小鼠中缝背核向屏状核投射神经通路的形态学特征

Morphological features of the neural projection pathway from the dorsal raphe nucleus to the claustrum in mice

目的探索小鼠中缝背核(DRN)向屏状核(CLA)投射神经通路的形态学特征。方法分别将逆行示踪剂594 retrobeads和顺行示踪剂生物素化的葡聚糖胺(BDA)注入CLA(n=3)和DRN(n=3),结合5-羟色胺(5-HT)免疫荧光染色,观察逆行标记神经元的分布和神经化学特征以及顺标神经纤维和终末在全脑和CLA内的分布;利用钙离子/钙调蛋白依赖性蛋白激酶Ⅱ(CaMKⅡ)-Cre、谷氨酸脱羧酶67(GAD67)-Cre动物结合狂犬逆行跨突触病毒(RV)标记,观察DRN-CLA通路的下游靶神经元类型。结果DRN的吻、中、尾段均能观察到594 retrobeads阳性神经元的胞体,中段的腹侧亚核(DRV)分布较多,且90%以上的逆行标记神经元为5-HT阳性。BDA顺标纤维密集分布于腹侧被盖区、束旁核、腹侧苍白球、杏仁中央核等区,CLA内的神经纤维和终末相对稀疏。RV跨突触逆行标记结果显示,CaMKⅡ-Cre动物的DRN中含有较多的突触前神经元,而GAD67-Cre动物DRN中突触前逆行标记神经元较少。结论DRN-CLA通路是以DRV分布为主的5-HT能投射通路,其在CLA内的纤维和终末较为稀疏,主要与CLA内的CaMKⅡ阳性神经元形成突触联系。

Objective To explore the morphological features of the neural projection pathway from the dorsal raphe nucleus(DRN)to the claustrum(CLA)in mice.Methods After injection of the retrograde tracer 594 retrobeads into the right CLA(n=3)or the anterograde tracer biotinylated dextran amine(BDA)into the DRN(n=3),the distribution and the neurochemical feature of the retrogradely labeled neurons in the DRN,as well as the locations of nerve fibers and terminals throughout the brain and within the CLA,were observed by a combined immunofluorescent staining for 5-hydrozytryptamine(5-HT).The downstream target of the DRN-CLA projection was studied by injection of rabies retrograde monosynaptic virus(RV)into calcium ion/calmodulin dependent protein kinaeⅡ(CaMKⅡ)-Cre or glutamate decarboxylase 67(GAD67)-Cre mice.Results Retrograde labeled neurons were observed in the rostral,middle,and caudal segments of the DRN,with those in the middle segment and in the ventral part of the nucleus(DRV)the densest.Over 90%of the retrograde labeled neurons were 5-HT positive.After injection of BDA into the DRN,dense fiber projections were observed in the ventral tegmental area,parafascicular nucleus,ventral pallidum,and central amygdala nucleus.In comparison,DRN derived fibers and terminals in the CLA were relatively sparse.After injection of RV trans-synaptic virus into the CLA of CaMKⅡ-Cre and GAD67-Cre mice,respectively,dense RV-labeled presynaptic neurons were observed in the DRN of CaMKⅡ-Cre mice,while those in the DRN of GAD67-Cre mice were rather sparse.Conclusion The DRN-CLA projection pathway is characterized by the dense 5-HTergic neurons in the DRV,the relatively sparse fibers or terminals in the CLA,and a primary synaptic connection with CaMKⅡpositive neurons in the CLA.