小鼠未定带腹侧区GABA能神经元参与慢性痒的形态学研究

Morphological study of GABAergic neurons in the ventral zona incerta of mice involved in chronic itch

目的:在慢性瘙痒模型上检测小鼠的痒行为和焦虑、抑郁样行为,并观察未定带腹侧区(ZIv)内γ-氨基丁酸(GABA)能神经元的激活情况,为其参与痒觉信息的调控提供形态学证据。方法:应用二苯基环丙烯酮(DCP)在谷氨酸脱羧酶67-绿色荧光蛋白(GAD67-GFP)基因敲入小鼠上建立慢性瘙痒模型,然后运用视频跟踪系统检测痒行为,以验证模型制备是否成功。运用高架十字迷宫实验、悬尾实验检测慢性痒模型小鼠的焦虑、抑郁样行为。利用GAD67-GFP小鼠观察未定带(ZI)各区域内GABA能神经元的分布情况,并结合免疫荧光染色方法分别观察对照组和DCP组小鼠ZIv内GABA能神经元与FOS的双标情况。结果:在GAD67-GFP小鼠的脑切片上可观察到GABA能神经元在未定带各亚区均有分布,且更集中于ZIv。DCP组小鼠抓挠次数显著高于对照组小鼠(P<0.001)。悬尾实验中DCP组小鼠完全不动时间显著高于对照组小鼠,出现抑郁样不动状态。高架十字迷宫实验结果显示DCP组小鼠与对照组相比,进入十字交叉区域的次数和时间占比均明显减少,表现出焦虑样行为。免疫荧光染色结果显示,DCP组小鼠ZIv内FOS阳性细胞数量明显高于对照组,且在该区域观察到大量的FOS与GABA能神经元的共标细胞。结论:小鼠未定带以GABA能神经元分布为主,且更集中于ZIv;慢性痒状态下,ZIv内GABA能神经元激活,为ZIv内GABA能神经元参与慢性痒及其伴发的负性情绪提供了形态学证据。

Objective:To detect itching,anxiety,depression behaviors in chronic itch models of mice and observe the activation of γ-aminobutiric acid(GABA)neurons in the ventral sector of the zona incerta(ZIv),and provide morphological evidence for their involvement in the modulation of itch information.Methods:Diphenylcyclopropenone(DCP)was used in glutamic acid decarboxylase 67-green fluorescent protein(GAD67-GFP)knock-in mice to establish chronic itch model.Itch behaviors were detected by video tracking system to verify whether the models were successfully established.The anxiety,depression behaviors of chronic itch model mice were detected by using elevated plus maze test(EPM)and tail suspention test(TST).By using GAD67-GFP mice,the distribution of GABAergic neurons in various sectors of the zona incerta(ZI)was observed.And combined with immunofluorescence staining method,double labeling of GABAergic neurons with FOS in ZIv were observed respectively in control and DCP group mice.Results:In brain slices of GAD67-GFP mice,GABAergic neurons can be observed within all sectors of ZI and are more concentrated in ZIv.Compared with control group mice,DCP group mice showed a significant increase in the bouts of scratching(P<0.001).The time of immobility in TST was significantly higher in DCP group mice than in control group mice,which displayed depression-like behavior.The EPM test showed that the numbers of entries and proportion of time in the cross region in DCP group mice were less than in control group mice.EPM test revealed that DCP group mice exhibited anxiety-like behavior.The results of immunofluorescence staining showed that the number of FOS-positive cells in ZIv was significantly higher in DCP group mice than in control group mice,and abundant co-labeled neurons of FOS and GABAergic neurons were observed in ZIv.Conclusion:GABAergic neurons were predominantly distributed in ZI,and were more concentrated in ZIv.The activation of GABAergic neurons in ZIv of DCP group mice provides morphological evidence on the involvement of GABAergic neurons in chronic itch and associated negative emotions.