POMC and Anxiety: Diaz Heijtz et al. (2011) showed that GF mice exhibited less anxiety-like behavior than conventional mice fed in a specific pathogen-free (SPF) environment. However, after the adult GF mice were transferred to the SPF environment, there was no significant increase or decrease in anxiety-like behavior, but the anxiety-like behavior of their offspring returned to normal (Diaz Heijtz et al., 2011). It has also been shown that ACTH and corticosterone levels under restraint stress are different in GF mice and SPF mice (Sudo et al., 2004).