DOPAMINE-D2 RECEPTOR SCINTIGRAPHY WITH I-123 IBZM

Iodobenzamide, a ligand of D2 dopamine receptors (RD2), was labeled with iodine 123 and injected for imaging purposes into 3 groups of subjects. No adverse effects was observed. Group 1 (n = 3): normal; group 2 (n = 5): 4 patients with Parkinson's disease and 1 patient with Alzheimer's disease; group 3 (n = 6): patients treated with dopaminergic agonists (L-dopa, bromocriptine) or antagonist (pipamperone). The activity was distributed throughout the body, with a transitory pulmonary phase followed by hepato biliary excretion. The mean brain uptake was 3 per cent. Three types of tomographic images of the brain were obtained : type I : exclusive uptake in the basal ganglia observed in normal subjects (group 1) and Parkinson's disease (group 2) ; type II : cortical activity without visualisation of the basal ganglia in 5 of the 6 treated patients (group 3) ; type III : uptake in the basal ganglia associated with cortical activity in Alzheimer's disease. The ratio of the mean activity in the striatum to that in the cerebellum was increased in untreated Parkinson's disease and decreased in Alzheimer's disease. These results confirm the feasibility and specificity of investigating neurlogical and psychiatric disorders with RD2 scintigraphy using a single-photon-emitting radio-ligand.