Charlton C G, Helke C J
J Neurosci. 1985 Jun;5(6):1653-61. doi: 10.1523/JNEUROSCI.05-06-01653.1985.
The presence of the neurotransmitter or neuromodulator, substance P (SP), in the spinal cord implies that a discrete localization of SP receptors also occurs. To map the distribution of and to characterize SP binding sites in the spinal cord, light microscopic autoradiography was used. SP binding sites occurred in the dorsal horn, intermediolateral cell column (IML) and lamina X-region. In the ventral horn, the phrenic, Onuf's and sacral ventromedial motor nuclei were densely labeled. Other regions of the ventral horn were moderately labeled for SP binding sites. The localization of binding sites parallels the regional distribution of SP-containing nerve fibers in the spinal cord. A close correlation between the binding sites for SP and the presence of cholinesterase-stained neurons occurred, and suggest that the SP receptors are located on or proximal to cholinergic neurons. The density of the binding sites in the dorsal horn was highest in the sacral section, followed by the lumbar, thoracic and cervical section. In the lamina X region, however, the density was highest in the thoracic followed by the sacral, lumbar and cervical sections. The high density binding of 125I-Bolton-Hunter reagent labeled SP was inhibited, in a dose-dependent manner, by unlabeled SP. Quantification of the dose-dependent inhibition binding, using computer densitometry, showed differences in the inhibition curves for the cervical lamina X-region and the IML as compared with the other loci containing high density binding sites. The differential sensitivity of the SP receptors to unlabeled SP suggests that there are heterogeneous receptors for SP in the spinal cord, which may be relevant to the role of SP in different spinal cord functions. The binding to specific motor nuclei in the ventral horn also suggest that SP may play a role in the function of specialized striated muscles.
神经递质或神经调质P物质（SP）在脊髓中的存在意味着SP受体也存在离散定位。为了绘制脊髓中SP结合位点的分布图并对其进行表征，采用了光学显微镜放射自显影术。SP结合位点出现在背角、中间外侧细胞柱（IML）和X层区域。在腹角，膈神经核、奥努夫核和骶腹内侧运动核被密集标记。腹角的其他区域对SP结合位点有中度标记。结合位点的定位与脊髓中含SP神经纤维的区域分布平行。SP结合位点与胆碱酯酶染色神经元的存在之间存在密切相关性，这表明SP受体位于胆碱能神经元上或其附近。背角结合位点的密度在骶段最高，其次是腰段、胸段和颈段。然而，在X层区域，密度在胸段最高，其次是骶段、腰段和颈段。未标记的SP以剂量依赖性方式抑制了125I - 博尔顿 - 亨特试剂标记的SP的高密度结合。使用计算机密度测定法对剂量依赖性抑制结合进行定量分析，结果显示，与其他含有高密度结合位点的位点相比，颈段X层区域和IML的抑制曲线存在差异。SP受体对未标记SP的不同敏感性表明脊髓中存在SP的异质性受体，这可能与SP在脊髓不同功能中的作用有关。腹角中特定运动核的结合也表明SP可能在特殊横纹肌的功能中发挥作用。
