Converging cellular processes for substances of abuse: endogenous morphine.

: Human and invertebrate tissues have the ability to synthesize morphine, making it an endogenous chemical messenger. Given this new insight we sought to investigate whether substances of abuse have the ability to interact with endogenous morphine processes. Moreover we have shown that cocaine, alcohol and nicotine significantly enhance (125)I-trace labeled morphine release from invertebrate ganglia and human white blood cells. These data and newer research contribute to an evolving hypothesis linking the reinforcing and addictive properties of a variety of drugs of abuse to convergent mechanisms, involving endogenous morphine signaling and establish an opiate foundation as a unifying principle by which we may advance our understanding of polymodal drug abuse mechanisms.