Repeated recall and PKMζ maintain fear memories in juvenile rats.

We examined the neural substrates of fear memory formation and maintenance when repeated recall was used to prevent forgetting in young animals. In contrast to adult rats, juveniles failed to show contextual fear responses at 4 d post-fear conditioning. Reconsolidation sessions 3 and 6 d after conditioning restored contextual fear responses in juveniles 7 d after initial training. In juveniles that received reconsolidation sessions, protein kinaseMzeta (PKM zeta) increased in the amygdala, but not in the hippocampus. These data suggest that repeated reminders and increased PKM zeta maintain fear responses in juvenile animals that otherwise would not exhibit this behavior.