[Neurobiology of addiction to drugs of abuse].

OBJECTIVE: In this review we study drug addiction from a neurobiological point of view, emphasizing the dopamine hypothesis. This is basic to explain how a genetic feature is related with an alteration of this neurotransmitter and can connect with environmental factors to develop the addiction problem.

DEVELOPMENT: Toxic addiction is defined as the physical or psychophysiological dependence on a special chemical substance, whose suppression arouses deprivation symptoms in the person. The study of addiction to different drugs gives us a new approach for knowing the strengthening systems. Because even thought we do not know precisely the nervous mechanism of these substances that cause pleasure, we suppose that they are in the same place as rewarding and strengthening the behaviour mechanisms. In this way the dopamine hypothesis has been developed: in this hypothesis drug addiction is closely connected with a genetic upset of this neurotransmitter, so there is a defect in the reward system. This in turn stimulates the substance abuse that increases the brain s dopamine levels.

CONCLUSION: Knowing the neurobiological mechanisms involved in addiction and its relation with dopamine and the reward system can help us understand that problem and aid the rational development of treatment