GLS2 and heroin dependence: These distinct, intrinsic cingulate circuit-behavioral associations are reflective of both the multi-faceted nature of dependence and the key role of the cingulate cortex in manifestations of different behavioral aspects of heroin dependence (i.e. escalation score and naloxone-induced increases in SA) in intravenously self-administered heroin-exposed rats using a LgA and ShA model.