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Previous neurochemical and behavioural studies show that tyrosine depletion using a nutritionally balanced tyrosine-free amino acid mixture attenuates the dopamine-releasing and psychostimulant properties of amphetamine. Here we investigate the effect of a tyrosine-free amino acid mixture on striatal binding of [(11)C]raclopride, and amphetamine-induced [(11)C]raclopride displacement, using positron emission tomography in the rat. Rats were scanned for 60 min after an i.v. injection of approximately 11 MBq [(11)C]raclopride using a quad-HIDAC system. Amphetamine (2 mg/kg i.p., 30 min prior to scan) caused a 12% reduction in [(11)C]raclopride distribution volume ratio (DVR) compared to saline-injected controls. The tyrosine-free amino acid mixture (1 g/kg i.p.) caused a small (+7%) but statistically insignificant increase in [(11)C]raclopride DVR and attenuated, although it did not fully block, the amphetamine-induced reduction. These data are in keeping with previous neurochemical, immunocytochemical, and behavioural studies showing that tyrosine-free amino acid mixtures reduce dopamine function and offer promise for future PET studies testing the effect of tyrosine-depleting paradigms on dopamine release in humans.

Original publication

DOI

10.1002/syn.10285

Type

Journal article

Journal

Synapse

Publication Date

02/2004

Volume

51

Pages

151 - 157

Keywords

Amino Acids, Amphetamine, Analysis of Variance, Animals, Brain Mapping, Carbon Isotopes, Carbon Radioisotopes, Central Nervous System Stimulants, Cerebellum, Corpus Striatum, Dopamine Antagonists, Male, Models, Animal, Raclopride, Rats, Rats, Sprague-Dawley, Tomography, Emission-Computed, Tyrosine