Morphological analysis of the amygdalostriatal pathway in the control of emotional movements

已知纹状体腹外侧部分（CPvl）接收来自口面运动区的皮质纤维，并将投射纤维发送到黑质网状部（SNdl）的背外侧部分，SNdl包含许多投射到口面运动核的运动前神经元池的神经元。最近，我们发现CPvl也接受来自基底外侧核（BLr）吻侧部的杏仁纤维。在本研究中，我们研究了可能的途径，从BLr通过CPvl的顺行和逆行追踪技术，顺行追踪结合免疫组织化学标记的纹状体黑质神经元。将生物素化葡聚糖胺（BDA）注射到BLr和将霍乱毒素B亚单位（CTB）注射到SNdl中的同侧后，在前连合交叉的水平处，在CPvl中发现BDA标记的纤维和CTb标记的神经元细胞体的显著重叠分布。在这个区域，电子显微镜观察显示，BDA标记的轴突终末含有密集包装，圆形突触囊泡的不对称突触接触主要与纹状体神经元的树突棘，其中一些被标记与CTb。此外，我们证明，BDA标记的BLr纤维形成突触与CPvl神经元显示免疫反应的前速激肽原A和前强啡肽原，这两个是化学标记的纹状体黑质神经元。因此，本研究揭示的BLr-CPvl-SNdl通路可能参与情绪/口面运动的控制。

It has been known that the ventrolateral part of the striatum (CPvl) receives cortical fibers from the orofacial motor area and send projection fibers to the dorsolateral part of the substantia nigra pars reticulata (SNdl), which contains many neurons projecting to the premotor neuron pools for the orofacial motor nuclei. Recently, we found that the CPvl also received amygdaloid fibers from the rostral part of the basolateral nucleus (BLr). In the present study, we examined the possible pathway from the BLr to the SNdl via the CPvl by using the combined anterograde and retrograde tracing technique, and the anterograde tracing combined with immunohistochemistry for chemical markers of the striatonigral neurons. After ipsilateral injections of biotinylated dextran amine (BDA) into the BLr and cholera toxin B subunit (CTb) into the SNdl, a prominent overlapping distribution of BDA-labeled fibers and CTb-labeled neuronal cell bodies was found in the CPvl at the level of the decussation of the anterior commissure. In this region, electron microscopic observations revealed that the BDA-labeled axon terminals containing densely-packed, round synaptic vesicles made asymmetrical synaptic contacts mostly with the dendritic spines of striatal neurons, some of which were labeled with CTb. Furthermore, we demonstrated that the BDA-labeled BLr fibers formed synapses with the CPvl neurons showing immunoreactivity for preprotachykinin A and preprodynorphin, both of which are chemical makers for the striatonigral neurons. Thus, the BLr-CPvl-SNdl pathway revealed by the present study may be involved in the control of emotional/orofacial movements.