Masonis A E, McCarthy M P
Center for Avanced Biotechnology and Medicine, UMDNJ-Robert Wood Johnson Medical School, Piscataway 08854, USA.
Neurosci Lett. 1995 Apr 7;189(1):35-8. doi: 10.1016/0304-3940(95)11445-3.
Various exogenous and endogenous steroids have been demonstrated to have both enhancing and inhibiting effects on ligand binding to the gamma-aminobutyric acid(A) receptor (GABAA receptor) in previous studies. In the present study we have explored the possibility that an additional class of synthetic steroidal compounds, anabolic/androgenic steroids (AAS), mediate some of their CNS effects through direct interaction with the GABAa receptor. At micromolar concentrations, two AAS, stanozolol and 17 alpha-methyltestosterone (17 alpha-MT), significantly inhibited 1 nM [3H]flunitrazepam ([3H]Fln) binding to rat brain cerebrocortical membranes. Inhibition of 1 nM [3H]Fln binding by stanozolol was similar for both males and females (approximately 50% inhibition at 50 microM stanozolol). 17 alpha-MT was much less efficacious, but did significantly inhibit 1 nM [3H]Fln binding at concentrations > 10 microM. In equilibrium binding assays, stanozolol (50 microM) raised the apparent KD for [3H]Fln binding. The observed changes in the [3H]Fln binding curve, when analyzed by Rosenthal analysis, reveal complex equilibrium binding behavior. In females, the Rosenthal plot was best fit by a two site binding model. Stanozolol (50 microM) inhibited binding to the higher affinity site in a manner consistent with competitive inhibition, increasing the KD without changing the BMAX. However, the effect of stanozolol on the binding to the low affinity site was more complex, with an increase in the the KD and the BMAX. In males the data were best fit by a single binding site model. This single site exhibited a slight increase in the KD and a decrease in the BMAX in the presence of 50 microM stanozolol.(ABSTRACT TRUNCATED AT 250 WORDS)
在先前的研究中，已证实多种外源性和内源性类固醇对配体与γ-氨基丁酸A受体（GABAA受体）的结合具有增强和抑制作用。在本研究中，我们探讨了另一类合成甾体化合物，即合成代谢/雄激素类固醇（AAS），通过与GABAa受体直接相互作用介导其部分中枢神经系统效应的可能性。在微摩尔浓度下，两种AAS，司坦唑醇和17α-甲基睾酮（17α-MT），显著抑制1 nM [3H]氟硝西泮（[3H]Fln）与大鼠脑皮质膜的结合。司坦唑醇对1 nM [3H]Fln结合的抑制作用在雄性和雌性中相似（在50 μM司坦唑醇时约50%抑制）。17α-MT的效力低得多，但在浓度>10 μM时确实显著抑制1 nM [3H]Fln结合。在平衡结合试验中，司坦唑醇（50 μM）提高了[3H]Fln结合的表观解离常数（KD）。当通过罗森塔尔分析进行分析时，观察到的[3H]Fln结合曲线变化揭示了复杂的平衡结合行为。在雌性中，罗森塔尔图最适合用双位点结合模型拟合。司坦唑醇（50 μM）以与竞争性抑制一致的方式抑制与高亲和力位点的结合，增加KD而不改变最大结合量（BMAX）。然而，司坦唑醇对与低亲和力位点结合的影响更为复杂，KD和BMAX均增加。在雄性中，数据最适合用单结合位点模型拟合。在存在50 μM司坦唑醇的情况下，这个单一位点的KD略有增加，BMAX降低。（摘要截短于250字）
