Davis B M, Krause J E, McKelvy J F, Cabot J B
Neuroscience. 1984 Dec;13(4):1311-26. doi: 10.1016/0306-4522(84)90300-2.
Substance P has been localized to the neuropil of sympathetic preganglionic neurons in light and electron microscopic studies. Two recent reports have suggested that the majority of substance P in the rat intermediolateral cell column was contained in synaptic terminals of bulbospinal axons. However, previous investigations in our laboratory indicated the presence of major substance P spinal-sympathetic preganglionic neuron circuitry in pigeon. The present study used radioimmunoassay and immunohistochemistry to examine substance P levels in rat intermediolateral cell column following various spinal lesions in order to assess the relative contributions of bulbospinal and intraspinal substance P neurons to the substance P content of the intermediolateral cell column. The results from these experiments support the existence of both bulbospinal and intraspinal substance P-containing projections to the rat intermediolateral cell column. In addition, characterization of spinal cord substance P-like immunoreactivity by combined high performance liquid chromatography and radioimmunoassay, revealed that substance P in rat intermediolateral cell column was indistinguishable from synthetic substance P. Following transection of thoracic spinal cord, substance P-immunoreactive staining was still evident in the intermediolateral cell column caudal to the lesion. These substance P-positive fibers were studded with bouton-like swellings and appeared normal. Following high cervical hemisection, depletion of substance P (radioimmunoassay measurements) was bilateral and equal in the intermediolateral cell column: 25% depletion was observed after 7 days and 35% depletion after 14 days. However, rats which were hemisected at low cervical and/or mid-thoracic levels contained normal or elevated amounts of substance P in the intermediolateral cell column. Since substance P remains in the intermediolateral cell column following total transection, substance P spinal-sympathetic preganglionic neuron circuitry must exist. Additionally, depletion of substance P following high cervical hemisection suggests the existence of a substance P-containing, bilateral bulbospinal pathway to the intermediolateral cell column. The observation that substance P levels were normal or elevated following low cervical lesions raises the possibility that intraspinal substance P neurons can compensate for loss of substance P in the spinal cord. Sprouting or altered substance P metabolism and/or release by intraspinal substance P neurons could be responsible, suggesting an important homeostatic mechanism for maintaining substance P content within the intermediolateral cell column.
在光学和电子显微镜研究中，P物质已被定位到交感神经节前神经元的神经毡中。最近的两份报告表明，大鼠中间外侧细胞柱中的大多数P物质包含在延髓脊髓轴突的突触终末中。然而，我们实验室先前的研究表明，鸽子存在主要的P物质脊髓-交感神经节前神经元回路。本研究使用放射免疫测定法和免疫组织化学来检测大鼠中间外侧细胞柱在各种脊髓损伤后的P物质水平，以评估延髓脊髓和脊髓内P物质神经元对中间外侧细胞柱P物质含量的相对贡献。这些实验结果支持存在向大鼠中间外侧细胞柱投射的延髓脊髓和脊髓内含有P物质的投射。此外，通过高效液相色谱和放射免疫测定法联合对脊髓P物质样免疫反应性进行表征，发现大鼠中间外侧细胞柱中的P物质与合成P物质无法区分。胸段脊髓横断后，损伤部位尾侧的中间外侧细胞柱中P物质免疫反应性染色仍然明显。这些P物质阳性纤维布满了纽扣样肿胀，看起来正常。高颈段半横断后，中间外侧细胞柱中P物质（放射免疫测定测量）的耗竭是双侧且相等的：7天后观察到25%的耗竭，14天后观察到35%的耗竭。然而，在低颈段和/或胸中段水平进行半横断的大鼠，其中间外侧细胞柱中的P物质含量正常或升高。由于在完全横断后P物质仍保留在中间外侧细胞柱中，因此必须存在P物质脊髓-交感神经节前神经元回路。此外，高颈段半横断后P物质的耗竭表明存在一条向中间外侧细胞柱投射的含有P物质的双侧延髓脊髓通路。低颈段损伤后P物质水平正常或升高的观察结果增加了脊髓内P物质神经元可以补偿脊髓中P物质损失的可能性。脊髓内P物质神经元的发芽或P物质代谢和/或释放的改变可能是原因，这表明存在一种重要的稳态机制来维持中间外侧细胞柱内的P物质含量。
