Study on molecular mechanism for regulation of maternal behavior with prolactin-knockout mice

1. 催乳素基因敲除（PRL-KO）小鼠表型分析通过靶向破坏催乳素基因产生催乳素缺陷小鼠。雄性prl - ko小鼠未见异常表型。然而，由于受精卵无法着床，该突变导致雌性小鼠不孕。PRL-KO小鼠的乳腺发育为正常的乳腺导管树，但乳腺导管未发育成小叶装饰。这些发现表明，PRL对雌性小鼠的生育和乳腺发育至关重要。PRL-KO小鼠母性行为分析PRL-KO小鼠对2 ~ 4日龄的饲养幼鼠的母性行为（取仔和蹲伏）进行测试。PRL- ko小鼠的母性行为与野生型小鼠相当，表明PRL对自发母性行为不是必需的。PRL对母性行为诱导的作用可能被其他激素如雌激素所补偿。孕激素和催产素。鸡脑prl受体在孵育过程中的表达水平分析。已知PRL通过作用于下丘脑的受体来诱导鸡的孵化行为。PRL受体在下丘脑高水平表达，但在孵育期间水平未升高。因此，PRL对诱导孵育行为的作用受配体水平调控，而不受受体水平调控。

1. Phenotype analysis of prolactin-knockout (PRL-KO) miceProlactin-deficient mice were produced by the turgeted disruption of prolactin gene. No abnormal phenotype was obserbed in malePRL-KO mice. However, the mutation caused infertility in female mice because of the inability of implantation of the firtilized eggs. Mammary glands of PRL-KO mice developed a normal ductal tree, but the ducts failed to develop lobular decorations. These findings indicate that PRL is essential for the fertility and mammary gland development of female mice.2. Analysis of maternal behavior of PRL-KO micePRL-KO mice were tested for maternal behavior (pup retrieval and crouching) toward 2-4 days old foster pups. The maternal behavior of PRL-KO mice were equivalent to those of wild-type mice, indicating that PRL, is not essential for the spontaneous maternal behavior. The PRL effect on induction of maternal behavior might be compensated by other hormones such as estrogen. progesteron and oxytocin.3. Analysis of expression levels of PRL-receptor in the chicken brain during incubation behavior.PRL is known to induce incubation behavior of chicken by acting on its receptor in the hypothalamus. High level expression of the PRL receptor was observed in the hypothalamus but the level was not increased during the incubating period. Therefore, the PRL effect on the induction of incubation behavior is regulated by the ligand level, not by the receptor level.