Direct hypertonic stimulation of the rat supraoptic nucleus increases c-fos expressionin glial cells rather than magnocellular neurones

M Ludwig, L E Johnstone, I Neumann, R Landgraf, J A Russell

Research output: Contribution to journalArticlepeer-review

Abstract

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.

Original languageEnglish
Pages (from-to)79-90
Number of pages12
JournalCell and tissue research
Volume287
Issue number1
Publication statusPublished - Jan 1997

Keywords

  • Animals
  • Cholecystokinin
  • Female
  • Gene Expression
  • Glial Fibrillary Acidic Protein
  • Immunoenzyme Techniques
  • In Situ Hybridization
  • Neuroglia
  • Neurons
  • Proto-Oncogene Proteins c-fos
  • Rabbits
  • Rats
  • Rats, Sprague-Dawley
  • Saline Solution, Hypertonic
  • Supraoptic Nucleus

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