Ludwig M, Johnstone L E, Neumann I, Landgraf R, Russell J A
Department of Physiology, University Medical School, Teviot Place, Edinburgh EH8 9AG, UK.
Cell Tissue Res. 1997 Jan;287(1):79-90. doi: 10.1007/s004410050733.
We investigated whether hypertonicity acts directly on supraoptic neurones to activate c-fos expression. Hypertonic artificial cerebrospinal fluid was infused into the supraoptic nucleus (SON) via a microdialysis probe implanted 24 h previously. The rats were decapitated after 90 min for immunohistochemistry with a Fos protein antibody. Direct hypertonic stimulation increased Fos protein expression in glial cells, identified by glial fibrillary acidic protein immunoreactivity, but not in magnocellular neurones. Similarly, with in situ hybridisation c-fos mRNA expression was predominantly seen in glial cells. Fos expression in SON neurones was stimulated by systemic hypertonicity even with a microdialysis probe in the SON, and magnocellular neurones expressed Fos after direct microinjection of cholecystokinin-8S into the SON. Thus, while direct hypertonic stimulation of SON neurones activates secretion of vasopressin and oxytocin, the c-fos gene is not activated, unlike following systemic hypertonic stimulation. This indicates that excitation of neuronal electrical and secretory activity does not necessarily lead to activation of the c-fos gene. Activation of c-fos expression in glial cells by direct hypertonic stimulation may reflect their role in regulating brain extracellular fluid composition.
我们研究了高渗状态是否直接作用于视上核神经元以激活c-fos表达。通过24小时前植入的微透析探针将高渗人工脑脊液注入视上核（SON）。90分钟后断头，用Fos蛋白抗体进行免疫组织化学检测。直接高渗刺激增加了由胶质纤维酸性蛋白免疫反应性鉴定的胶质细胞中Fos蛋白的表达，但在大细胞神经元中未增加。同样，通过原位杂交，c-fos mRNA表达主要见于胶质细胞。即使在视上核中有微透析探针，全身高渗状态也能刺激视上核神经元中的Fos表达，并且在将胆囊收缩素-8S直接微量注射到视上核后，大细胞神经元表达Fos。因此，虽然对视上核神经元的直接高渗刺激会激活血管加压素和催产素的分泌，但与全身高渗刺激后不同，c-fos基因未被激活。这表明神经元电活动和分泌活动的兴奋不一定会导致c-fos基因的激活。直接高渗刺激激活胶质细胞中的c-fos表达可能反映了它们在调节脑细胞外液成分中的作用。
