Dr. Senckenbergische Anatomie, Institut für Anatomie II, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany.
Cell Tissue Res. 2010 Apr;340(1):127-36. doi: 10.1007/s00441-010-0930-7. Epub 2010 Feb 18.
The hypophysial pars tuberalis (PT), an important interface between neuroendocrine brain centers (hypothalamus, pineal organ) and the pars distalis (PD) of the hypophysis, plays a central role in regulating seasonal reproduction and prolactin release. However, the signaling molecules that transmit photoperiodic information from the PT to the PD and control prolactin release (the so-called "tuberalins") have not yet been identified, despite an intense search for more than three decades. Here, we demonstrate an endocannabinoid system in the PT of the Syrian hamster, a photoperiodic species. By means of in situ hybrization, the PT was found to express N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD), fatty acid amide hydrolase (FAAH), sn-1-selective diacylglycerol lipases (DAGLalpha and DAGLbeta), and monoacylglycerol lipase (MAGL), enzymes involved in endocannabinoid synthesis and degradation. The expression of NAPE-PLD, FAAH, and DAGLalpha was confirmed by immunohistochemistry. Expression and protein levels of DAGLs controlling the synthesis of 2-arachidonoyl glycerol (2-AG), a major endocannabinoid, were upregulated in the PT of Syrian hamsters kept under long-day conditions. Consequently, 2-AG levels were increased in the PT of these hamsters. A primary target of 2-AG, the cannabinoid receptor 1 (CB1), was expressed in the PD. Double-immunolabeling revealed that most of the CB1-immunoreactive cells in the PD were folliculostellate cells that were also immunoreactive for S-100 protein. Thus, the PT comprises an endocannabinoid system, and 2-AG may act as a photoperiodic messenger from the PT to the PD for the regulation of hypophysial hormonal secretion.
垂体中间部（PT）是神经内分泌脑中枢（下丘脑、松果体器官）与垂体远侧部（PD）之间的重要接口，在调节季节性繁殖和催乳素释放方面发挥着核心作用。然而，尽管已经进行了三十多年的密集搜索，仍然没有发现将光周期信息从 PT 传递到 PD 并控制催乳素释放的信号分子（所谓的“tuberalins”）。在这里，我们展示了叙利亚仓鼠（一种光周期物种）PT 中的内源性大麻素系统。通过原位杂交，发现 PT 表达 N-酰基磷脂酰乙醇胺特异性磷脂酶 D（NAPE-PLD）、脂肪酸酰胺水解酶（FAAH）、sn-1 选择性二酰基甘油脂肪酶（DAGLalpha 和 DAGLbeta）和单酰基甘油脂肪酶（MAGL），这些酶参与内源性大麻素的合成和降解。免疫组织化学证实了 NAPE-PLD、FAAH 和 DAGLalpha 的表达。控制 2-花生四烯酰甘油（2-AG）合成的 DAGL 的表达和蛋白水平在长日照条件下饲养的叙利亚仓鼠的 PT 中上调。因此，这些仓鼠的 PT 中 2-AG 水平增加。2-AG 的主要靶标，大麻素受体 1（CB1），在 PD 中表达。双免疫标记显示，PD 中大多数 CB1 免疫反应性细胞是滤泡星状细胞，这些细胞也对 S-100 蛋白呈免疫反应性。因此，PT 包含一个内源性大麻素系统，2-AG 可能作为 PT 到 PD 的光周期信使，调节垂体激素分泌。
