Meller S T, Dennis B J
Department of Physiology, University of Adelaide, SA, Australia.
Neuroscience. 1991;40(1):191-216. doi: 10.1016/0306-4522(91)90185-q.
The efferent projections of the periaqueductal gray in the rabbit have been described by anterograde tract-tracing techniques following deposits of tritiated leucine, or horseradish peroxidase, into circumscribed sites within dorsal, lateral or ventral periaqueductal gray. No attempts were made to place labels in the fourth, extremely narrow (medial), region immediately surrounding the aqueduct whose size and disposition did not lend itself to confined placements of label within it. These anatomically distinct regions, defined in Nissl-stained sections, corresponded to the same regions into which deposits of horseradish peroxidase were made in order for us to describe afferent projections to the periaqueductal gray. In this present study distinct ascending and descending fibre projections were found throughout the brain. Terminal labelling was detected in more than 80 sites, depending somewhat upon which of the three regions of the periaqueductal gray received the deposit. Therefore, differential projections with respect to both afferent and efferent connections of these three regions of the periaqueductal gray have now been established. Ventral deposits disclosed a more impressive system of ramifying, efferent fibres than did dorsal or lateral placements of labels. With ventral deposits, ascending fibres were found to follow two major pathways from periaqueductal gray. The periventricular bundle bifurcates at the level of the posterior commissure to form hypothalamic and thalamic components which distribute to the anterior pretectal region, lateral habenulae, and nuclei of the posterior commissure, the majority of the intralaminar and midline thalamic nuclei, and to almost all of the hypothalamus. The other major ascending pathway from the periaqueductal gray takes a ventrolateral course from the deposit site through the reticular formation or, alternatively, through the deep and middle layers of the superior colliculus, to accumulate just medial to the medial geniculate body. This contingent of fibres travels more rostrally above the cerebral peduncle, distributing terminals to the substantia nigra, ventral tegmental area and parabigeminal nucleus before fanning out and turning rostrally to contribute terminals to ventral thalamus, subthalamus and zona incerta, then continuing on to supply amygdala, substantia innominata, lateral preoptic nucleus, the diagonal band of Broca and the lateral septal nucleus. Caudally directed fibres were also observed to follow two major routes. They either leave the periaqueductal gray dorsally and pass through the gray matter in the floor of the fourth ventricle towards the abducens nucleus and ventral medulla, or are directed ventrally after passing through either the inferior colliculus or parabrachial nucleus. These ventrally directed fibres merge just dorsal to the pons on the ventral surface of the brain.(ABSTRACT TRUNCATED AT 400 WORDS)
通过将氚标记的亮氨酸或辣根过氧化物酶注入家兔中脑导水管周围灰质的背侧、外侧或腹侧特定部位，运用顺行示踪技术描绘了中脑导水管周围灰质的传出投射。未尝试将标记物置于紧邻导水管的第四区，即极其狭窄的（内侧）区域，因其大小和位置不利于在其中进行局限的标记物放置。在尼氏染色切片中定义的这些解剖学上不同的区域，与注入辣根过氧化物酶以描述传入中脑导水管周围灰质投射的区域相同。在本研究中，在整个脑内发现了明显的升支和降支纤维投射。根据中脑导水管周围灰质三个区域中哪个区域接受了标记物注入，在80多个位点检测到了终末标记。因此，现已确定了中脑导水管周围灰质这三个区域在传入和传出连接方面的差异投射。与背侧或外侧标记物注入相比，腹侧注入揭示了一个更显著的分支传出纤维系统。腹侧注入时，发现升支纤维从中脑导水管周围灰质沿两条主要路径走行。室周束在后连合水平分叉，形成下丘脑和丘脑成分，分布至前顶盖前区、外侧缰核和后连合核、丘脑的大多数板内核和中线核，以及几乎整个下丘脑。从中脑导水管周围灰质发出的另一条主要升支路径从注入部位沿腹外侧方向穿过网状结构，或者穿过上丘的深层和中层，在膝状体内侧核内侧聚集。这群纤维在大脑脚上方更靠前的位置走行，将终末分布至黑质、腹侧被盖区和副视束核，然后散开并向前转向，为腹侧丘脑、下丘脑和未定带提供终末，接着继续供应杏仁核、无名质、外侧视前核布罗卡斜带和外侧隔核。还观察到尾侧走行的纤维沿两条主要路径。它们要么从中脑导水管周围灰质背侧离开，穿过第四脑室底部的灰质，朝向展神经核和延髓腹侧，要么在穿过下丘或臂旁核后朝腹侧走行。这些腹侧走行的纤维在脑腹侧表面的脑桥背侧汇合。（摘要截断于400字）
