Prolactin stimulates the growth and development of specialized epithelial cells lining the cropsac of pigeons and doves (family Columbidae), leading to formation of "cropmilk," which is fed to the newly hatched squab. This system of milk feeding is unique among birds. To support the feeding of cropmilk, a complex array of behavioral adaptations are also supported by high levels of prolactin secretion in columbids during parenting. These specializations include elevated food intake (hyperphagia), nest attendance, and regurgitation feeding of the squab. Although prolactin is clearly important for these behavioral adaptations, the precise physiological and mechanistic bases for these behavioral effects remain controversial. The molecular mechanisms of prolactin action in the cropsac epithelium have been studied by cloning prolactin-induced genes, by cloning and expressing the pigeon prolactin receptor, and by analyzing the transcription factors that are activated after prolactin treatment. The avian (pigeon) prolactin receptor is a member of the cytokine receptor superfamily and uniquely contains a complete duplication of the extracellular ligand-binding domain. One of the early signal-transducing actions of prolactin in cropsac epithelium is the activation of signal transducer and activator of transcription (STAT) proteins via tyrosine phosphorylation. This fundamental signaling pathway is shared with mammalian prolactin target tissues. The convergent evolution of milk feeding and the behaviors that support parenting in columbids and mammals has depended on adaptation of both conserved mechanisms and divergent physiological processes.

中文翻译：

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催乳素对鸽子豆浆分泌和父母行为的调节。

催乳素刺激着鸽子和鸽子（科伦比科）的作物内衬的专门上皮细胞的生长和发育，导致“ cropmilk”的形成，该“ cropmilk”被喂给刚孵化的雏鸟。这种喂奶系统在鸟类中是独一无二的。为了支持母乳的喂养，育儿过程中co中催乳素的高水平分泌也支持一系列行为适应。这些专长包括食物摄入量增加（食欲亢进），巢照看情况和壁球反流喂养。尽管催乳素对于这些行为适应显然很重要，但这些行为影响的确切生理学和机理基础仍存在争议。通过克隆催乳素诱导的基因，克隆和表达鸽催乳素受体，以及分析经催乳素处理后激活的转录因子，已经研究了催乳素在作物囊上皮中的分子机制。禽（催乳激素）催乳激素受体是细胞因子受体超家族的成员，并且独特地包含细胞外配体结合域的完全重复。催乳素在角膜上皮中的早期信号转导作用之一是通过酪氨酸磷酸化激活信号转导子和转录激活子（STAT）。该基本信号传导途径与哺乳动物催乳激素靶组织共有。