5-HT transporter function: Interaction of hormones and antidepressants

描述（由申请人提供）： 本研究旨在探讨雌二醇对选择性5-羟色胺再摄取抑制剂（SSRIs）的影响，SSRIs是一类广泛用于治疗重度抑郁症（MDD）的药物。对于正在接受SSRIs治疗的绝经后抑郁症妇女，是否应增加雌激素替代疗法（ERT），目前尚无临床共识。我们的临床前研究直接解决了这个问题。我们以前在3个月大的卵巢切除（OVX）大鼠中发现，雌二醇（E2）急性或长期给药抑制SERT，从而产生抗抑郁（AD）样作用。然而，E2也阻断SSRI对SERT的抑制作用，从而防止其AD样效应。雌激素受体β（ER β）介导E2的AD样作用，而ER β激活介导其阻断SSRI的AD作用的能力。使用计时电流法技术直接测量SERT在体内的功能，可以看到这些效果。强迫游泳试验（FST）也获得了类似的结果，该试验提供了SSRIs对SERT影响的更间接但行为评估。这项建议通过以下临床相关的方式扩展了这些观察结果：1）大鼠的年龄是否影响E2的作用; 2）卵巢切除术后的时间长短是否影响E2的作用。 激素给药影响E2的作用; 3）E2和年龄在大鼠中的作用，大鼠由于暴露于慢性不可预测的应激（CUS）而表现出抑郁症状。虽然可能没有完美的动物模型来研究人类绝经期雌激素缺乏的影响，但老年OVX大鼠肯定比年轻大鼠更适合这些问题。在具体目标1中，我们将使用10、14和18月龄的OVX大鼠研究年龄的影响，研究在OVX后18天进行。在具体目标2中，我们将讨论激素作用的“临界窗口”假说，该假说预测，ERT必须在绝经后早期或OVX后使用才能产生积极作用。我们将使用10个月大的OVX大鼠，在OVX后4个月和8个月进行研究。因此，在麻醉动物中进行的体内计时电流法将用于测量海马CA 3区细胞外液中5-羟色胺（5-HT）的清除率，海马CA 3区是研究AD和E2作用的适当脑区。ER亚型选择性激动剂以及拮抗剂将用于评价ER亚型在雌激素阻断SERT的能力以及其干扰SSRI对SERT的抑制作用的能力中的重要性。此外，还将使用行为测量来检查长期激素或药物给药的影响：（1）FST，以评价激素和SSRI的AD样作用;和（2）新奇抑制进食试验（NSFT），以测量其抗焦虑样作用。将采用特定ER的激动剂和拮抗剂来观察它们如何改变长期施用激素或SSRIs的行为效应。蛋白质印迹分析还将用于研究年龄或长期激素耗竭是否会改变ER亚型和/或其相关信号通路的水平，以及长期E2治疗是否会诱导这些参数的变化。最后一个具体的目的是检查E2在大鼠中的作用，这些大鼠由于暴露于慢性不可预测的压力（CUS）而表现出抑郁症状。这些实验将在3个月大的OVX大鼠中进行，以将结果与相同年龄的幼稚大鼠中获得的结果进行比较。此外，为了研究年龄对CUS产生抑郁性抑郁症的能力的影响，还将在10和18月龄的OVX大鼠中进行这些实验。将使用FST和蔗糖偏好试验评价E2、舍曲林和亚型选择性ER激动剂和拮抗剂的长期作用。我们的总体目标是提供绝经前和绝经后抑郁症患者使用雌激素替代疗法的相关临床前信息。

DESCRIPTION (provided by applicant): This proposal examines the ability of estradiol to modify effects of selective serotonin reuptake inhibitors (SSRIs), a class of drugs widely-used for the treatment of major depressive disorder (MDD). There is no clinical consensus that it is useful to add estrogen replacement therapy (ERT) to postmenopausal women with depression who are being treated with SSRIs. Our preclinical studies address this issue directly. We showed previously in 3 month old ovariectomized (OVX) rats, that estradiol (E2) administered either acutely or longer-term inhibits the SERT so as to produce antidepressant (AD)-like effects. However, E2 also blocks the inhibitory effect of SSRIs on the SERT so as to prevent their AD-like effects. Estrogen receptor � (ER�) mediates the AD-like effects of E2 whereas ER� activation mediates its ability to block the AD effects of SSRIs. These effects were seen using the technique of chronoamperometry to measure directly SERT function in vivo. Similar results were also obtained with the forced swim test (FST), which provides a more indirect but behavioral assessment of the effects of SSRIs on the SERT. This proposal extends these observations in clinically-relevant ways by examining 1) if the age of the rats influences the effects of E2; 2) whether the length of time from ovariectomy to hormone administration impacts the effects of E2; 3) effects of E2 and age in rats expressing depressive symptoms due to exposure to chronic unpredictable stress (CUS). Although there may be no perfect animal model for the effects of estrogen deprivation in human menopause, older OVX rats are certainly more appropriate for these questions than younger ones. In Specific Aim 1 we will study the effect of age, by using OVX rats 10, 14 and 18 months old, with studies carried out 18 days post-OVX. In Specific Aim 2 we will address the "critical window" hypothesis of hormone action which predicts that ERT must be administered early after the menopause or after OVX to have a positive effect. We will use 10 month old OVX rats with studies carried out 4 and 8 months post-OVX. I n b o t h A i m s , in vivo chronoamperometry, carried out in anesthetized animals, will be used to measure the clearance of serotonin (5-HT) from extracellular fluid in the CA3 region of the hippocampus, which is an appropriate area of brain to study effects of both ADs and E2. ER subtype-selective agonists as well as antagonists will be used to evaluate the importance of ER subtypes in estrogen's ability to block the SERT as well as its ability to interfere with the inhibitory effect of SSRIs on the SERT. In addition, to behavioral measures will be used to examine effects of chronic hormone or drug administration: (1) the FST to evaluate AD-like effects of the hormones and SSRIs; and (2) the novelty-suppressed feeding test (NSFT) to measure their anxiolytic-like effects. Both agonist and antagonists of specific ERs will be employed to see how they alter the behavioral effects of chronic administration of hormones or SSRIs. Western blot analysis will also be used to study whether age or long term hormone depletion alters levels of ER subtypes and/or their associated signaling pathways and if long-term E2 treatment induces changes in these parameters. A final specific aim examines the effects of E2 in rats expressing depressive symptoms due to exposure to chronic unpredictable stress (CUS). These experiments will be carried out in 3 month old OVX rats to compare results to those obtained already in na�ve rats of the same age. In addition, to study effects of age on the ability of CUS to produce depressive symptomatology, these experiments will also be carried out in 10 and 18 month old OVX rats. Long term effects of E2, sertraline and subtype-selective ER agonists and antagonists will be evaluated using the FST and sucrose preference test. Our overall goal is to provide pre-clinical information relevant for the use of estrogen replacement therapy in peri- and post-menopausal depressed patients.