Watts A G, Sanchez-Watts G
Department of Biological Sciences, University of Southern California, Los Angeles 90089-2520, USA.
J Comp Neurol. 1995 Feb 20;352(4):501-14. doi: 10.1002/cne.903520403.
In the present study, we used subcutaneous polyethylene glycol injections to show that a physiologically relevant stimulus, hypovolemia, will selectively increase the expression of neuropeptide genes in a restricted population of parvicellular corticotropin-releasing hormone-containing neurons in the hypothalamic paraventricular nucleus. Our results show that a large reduction in extracellular fluid maintained over approximately 20 hours is associated with a significant increase in the level of corticotropin-releasing hormone mRNA in the medial parvicellular division of the paraventricular nucleus. Additionally, there are concomitant increases in cellular levels of both neurotensin/neuromedin N and proenkephalin mRNAs. Our colocalization results show that the increases in neurotensin/neuromedin N and proenkephalin mRNAs after polyethylene glycol injection occur to a significant degree in cells that also contain corticotropin-releasing hormone mRNA. Furthermore, significant numbers of cells containing proenkephalin mRNA also contain neurotensin/neuromedin N mRNA, raising the possibility that some neurons have increased levels of all three mRNAs. Finally, in the medial parvicellular division of the paraventricular nucleus, the number of identified corticotropin-releasing hormone neurons also containing vasopressin mRNA is very low in control animals and is not increased by polyethylene glycol injections, suggesting that, within this period, activation of the vasopressin gene may not be a critical event in the neuroendocrine response of corticotropin-releasing hormone neurosecretory neurons to extracellular dehydration. Considered together with the effects of adrenalectomy on peptide colocalization, our results suggest the existence of several phenotypically distinct sets of neurons within the medial parvicellular division of the paraventricular nucleus, each characterized by its ability to regulate the expression of neuropeptide genes in a stimulus-specific manner.
在本研究中，我们通过皮下注射聚乙二醇来表明，一种生理相关刺激——血容量减少，会选择性地增加下丘脑室旁核中一小部分含有促肾上腺皮质激素释放激素的小细胞神经元群体中神经肽基因的表达。我们的结果表明，在大约20小时内维持细胞外液的大幅减少与室旁核内侧小细胞区促肾上腺皮质激素释放激素mRNA水平的显著增加相关。此外，神经降压素/神经介素N和前脑啡肽mRNA的细胞水平也随之增加。我们的共定位结果表明，聚乙二醇注射后神经降压素/神经介素N和前脑啡肽mRNA的增加在很大程度上发生在也含有促肾上腺皮质激素释放激素mRNA的细胞中。此外，大量含有前脑啡肽mRNA的细胞也含有神经降压素/神经介素N mRNA，这增加了一些神经元三种mRNA水平都升高的可能性。最后，在室旁核内侧小细胞区，对照动物中同时含有血管加压素mRNA的已鉴定促肾上腺皮质激素释放激素神经元数量非常少，且聚乙二醇注射后并未增加，这表明在此期间，血管加压素基因的激活可能不是促肾上腺皮质激素释放激素神经分泌神经元对细胞外脱水的神经内分泌反应中的关键事件。结合肾上腺切除术对肽共定位的影响，我们的结果表明室旁核内侧小细胞区内存在几组表型不同的神经元，每组神经元的特征在于其以刺激特异性方式调节神经肽基因表达的能力。
