ABSTRACT
The cerebral distribution of the positron-emitting agent [1-11C]beta-(3,4-dihydroxyphenyl)-D,L-alpha-alanine ([11C]DOPA) was studied after intravenous injection in rats pretreated with the peripheral decarboxylase inhibitor, carbidopa. Within 15 min of injection the accumulation of carbon-11 was almost twice as high in cortical areas and cerebellum as in the striatum and the brain stem. After destruction of catecholamine-containing nerve endings with 6-hydroxydopamine, the level of carbon-11 in the striatum was higher than in rats not treated with this neurotoxin. Pretreatment of rats with haloperidol or L-DOPA did not change the distribution pattern of carbon-11. Without pretreatment with carbidopa a uniform distribution of the label in the brain was observed. We suggest that [11C]DOPA is a potentially useful agent for external detection with positron imaging systems in patients and large animals of brain regions rich in the enzyme dopa-decarboxylase. (EC 4.1.1.26).
Subject(s)
Brain/diagnostic imaging , Carbon Radioisotopes/metabolism , Dihydroxyphenylalanine/metabolism , Animals , Brain/metabolism , Brain Stem/metabolism , Carbidopa/administration & dosage , Carbon Radioisotopes/blood , Cerebellum/metabolism , Corpus Striatum/metabolism , Dihydroxyphenylalanine/blood , Hydroxydopamines/administration & dosage , Male , Occipital Lobe/metabolism , Premedication , Radionuclide Imaging , Rats , Receptors, Cholinergic/drug effects , Receptors, Dopamine/metabolismABSTRACT
Carbon-11 (t1/2 equals 20.4 min, beta-+) labelled DL-alpha-phenylalanine and DL-alpha-phenylglycine were administered intravenously to rats and the distribution of the radioactive amino acids over pancreas, liver, spleen, kidneys and blood was measured after several time intervals. From these results the ratios of the concentration in pancreas and liver were calculated and compared with the corresponding ratios from the literature for some 18-F-labelled aromatic amino acids and L-selenomethionine-75-Se. On the basis of this study it appears that DL-alpha-phenylglycine-1-11-C, in spite of a small percentage of the administered dose reaching the pancreas, and DL-alpha-phenylalanine-1-11-C are better suited to pancreas scintigraphy than L-selenomethionine-75-Se.
