本研究用顺行与逆行追踪相结合的双标技术对伏核下行投射纤维与中脑导水管周围灰质（ＰＡＧ）向中缝大核（ＮＲＭ）投射神经元和外侧缰核（ＬＨｂ）向ＰＡＧ投射神经元间的突触联系进行了观察。将顺行标记物ＰＨＡＬ电泳入伏核和逆行标记物ＨＲＰ分别注入ＮＲＭ或ＰＡＧ后，在ＰＡＧ的尾段腹外侧区和中缝背核（ＤＲ）或ＬＨｂ内侧部分别可见ＰＨＡＬ顺标终末与ＨＲＰ逆标神经元的主要分布区重叠。电镜下分别在ＰＡＧ的腹外侧区、ＤＲ或ＬＨｂ内侧部观察到ＰＨＡＬ顺标终末与ＨＲＰ逆标神经元的胞体和树突形成以非对称性为主的轴体和轴树突触。上述结果说明伏核的直接下行投射纤维主要与ＰＡＧ和ＤＲ内向ＮＲＭ投射神经元形成突触联系，伏核的部分下行投射纤维在ＬＨｂ内侧部中继后再间接投射到ＰＡＧ，伏核的直接和间接下行投射对ＰＡＧ内神经元的活动可能产生调制作用 In this study, the combination of both normal and retrograde tracing techniques was used to predict the projection of neurons projecting to the medullar nucleus (NRM) and lateral habenula (LHb) to the PAG in the descending projectile of the nucleus accumbens and the periaqueductal gray (PAG) Synaptic connections between neurons were observed. The PHA-L electrophoretic paracentesis and retrograde label HRP were injected into NRM or PAG respectively, and then the PHALcitame end was observed in the rostral ventrolateral medullary region and dorsal raphe nucleus (DR) or LHb in the PAG respectively At the end of the HRP superscript neurons overlap the main distribution area. Electron microscopy in the ventral region of the PAG, DR or LHb inner side of the observed PHA  L-terminal and HRP retrograde neurons of the cell body and dendrites to form a non-symmetrical axis  body and axis  tree Synapse. The above results indicate that the direct descending projection fibers of the nucleus accumbens mainly form synaptic connections with PAG and DR introverted NRM projection neurons. Partially descended projectile fibers in the nucleus accumbens indirectly relay to the PAG after medial LHb relay, and the direct and Indirect down-projection may modulate neuronal activity in the PAG