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.
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Received: 11 March 1996 / Accepted: 24 July 1996
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Ludwig, M., Johnstone, L., Neumann, I. et al. Direct hypertonic stimulation of the rat supraoptic nucleus increases c-fos expressionin glial cells rather than magnocellular neurones. Cell Tissue Res 287, 79–90 (1996). https://doi.org/10.1007/s004410050733
- Key words: Hypertonic stimulation
- Glial fibrillary acidic protein
- Vasopressin neurones
- Oxytocin neurones
- Rat (Spraque Dawley)