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用束路追踪和免疫电镜方法研究了大鼠三叉神经尾侧亚核丘脑投射神经元与初级传入和中缝大核下行投射纤维间的突触联系。光镜观察发现，HRP跨节标记三叉神经传入终末与中缝大核（RMg）顺行追踪的PHA－L标记终末在三叉神经尾侧亚核（Vc）浅层有重叠分布。在Vc浅层丘脑投射神经元与初级传入和RMg下行投射的分布也有重叠。电镜观察发现初级传入终末和丘脑投射神经元树突形成非对称性轴树突触；而RMg下行投射终末与三叉丘脑投射神经元树突形成对称性或非对称性轴树突触，提示RMg下行投射纤维可能通过直接作用于丘脑投射神经元对初级传入的伤害性信息进行调控。
Beam tracking and immunoelectron microscopy were used to investigate the synaptic connections between the projecting neurons of the subnucleus caudatum in the rat trigeminal nerve and the descending projection fibers of the primary afferent and the nucleus raphe magnus. Light microscopic observation showed that the PHA-L marker terminal traced by HRP cross-sectioned trigeminal afferent terminals and the middle of the stitched large nucleus (RMg) was overlappingly distributed in the superficial layer of the trigeminal subnucleus (Vc). There is also an overlap in the distribution of neurons in the Vc superficial thalamus with primary afferent and RMg downstream projections. Electron microscopy showed that primary afferent terminal and thalamic neurons dendrites form asymmetric axonal dendrites, whereas the RMg descending projection terminus and trigeminothalamic neuron dendrites form symmetric or asymmetric axonal dendrites, Suggesting that RMg downstream projection fibers may regulate the primary afferent nostrils by directly acting on the neurons of the thalamus.