Llewellyn-Smith I J, Martin C L, Minson J B, Pilowsky P M, Arnolda L F, Basbaum A I, Chalmers J P
Department of Medicine and Centre for Neuroscience, Flinders University, Bedford Park, South Australia.
Neuroscience. 1997 Apr;77(4):1137-49. doi: 10.1016/s0306-4522(96)00534-9.
Substance P is involved in cardiovascular control at the spinal cord level, where it acts through neurokinin-1 receptors. In this study we used immunocytochemistry and retrograde tracing to investigate the presence of the neurokinin-1 receptor and its ultrastructural localization in rat sympathetic preganglionic neurons that project to the superior cervical ganglion or the adrenal medulla. Immunofluorescence for the neurokinin-1 receptor outlined the somatic and dendritic surfaces of neurons in autonomic subnuclei of spinal cord segments T1-T12, whereas immunofluorescence for the tracer, cholera toxin B subunit, filled retrogradely labelled cells. There was a significant difference in the proportion of neurokinin-1 receptor-immunoreactive sympathetic preganglionic neurons supplying the superior cervical ganglion and the adrenal medulla. Thirty-eight percent of the neurons that projected to the superior cervical ganglion were immunoreactive for the neurokinin-1 receptor compared to 70% of neurons innervating the adrenal medulla. Of neurons projecting to the superior cervical ganglion, significantly different proportions showed neurokinin-1 receptor immunoreactivity in spinal cord segment T1 (15%) versus segments T2 T6 (45%). At the ultrastructural level, neurokinin-1 receptor staining occurred predominantly on the inner leaflets of the plasma membranes of retrogradely labelled sympathetic preganglionic neurons. Deposits of intracellular label were often observed in dendrites and in the rough endoplasmic reticulum and Golgi apparatus of cell bodies. Neurokinin-1 receptor immunoreactivity was present at many, but not all, synapses as well as at non-synaptic sites, and occurred at synapses with substance P-positive as well as substance P-negative nerve fibres. Only 37% of the substance P synapses occurred on neurokinin-1-immunoreactive neurons in the intermediolateral cell column. These results show that presence of the neurokinin-1 receptor in sympathetic preganglionic neurons is related to their target. The ultrastructural localization of the receptor suggests that sympathetic preganglionic neurons may be affected (i) by substance P released at neurokinin-1 receptor-immunoreactive synapses, (ii) by other tachykinins (e.g., neurokinin A), which co-localize in substance P fibres in the intermediolateral cell column, acting through other neurokinin receptors, and (iii) by substance P that diffuses to neurokinin-1 receptors from distant sites.
P物质参与脊髓水平的心血管控制，它通过神经激肽-1受体发挥作用。在本研究中，我们使用免疫细胞化学和逆行追踪技术，来研究神经激肽-1受体在投射至上颈神经节或肾上腺髓质的大鼠交感神经节前神经元中的存在情况及其超微结构定位。神经激肽-1受体的免疫荧光勾勒出脊髓T1-T12节段自主神经亚核中神经元的胞体和树突表面，而示踪剂霍乱毒素B亚基的免疫荧光则填充了逆行标记的细胞。供应上颈神经节和肾上腺髓质的神经激肽-1受体免疫反应性交感神经节前神经元的比例存在显著差异。投射至上颈神经节的神经元中，38%对神经激肽-1受体有免疫反应，而支配肾上腺髓质的神经元中这一比例为70%。在投射至上颈神经节的神经元中，脊髓T1节段（15%）与T2-T6节段（45%）显示神经激肽-1受体免疫反应性的比例有显著差异。在超微结构水平上，神经激肽-1受体染色主要出现在逆行标记的交感神经节前神经元质膜的内小叶上。细胞内标记物沉积常出现在树突以及胞体的粗面内质网和高尔基体中。神经激肽-1受体免疫反应性存在于许多但并非所有的突触以及非突触部位，并且出现在与P物质阳性和P物质阴性神经纤维形成的突触处。仅37%的P物质突触出现在中间外侧细胞柱中对神经激肽-1有免疫反应的神经元上。这些结果表明，交感神经节前神经元中神经激肽-1受体的存在与它们的靶标有关。受体的超微结构定位表明，交感神经节前神经元可能受到以下因素的影响：（i）在神经激肽-1受体免疫反应性突触处释放的P物质；（ii）其他速激肽（如神经激肽A），它们与中间外侧细胞柱中P物质纤维共定位，通过其他神经激肽受体发挥作用；（iii）从远处部位扩散到神经激肽-1受体的P物质。
