PPARA and Anxiety: While there are some important differences between the PPAR subtypes in terms of tissue expression, endogenous and synthetic ligands and physiological roles, all three subtypes of PPARs are expressed in brain regions that are commonly implicated in pain, anxiety and cognition such as the amygdala [18], PFC [18,19,20], hippocampus [10,19] and periaqueductal grey (PAG) [21].