Smith Sheryl S, Ruderman Yevgeniy, Frye Cheryl, Homanics Gregg, Yuan Maoli
Department of Physiology and Pharmacology, SUNY Downstate Medical Center, 450 Clarkson Ave., Box 31, Brooklyn, NY 11203, USA.
Psychopharmacology (Berl). 2006 Jun;186(3):323-33. doi: 10.1007/s00213-005-0168-3. Epub 2005 Sep 29.
3alpha-OH-5alpha[beta]-pregnan-20-one (THP) is a positive modulator of the GABAA receptor (GABAR), which underlies its reported anxiolytic effect. However, there are conditions such as premenstrual dysphoric disorder (PMDD) where increases in THP levels can be associated with adverse mood.
In order to test for conditions where THP might be anxiogenic, we developed a mouse model of THP withdrawal. Because delta-containing GABAR are highly sensitive to THP modulation, results were compared in wild-type and delta knockout mice.
Finasteride, a 5alpha-reductase blocker, was administered for 3 days to female wild-type or delta knockout mice. Then, animals were tested in the elevated plus maze, following acute administration of THP, lorazepam, flumazenil, or 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), and results compared to vehicle-injected controls. CA1 hippocampal GABAR alpha4 subunit levels were assessed by Western blot.
After THP withdrawal, THP produced anxiogenic effects, decreasing open arm entries on the elevated plus maze, following a brief shock, in contrast to its expected anxiolytic effects. As we have shown in rats, THP withdrawal also resulted in increased expression of the alpha4 subunit in mouse CA1 hippocampus. As expected for increases in alpha4-containing GABAR, THP withdrawn mice were relatively insensitive to the benzodiazepine (BDZ) lorazepam and had atypical responses to the BDZ antagonist flumazenil when tested on the plus maze. In contrast, they showed a greater anxiolytic response to THIP, which has greater efficacy at alpha4betadelta than other GABAR. Although THP withdrawal in delta knockout mice also increased the alpha4 GABAR subunit, the anxiogenic effects of THP and the anxiolytic effects of THIP were not observed, implicating alpha4betadelta GABAR in these effects.
Based on these behavioral and pharmacological findings, we suggest that THP withdrawal in the mouse may serve as a rodent model of PMDD.
3α-羟基-5α[β]-孕烷-20-酮（THP）是γ-氨基丁酸A型受体（GABAR）的正向调节剂，这是其具有抗焦虑作用的基础。然而，在经前烦躁障碍（PMDD）等情况下，THP水平升高可能与不良情绪有关。
为了测试THP可能产生致焦虑作用的情况，我们建立了THP戒断的小鼠模型。由于含δ亚基的GABAR对THP调节高度敏感，因此在野生型和δ亚基基因敲除小鼠中比较了结果。
对雌性野生型或δ亚基基因敲除小鼠给予5α-还原酶阻滞剂非那雄胺3天。然后，在急性给予THP、劳拉西泮、氟马西尼或4,5,6,7-四氢异恶唑并[5,4-c]吡啶-3-醇（THIP）后，将动物置于高架十字迷宫中进行测试，并将结果与注射溶剂的对照组进行比较。通过蛋白质免疫印迹法评估海马CA1区GABARα4亚基水平。
THP戒断后，THP产生了致焦虑作用，与预期的抗焦虑作用相反，在短暂电击后，高架十字迷宫中的开放臂进入次数减少。正如我们在大鼠中所显示的，THP戒断还导致小鼠海马CA1区α4亚基表达增加。正如含α4亚基的GABAR增加所预期的那样，THP戒断的小鼠对苯二氮䓬类（BDZ）药物劳拉西泮相对不敏感，并且在高架十字迷宫测试时对BDZ拮抗剂氟马西尼有非典型反应。相反，它们对THIP表现出更大的抗焦虑反应，THIP在α4βδ亚基上比其他GABAR具有更高的效能。尽管δ亚基基因敲除小鼠中的THP戒断也增加了α4 GABAR亚基，但未观察到THP的致焦虑作用和THIP的抗焦虑作用，提示α4βδ GABAR参与了这些作用。
基于这些行为学和药理学研究结果，我们认为小鼠中的THP戒断可能作为PMDD的啮齿动物模型。
