1st,3rd and 7th day after CFA injection decreased significantly(P<0.05);But there was no significant difference between DEX+CFA group and CFA group(P>0.05).Compared with the NS group,the time spent in the inner ares(P<0.01),number of entering the central grid area(P<0.01)and distance travelled in the inner area(P<0.01)of CFA group mice reduced significantly,while the time(P<0.01),numbers(P<0.05)and distance(P<0.05)of DEX+CFA group mice entering the central grid area enhanced significantly.The result of depression-like behavior tests showed that the sucrose preference percentage(P<0.05)reduced significantly in CFA group when compared with NS group,and the immobility time increased significantly in tail suspension test(P<0.01)and forced swimming test(P<0.001)in CFA mice when compared with NS group,while DEX intervention could significantly increase the sucrose preference scores(P<0.05)and decreased the immobility time in tail suspension test(P<0.05)and forced swimming test(P<0.05).The result of Western blotting showed that compared with the NS group,the levels of ADRB2(P<0.0010),BDNF(P<0.001),TrkB(P<0.01),GluR1(P<0.001)and GluR2(P<0.001)in the hippocampus of CFA group were significantly decreased,while DEX intervention could significantly increase the expression of ADRB2(P<0.05),BDNF(P<0.001),TrkB(P<0.001),GluR1(P<0.001)and GluR2(P<0.001).Immunohistochemical result showed that compared with the NS group,the average absorbance(AA)of DCX decreased significantly in hippocampus of CFA group(P<0.05),but increased significantly in DEX+CFA group(P<0.05).Conclusion Dexmedetomidine may promote hippocampal neurogenesis through upregulated the expression of BDNF-TrkB,thus improving CFA-induced anxiety-like and depression-like behaviors in mice.