Despite numerous revisions and reformulations, dopamine (DA) hypothesis of schizophrenia remains a pivotal neurochemical
hypothesis of this illness. The aim of this review is to expose and discuss findings from positron emission tomography (PET) or singlephoton-
emission computed tomography (SPECT) studies investigating DA function in the striatum of medicated, drug-naïve or drug-free
patients with schizophrenia and in individuals at risk compared with healthy volunteers.
DA function was studied at several levels: i) at a presynaptic level where neuroimaging studies investigating DOPA uptake capacity
clearly show an increase of DA synthesis in patients with schizophrenia; ii) at a synaptic level where neuroimaging studies investigating
dopamine transporter availability (DAT) does not bring any evidence of dysfunction; iii) and finally, neuroimaging studies investigating
DA receptor density show a mild increase of D2 receptor density in basic condition and, an hyperreactivity of DA system in dynamic
These results are discussed regarding laterality, sub-regions of striatum and implications for the at-risk population. Striatal DA abnormalities
are now clearly demonstrated in patients with schizophrenia and at risk population and could constitute an endophenotype of
schizophrenia. Subtle sub-clinical striatal DA abnormalities in at risk population could be a biomarker of transition from a vulnerability
state to the expression of frank psychosis.