Regulation of synaptic plasticity in amygdala mediated by neuron-synthetized sexual hormones (sex neurosteroids)

神经元能够合成性类固醇激素，其作为神经类固醇释放并影响神经元连接。这些性神经类固醇的功能在海马中得到了深入的研究，其中内源性合成的17 β-雌二醇（E2）和双氢睾酮（DHT）已被证明以性别特异性方式调节兴奋性突触的稳定性和性质。我们最近发现类似的机制在杏仁核中也有效。我们发现在基底外侧杏仁核（BLA）的E2合成酶芳香化酶（AROM）的一个强大的表达，并表明，抑制AROM的结果在改变脊柱突触密度和LTP的性别特异性。此外，在中央杏仁核（CeAl）的外侧部分发现了强大的AROM表达，其与BLA一起对于恐惧反应至关重要。这就提出了一个问题，即E2对突触可塑性的性别特异性调节的机制是什么，以及它们是否依赖于性别影响恐惧行为。在本提案中，我们建议进行旨在全面解决这些问题的实验。由于5 α-还原酶2型（5 α-R2），产生DHT的酶，也在BLA和CeAl中强烈表达，我们进一步将解决DHT功能的研究纳入我们的提案。实验模型包括：a）AROM和雄激素受体（AR）缺陷小鼠的分析，和B）将AROM和5 α-R2的抑制剂（分别为来曲唑和非那肽）心室内输注到性腺切除的成年大鼠中。随后分析动物BLA和CeAl中改变的突触可塑性，以及改变的恐惧相关行为。c）包括杏仁核的器官型培养物，其将用于鉴定BLA中性神经类固醇信号传导的分子机制。此外，我们将d）确定在BLA和CeAl中表达AROM、5 α-R2、雌激素和/或雄激素受体的神经元的表达谱。我们相信，这些研究将提供有价值的信息，可能有助于更好地了解情绪障碍的某些性别差异以及抑制剂的副作用，这些抑制剂经常用于癌症治疗（分别为乳腺癌和前列腺癌）。

Neurons are capable of synthesizing sex steroid hormones which are released as neurosteroids and influence neuronal connectivity. The functions of these sex neurosteroids have been intensely studied in hippocampus, where endogenously synthesized 17beta-estradiol (E2) and dihydrotestosterone (DHT) have been shown to regulate the stability and properties of excitatory synapses in a sex-specific manner. We recently showed that similar mechanisms are also effective in amygdala. We found in basolateral amygdala (BLA) a robust expression of the E2-synthesizing enzyme aromatase (AROM) and showed that inhibition of AROM results sex-specifically in altered spine synapse density and LTP. In addition, robust AROM expression was found in the lateral part of the central amygdala (CeAl), which together with BLA is pivotal for the fear response. This raises the questions what mechanisms underlie the sex-specific regulation of synaptic plasticity by E2, and whether they influence fear behavior sex-dependently. In the present proposal, we suggest experiments aimed at comprehensively addressing these questions. As 5alpha-reductase type 2 (5alpha-R2), the enzyme that generates DHT, is also strongly expressed both in BLA and CeAl, we further include studies addressing the function of DHT into our proposal. Experimental models include: a) Analysis of AROM- and androgen receptor (AR)-deficient mice, and b) intraventricular infusion of inhibitors of AROM and 5alpha-R2 (letrozole and finasteride, respectively) into adult gonadectomized rats. Animals are subsequently analyzed for altered synaptic plasticity in BLA and CeAl, and for altered fear-related behavior. c) Organotypic cultures including amygdala, which will be used to identify the molecular mechanisms of sex neurosteroid signaling in BLA. In addition, we will d) determine expression profiles of neurons which express AROM, 5alpha-R2, estrogen and/or androgen receptors in BLA and CeAl. We believe that these studies will provide valuable information that may help to better understand certain sex differences in mood disorders as well as side effects of the inhibitors, which are frequently used for cancer therapy (breast and prostate cancer, respectively).