Estimation of baseline dopamine D2 receptor occupancy in striatum and extrastriatal regions in humans with positron emission tomography with [18F] fallypride.

Background: This study examined whether positron emission tomography (PET) studies with [18F] fallypride performed before and after alpha-methyl-para-tyrosine (AMPT) administration can be used to estimate baseline dopamine (DA) D2 receptor occupancy in striatal and extrastriatal regions.

Methods: Six normal subjects underwent PET with [18 F] fallypride before and after administration of AMPT. The DA D2 receptor binding potentials (bp) were calculated with the reference region method. Percent changes in bp in striatal and extrastriatal regions were calculated with both region-of-interest analysis and on a voxel by voxel basis with parametric images of DA D2 receptor levels.

Results: The results of the current study indicate that AMPT treatment significantly increased the bp in the caudate, putamen, ventral striatum, and substantia nigra. A trend level increase was seen in the medial thalamus.

Conclusions: This study demonstrates that PET with [18F] fallypride can be used to estimate baseline DA D2 receptor occupancy in striatal and extrastriatal regions.