不同高渗刺激对下丘脑视上核和室旁核神经元功能状态的影响

视上核和室旁核是下丘脑中两个与渗透压感受、加压素分泌以及水平衡调节密切相关的核团。为了搞清楚这两个核团在不同刺激条件下的激活状态和反应特性,本文采用慢性和急性渴觉刺激模型,免疫组化和ELISA检测相结合的方法对视上核和室旁核内的Fos表达以及血清加压素水平进行了测定。慢性刺激组动物给予2% NaCl盐水持续2d,而急性刺激组动物皮下直接注射2mol/L的NaCl盐水2.5ml,两组动物的进食保持正常。结果表明,这两种不同的刺激方式引发的Fos表达模式基本相似,视上核、室旁核、下丘脑外侧区以及正中视前区、穹窿下器和终板血管下器等区都检测到大量的Fos阳性胞核。但Fos染色的深浅程度和Fos胞核的数量却在两组之间有明显的差异:急性组胞核浓染,数量多;慢性组胞核淡染,数量少。ELISA检测的结果与此相反,急性组动物血清中加压素的水平很低,与对照组没有明显差异;而慢性组动物血清中的加压素水平很高,几乎是对照组的2倍。以上结果提示,下丘脑神经元的激活和分泌功能与刺激方式密切相关,选择单一刺激模式、单一指标来揭示和衡量其功能状态是缺乏说服力的。

The effect of differential hypertonic stimuli on the functional status of supraoptic nucleus and paraventricular nucleus in hypothalamus

Supraoptic nucleus (SON) and paraventricular nucleus (PVN) are two hypothalamic nuclei essentially involved in osmolarity sensing, vasopressin secretion and subsequent regulation of water balance. To clearly understand the activating and functioning properties of these two nuclei under differential stimuli, we employed chronic and acute thirsty animal models and examined the expression of Fos in neurons and the concentration of vasopressin in blood by immunohistochemical staining and ELISA assay, respectively. Rats were given access to food and a 2% NaCl solution, but not water for 48 h to induce chronic thirst. 2.5 ml of 2 mol/L NaCl solution was s.c injected to make acute thirsty rats. The results showed that the expression patterns of Fos under these two stimuli were quite similar, with preferential expressing in SON, PVN, lateral hypothalamic area, median preoptic nucleus, subfornical nucleus and organum vasculosum of the lamina terminalis. The expressing intensity and the number of Fos positive nuclei were, however, quite different between these two groups, with more densely-stained Fos and higher number of Fos positive nuclei in the acute group. By contrast, the vasopressin level in chronic group was significantly higher than that in control, while its level in acute group was nearly the same to control. These results suggest that the level of vasopressin in blood is not synchronized with Fos expression in SON and PVN, and it is less persuasive to choose the sole stimulus and the sole parameter to disclose and evaluate the activating and secreting properties of hypothalamic neurons.