Regional analysis of D2 dopamine receptors in Parkinson's disease using SPECT and iodine-123-iodobenzamide.
The goal of this study was to examine the relationship between D2 dopamine receptor density and levodopa dosage, disease duration and dyskinesia in Parkinson's disease (PD).


METHODS
Iodine-123-iodobenzamide SPECT scans were obtained from 14 PD patients and 12 age-matched controls using a three-headed camera in conjunction with MRI and a fiducial-based image registration system to define regions of interest. Basal ganglia/cerebellum counts/voxel ratios in dorsal and ventral head of caudate and anterior and posterior putamen were measured at 30, 60, 120 and 180 min postinjection. As in 11C-raclopride studies, ratios obtained at that time when they asymptomatically approach a maximum value (180 min) were accepted as the best measure of receptor density.


RESULTS
Among PD patients, a trend towards an inverse correlation between regional basal ganglia/cerebellum ratios and levodopa dosage achieved significance in ventral caudate (F = 6.244, p = 0.037); similarly, an inverse correlation between these ratios and disease duration achieved significance in anterior putamen (F = 13.144, p = 0.007). Ratios were significantly lower in anterior putamen in patients with dyskinesia (t = 3.068, p = 0.042).


CONCLUSIONS
In PD, the previously observed inverse correlation between levodopa dosage and D2-receptor density appears to be most prominent in the least dopamine-depleted region, ventral caudate. There may be a genuine effect of disease duration on receptor density in putamen and reduced receptor density in anterior putamen may be associated with dyskinesia.
Nadeau
S E
SE
Geriatric Research, Education and Clinical Center, Department of Veterans Affairs Medical Center, Gainesville, FL 32608-1197.
Couch
M W
MW
Devane
C L
CL
Shukla
S S
SS
D000368:Aged; D000369:Aged, 80 and over; D001549:Benzamides / Q000493:pharmacokinetics; D001921:Brain / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000378:metabolism*; D011759:Pyrrolidines / Q000493:pharmacokinetics; D017448:Receptors, Dopamine D2 / Q000032:analysis*; D012044:Regression Analysis; D015899:Tomography, Emission-Computed, Single-Photon
D001549:Benzamides; D007457:Iodine Radioisotopes; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide