Payza K, Akar C A, Yang H Y
Section on Neuropeptides, National Institute of Mental Health Neuroscience Center, St. Elizabeth's Hospital, Washington, DC 20032.
J Pharmacol Exp Ther. 1993 Oct;267(1):88-94.
Neuropeptide FF (FLFQPQRFamide, NPFF) is an octapeptide implicated in morphine analgesia, tolerance and dependence. Many of the behavioral effects of NPFF have also been observed with the invertebrate neuropeptide Phe-Met-Arg-Phe-amide (FMRFamide), which binds to NPFF receptors because of its low homology to the C-terminal portion of NPFF. A competitive ligand binding assay was used to characterize NPFF receptors in rat spinal cord and a strong requirement was found for the C-terminal Arg-Phe-amide. It was found that FMRFamide (Ki = 1.8 nM) bound with lower affinity than NPFF (0.26 nM) but it was about 7-fold more potent than PQRFamide (12 nM). This finding explains the similar bioactivities of NPFF and FMRFamide. The Gln2 appeared to be the cause of the relatively low potency of PQRFamide, based on the binding specificity of NPFF receptors for a series of FMRFamide analogs. In contrast to the Arg-Phe-amide, substitutions at the first and second positions of FMRFamide were generally tolerated, with the most potent analogs being PMRFamide (Ki = 0.54 nM), FFRFamide (0.25 nM) and FWRFamide (0.42 nM). Among the most potent ligands was a pentapeptide containing a photoreactive Phe analog, D-Tyr-(p-benzoyl-Phe)-norLeu-Arg-Phe-amide (Ki = 0.23 nM). It was found that dansyl-PQRFamide and dansyl-RFamide also bound to NPFF receptors with Ki values of 6.1 and 73 nM, respectively. The radioligand binding and G-protein coupling of NPFF receptors were not altered by chronic morphine treatment.
神经肽FF（FLFQPQRFamide，NPFF）是一种八肽，与吗啡镇痛、耐受性和依赖性有关。无脊椎动物神经肽苯丙氨酸 - 蛋氨酸 - 精氨酸 - 苯丙氨酸酰胺（FMRFamide）也观察到了NPFF的许多行为效应，由于其与NPFF的C末端部分同源性低，它能与NPFF受体结合。采用竞争性配体结合试验对大鼠脊髓中的NPFF受体进行表征，发现对C末端的精氨酸 - 苯丙氨酸酰胺有强烈需求。结果发现，FMRFamide（Ki = 1.8 nM）的结合亲和力低于NPFF（0.26 nM），但其效力比PQRFamide（12 nM）高约7倍。这一发现解释了NPFF和FMRFamide相似的生物活性。基于NPFF受体对一系列FMRFamide类似物的结合特异性，Gln2似乎是PQRFamide效力相对较低的原因。与精氨酸 - 苯丙氨酸酰胺不同，FMRFamide第一和第二位的取代通常是可以耐受的，最有效的类似物是PMRFamide（Ki = 0.54 nM）、FFRFamide（0.25 nM）和FWRFamide（0.42 nM）。最有效的配体之一是一种含有光反应性苯丙氨酸类似物的五肽，即D - 酪氨酸 - （对苯甲酰基 - 苯丙氨酸） - 正亮氨酸 - 精氨酸 - 苯丙氨酸酰胺（Ki = 0.23 nM）。结果发现，丹磺酰 - PQRFamide和丹磺酰 - RFamide也能与NPFF受体结合，其Ki值分别为6.1和73 nM。慢性吗啡处理不会改变NPFF受体的放射性配体结合和G蛋白偶联。
