大鼠中脑导水管周围灰质向三叉神经脊束核尾侧亚核的5-羟色胺能投射

大鼠中脑导水管周围灰质(PAG)向三又神经脊束核尾侧亚核(Sp 5 C)投射的起源细胞在其吻、中、尾三个部分的分布不同,且由尾段向吻段有从腹侧向背侧移行的趋势。尾段的HRP逆标细胞主要位于PAG的腹外侧区、内侧区腹侧部;中段的标记细胞较多,主要见于腹外侧区、背侧区和背外侧区腹侧部,尚可见一些顺行标记的终末;吻段的标记细胞主要位于背外侧区,在上丘深层、Cajal氏中介核、Darkschewitsch氏核内,也可见标记细胞。标记细胞和终末均主要位于注射侧的PAG内。PAG向Sp 5 C投射的5-羟色胺(5-HT)样神经元主要位于PAG的中、尾段的腹外侧区和内侧区腹侧部。中段的双标细胞占全部双标细胞数的57％,尾段占41％,吻段占2％。在背中缝核(DR)内,亦可见到一些双标细胞。PAG内的双标细胞占其HRP标记细胞总数的37％,但仅占5-HT样阳性细胞总数的4.5％。标记细胞主要为中型(20—30μm)梭形及三角形,小型(<20μm)梭形和大型(>30μm)多角形细胞较少见。

THE SEROTONINERGIC PROJECTIONS FROM THE MIDBRAIN PERIAQUEDUCTAL GRAY TO THE SPINAL TRIGEMINAL NUCLEUS CAUDALIS IN THE RAT

The distribution of neurons in the midbrain periaqueductal gray (PAG) projecting: to the spinal trigeminal nucleus caudalis (Sp5C) was different at rostral, middle and caudal levels of PAG and there was a tendency that the distribution of them shifted from ventrolateral subdivision (VL) at caudal level to dorsal subdivision at rostral level. HRP retrogradely labeled neurons could be seen in the VL ventral part of medial subdivision (MV) at the caudal level. The number of HRP labeled neurons at the middle level was more than at the caudal and rostral levels. And the neurons were mainly located in the VL, dorsal part of VL and ventral part of dorsolateral subdivision (DL). HRP labeled neurons were also seen in the interstitial nucleus of Cajal, nucleus of Darkschewitsch, deep layers of superior colliculus and nucleus raphe dorsalis (DR). The efferent projections from PAG to Sp5C were predominant on the side of the HRP injection in the Sp5C. HRP anterogradely labeled terminals were also seen in the entire length of PAG, but the major termination field was on the same side of the HRP injection at the middle level of PAG. The serotoninergic neurons of PAG projecting to Sp5C mainly originated from the middle (57％) and caudal (41％) levels 5-HT- HRP double-labeled neurons were located in the VL and MV subdivisions at middle and caudal levels, Only a few doubly labeled neurons could be observed at the rostral level (2％). The serotoninergic projections were also predominant on the ipsilateral side, Most of the labeled neurons were medium-sized (20-30μm) fusiform, triangular and small sized (<20μm) fusiform and triangular, only a few were large (>30μm) multipolar neurons