Brain imaging of schizophrenia--the dopamine hypothesis.

The dopamine hypothesis of schizophrenia was formulated 30 years ago and postulates that the symptoms of schizophrenia are related to an increased central dopaminergic neurotransmission. The two fundamental assumptions that underlay the dopamine hypothesis of schizophrenia have received support from brain imaging studies on the dopamine system. There is a high occupancy of central D2-dopamine receptors in patients that are treated with clinically effective doses of classical antipsychotic drugs and recent studies indicate an abnormal function of the presynaptic dopaminergic neuron. Early reports of elevated postsynaptic D2-dopamine receptors in schizophrenic brains post mortem have, however, not been consistently confirmed by brain imaging studies of young neuroleptic-naïve patients with schizophrenia. Suitable methods are now being developed for brain imaging of the dopamine system in the limbic and neocortical regions that are of central interest in schizophrenia research.