中脑导水管周围灰质、中缝背核、中缝大核和巨细胞网状核α部向孤束核的定位投射

本文用荧光金逆行追踪技术对大鼠下行抑制系统的中脑导水管周围灰质、中缝背核、中缝大核和巨细胞网状核a部向孤束核的投射进行了研究．将荧光金分别注入到孤束核的吻段、中段和尾段后，上述核团内出现的逆行标记神经元分布如下：（1）在冠状切面上，中脑导水管周围灰质内的荧光金标记细胞群集存在；在吻尾方向上呈柱状分布．三个实验组中，除吻段注射组的标记细胞数量少于其它2组外．在分布上完全一致。腹外侧区的标记细胞数量最多，但从尾侧到吻侧逐渐减少；背内侧区的标记细胞数量较少，以中、吻段较多；背外侧区的标记细胞出现于中脑导水管周围灰质的中、尾段，尾段最多，吻段内未见标记细胞．所有实验动物的中脑导水管周围灰质的内侧区均未出现标记细胞．（2）中缝背核内的标记细胞，多数位于其吻段的背侧都与收侧部的移行部，并且以注射区在孤束核的吻段者标记细胞较多；中缝背核的中尾段标记细胞量少，且散在于背外侧部，以注射区在孤束核的中段者标记细胞较多．（3）中缝大核内的标记细胞以核的尾段较多，吻段较少；巨细胞同状核a部内的标记细胞在吻尾方向上分布均匀。此两核团内的标记细胞数量以注射区在孤束核的中、尾段者较多。（4）上述脑区内标记细胞的数量均为注射区的同侧多于对侧。本研

DIRECT PROJECTIONS FROM THE MIDBRAIN PERIAQUEDUCTAL GRAY,DORSAL RAPHE NUCLEUS,NUCLEUS RAPHE MAGNUS AND α PART OF GIGANTOCELLULAR NUCLEUS TO THE NUCLEUS TRACTUS SOLITARIUS IN THE RAT

Direct projections from the midbrain periaqueductal gray (PAG), dorsal raphe nucleus (DR), nucleus raphe mag-nus (RM) and a part of gigantocellular nucleus (GiA) to the nucleus tactus solitarius (NTS) were examined in the rat by using flourogold (FG) retrograde tracing technique. After injection of FG into the rostral part, middle part and caudal part of the NTS respectively, the distribution of FG-labeled neurons were found in the following regions: (1). In the PAG, the FG-labeled neurons in the section of coronal plane were clustered and formed columins in nuclear subdivisions from rostral part to caudal part of the PAG. The distribution of the FG-labeled n eurons in the PAG was similar after injection of FG into the middle and caudal part or rostral part of the NTS, but less FG-labeled neurons were seen in the PAG when FG was in-jected into the rostral NTS. A large nurmber of FG-labeled neurons were found in the ventrolateral and the number of FG-la-beled neurons in the ventrolateral region were reduced gradually from the caudal PAG to rostral PAG. In the dorsomedial re-gion of the PAG, most of FG-labeled neurons were found in its middle and rostral part. In the dorsolateraI region of the PAG, however , FG-labeled neurons were mainly distributed in the caudal part ; a few were scattered in the middle part, but no FG-labeled neurons were found in the rostral part of the PAG. In addition, no FG-labeled neurons were seen in the medi-al regio, in all of the experirnental rats. (2) In the DR, the majority of FG-labeled neurons were located in the junctional part between dorsal and ventraI parts of the DR at 1he rostral level, while a small number were scattered in the dorsolateral parts of the DR at middle and caudal levels. (3 ) Many FG-labeled neurons were ulso found in the caudal part of the RM and GiA. (4) FG-labe1ed neuron in the brain regions showed an ipsilateral dominance. In the present study many neurons were found in the PAG, DR, RM and GiA to project to the NTS with an ipsilateral dominance. and suggested that the descending pain inhibitory system may modulate the transmission of the visceral nociceptive information at the NTS.