Lockerbie R O, Beaujouan J C, Saffroy M, Glowinski J
Collège de France-INSERM U 114, Chaire de Neuropharmacologie, Paris.
Brain Res. 1988 May 1;468(1):1-9. doi: 10.1016/0165-3806(88)90002-8.
A fraction enriched in neuronal growth cones isolated from developing rat forebrain was shown to possess binding sites for the substance P analog, Bolton-Hunter substance P [( 125I]BHSP). Specific binding of this ligand reached an equilibrium after 10 min at 20 degrees C, and was reversible and temperature-dependent. Removal of extracellular Na+ did not block but rather augmented [125I]BHSP binding suggesting that the labeled analog was not transported into the growth cone fraction. Scatchard analysis of the binding indicated a single class of non-interacting binding sites in the growth cone fraction (Kd: 257 pM; Bmax: 56 fmol/mg protein). From competition studies using substance P and other tachykinins, their rank order of potency for inhibiting [125I]BHSP binding was SP greater than physalaemin much greater than eledoisin greater than kassinin greater than NKB greater than or equal to NKA. Such order is consistent with the presence of an SP receptor (Neurokinin-1) in the growth cone fraction. The N-terminal fragments of substance P, SP1-7 and SP1-11 free acids, and the C-terminal fragment, SP7-11, were devoid of affinity for the [125I]BHSP binding site. However SP6-11 and SP1-11 methyl esters showed more potency.
从发育中的大鼠前脑分离出的富含神经元生长锥的部分被证明含有P物质类似物博尔顿-亨特P物质[（125I）BHSP]的结合位点。该配体的特异性结合在20℃下10分钟后达到平衡，并且是可逆的且依赖温度。去除细胞外Na+并未阻断而是增强了[125I]BHSP的结合，这表明标记的类似物没有被转运到生长锥部分。对结合的Scatchard分析表明在生长锥部分存在一类单一的非相互作用结合位点（解离常数：257 pM；最大结合量：56 fmol/mg蛋白质）。通过使用P物质和其他速激肽的竞争研究，它们抑制[125I]BHSP结合的效力顺序为：P物质＞雨蛙肽＞蛙皮素＞卡辛＞神经激肽B＞或等于神经激肽A。这样的顺序与生长锥部分中存在P物质受体（神经激肽-1）一致。P物质的N端片段、SP1-7和SP1-11游离酸以及C端片段SP7-11对[125I]BHSP结合位点没有亲和力。然而，SP6-11和SP1-11甲酯表现出更强的效力。
