CRHR1 and Anxiety: For example, when exposed to the short, winter photoperiods associated with the transition from solitary to group living in the wild, meadow voles undergo changes in CRF (corticotropin-releasing factor) receptor densities, glucocorticoid secretion, behavioral indicators of anxiety, and aggression (Ossenkopp et al., 2005; Beery et al., 2014; Anacker et al., 2016).