Transitions in infant learning are modulated by dopamine in the amygdala.

Behavioral transitions characterize development. Young infant rats paradoxically prefer odors that are paired with shock, but older pups learn aversions. This transition is amygdala and corticosterone dependent. Using microarrays and microdialysis, we found downregulated dopaminergic presynaptic function in the amygdala with preference learning. Corticosterone-injected 8-d-old pups and untreated 12-d-old pups learned aversions and had dopaminergic upregulation in the amygdala. Dopamine injection into the amygdala changed preferences to aversions, whereas dopamine antagonism reinstated preference learning.