Liposits Z, Merchenthaler I, Paull W K, Flerkó B
Department of Anatomy, University Medical School, Pécs, Hungary.
Histochemistry. 1988;89(3):247-52. doi: 10.1007/BF00493148.
Growth hormone (GH) production of the anterior pituitary gland is controlled by inhibiting and releasing hormones that are synthesized in the diencephalon. In order to elucidate the possible interrelationships between somatostatin and growth hormone-releasing factor (GRF) synthesizing neurons at the hypothalamic level, immunocytochemical double labelling studies were performed on sections containing the arcuate nucleus (ARC) of the rat. Somatostatin producing neurons were located in the dorsomedial part of the ARC, while somatostatin immunoreactive (IR) axons were found in the ventro-lateral part of the nucleus, an area containing GRF-synthesizing cells. The use of the dual antigen localization technique revealed the approach and juxtaposition of somatostatin containing axons to dendrites and cell bodies of GRF-synthesizing neurons. At the light microscopic level, several somatostatinergic axon varicosities were clustered around single GRF-synthesizing cells. Ultrastructural analysis of the ventro-lateral part of the ARC showed that (i), somatostatinergic axons established synaptic connections (ii), GRF-producing neurons received axons terminals on their somata and dendrites and (iii), somatostatin-IR axons formed asymmetric synaptic specializations with both dendrites and somata of GRF-synthesizing neurons. These morphological findings indicate that the hormone production and release of hypophysiotrophic GRF-IR neurons can be influenced by the central somatostatin system via direct synaptic mechanisms. The data support the concept, that the interaction of inhibiting and releasing hormones, which determines responses of the pituitary target cells, may take place also at the hypothalamic level.
腺垂体生长激素（GH）的分泌受在间脑合成的抑制激素和释放激素的控制。为了阐明下丘脑水平生长抑素和生长激素释放因子（GRF）合成神经元之间可能的相互关系，对含有大鼠弓状核（ARC）的切片进行了免疫细胞化学双重标记研究。产生生长抑素的神经元位于ARC的背内侧部分，而生长抑素免疫反应性（IR）轴突则见于该核的腹外侧部分，此区域含有合成GRF的细胞。采用双抗原定位技术显示，含有生长抑素的轴突靠近合成GRF神经元的树突和胞体。在光学显微镜水平，几个生长抑素能轴突膨体聚集在单个合成GRF的细胞周围。对ARC腹外侧部分的超微结构分析显示：（i）生长抑素能轴突建立了突触连接；（ii）产生GRF的神经元在其胞体和树突上接受轴突终末；（iii）生长抑素IR轴突与合成GRF神经元的树突和胞体形成不对称突触特化。这些形态学发现表明，垂体营养性GRF-IR神经元的激素分泌和释放可通过直接突触机制受中枢生长抑素系统的影响。这些数据支持这样的概念，即决定垂体靶细胞反应的抑制激素和释放激素之间的相互作用也可能发生在下丘脑水平。
