Induction of the c-fos proto-oncogene in rat amygdala during unconditioned and conditioned fear.

Induction of the nuclear proto-oncogene c-fos in rat amygdala was investigated 30-40 min following the presentation of mild footshocks (unconditioned fear) or of contextual cues associated with similar footshocks 24 h earlier (conditioned fear). Initially, it was found that handling rats for the first time elevated c-fos mRNA levels, but this response could be blocked completely by repeated handling. Unconditioned and conditioned fear both elevated amygdala c-fos mRNA dramatically above control levels.