Augustine R A, Kokay I C, Andrews Z B, Ladyman S R, Grattan D R
Department of Anatomy and Structural Biology, School of Medical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand.
J Mol Endocrinol. 2003 Aug;31(1):221-32. doi: 10.1677/jme.0.0310221.
Prolactin receptor (PRL-R) expression in the brain is increased in lactating rats compared with non-pregnant animals. The aim of the present study was to determine the time-course of changes in PRL-R mRNA levels during pregnancy and/or lactation, and to determine relative levels of the two forms (short and/or long form) of receptor mRNA in specific brain regions. Brains were collected from female rats on dioestrus, days 7, 14 or 21 of pregnancy, day 7 of lactation or day 7 post-weaning. Frozen, coronal sections were cut (300 microm) and specific hypothalamic nuclei and the choroid plexus were microdissected using a punch technique. Total RNA was extracted and reverse transcribed, then first strand cDNA was amplified using quantitative real-time PCR. Results showed an up-regulation of long-form PRL-R mRNA in the choroid plexus by day 7 of pregnancy compared with dioestrus, which further increased on days 14 and 21 of pregnancy and day 7 of lactation, and then decreased to dioestrous levels on day 7 post-weaning. Short-form PRL-R mRNA levels increased on day 14 of pregnancy relative to dioestrus, increased further on day 7 of lactation and decreased on day 7 post-weaning. Changes in mRNA were reflected in increased levels of PRL-R immunoreactivity in the choroid plexus during pregnancy and lactation, compared with dioestrus. In the arcuate nucleus, long-form PRL-R mRNA was increased during pregnancy. In contrast to earlier work, no significant changes in short- or long-form PRL-R mRNA expression were detected in several other hypothalamic nuclei, suggesting that changes in hypothalamic mRNA levels may not be as marked as previously thought. The up-regulation of PRL-R mRNA and protein expression in the choroid plexus during pregnancy and lactation suggest a possible mechanism whereby increasing levels of peripheral prolactin during pregnancy may have access to the central nervous system. Together with expression of long-form PRL-R mRNA in specific hypothalamic nuclei, these results support a role for prolactin in regulating neuroendocrine and behavioural adaptations in the maternal brain.
与未怀孕的动物相比，哺乳期大鼠大脑中催乳素受体（PRL-R）的表达增加。本研究的目的是确定怀孕和/或哺乳期PRL-R mRNA水平变化的时间进程，并确定特定脑区中两种形式（短形式和/或长形式）受体mRNA的相对水平。在动情后期、怀孕第7天、14天或21天、哺乳期第7天或断奶后第7天从雌性大鼠收集大脑。将冷冻的冠状切片切成300微米厚，使用打孔技术对特定的下丘脑核和脉络丛进行显微切割。提取总RNA并进行逆转录，然后使用定量实时PCR扩增第一链cDNA。结果显示，与动情后期相比，怀孕第7天时脉络丛中长形式PRL-R mRNA上调，在怀孕第14天和21天以及哺乳期第7天进一步增加，然后在断奶后第7天降至动情后期水平。与动情后期相比，怀孕第14天时短形式PRL-R mRNA水平增加，在哺乳期第7天进一步增加，在断奶后第7天下降。mRNA的变化反映在怀孕和哺乳期脉络丛中PRL-R免疫反应性水平相对于动情后期增加。在弓状核中，长形式PRL-R mRNA在怀孕期间增加。与早期研究不同，在其他几个下丘脑核中未检测到短形式或长形式PRL-R mRNA表达的显著变化，这表明下丘脑mRNA水平的变化可能不像以前认为的那样明显。怀孕和哺乳期脉络丛中PRL-R mRNA和蛋白质表达的上调表明一种可能的机制，即怀孕期间外周催乳素水平升高可能进入中枢神经系统。这些结果与特定下丘脑核中长形式PRL-R mRNA的表达一起，支持催乳素在调节母体大脑神经内分泌和行为适应中的作用。
