adolescent expression. GRPR is enriched in amygdala and GRPR deficient mice show enhanced fear conditioning with normal spatial learning and no anxiety-like behavior in the water maze and elevated plus maze, respectively (Shumyatsky et al., 2002). Environmental enrichment during adolescence increases GRPR expression and reduces fearfulness (Qian et al., 2008), suggesting that environmental amygdala plasticity during adolescence is in part reflected in GRPR expression and lifelong sensitivity to amygdala fear conditioning. COMT polymorphisms have been implicated in many disorders including addiction (Enoch, 2006), schizophrenia (Tan et al., 2007), aggression (Volavka et al., 2004), and Alzheimer's disease (Serretti et al., 2007). These findings indicate that AE exposure alters expression of neurotransmitter genes in the young adult brain that are associated with psychopathology.
