This article summarizes the achievements that have been accumulated about the role of c-
Fos as a transcription factor and as a functional marker of activated neurons. Since its
discovery, more than a decade ago, as an inducible immediate-early gene encoding a
transcription factor, or third messenger, involved in stimulus-transcription coupling and
mediation of extracellular signals to long-term changes in cellular phenotype, c-fos became
the most widely used powerful tool to delineate individual neurons as well as extended …