The study of neurotransmitter interactions with PET and SPECT using pharmacological challenge paradigms

Functional brain imaging with positron emission tomography (PET) and single photon emission computerized tomography (SPECT) enables the in vivo study of specific neurochemical processes in the context of normal regulatory mec hanisms and pathophysiological alterations of the brain. By combining these methods with pharmacological challenge-paradigms, the study of functional interactions of different neurotransmitter systems is possible. This review will present data from animal and healthy Volunteer studies as well as fir st data from investigations in different patient populations with regard to this research direction. Especially, interactions of different neurotransm itter systems with the dopaminergic and the cholinergic system will be disc ussed. The database acquired so far confirms existing models of neuronal fe edback circuits, and the first clinical results are consistent with the hyp othesis of an increased dopaminergic responsivity in schizophrenic patients . These results open up new perspectives for a further evaluation of treatm ent response predictors from drug-challenge studies and for the development of new drug treatments for neuropsychiatric disorders.