Laboratory of Integrative Physiology, Graduate School of Integrated Arts & Sciences, Hiroshima University, Hiroshima, Japan.
Cell Tissue Res. 2013 Sep;353(3):525-38. doi: 10.1007/s00441-013-1663-1.
Systemic angiotensin II (Ang II) is a dipsogen in terrestrial vertebrates and seawater teleosts. In eels, Ang II acts on the area postrema, a sensory circumventricular organ (CVO) and elicits water intake but other sensory CVOs have not yet been found in the eel forebrain. To identify sensory CVOs in the forebrain, eels were peripherally injected with Evans blue, which immediately binds to albumin, or a rabbit IgG protein. Extravasation of these proteins, which cannot cross the blood–brain barrier (BBB), was observed in the brain parenchyma of the anteroventral preoptic recess (PR) walls. Fenestrated capillaries were observed in the parenchymal margin of the ventral wall of the PR, confirming a deficit of the BBB in the eel forebrain. Immunostaining for tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) detected neurons in the lateral region of the anterior parvocellular preoptic nucleus (PPa), which were strongly stained by BBB-impermeable N-hydroxysulfosuccinimide. In the periventricular region of the PPa, many neurons incorporated biotinylated dextran amine conjugated to fluorescein, a retrograde axonal tracer, injected into the magnocellular preoptic nucleus (PM), indicating neuronal connections from the PPa to the PM. The mammalian paraventricular and supraoptic nuclei, homologous to the teleost PM, receive principal neuronal projections from the organum vasculosum of the lamina terminalis (OVLT). These results strongly suggest that the periventricular subpopulation of the PPa, which is most likely to be a component of the OVLT, serves as a functional window of access for systemic signal molecules such as Ang II.
系统性血管紧张素 II (Ang II) 是陆生脊椎动物和海水硬骨鱼的一种摄水剂。在鳗鱼中，Ang II 作用于后区，这是一种感觉室周器官 (CVO)，并引起水的摄入，但在鳗鱼前脑中尚未发现其他感觉 CVO。为了鉴定前脑中的感觉 CVO，将 Evans 蓝，一种立即与白蛋白或兔 IgG 蛋白结合的物质，注射到鳗鱼外周。这些不能穿过血脑屏障 (BBB) 的蛋白质的漏出，在腹侧前视前区（PR）壁的脑实质中观察到。在 PR 腹侧壁的实质边缘观察到有孔毛细血管，证实了鳗鱼前脑 BBB 的缺陷。酪氨酸羟化酶 (TH) 和胆碱乙酰转移酶 (ChAT) 的免疫染色检测到前小细胞视前核 (PPa) 侧区的神经元，这些神经元被不透 BBB 的 N-羟基磺基琥珀酰亚胺强烈染色。在 PPa 的室周区，许多神经元摄取了与荧光素偶联的生物素化葡聚糖胺，这是一种逆行轴突示踪剂，注入大细胞视前核 (PM)，表明来自 PPa 到 PM 的神经元连接。与硬骨鱼 PM 同源的哺乳动物室旁核和视上核，接收来自终板血管器 (OVLT) 的主要神经元投射。这些结果强烈表明，PPa 的室周亚群，很可能是 OVLT 的一个组成部分，作为系统信号分子如 Ang II 的功能入口窗口。
