Lee D, Huang W, Lim A T
Cell Biology Unit, Mental Health Research Institute of Victoria, Royal Park Hospital, Parkville, Australia.
Endocrinology. 1995 Feb;136(2):591-7. doi: 10.1210/endo.136.2.7835293.
Atrial natriuretic factor (ANF) and its smaller congeners are produced and released from rat brains to regulate the cardiovascular system, drinking behavior, and neurohormone release at the central level. In the hypothalamus, the adenylyl cyclase-cAMP system plays an important role in modulating the function of ANF neurons in the paraventricular nuclei and the periventricular regions that receive rich dopaminergic inputs. We report here a novel observation of a dopamine (DA) D1 agonist, SKF-38393, modulating immunoreactive (ir) ANF and pro-ANF messenger RNA (mRNA) expression in rat hypothalamic neurons. In long term primary cultures of neonatal rat hypothalamic cells, treatment with SKF-38393 increased irANF secretion in a time-related and dose-dependent manner, with an ED50 of approximately 10(-7) M and a concentration producing maximum effect of 10(-5) M. This stimulating effect of SKF-38393 was mimicked by 10(-5) M DA, a physiological ligand for D1 receptors. Furthermore, both of the stimulatory effects were abolished by SCH-23390, a D1 antagonist. These immunoassay findings were accompanied by corresponding changes in the abundance of pro-ANF mRNA in the cultures, as examined by colorimetric Northern blot analysis. By combining the techniques of in situ hybridization and immunocytochemistry, the mRNA of D1 receptor was colocalized in approximately 90% of the irANF-positive cells in the cultures. In addition, cholera toxin, an irreversible activator of adenylyl cyclases, markedly increased irANF secretion and cAMP production in a dose-dependent manner. This effect mimicked that of D1 agonist-stimulated ANF release, in that the latter also concurrently enhanced cAMP production in the hypothalamic cultures. Furthermore, the stimulatory effect of D1 agonist on irANF release was markedly suppressed by rp-cAMPS, a cAMP antagonist. We, thus, conclude that the release and gene expression of ANF in rat hypothalamic neurons are directly stimulated by DA acting through its D1 receptors on ANF neurons; this effect may operate at the genomic level and is mediated at least in part through activation of the cAMP-dependent kinase-A pathway.
心房利钠因子（ANF）及其较小的同类物由大鼠脑产生并释放，以在中枢水平调节心血管系统、饮水行为和神经激素释放。在下丘脑中，腺苷酸环化酶 - cAMP系统在调节室旁核和接受丰富多巴胺能输入的室周区域中ANF神经元的功能方面发挥重要作用。我们在此报告一项关于多巴胺（DA）D1激动剂SKF - 38393调节大鼠下丘脑神经元中免疫反应性（ir）ANF和前ANF信使核糖核酸（mRNA）表达的新观察结果。在新生大鼠下丘脑细胞的长期原代培养中，用SKF - 38393处理以时间和剂量依赖的方式增加了irANF分泌，ED50约为10^(-7) M，产生最大效应的浓度为10^(-5) M。SKF - 38393的这种刺激作用被10^(-5) M DA模拟，DA是D1受体的生理配体。此外，D1拮抗剂SCH - 23390消除了这两种刺激作用。通过比色法Northern印迹分析检测，这些免疫测定结果伴随着培养物中前ANF mRNA丰度的相应变化。通过结合原位杂交和免疫细胞化学技术，D1受体的mRNA在培养物中约90%的irANF阳性细胞中共同定位。此外，霍乱毒素是腺苷酸环化酶的不可逆激活剂，以剂量依赖的方式显著增加irANF分泌和cAMP产生。这种效应模拟了D1激动剂刺激的ANF释放，因为后者也同时增强了下丘脑培养物中的cAMP产生。此外，cAMP拮抗剂rp - cAMPS显著抑制了D1激动剂对irANF释放的刺激作用。因此，我们得出结论，大鼠下丘脑神经元中ANF的释放和基因表达受到DA通过其在ANF神经元上的D1受体直接刺激；这种效应可能在基因组水平起作用，并且至少部分通过激活cAMP依赖性蛋白激酶 - A途径介导。
