大鼠中脑导水管周围灰质－中缝大核－三叉神经脊束核尾侧亚核通路的电镜研究

用ＰＨＡ－Ｌ顺行追踪和ＨＲＰ逆行追踪结合的方法，在电镜下观察到来自中脑导水管周围灰质的ＰＨＡ－Ｌ顺行标记轴突终末与中缝大核向三叉神经脊束核尾侧亚核投射的ＨＲＰ逆行标记神经元形成以非对称性为主的轴树突触。另外，发现顺行标记的轴突终末也与中缝大核内其它神经元之间形成多种突触联系。本研究结果首次在突触水平证明了中脑导水管周围灰质中缝大核－三叉神经脊束核尾侧亚核的间接通路，同时又发现中脑导水管周围灰质下行投射的终末与中缝大核内的神经元成分之间还形成比较复杂的突触联系，并对之进行了讨论。

AN ELECTRON MICROSCOPIC STUDY ON THE FIBER CONNECTIONS FROM THE MIDBRAIN PERIAQUEDUCTAL GRAY TO THE CAUDAL SUBNUCLEUS OF THE SPINAL TRIGEMINAL NUCLEUS RELAY AT THE NUCLEUS RMHE MAGNUS IN THE RAT

A horseradish peroxdase (HRP) retrograde tracing combined with the phaseolus vulgaris leucoagglutinin (PHA-L) anterograde transport methed was used in the present study to investigate the indirect fiber connertions from the midbrain periaqueoiuctal gray (PAG) to the caudal subnucleus of the spinal trigeminal nucleus (Vc) in the rat. In 10 adult SD rats, PHA-L was iontophoretically applied to the caudal level of the PAG and HRP was made into the Vc by aquetic pressure. After histochemical procedure to demonstrate the injected and retrogradely transported HRP and immunocytorhemical procease to reveal the applied and anterogradely transported PHA-L, the sections were embedded in the Epon. The ultrathin sections were observed under electron microscope. In the NRM, the following synaptic connections were found: (1)Two PHA-L anterogradely labeled axonal termimals of the PAG neurons contacted with each other, and then one of them made axo-dendritic synapse with an HRP retrogradely liibeled dendrite. (2)The PHAL laheled axonal terminal contacted with a non-labeled axonal terminal, the non-labeled axonal terminal formed symmetric axo-dendritic synapse with a non-labeled dendrite. (3) The PHA-L labeled axonal terminal contacted with an adjacent non-labeled axonal terminal, these axonal terminals also made asymmetric or symmetric synaptic ronnections with nonlabeled dendrites or non-labeled dendritic spines (4)The mapr form of the synapses made by the PHA-L labeled axonal terminals with the non-labeled dendntes were asymmetric synapses.(5) There were a large number of non-labeled axonal terminals formed asymmetric and symmetric axo-somatic and axo-dendritic synapses with the HRP labeled neuronal cell bodies and dendrites.The present results indicated the existence of the indirect fiber connections from the PAG to the Vc which relayed at the NRM, that is, the PAG neurons project to the VRM and neurons in the latter in turn project to the Vc, and the terminals of the descending projection fibers from the PAG formed quite complicated synaptic connections within the VRM.