This Program Project Grant supports a series of highly interactive and multidisciplinary studies aimed at delineating the molecular and cellular mechanisms underlying opiate and cocaine addiction. Each research area represents an integration of molecular, biochemical, electrophysiological, neuropharmacological, neuroanatomical, and behavioral levels of analysis, which are focused on the roles played by two transcription factors, CREB and ΔFosB, and their target genes, in the brain's reward pathways in drug action.