后叶加压素在下丘脑的分布和释放途径及失水对正中隆起中后叶加压素的影响

我们用免疫细胞化学方法(ICC)对大白鼠下丘脑中加压素(VP)免疫反应阳性的神经元作了较详细研究。观察到VP阳性神经元存在于下丘脑室旁核(PVN)各亚核、视上核(SON)、交叉上核(SCN)、室周核(PN)及一些附属核团,包括环状核(CN)、交叉后核(RCN)、下丘脑外侧核(HLN)、穹窿周围核(PFN)。且发现一特殊的VP阳性胞体聚集区—很可能是多巴胺神经元聚集区A_(14)中的细胞,位于第三脑室侧壁中1/3段两侧,腹内侧核背侧。本文首次观察到在PVN和SON之间有VP阳性的神经纤维相联系。ICC和免疫电镜研究进一步证明在正中隆起外带存在VP阳性纤维,含大颗粒囊泡的VP末梢紧邻门脉毛细血管。将HRP注入第四脑室用HRP逆行追踪与ICC方法相结合,在PVN中观察到双标细胞,与直接用ICC法所见VP阳性轴突伸入第三脑室腔的结果一致。说明PVN中存在接触脑脊液神经元。干渴动物正中隆起的内、外带中的VP免疫反应明显减弱。

DISTRIBUTION AND RELEASING PATHWAYS OF VASOPRESSIN IN HYPOTHALAMUS AND THE INFLUENCE OF DEHYDRATION ON VASOPRESSIN IMMUNOREACTIVITY OF THE MEDIAN EMINENCE IN THE RAT

The distribution of vasopreessin (VP) immunoreactive neurons in the hypothalamus of the rat was studied in detail by immunocytochemical (ICC) method. VP-containing neurons have been observed in various hypothalamic nuclei: all subdivisions of paraventricular nucleus(PVN); supraoptic nucleus(SON); suprachiasmatic nucleus (SCN); periventricular nucleus(PN) and some of hypothalamic accessory nuclei including circle nucleus, retrochiasmatic nucleus, lateral hypothalamic nucleus, perifornical nucleus. Furthermore, special VP-positive neurons possibly in A14 region have been observed. It appeared as sphere shape with densely packed cells close to the middle third of the lateral wall of the third ventricle, dorsal to the ventromedial hypothalamic nucleus and ventral to the medial paraventricular nucleus. VP-positive fibers between PVN and SON were observed for the first time. It was identified by light and immunoelectron microscopy that the VP-fibers project to the external zone of median eminence and the terminals containing large granular vesicles end on the basal membrane of portal capillaries. This indicated that VP may be directly released into the portal blood of median eminence and therefore control the hormone secretion of anterior pituitary gland. Using HRP retrograde tracing combined with ICC technique, double labeled cells in the PVN have been observed after HRP were injected into the cavity of the fourth ventricle. The result was consistent with that of ICC method by which VP-positive axons entering into the lumen of the third ventricle were demonstrated. It was identified that there were cerebro-spinal fluid-contacting neurons in the PVN, which may release VP into the cerebro-spinal fluid. The dehydrating test indicated that the VP immunoreactivity in median eminence of dehydrated rats was dramatically decreased.