Housing in an enriched environment can increase adrenal gland size (Moncek et al., 2004) and circulating glucocorticoid levels (Benaroya-Milshtein et al., 2004). However, environmental enrichment increases differentiation and survival of new neurons (van Praag et al., 1999) and buffers against aged-related decreases in neurogenesis (Kempermann et al., 2002) in adult mice. Enriched environment living also rescues stress-induced decreases in cell proliferation, neuronal differentiation and survival of new neurons in the adult rat (Veena et al., 2009a; 2009b). Again, this suggests some protective mechanism of enriched environment living that allows for neuronal growth despite elevated glucocorticoid levels.
