Journal
JOURNAL OF CEREBRAL BLOOD FLOW AND METABOLISM
Volume 21, Issue 9, Pages 1034-1057Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1097/00004647-200109000-00002
Keywords
dopamine; D-2 receptor; nucleus accumbens; partial volume effects; positron emission tomography; [C-11]Raclopride; ventral striatum
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Funding
- NIDA NIH HHS [R01-DA10219-01] Funding Source: Medline
- NIMH NIH HHS [R01-MH54192, K02 MH01603-0] Funding Source: Medline
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Dopamine transmission in the ventral striatum (VST), a structure which includes the nucleus accumbens. ventral caudate, and ventral putamen, plays a critical role in the pathophysiology of psychotic states and in the reinforcing effects of virtually all drugs of abuse. The aim of this study was to assess the accuracy and precision of measurements of D-2 receptor availability in the VST obtained with positron emission tomography on the high-resolution ECAT EXACT HR+ scanner (Siemens Medical Systems, Knoxville, TN, U.S.A.). A method was developed for identification of the boundaries of the VST on coregistered high-resolution magnetic resonance imaging scans. Specific-to-nonspecific partition coefficient (V-3) and binding potential (BP) of [C-11]raclopride were measured twice in 10 subjects, using the bolus plus constant infusion method. [C-11]Raclopride V-3 in the VST (1.86 +/- 0.29) was significantly lower than in the dorsal caudate (DCA, 2.33 +/- 0.28) and dorsal putamen (DPU, 2.99 +/- 0.26), an observation consistent with postmortem studies. The reproducibility of V-3 and BP were appropriate and similar in VST (V-3 test-retest variability of 8.2% +/- 6.2%. intraclass correlation coefficient = 0.83). DCA (7.7% +/- 5.1%, 0.77). DPU (6.0% +/- 4.1%, 0.71), and striatum as a whole (6.3% +/- 4.1%, 0.78). Partial volume effects analysis revealed that activities in the VST were significantly contaminated by counts spilling over from the adjacent DCA and DPU: 70% +/- 5% of the specific binding measured in the VST originated from D-2 receptors located in the VST, whereas 12% +/- 3% and 18% +/- 3% were contributed by D-2 receptors in the DCA and DPU, respectively. Thus, accuracy of D-2 receptor measurement is improved by correction for partial voluming effects. The demonstration of an appropriate accuracy and precision of D2 receptor measurement with [C-11]raclopride in the VST is the first critical step toward the use of this ligand in the study of synaptic dopamine transmission at D2 receptors in the VST using endogenous competition techniques.
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