Jöhren O, Sanvitto G L, Egidy G, Saavedra J M
Section on Pharmacology, National Institute of Mental Health, Bethesda, Maryland 20892, USA.
J Neurosci. 1997 Nov 1;17(21):8283-92. doi: 10.1523/JNEUROSCI.17-21-08283.1997.
Brain angiotensin II (Ang II) inhibits pituitary prolactin release by an indirect mechanism requiring stimulation of dopamine formation and release. We report that [125I]Sar1-Ang II binding to AT1 receptors and AT1A receptor mRNA expression increase selectively in the dorsomedial arcuate nucleus of 17beta-estradiol-primed ovariectomized rats after treatment with progesterone. In hormone-treated rats, arcuate nucleus AT1A receptor mRNA expression is associated with tyrosine hydroxylase-positive neurons. No AT1A receptor mRNA was detected in tyrosine hydroxylase-positive cells of the arcuate nucleus of intact male rats. Conversely, in the anterior pituitary, where local or circulating Ang II stimulates prolactin release, [125I]Sar1-Ang II binding to AT1 receptors and AT1B receptor mRNA expression are decreased in 17beta-estradiol/progesterone-treated ovariectomized rats. Thus, AT1A receptors in the dorsal arcuate nucleus and AT1B receptors in the anterior pituitary are regulated inversely by estrogen/progesterone treatment, supporting the hypothesis of a dual role for brain and pituitary Ang II on prolactin release. The colocalization of AT1A receptor mRNA and tyrosine hydroxylase in neurons of the arcuate nucleus furthermore indicates that within this area central Ang II acts directly on dopaminergic neurons. These results support the hypothesis that central Ang II inhibits pituitary prolactin release indirectly via modulation of dopaminergic activity in the arcuate nucleus.
脑内血管紧张素II（Ang II）通过一种间接机制抑制垂体催乳素释放，该机制需要刺激多巴胺的生成和释放。我们报告，在用孕酮处理的17β-雌二醇预处理的去卵巢大鼠的背内侧弓状核中，[125I]Sar1-Ang II与AT1受体的结合及AT1A受体mRNA表达选择性增加。在激素处理的大鼠中，弓状核AT1A受体mRNA表达与酪氨酸羟化酶阳性神经元相关。在完整雄性大鼠的弓状核酪氨酸羟化酶阳性细胞中未检测到AT1A受体mRNA。相反，在局部或循环中的Ang II刺激催乳素释放的垂体前叶，在17β-雌二醇/孕酮处理的去卵巢大鼠中，[125I]Sar1-Ang II与AT1受体的结合及AT1B受体mRNA表达降低。因此，雌激素/孕酮处理可反向调节背内侧弓状核中的AT1A受体和垂体前叶中的AT1B受体，支持脑和垂体Ang II在催乳素释放中具有双重作用的假说。弓状核神经元中AT1A受体mRNA与酪氨酸羟化酶的共定位进一步表明，在该区域内，中枢Ang II直接作用于多巴胺能神经元。这些结果支持以下假说：中枢Ang II通过调节弓状核中的多巴胺能活性间接抑制垂体催乳素释放。
