Aronin N, DiFiglia M, Liotta A S, Martin J B
J Neurosci. 1981 Jun;1(6):561-77. doi: 10.1523/JNEUROSCI.01-06-00561.1981.
Leu-enkephalin is an opioid peptide that has been found to modulate nociception in the spinal cord. Both pre- and postsynaptic interactions by enkephalins have been proposed. By the peroxidase . anti-peroxidase immunocytochemical method, we studied the distribution and ultrastructure of neuronal elements in the monkey dorsal horn to elucidate possible morphological substrates for postulated opioid actions. Biochemical analysis of immunoreactive Leu-enkephalin-like peptides in the cord was performed to characterize the forms present in labeled neurons and terminals. At the light microscopic level, fiber immunostaining was found in most areas of gray matter, especially in laminae I to V, and in the dorsolateral funiculus. Cell bodies were located in laminae I, II, III, and V. At the ultrastructural level, in the superficial dorsal horn, we found that neurons with Leu-enkephalin receive numerous types of axon inputs, some of which have been identified previously as originating from the dorsal root. Leu-enkephalin terminals formed primarily axosomatic and axodendritic synapses and less frequently synapsed with other axons. With the same Leu-enkephalin antiserum as used in the immunocytochemistry, a peptide physicochemically similar to intact Leu-enkephalin and two larger Leu-enkephalin-like peptides were identified in monkey spinal cord extracts. It is likely that a family of Leu-enkephalin-like peptides is present in monkey spinal cord and that the labeled elements may contain any or all of these substances. It is concluded that both pre- and postsynaptic physiologic effects of Leu-enkephalin are possible, although the preponderance of axodendritic synapses favors a principal postsynaptic site of action. The anatomical results suggest that neurons containing immunoreactive Leu-enkephalin in the dorsal horn, some of which may receive input from primary afferents, modulate nociception by directly synapsing with cells of origin of the spinothalamic tract and also by interacting with primary afferent terminals.
亮脑啡肽是一种阿片肽，已被发现可调节脊髓中的伤害感受。脑啡肽的突触前和突触后相互作用均已被提出。通过过氧化物酶-抗过氧化物酶免疫细胞化学方法，我们研究了猴背角神经元成分的分布和超微结构，以阐明假定的阿片样作用可能的形态学基础。对脊髓中免疫反应性亮脑啡肽样肽进行生化分析，以表征标记神经元和终末中存在的形式。在光镜水平，在灰质的大多数区域发现纤维免疫染色，尤其是在I至V层以及背外侧索。细胞体位于I、II、III和V层。在超微结构水平，在背角浅层，我们发现含有亮脑啡肽的神经元接受多种类型的轴突输入，其中一些先前已被确定源自背根。亮脑啡肽终末主要形成轴-体和轴-树突触，较少与其他轴突形成突触。用免疫细胞化学中使用的相同亮脑啡肽抗血清，在猴脊髓提取物中鉴定出一种在物理化学性质上与完整亮脑啡肽相似的肽以及两种更大的亮脑啡肽样肽。猴脊髓中可能存在亮脑啡肽样肽家族，并且标记的成分可能含有这些物质中的任何一种或全部。结论是，亮脑啡肽的突触前和突触后生理效应都是可能的，尽管轴-树突触占优势有利于主要的突触后作用部位。解剖学结果表明，背角中含有免疫反应性亮脑啡肽的神经元，其中一些可能接受初级传入纤维的输入，通过直接与脊髓丘脑束起源细胞形成突触以及与初级传入终末相互作用来调节伤害感受。
