NPY and drug dependence: In fact, evidence indicates that the activity of the NPY system affects motivated behaviors, as demonstrated by studies showing that alcohol-preferring rats display lower NPY levels in the hippocampus, amygdala, and frontal cortex than non-preferring rats (Ehlers et al., 1998), whereas increased production of NPY in the amygdala of transgenic rats prevents escalated ethanol intake in a model of drug dependence (Thorsell et al., 2007).