[The dopaminergic system and addictions].
OBJECTIVE
All psychoactive substances with a high abuse potential are characterized by altering the mesocorticolimbic dopaminergic neurotransmission system. In this article it is proposed to review the neurobiological mechanisms that comprise the foundation of the development of addiction.


METHODS
The acute drug intake provokes an increase in extracellular dopamine which, in vulnerable individuals, could be the start of the addictive process. Chronic drug use is accompanied by a reduction in the dopaminergic function with the development of neuroadaptive changes in the mesolimbic and mesocortical pathways. In the prefrontal cortex, the changes in dopaminergic function produce an inbalance between receptors D1 and D2, which leads to a predominance of inhibitatory function. Dopaminergic innervation in the amygdala and its interaction with the nucleus accumbens plays an essential role in the conditioning of environmental stimuli, and can trigger the craving and relapse. In drug dependent patients, dopaminergic changes extend from the limbic regions to the associative and sensorimotor striatum, and affect the cortico-striatico-cortical circuits.


CONCLUSIONS
The involvement of the dopaminergic systems is crucial in the development of addiction, from the early phases in which drug use begins as an object-directed instrumental behavior, to the consolidation of the addiction as a compulsive habit, controlled by stimulus-response mechanisms, which progressively invade all aspects of the life of an individual.
Corominas-Roso
M
M
Servicio de Psiquiatría, Hospital General Universitari Vall d'Hebron, Universitat Autònoma de Barcelona, 08035 Barcelona, España. mcoromin@vhebron.net
Roncero
C
C
Bruguera
E
E
Casas
M
M
D004298:Dopamine / Q000502:physiology; D006184:Habits; D006801:Humans; D011954:Receptors, Dopamine / Q000502:physiology*; D019966:Substance-Related Disorders / Q000209:etiology*
D011954:Receptors, Dopamine; D004298:Dopamine