Kadan M J, Krohn A M, Evans M J, Waltz R L, Hartig P R
J Neurochem. 1984 Sep;43(3):601-6. doi: 10.1111/j.1471-4159.1984.tb12777.x.
125I-Lysergic acid diethylamide (125I-LSD) is the first 125I-labeled ligand for serotonin receptor studies. Its binding to rat frontal cortex membranes is saturable, reversible, and stereospecific. Specific binding is linearly dependent on tissue concentration and represents 70-80% of the total binding. Scatchard plots of the binding data are linear with a KD of 1.5 nM, a Bmax of 12.4 fmol/mg wet weight tissue, and a Hill slope of 1.02. The binding kinetics are highly temperature-dependent. At 37 degrees C the bimolecular association rate constant is 1.28 X 10(8) min-1 M-1 and the dissociation rate constant is 0.087 min-1 (t 1/2 = 8.0 min). At 0 degrees C less than 4% dissociation occurs over 40 min and the association rate is similarly depressed. Inhibition of 125I-LSD binding by a variety of serotonergic, dopaminergic, and adrenergic ligands reveals a 5-hydroxytryptamine2 (5-HT2) serotonergic profile for this binding site. Regional distribution studies of 125I-LSD binding in rat brain show that areas with the highest levels of binding include the cortex and striatum. Iodinated radioligands can be synthesized with specific activities exceeding 2,000 Ci/mmol, which makes them approximately 75-fold more sensitive than tritiated radioligands. This high specific activity, coupled with the selectivity of 125I-LSD for 5-HT2 sites, makes this ligand a sensitive new probe for 5-HT2 serotonin receptors.
125I-麦角酸二乙胺（125I-LSD）是用于血清素受体研究的首个125I标记配体。它与大鼠额叶皮质膜的结合具有饱和性、可逆性和立体特异性。特异性结合与组织浓度呈线性相关，占总结合量的70 - 80%。结合数据的Scatchard图呈线性，解离常数（KD）为1.5 nM，最大结合量（Bmax）为12.4 fmol/mg湿重组织，希尔系数为1.02。结合动力学高度依赖温度。在37℃时，双分子缔合速率常数为1.28×10(8) min-1 M-1，解离速率常数为0.087 min-1（半衰期=8.0分钟）。在0℃时，40分钟内解离率低于4%，缔合速率同样降低。多种血清素能、多巴胺能和肾上腺素能配体对125I-LSD结合的抑制作用揭示了该结合位点的5-羟色胺2（5-HT2）血清素能特征。大鼠脑内125I-LSD结合的区域分布研究表明，结合水平最高的区域包括皮质和纹状体。碘化放射性配体的比活度可超过2000 Ci/mmol，这使其比氚标记的放射性配体灵敏度高约75倍。这种高比活度，加上125I-LSD对5-HT2位点的选择性，使该配体成为5-HT2血清素受体的一种灵敏新探针。
