Neuroendo Signal Transduction in Reproductive Physiology

描述(申请人提供)：催乳素(PRL)是一种脑下垂体前叶激素，对女性生育能力有深远的影响。催乳素高分泌是女性不孕症的主要神经内分泌相关病理。单纯性催乳素缺乏症虽然罕见，但也会导致女性生育力下降和哺乳失败。导致PRL常见高分泌的潜在缺陷仍然不清楚，许多与间歇性PRL释放的正常调节有关的机制也是如此。通常，PRL的分泌受到下丘脑多巴胺(DA)的紧张性抑制。女性体内周期性的生理性催乳素激增需要从这种多巴胺能抑制中撤退。事实上，对DA的反应性降低是高催乳素血症综合征的一个标志，这要求我们将注意力集中在DA对催乳素分泌的细胞和分子基础上。 我们已经在正常女性乳汁中发现并广泛描述了DA激活的内向整流钾通道(KDA)。DA通过激活KDA来调节乳酸膜的兴奋性，体外研究表明KDA通道在DA调节PRL释放中起着关键作用。此外，KDA的功能表达依赖于雌激素，这可能解释了长期以来公认的雌激素对该系统的调节作用。在这些方面，KDA通道在多巴胺能调节PRL分泌的事件层级中占有首要位置。 我们已经提出通过转基因技术在整个动物的生理环境中评估这种效应器K通道的作用。为此，我们设计并构建了能够抑制乳酸菌中野生型KDA功能的“显性负性”突变体。然后，我们创建了一个转基因小鼠模型(“功能丧失”)，在该模型中，使用PRL启动子将该突变体的表达定向到脑下垂体促乳素。另一种转基因模型(“功能获得”)也已经产生，在该模型中，具有与KDA相同的生物物理性质的结构性活性K通道在乳汁中过度表达。两种模型都表现出PRL分泌活性的改变。这两个模型将使我们能够研究KDA和膜兴奋性在调节基础和阵发性PRL释放中的生理作用。这类研究最终将深入了解催乳素分泌紊乱的基础，催乳素是哺乳动物生育、怀孕和哺乳的核心激素。

DESCRIPTION (provided by applicant): Prolactin (PRL), an anterior pituitary hormone, has profound effects on female fertility. Hypersecretion of PRL is the major neuroendocrine-related pathology associated with female infertility. Isolated PRL deficiency, while rare, also results in reduced fertility and lactational failure in women. The underlying defects which lead to the common hypersecretion of PRL remain ill-defined, as do many of the mechanisms involved in the normal regulation of episodic PRL release. Usually, PRL secretion is under tonic inhibition by hypothalamic dopamine (DA). Periodic, physiological surges of PRL in females require a withdrawal from this dopaminergic inhibition. The fact that reduced responsiveness to DA is a hallmark of hyperprolactinemic syndromes demanded that we focus our attention on the cellular and molecular basis of DA action on the lactotrope. We have discovered and extensively characterized a DA-activated inwardly-rectifying potassium channel (KDA) in normal female lactotropes. DA regulates lactotrope membrane excitability through activation of KDA and in vitro studies have demonstrated a critical role for this KDAchannel in the regulation of PRL release by DA. Furthermore, the functional expression of KDAis dependent upon estrogen, which may explain a long-recognized modulatory action of estrogen on this system. In these regards, the KDA channel occupies a primal position in the hierarchy of events in dopaminergic regulation of PRL secretion. We have proposed to evaluate the role of this effector K channel within its physiological context - the whole animal through transgenic technology. To this end, we have designed and constructed "dominant negative" mutants, capable of inhibiting wild-type KDA function in lactotropes. We then created a transgenic mouse model ("Loss of Function") in which expression of this mutant is directed to pituitary lactotropes using the PRL promoter. A second transgenic model ("Gain of Function") has also been produced in which a constitutively active K channel, with the same biophysical properties as KDA, is over expressed in the lactotropes. Both models exhibit altered PRL secretory activity. These two models will enable us to study the physiological role of KDAand membrane excitability in the regulation of both basal and episodic release of PRL. Such studies will ultimately provide insight into the basis of secretory disorders in PRL, a hormone at the core of mammalian fertility, gestation and lactation.