Basic study for application of stress-resistant effect of prolactin to animals

（1）低催乳素乳对成年大鼠应激能力和母性行为的影响本实验观察了乳源性催乳素对大鼠脑功能发育的影响。溴隐亭，一种催乳素分泌抑制剂，在怀孕的第20和21天被注入腹腔，并在成年期测试溴隐亭给药的母亲的应激耐受性和母性行为。与对照组母亲饲养的大鼠相比，溴隐亭给药母亲饲养的大鼠中由水约束应激引起的胃溃疡程度和母亲行为对寄养幼仔的潜伏期均显著增加。这些结果表明，乳源性催乳素在应激耐受和母性行为的神经网络建立中起重要作用。（2）大鼠催乳素受体基因一个新的第一外显子的鉴定及性类固醇激素对肝脏催乳素受体基因表达的调控在大鼠催乳素受体基因中，除了已知的四个第一外显子E1-1、E1-2、E1-3和E1-4外，还鉴定了另一个第一外显子E1-5。对肝脏中每个第一外显子的表达分析表明，性类固醇激素特异性地调节E1-2第一外显子的表达。（3）大鼠催乳素受体基因表达的脑特异性调节机制发现脑特异性外显子1，E1-4，位于大鼠催乳素受体基因的外显子2和3之间，对大脑中每个第一外显子表达的分析表明，发育过程中催乳素基因表达的诱导依赖于E1-4的表达。

(1)Effects of rearing with low-prolactin milk on the stress-resistance and maternal behavior of rats at adulthoodEffects of milk-born prolactin on the development of brain function were examined in rats. Bromocriptin, a prolactin secretion inhibitor, was administrated into intraperitoneal cavity at days 20 and 21 of pregnancy, and stress-tolerance and maternal behavior reared by the bromocriptin-administrated mothers were tested at adulthood. Both the extent of gastric ulcer caused by water-restraint stress and latency of maternal behavior to foster pups were significantly increased in the rats reared by the bromocriptin-administrated mothers compared to those in rats reared by control mothers. These results suggest that milk-born prolactin plays an important role in establishment of neural networks for stress tolerance and maternal behavior.(2)Identification of a novel first exon of rat prolactin receptor gene and regulation of the prolactin receptor gene expression in the liver by sex steroid hormonesIn addition to the known four first exones, E1-1,E1-2,E1-3 and E1-4, another first exon, E1-5,was identified in the rat prolactin receptor gene. Analysis of expression of each first exon in the liver revealed that sex steroid hormones specifically regulate the expression of E1-2 first exon(3)Mechanism of brain-specific regulation of prolactin receptor gene expression in the ratThe brain-specific exon 1,E1-4,was found to localize between exons 2 and 3 of rat prolactin receptor gene, and analysis of expression of each first exon in the brain revealed that induction of prolactin gene expression during development depends on the expression of E1-4.