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- Title
Further evaluation of the carbon11-labeled D<sub>2/3</sub> agonist PET radiotracer PHNO: Reproducibility in tracer characteristics and characterization of extrastriatal binding.
- Authors
Egerton, Alice; Hirani, Ella; Ahmad, Rabia; Turton, David R.; Brickute, Diana; Rosso, Lula; Howes, Oliver D.; Luthra, Sajinder K.; Grasby, Paul M.
- Abstract
[11C]-(+)-PHNO is a new dopamine D2/3 receptor agonist radiotracer which has been successfully used to measure D2/3 receptor availability in experimental animals and man. Here we report in vivo evaluation in the rat of the biodistribution, metabolism, specificity, selectivity, and dopamine sensitivity of carbon11-labeled PHNO ([11C]-3-PHNO) produced by an alternative radiochemical synthesis method. [11C]-3-PHNO showed rapid metabolism and clearance from most peripheral organs and tissues. [11C]-3-PHNO, but not its polar metabolite, readily crossed the blood-brain barrier and showed high levels of uptake in the D2/3-rich striatum. Pretreatment with unlabeled PHNO and the D2/3 receptor antagonist raclopride indicated that binding in the striatum was specific and selective to D2/3 receptors. PET studies in anesthetized rats revealed significant reductions in [11C]-3-PHNO binding in the striatum following amphetamine administration, indicating sensitivity to increases in endogenous dopamine concentrations. D2/3 antagonist pretreatment additionally indicated moderate levels of [11C]-3-PHNO specific binding in several extrastriatal brain areas-most notably the olfactory bulbs and tubercles, thalamus, and hypothalamus. Of particular interest, approximately 30% of [11C]-3-PHNO signal in the cerebellum-a region often used as a 'low-binding' reference region for PET quantification-was attributable to specific signal. These data demonstrate that [11C]-3-PHNO shows similar tracer characteristics to [11C]-(+)-PHNO, but additionally indicate that radiolabeled PHNO may be used to estimate D2/3 receptor availability in select extrastriatal brain regions with PET. Synapse 64:301-312, 2010. © 2009 Wiley-Liss, Inc.
- Publication
Synapse, 2010, Vol 64, Issue 4, p301
- ISSN
0887-4476
- Publication type
Article
- DOI
10.1002/syn.20718