VISUAL-STIMULATION REGULATES THE EXPRESSION OF TRANSCRIPTION FACTORS AND MODULATES THE COMPOSITION OF AP-1 IN VISUAL-CORTEX

It is believed that long-term changes in neuronal function are orchest rated by transcription factors, such as AP-1 and ZIF 268, which are in turn regulated by synaptic stimulation. To further our understanding of the functional effects of such expression, we have examined the DNA -binding activities of both AP-1 and ZIF 268 by way of electrophoretic mobility shift assays (EMSA) on nuclear extracts from visual cortices of rats treated with selective light exposure. Visual stimulation aft er dark rearing increased the DNA-binding activities of both AP-1 and ZIF 268 to their highest levels within 2 hr. ZIF 268 thereafter droppe d to levels similar to that observed in naive animals, whereas AP-1 DN A-binding activity continued to remain elevated even after 24 hr of st imulation. The components of the AP-1 complex, when assessed by EMSA-s upershift analysis, showed considerable variability under different co nditions of exposure. FosB and JunD were the major constituents of AP- 1 in both naive and dark-reared animals. Brief visual stimulation (2 h r) added c-Fos, c-Jun, and JunB to this complex, whereas prolonged sti mulation (6-24 hr) reduced c-Fos and c-Jun levels significantly, leavi ng only FosB, JunB, and JunD as the major components of AP-1. These re sults suggest that transcriptional control by AP-1 may be generated by selective combinatorial interactions of different members of the Fos and Jun families and that are guided by activity-dependent processes.