Hökfelt T, Ljungdahl A, Terenius L, Elde R, Nilsson G
Proc Natl Acad Sci U S A. 1977 Jul;74(7):3081-5. doi: 10.1073/pnas.74.7.3081.
The distribution of Met-enkephalin- and substance P-immunoreactive neurons was studied by indirect immunofluorescence in some areas related to pain and analgesia. Met-enkephalin- and substance P-positive cell bodies and nerve terminals were observed in the periaqueductal central gray, the nucleus raphe magnus, the marginal layers and substantia gelatinosa of the spinal trigeminal nucleus, and the dorsal horn of the spinal cord. Lesion experiments suggest that Met-enkephalin neurons in the dorsal horn and possibly in the spinal trigeminal nucleus are interneurons or propriospinal neurons with nerve terminals in the laminae I and II of the cord and in the superficial layers of the spinal trigeminal nucleus, respectively. These areas are also very rich in substance P-positive nerve terminals, mainly representing central branches of primary afferent neurons. The present immunohistochemical-anatomical findings support the hypothesis that stimulation-produced analgesia is related to activation of spinal and spinal trigeminal enkephalin interneurons forming axo-axonic synapses with (substance P?) pain afferents in the superficial laminae of the dorsal horn and the spinal trigeminal nucleus. These interneurons may be activated by sensory fibers and by descending fibers from medullary stimulation sites. Transmitter substances in these descending fibers may be 5-hydroxytryptamine and substance P.
通过间接免疫荧光法，研究了甲硫氨酸脑啡肽和P物质免疫反应性神经元在一些与疼痛和镇痛相关区域的分布。在导水管周围中央灰质、中缝大核、三叉神经脊束核边缘层和胶状质以及脊髓背角中观察到了甲硫氨酸脑啡肽和P物质阳性细胞体及神经终末。损伤实验表明，脊髓背角以及可能三叉神经脊束核中的甲硫氨酸脑啡肽神经元是中间神经元或脊髓固有神经元，其神经终末分别位于脊髓I层和II层以及三叉神经脊束核浅层。这些区域也富含P物质阳性神经终末，主要代表初级传入神经元的中枢支。目前的免疫组织化学解剖学发现支持这样的假说，即刺激产生的镇痛与脊髓和三叉神经脑啡肽中间神经元的激活有关，这些中间神经元在脊髓背角和三叉神经脊束核浅层与（P物质？）痛觉传入纤维形成轴-轴突触。这些中间神经元可能被感觉纤维以及来自延髓刺激部位的下行纤维激活。这些下行纤维中的递质可能是5-羟色胺和P物质。
