LaMotte C C, Shapiro C M
Section of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06510.
J Comp Neurol. 1991 Apr 8;306(2):290-306. doi: 10.1002/cne.903060206.
The ultrastructural localization of substance P (SP), met-enkephalin (MENK), and somatostatin (SS) in the lamina X area surrounding the central canal of the macaque monkey was examined by the indirect peroxidase-antiperoxidase method. The most common synaptic terminals in lamina X were simple terminals (S) with small rounded or pleomorphic clear vesicles; one to two dense-core vesicles were occasionally also present. These were found on soma, dendrites, and dendritic spines, in all regions of lamina X. A second class of terminal with round or oval clear vesicles was glomerular (G) in shape, with scalloped edges, and contained many mitochondria. These large terminals had several synaptic contacts onto dendrites, spines, and small terminals and were found mainly in the lateral region. The third class (L) contained small clear vesicles and several vesicles with large, dense cores (100-125 nm), and also contacted dendrites, mainly lateral to the canal. The fourth class of terminal (D) contained small clear vesicles and several vesicles with small, dense cores (75-100 nm); these contacted dendrites and somata in all areas. Very few terminals with flat vesicles were identified. There was an unequal distribution of immunoreactivity among the several terminal classes identified in lamina X. Most SP terminals were S terminals, but SP L terminals were also common; few were D terminals. MENK terminals were usually either S terminals or D terminals; L terminals were rarely MENK positive. SS terminals were commonly D terminals or S terminals; L terminals were also rarely SS positive. Only SP terminals were identified as G terminals. Synaptic targets of SP, MENK, and SS terminals were most commonly dendrites. In addition to unlabelled neurons, peptidergic neurons and their processes were also synaptic targets of terminals containing the same peptide. The distributions of these peptides in primate lamina X differ from that of the same peptides in primate superficial dorsal horn. These differences are important, in consideration of some of the parallels that may be drawn between the lamina X area and the superficial dorsal horn; both areas have high concentrations of the same peptides, receive nociceptive primary afferents, and contain spinothalamic and other projection neurons. Nevertheless, comparison of the distribution of immunoreactivity among terminal classes indicates that neurochemical organization at the ultrastructural level is quite distinct in each of the two areas. This may also reflect other roles of the lamina X area, including its involvement in visceral functions, although it would be expected that this element might be less prominent at the cervical levels we investigated.
采用间接过氧化物酶 - 抗过氧化物酶法研究了猕猴中央管周围X层区域内P物质（SP）、甲硫氨酸脑啡肽（MENK）和生长抑素（SS）的超微结构定位。X层中最常见的突触终末是具有小圆形或多形性清亮小泡的简单终末（S）；偶尔也可见一到两个致密核心小泡。这些终末见于X层所有区域的胞体、树突和树突棘上。第二类终末具有圆形或椭圆形清亮小泡，呈肾小球样（G），边缘呈扇贝状，含有许多线粒体。这些大终末在树突、棘和小终末上有多个突触联系，主要见于外侧区域。第三类（L）含有小清亮小泡和几个大的致密核心小泡（100 - 125 nm），也与树突接触，主要在中央管外侧。第四类终末（D）含有小清亮小泡和几个小的致密核心小泡（75 - 100 nm）；这些终末与所有区域的树突和胞体接触。仅发现极少数具有扁平小泡的终末。在X层鉴定出的几类终末中，免疫反应性分布不均。大多数SP终末是S终末，但SP L终末也常见；D终末很少。MENK终末通常是S终末或D终末；L终末很少呈MENK阳性。SS终末通常是D终末或S终末；L终末也很少呈SS阳性。仅SP终末被鉴定为G终末。SP、MENK和SS终末的突触靶点最常见的是树突。除了未标记的神经元外，肽能神经元及其突起也是含有相同肽的终末的突触靶点。这些肽在灵长类动物X层的分布与在灵长类动物浅表背角的分布不同。考虑到X层区域和浅表背角之间可能存在的一些相似之处，这些差异很重要；这两个区域都有高浓度的相同肽，接受伤害性初级传入纤维，并且含有脊髓丘脑束和其他投射神经元。然而，终末类之间免疫反应性分布的比较表明，在超微结构水平上，这两个区域的神经化学组织相当不同。这也可能反映了X层区域的其他作用，包括其在内脏功能中的参与，尽管预计在我们研究的颈段水平这种作用可能不太明显。
