Neuropharmacological studies with SPECT in neuropsychiatric disorders

The last decade saw a rapid development of single photon emission computed tomography (SPECT) from a tool to assess cerebral blood flow to the stud!: of specific neurotransmitter systems. Because of the relatively long half l ife of SPECT radioisotopes, it is practical to measure the availability of neuroreceptors and transporters in conditions approaching equilibrium. The cost-efficiency of SPECT allowed studies in relatively large samples of pat ients with various neuropsychiatric disorders, We have applied this approac h in studies of dopaminergic, serotonergic, and muscarinergic neurotransmis sion in patients with dementia, extrapyramidal disorders, schizophrenia, an d alcoholism. No simple associations were observed between a single defect in one neurotransmitter system and a certain neuropsychiatric disease. Inst ead, complex dysfunction of several neurotransmitter systems in multiple, p artially connected brain circuits have been implicated. Treatment effects a lso have been characterized. Microdialysis and neurotransmitter depletion s tudies showed that most radioligands and endogenous neurotransmitters compe te for binding at receptors and transporters. Future research directions in clude the assessment of endogenous neurotransmitter concentrations measured by depletion studies and of genetic effects on neuroreceptor and transport er expression. NUCL MED BIOL 27;7:677-682, 2000. (C) 2000 Elsevier Science Inc. All rights reserved.