Imaging of dopaminergic transmission in neuropsychiatric disorders

The present review addresses recent advances in imaging dopaminergic neurotransmission in vivo. Radiotracer imaging with positron emission tomography and single-photon emission computed tomography can be used to measure pre-, post- and intrasynaptic aspects of dopaminergic transmission. The presynaptic sites can be labelled with radiotracers for the dopamine transporter or the synthetic enzyme aromatic L-amino acid decarboxylase. The postsynaptic sites can be labelled with radiotracers for the dopamine D1 receptor or the dopamine D2 receptor. Estimates of synaptic endogenous dopamine release are made indirectly by measurements of the displacement of receptor tracers by dopamine. Agents are used that either release (e.g. amphetamine) or deplete (e.g. alpha -methyl-paratyrosine, an inhibitor of tyrosine hydroxylase) dopamine tissue stores. Functional magnetic resonance imaging and positron emission tomography can provide measures of the effect of changes in dopaminergic transmission on neuronal function, as indexed by a change in regional cerebral blood flow, oxygen utilization or glucose metabolism. Magnetic resonance spectroscopy can provide measures of the effect of changes in dopaminergic transmission on the concentration of various neurochemical substances in cerebral tissue. Examples of recent applications of these imaging techniques in some neuropsychiatric diseases are provided. Curr Opin Psychiatry 14:227-239. (C) 2001 Lippincott Williams & Wilkins.