Determining the biological basis for phenotypic sex differences in kappa opioid receptor function

Kappa阿片受体(KOR)是脊椎动物中四种相关的阿片受体蛋白之一。KOR激动剂既有止痛作用，又有烦躁不安的作用。我以前已经证明，KOR镇痛的一部分是由于参与了导致应激诱导止痛的烦躁通路。因此，全身KOR镇痛是由这些止痛和应激通路的汇聚所介导的。KOR系统还以显著的性别差异而闻名，女性的止痛效果明显低于男性。目前尚不清楚KOR激动剂的应激效应中是否存在类似的性别二分法，以及这可能如何影响KOR的止痛。性二型特征可能是由于性腺激素(睾酮或雌激素)的影响，也可能是X或Y染色体上表达的基因的补充。在历史上，切除性腺(睾丸或卵巢)一直被用来检查性别差异。然而，这种方法不能揭示性染色体上表达的基因的影响，因为性染色体只与其相应的性腺(X与卵巢，Y与睾丸)一起表达。为了克服这一局限，我采用了两种创新的遗传方法来操纵性染色体和性腺激素的表达。我测试了这样一种假设，即女性由于X染色体基因介导的应激反应的差异而表现出较低的KOR介导的止痛性。 第一个目的是，我通过使用各种疼痛和焦虑的行为测试，并结合应激反应的药物操作，来检验KOR止痛的不同是由于应激反应的不同而导致的假说。在第二个目标中，我将使用转基因小鼠模型来分离和评估性腺激素和性染色体在调节这些性别差异中的作用。这些模型通过性腺控制X和Y染色体的表达(即：产生带有睾丸的XX小鼠和带有卵巢的XY小鼠)。这个强大的工具让我可以同时测试性腺激素和性染色体对观察到的性别差异的影响。 现在人们普遍认为，正常和病理的大脑功能表现出重要的性别差异，但人们对此知之甚少。这项研究通过研究男性和女性KOR功能差异的神经生物学基础直接解决了这个问题。从这些实验中收集到的见解可以用来阐明男性和女性在压力和疼痛处理方面的根本差异。这些信息不仅将提高我们对女性基本神经生物学的理解，还将促进未来疼痛和止痛疗法的发展，无论男女。最后，这项研究计划将允许我为这些遗传模型建立繁育群体，从而将我的实验室定位为一个精英培训环境，研究许多表型模式的性别差异的机制基础。

The kappa opioid receptor (KOR) is one of four related opioid receptor proteins in vertebrates. KOR agonists are both analgesic and dysphoric. I have shown previously that a portion of KOR analgesia is due to engagement of dysphoric pathways leading to stress-induced analgesia. Therefore, systemic KOR analgesia is mediated by a convergence of these analgesic and stress pathways. The KOR system is also notable for a prominent sex-difference, where females show significantly less analgesia than males. It is unknown if a similar sexual dichotomy exists in the stress effects of KOR agonists, and how this might impact KOR analgesia. Sexually dimorphic traits can be due to either the influence of gonadal hormones (testosterone or estrogen) or the complement of genes expressed on the X or Y chromosome. Historically, removal of the gonads (testes or ovaries) has been used to examine sex differences. However, the influence of genes expressed on the sex chromosomes cannot be revealed by this approach, because the sex chromosomes are only ever expressed with their appropriate gonad (X with ovaries, Y with testes). To overcome this limitation, I employ two innovative genetic approaches to manipulate the expression of sex chromosome with gonadal hormones. I test the hypothesis that females exhibit lower KOR-mediated analgesia due to differences in the stress response mediated by X chromosome genes. For the first aim, I test the hypothesis that differences in KOR analgesia are due to differences in stress response by using a variety of behavioral tests of pain and anxiety in combination with pharmacological manipulation of the stress response. In the second aim, I will use transgenic mouse models to isolate and assess the contribution of gonadal hormones and sex chromosomes in mediating these sex differences. These models manipulate the expression of X and Y chromosomes with the gonads (i.e: generate XX mice with testes and XY mice with ovaries). This powerful tool allows me to test, simultaneously, the impact of gonadal hormones and sex chromosomes on the observed sex difference. It is now widely accepted that normal and pathological brain function exhibits important yet poorly understood sex differences. This study directly addresses this issue by examining the neurobiological basis for the difference in KOR function between males and females. Insights gleaned from these experiments can be used to illuminate fundamental differences in stress and pain processing between males and females. Not only will this information improve our understanding of basic neurobiology in females, but will improve the development of future therapies for pain and analgesia in both sexes. Finally, this research program will allow me to establish breeding colonies for these genetic models, thus positioning my lab to be a an elite training environment examining the mechanistic basis for sex differences across many phenotypic modalities.