THE NEUROBIOLOGY OF DRUG-ADDICTION

Animal models have begun to provide insights into the neurobiological basis of reinforcement in drug addiction. The reinforcing effects of i ndirect sympathomimetics such as cocaine and amphetamine appear to dep end on release of dopamine in the terminal fields of the mesocorticoli mbic dopamine system. The acute reinforcing effects of opiates involve not only an activation of dopamine, but also dopamine-independent ele ments in the terminal regions of the mesocorticolimbic dopamine system . Nicotine's reinforcing effects may involve both dopaminergic and opi oid peptidergic systems. Ethanol's reinforcing effects may result from multiple neurotransmitter interactions including gamma-aminobutyric a cid, glutamate, dopamine, opioid peptides, and serotonin. Subtle chang es in neurochemical function and signal transduction and transcription mechanisms in sensitive neuronal elements in the extended amygdala ma y be mediators of chronic drug action that lead to vulnerability to re lapse and may provide exciting insight into the neuroadaptations assoc iated with drug addiction.