慢性痛伴焦虑小鼠中脑腹侧被盖区向伏隔核及腹侧海马的分支投射

Collateral projections from the ventral tegmental area to nucleus accumbens and ventral hippocampus in mice with chronic pain and anxiety-like behavior

目的:观察小鼠中脑腹侧被盖区(VTA)多巴胺能神经元向伏隔核(NAc)及腹侧海马(vHIP)的分支投射,并为其参与慢性痛伴焦虑信息的传递提供形态学证据。方法:将实验小鼠随机分为慢性痛组(cuff)和假手术组(sham),于术后1、3、7、14 d对小鼠进行机械痛敏检测,于术后7 d采用立体定位注射方法在cuff组小鼠的左侧NAc及vHIP分别注射四甲基罗达明(TMR)和荧光金(FG),于术后14 d对小鼠进行旷场实验(OFT)、高架十字迷宫实验(EPM)检测。结合免疫荧光组织化学染色方法观察慢性痛伴焦虑小鼠中脑VTA内FG/TMR双标神经元,及酪氨酸羟化酶(TH)、FOS蛋白的表达情况。结果:(1)与sham组相比,cuff组小鼠术后第1 d就出现了机械痛阈的降低,并一直持续至第14 d,而且呈现出明显的焦虑样情绪反应;(2)慢性痛伴焦虑小鼠中脑VTA内有部分神经元为FG/TMR双标神经元,大约有(58.19±7.67)%及(76.40±0.67)%的FG/TMR双标神经元分别表达FOS及TH。结论:小鼠中脑VTA内多巴胺能神经元可以同时向NAc及vHIP发出分支投射,其中部分分支投射神经元可能参与了慢性痛伴焦虑信息的传递。

Objective:To explore whether the ventral tegmental area(VTA)dopaminergic neurons send collateral projections to the nucleus accumbens(NAc)and ventral hippocampus(vHIP),and provide evidence for collateral VTA projection neurons involved in chronic pain and anxiety comorbidity.Methods:Mice were randomly divided into chronic pain and sham groups.Mechanical allodynia was tested at 1th,3th,7th,and 14th day after cuffing operation.Mice in cuff group were stereotactically injected with tetramethylrhodamine-dextran(TMR)into the left NAc and Fluoro-gold(FG)into the left vHIP at 7th day after cuffing operation.Open field test(OFT)and elevated plus-maze test(EPM)were performed to test the anxiety-like behavior at 14th after cuffing operation.Combining the immunofluorescence histochemical staining method,the FG/TMR double-labeled neurons,FG/TMR/FOS,and FG/TMR/TH triple-labeled VTA neurons were observed in mice with chronic pain and anxiety-like behavior.Results:(1)Compared with the sham group,mice in cuff group showed mechanical allodynia at 1th day after cuffing operation,which last until 14th day.And mice in cuff group showed anxiety-like behavior at 14th day;(2)Some VTA neurons were FG/TMR double-labeled neurons in mice with chronic pain and anxiety-like behavior.About(58.19±7.67)%and(76.40±0.67)%FG/TMR double-labeled VTA neurons were FG/TMR/FOS and FG/TMR/TH triple-labeled neurons.Conclusions:Mice VTA dopaminergic neurons can send collateral projections to the NAc and vHIP.Some collateral VTA projection neurons may be involved in chronic pain and anxiety comorbidity.