Neuroendo Signal Transduction in Reproductive Physiology

描述（由申请人提供）：催乳素（PRL）是一种垂体前叶激素，对女性生育能力有深远的影响。催乳素分泌过多是与女性不孕症相关的主要神经内分泌病理。孤立的PRL缺乏症虽然罕见，但也会导致女性生育能力降低和哺乳失败。导致PRL常见分泌过多的潜在缺陷仍然不明确，就像参与发作性PRL释放的正常调节的许多机制一样。通常，PRL分泌受到下丘脑多巴胺（DA）的紧张性抑制。周期性的，生理激增的催乳素在女性需要退出这种多巴胺能抑制。事实上，降低反应性DA是一个标志性的高催乳素血症综合征要求我们把注意力集中在细胞和分子基础上的DA行动的催乳素。 我们发现并广泛表征了正常女性催乳素中DA激活的内向整流钾通道（KDA）。DA通过激活KDA调节催乳细胞膜的兴奋性，体外研究表明，KDA通道在DA调节PRL释放中起关键作用。此外，KDA的功能表达依赖于雌激素，这可能解释了雌激素对该系统的长期调节作用。在这些方面，KDA通道在多巴胺能调节PRL分泌的事件层次中占据主要位置。 我们建议通过转基因技术在整个动物的生理环境中评估这种效应钾通道的作用。为此，我们设计并构建了“显性负性”突变体，能够抑制野生型KDA功能的催乳素。然后，我们创建了转基因小鼠模型（“功能丧失”），其中使用PRL启动子将该突变体的表达导向垂体催乳素。还产生了第二种转基因模型（“功能增益”），其中具有与KDA相同生物物理性质的组成型活性K通道在催乳素中过表达。两种模型均表现出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间歇性PRL释放中的生理作用。这些研究将最终提供对PRL分泌紊乱的基础的深入了解，PRL是哺乳动物生育、妊娠和哺乳的核心激素。

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.