title: Synaptic regulation of immediate early gene expression in primary cultures of cortical neurons.
abstract: Neuronal stimulation can rapidly activate several immediate early genes that code for transcription factors. We have used primary cortical cultures to study the regulation of four of these genes, c-fos, c-jun, jun-B, and zif268. Immunocytochemical studies with antibodies to Jun-B, c-Jun, and c-Fos demonstrate intense staining in the nuclei of a subset of cortical neurons in mature cultures (21-25 days in vitro) but not young cultures (3-7 days in vitro). To assess whether this immunoreactivity may be induced by spontaneous synaptic activity that develops with a similar profile, we examined the effects of agents that reduce this synaptic activity. Tetrodotoxin or N-methyl-D-aspartate receptor antagonists suppress basal immunoreactivity to Jun-B and c-Fos, but not c-Jun, indicating that the basal level of c-Jun expression is not dependent on electrical activity. Picrotoxin, an agent that increases synaptic excitation indirectly by blocking inhibitory synaptic currents mediated by gamma-aminobutyric acidA receptors, markedly increases the percentage of neurons displaying immunoreactivity to c-Fos, c-Jun, Jun-B, and Zif268. Northern analysis suggests that the increases in immunostaining induced by picrotoxin are secondary to a rapid increase in mRNA for these proteins. These findings provide evidence for rapid transcriptional regulation of immediate early genes in cortical neurons by synaptic activity.
authors.affiliation: Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
authors.forename: T H
authors.initials: TH
authors.lastname: Murphy
authors.forename: P F
authors.initials: PF
authors.lastname: Worley
authors.forename: Y
authors.initials: Y
authors.lastname: Nakabeppu
authors.forename: B
authors.initials: B
authors.lastname: Christy
authors.forename: J
authors.initials: J
authors.lastname: Gastel
authors.forename: J M
authors.initials: JM
authors.lastname: Baraban
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D004594:Electrophysiology; D005786:Gene Expression Regulation / Q000187:drug effects; D016762:Genes, fos; D016758:Genes, jun; D007158:Immunologic Techniques; D009474:Neurons / Q000502:physiology*; D010852:Picrotoxin / Q000494:pharmacology; D013194:Staining and Labeling; D013569:Synapses / Q000502:physiology*
chemical_list: D010852:Picrotoxin