C-FOS INDUCTION BY ESTROGEN IN SPECIFIC RAT-BRAIN AREAS

The present study was undertaken to determine whether estrogen modulates the expression of the c-fos gene in the CNS of rats. The analysis of the levels of c-fos mRNA was performed by slot blot assay. Administration of estradiol to ovariectomized rats determined a rapid and transient increase in the levels of c-fos mRNA in rat mid-brain and hippocampus, but not in the cerebellum (a brain area which does not express estrogen receptors). Such a change in the levels of c-fos mRNA was not observed after administration of alpha-estradiol or other steroid hormones. The presence of an estrogen responsive element-like sequence, revealed in the 5' flanking region of the murine c-fos gene, strengthens the hypothesis that c-fos gene transcription is directly enhanced by the interaction of the estrogen receptor complex with the promoter region of the proto-oncogene.