5-HT transporter function: Interaction of hormones and antidepressants

描述（由申请人提供）： 一些妇女易患重度抑郁症（MDD）与荷尔蒙波动有关。性腺激素的影响可能会导致抑郁症（以及产后抑郁症）的发生，这可能是抑郁症在女性中比男性更常见的部分原因。尽管如此，临床前研究检查抗抑郁药，特别是选择性5-羟色胺再摄取抑制剂（SSRIs）-治疗MDD的药物类别-对行为或神经化学参数的影响，主要使用男性受试者。在我们的实验中，研究了SSRIs对雌性大鼠的影响。使用体内计时电流法技术发现，全身或局部给予海马CA 3区的卵巢激素（苯甲酸雌二醇（EB）或孕酮（P））的急性给药干扰了SSRI抑制脑中被广泛认为是其初始细胞靶点的功能的能力-血清素转运蛋白（SERT）。此外，EB阻断SERT的功能，而P不阻断。此外，似乎有一些不同的机制（S）调解这两个影响的雌二醇。此外，预期EB的这两种作用会对雌二醇或雌二醇加孕酮的能力产生抵消作用，从而在与此类治疗联合给药时提高SSRI的疗效。有证据表明，雌二醇的这些作用是通过激活膜以及核雌激素受体（ER）介导的。相比之下，孕酮的作用似乎主要由核受体介导。这些先前的结果为当前提案中的研究提供了理论基础，其主要目标是使用神经化学或行为测量来扩展这些研究，以查看是否可以获得进一步的证据，表明女性性激素治疗影响SERT功能和/或干扰SSRI抑制SERT的能力。实验将在切除卵巢的雌性大鼠中进行。新的技术将被使用的是在体内微透析和强迫游泳试验（FST）。我们的假设是，无论是雌二醇或孕酮急性治疗将阻止局部应用氟伏沙明，SSRI的能力，无论是提高细胞外水平的5-羟色胺在海马或其能力，以减少不动或增加游泳行为的FST。此外，为了研究激素作用的可能机制：（1）进行突触体膜生物素化研究，以检查激素处理后SERT的质膜分布;（2）采用计时电流法，将使用两种方法，即使用特异性雌激素受体（ER 1或ER 2）基因敲除小鼠和选择性雌激素受体激动剂对大鼠的影响，研究这些雌激素受体亚型在介导雌激素效应中的作用;再次使用计时电流分析法（3）通过使用脑源性神经营养因子（BDNF）受体的拮抗剂来检测脑源性神经营养因子（BDNF）作为雌二醇对SSRI作用的影响的中间体的可能参与。最后，我们将研究是否长期，更临床适当的治疗与E2单独或E2+P改变SERT功能和/或产生的SSRI长期给予的影响。

DESCRIPTION (provided by applicant): The vulnerability of some women to develop major depressive disorder (MDD) is associated with hormonal fluctuations. It is likely that effects of gonadal hormones contribute to the development of MDD (as well as postpartum depression) and this may be part of the reason why MDD is more common in females than in males. In spite of this, preclinical research examining the effects of antidepressants, particularly selective serotonin reuptake inhibitors (SSRIs)- the drug class of choice for the treatment of MDD- on either behavioral or neurochemical parameters, have mainly used male subjects. In our experiments, effects of SSRIs in female rats were examined. It was found, using the technique of in vivo chronoamperometry, that acute administration of ovarian hormones (estradiol benzoate (EB) or progesterone (P)), either given systemically or locally into the CA3 region of the hippocampus, interferes with the ability of SSRIs to inhibit the function of what is widely considered their initial cellular target in brain- the serotonin transporter (SERT). In addition, EB but not P blocked the function of the SERT. Further, there appears to be some difference in the mechanism(s) mediating these two effects of estradiol. Further, these two effects of EB would be expected to exert counteracting effects on the ability of estradiol, or estradiol plus progesterone, to improve the efficacy of SSRIs when given in combination with such treatment. Evidence was obtained that these effects of estradiol are mediated via activation of membrane as well as nuclear estrogen receptors (ER). By contrast, the effect of progesterone seems to be mediated primarily by nuclear receptors. These previous results provide the rationale for the studies in the current proposal, whose principal goal is to extend these studies using neurochemical or behavioral measures to see if further evidence can be obtained that treatment with female sex hormones either influences SERT function and/or interferes with the ability of SSRIs to inhibit the SERT. Experiments will be carried out in ovariectomized female rats. The new techniques to be used are in vivo microdialysis and the forced swimming test (FST). Our hypotheses are that acute treatment with either estradiol or progesterone will block the ability of locally applied fluvoxamine, an SSRI, either to elevate extracellular levels of serotonin in the hippocampus or its ability to decrease immobility or increase swimming behavior in the FST. In addition, to examine possible mechanisms underlying the hormonal effects: (1) biotinylation studies on synaptosomal membranes will be carried out to examine the plasma membrane distribution of the SERT after hormone treatment; (2) using chronoamperometry, two approaches will be used, namely the use of specific estrogen receptor (ER1 or ER2) knockout mice and the effects of selective estrogen receptor agonists in rats, to study the role of these estrogen receptor subtypes in mediating the effects of estrogen; and again using chronoamperometry (3) the possible involvement of brain-derived neurotrophic factor (BDNF) as an intermediary in the effect of estradiol on the action of an SSRI will be examined by using an antagonist of the receptor for BDNF. Finally, we will investigate if longer-term, more clinically appropriate treatment with E2 alone or E2+P alters SERT function and/or effects produced by an SSRI given chronically.