Imaging brain function in animals to understand drugs of abuse and potential pharmacotherapies

Brain imaging studies can be used to enhance current understanding of how CNS drugs act. Because the brain is in reality a collection of independent, albeit interconnected, neural organs, identification of sites of brain action are critical to an appraisal of how each drug exerts its different behavioral and physiological effects. For new drugs not yet tested in humans, identification of which neuronal structures are affected by a drug can give clues as to what to expect from the drug if it is eventually exposed to clinical testing. Receptor binding autoradiography, more than any other technique, pinpoints the distribution of those sites at which a given drug acts. When combined with 2-DG autoradiography, the intensity and direction of the action at each of these sites, as well as the impact of these actions on additional sites, can be appreciated. In addition to identification of sites of drug action, brain imaging studies can be used to identify classes of drug action, interactions between drugs, and, perhaps more than any other technique, enhance the appreciation of the similarities and differences between the effects in animals and those in humans. When applied to drugs of abuse, brain imaging studies can be used to help identify key physiological events underlying drug reinforcement as well as those important for various physiological effects of each drug. Armed with such information, brain imaging techniques can play a unique role as one component of an effort to discover pharmacotherapies for drug abuse.