Morphological analysis of the neuronal circuits in the brainstem motor system

我们已经报道了从黑质网状部（SNr）到小细胞网状结构（RFp）的直接通路，SNr是已知存在与口面运动相关的神经元的地方，RFp是许多口面运动核的运动前神经元的分布地。本研究进一步探讨了大鼠SNr到RFp的间接投射途径。结果表明，来自SNr背外侧部的同侧黑质纤维终止于上级丘的近外侧部和红核的背侧部，向对侧RFp发出投射纤维。我们进一步发现，这些黑质轴突对GABA呈免疫反应性，并与顶盖和红核神经元的胞体和树突形成对称性突触接触，将轴突送到RFp，除了SNr到RFp的直接通路外，SNr还通过黑质-顶盖-延髓和黑质-红核-延髓通路间接地对口面运动产生控制作用。

We had reported the direct pathway from the substantia nigra pars reticulata (SNr), where the neurons related to orofacial movements had been known to exist, to the parvicellular reticular formation (RFp), where many premotor neurons for the orofacial motor nuclei had been reported to be distributed. In the present study, we further examined the indirect pathways from the SNr to the RFp in the rat.The present results indicated that the lateralmost part of the superior colliculus and dorsal part of the red nucleus, where the ipsilateral nigral fibers from the dorsolateral part of the SNr terminated, sent projection fibers to the contralateral RFp. We further showed that these nigral axons were immunoreactive for GABA and made symmetrical synaptic contacts with somata and dendrites of the tectal and rubral neurons sending their axons to the RFp.In addition to the direct pathway from the SNr to the RFp, the SNr was suggested to exert control influences upon orofacial movements indirectly through the nigrotectobulbar and nigrorubrobulbar pathways to the RFp.