Blume Annegret, Torner Luz, Liu Ying, Subburaju Sivan, Aguilera Greti, Neumann Inga D
Department of Behavioural and Molecular Neuroendocrinology, Institute of Zoology, University of Regensburg, 93053 Regensburg, Germany.
Endocrinology. 2009 Apr;150(4):1841-9. doi: 10.1210/en.2008-1023. Epub 2008 Nov 20.
Prolactin (PRL) modulates maternal behavior and mediates hypothalamic pituitary adrenal axis inhibition during lactation via PRL receptors in the brain. To identify mechanisms mediating these effects, we examined the effects of PRL on signaling and CRH transcription in hypothalamic neurons in vivo and in vitro. Western blot of hypothalamic proteins from rats receiving intracerebroventricular PRL injection revealed increases in phosphorylation of the MAPK and ERK. Double-staining immunohistochemistry demonstrated phosphorylated ERK localization in parvocellular CRH neurons as well as magnocellular vasopressin and oxytocin neurons of the hypothalamic paraventricular (PVN) and supraoptic nuclei. PRL also induced ERK phosphorylation in vitro in the hypothalamic cell line, 4B, which expresses PRL receptors, and in primary hypothalamic neuronal cultures. Using reporter gene assays in 4B cells, or quantitative RT-PCR for primary transcript in hypothalamic cell cultures, PRL potentiated forskolin-stimulated CRH transcription through activation of the ERK/MAPK pathway. The effect of PRL in hypothalamic cell cultures was unaffected by tetrodotoxin, suggesting a direct effect on CRH neurons. The data show that PRL activates the ERK/MAPK pathway and facilitates CRH transcription in CRH neurons, suggesting that the inhibitory effect of PRL on hypothalamo-pituitary-adrenal axis activity reported in vivo is indirect and probably mediated through modulation of afferent pathways to the PVN. In addition, the prominent stimulatory action of PRL on the ERK/MAPK pathway in the hypothalamic PVN and supraoptic nucleus is likely to mediate neuroplasticity of the neuroendocrine system during lactation.
催乳素（PRL）可调节母性行为，并通过大脑中的PRL受体在哺乳期间介导下丘脑-垂体-肾上腺轴的抑制。为了确定介导这些作用的机制，我们在体内和体外研究了PRL对下丘脑神经元信号传导和促肾上腺皮质激素释放激素（CRH）转录的影响。对接受脑室内注射PRL的大鼠下丘脑蛋白进行的蛋白质印迹分析显示，丝裂原活化蛋白激酶（MAPK）和细胞外信号调节激酶（ERK）的磷酸化增加。双重免疫染色免疫组化显示，磷酸化的ERK定位于下丘脑室旁核（PVN）和视上核的小细胞CRH神经元以及大细胞加压素和催产素神经元中。PRL还在体外的下丘脑细胞系4B（该细胞系表达PRL受体）和原代下丘脑神经元培养物中诱导ERK磷酸化。使用4B细胞中的报告基因测定法，或对下丘脑细胞培养物中的初级转录本进行定量逆转录聚合酶链反应（RT-PCR），PRL通过激活ERK/MAPK途径增强了福斯高林刺激的CRH转录。PRL在下丘脑细胞培养物中的作用不受河豚毒素的影响，表明对CRH神经元有直接作用。数据表明，PRL激活ERK/MAPK途径并促进CRH神经元中的CRH转录，这表明体内报道的PRL对下丘脑-垂体-肾上腺轴活性的抑制作用是间接的，可能是通过调节PVN的传入通路介导的。此外，PRL对下丘脑PVN和视上核中ERK/MAPK途径的显著刺激作用可能介导了哺乳期间神经内分泌系统的神经可塑性。
