Norman A B, Battaglia G, Creese I
Mol Pharmacol. 1985 Dec;28(6):487-94.
In the presence of a 30 nM prazosin mask, [3H]-2-(2,6-dimethoxyphenoxyethyl) aminomethyl-1,4-benzodioxane ([3H]WB4101) can selectively label 5-HT1 serotonin receptors. Serotonin exhibits high affinity (Ki = 2.5 nM) and monophasic competition for [3H] WB4101 binding in cerebral cortex. Furthermore, we have found a significant correlation (r = 0.96) between the affinities of a number of serotonergic and nonserotonergic compounds at [3H]WB4101-binding sites in the presence of 30 nM prazosin and [3H] lysergic acid diethylamide ([3H]LSD)-labeled 5-HT1 serotonin receptors in homogenates of rat cerebral cortex. Despite similar pharmacological profiles, distribution studies indicate that, in the presence of 5 mM MgSO4, the Bmax of [3H]WB4101 is significantly lower than the Bmax of [3H]LSD in various brain regions. WB4101 competition for [3H] LSD-labeled 5-HT1 receptors fits best to a computer-derived model assuming two binding sites, with the KH for WB4101 being similar to the KD of [3H]WB4101 binding derived from saturation experiments. This suggests that [3H]WB4101 labels only one of the subtypes of the 5-HT1 serotonin receptors labeled by [3H]LSD. Interestingly, the selective 5-HT1A serotonin receptor antagonist, spiperone, and the selective 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino) tetraline, exhibit high affinity and monophasic competition for [3H]WB4101 but compete for multiple [3H]LSD 5-HT1 binding sites. These data indicate that [3H]WB4101 selectively labels the 5-HT1A serotonin receptor, whereas [3H] LSD appears to label both the 5-HT1A and the 5-HT1B serotonin receptor subtypes. The divalent cations, Mn2+, Mg2+, and Ca2+ were found to markedly increase the affinity and Bmax of [3H]WB4101 binding in cerebral cortex. Conversely, the guanine nucleotides guanylylimidodiphosphate and GTP, but not the adenosine nucleotide ATP, markedly reduce the Bmax of [3H]WB4101 binding. These characteristics are typical of agonists interacting with receptors which modulate cellular function via a guanine nucleotide-regulatory subunit.
在存在30 nM哌唑嗪的情况下，[3H]-2-(2,6-二甲氧基苯氧基乙基)氨甲基-1,4-苯并二恶烷([3H]WB4101)可选择性标记5-羟色胺1型（5-HT1）血清素受体。血清素在大脑皮层中对[3H]WB4101结合表现出高亲和力（Ki = 2.5 nM）和单相竞争。此外，我们发现在存在30 nM哌唑嗪的情况下，许多血清素能和非血清素能化合物在[3H]WB4101结合位点的亲和力与大鼠大脑皮层匀浆中[3H]麦角酸二乙胺([3H]LSD)标记的5-HT1血清素受体之间存在显著相关性（r = 0.96）。尽管药理学特征相似，但分布研究表明，在存在5 mM硫酸镁的情况下，[3H]WB4101的Bmax在各个脑区均显著低于[3H]LSD的Bmax。WB4101对[3H]LSD标记的5-HT1受体的竞争最符合假设两个结合位点的计算机推导模型，WB4101的KH与饱和实验得出的[3H]WB4101结合的KD相似。这表明[3H]WB4101仅标记[3H]LSD标记的5-HT1血清素受体亚型之一。有趣的是，选择性5-HT1A血清素受体拮抗剂螺哌隆和选择性5-HT1A激动剂8-羟基-2-(二正丙基氨基)四氢萘对[3H]WB4101表现出高亲和力和单相竞争，但对多个[3H]LSD 5-HT受体结合位点存在竞争。这些数据表明，[3H]WB4101选择性标记5-HT1A血清素受体，而[3H]LSD似乎标记5-HT1A和5-HT1B血清素受体亚型。发现二价阳离子Mn2+、Mg2+和Ca2+可显著增加大脑皮层中[3H]WB结合的亲和力和Bmax。相反，鸟嘌呤核苷酸鸟苷酰亚胺二磷酸和GTP，但不是腺苷核苷酸ATP，可显著降低[3H]WB4101结合的Bmax。这些特征是激动剂与通过鸟嘌呤核苷酸调节亚基调节细胞功能的受体相互作用的典型特征。
