N-(llC) methyl, N-(methyl-1 propyl), (chloro-2 phenylj-1 isoquinoleine carboxamide-3 (PK 11195) o r ( l l C ) MPCI was synthetized in a short time (45 min) and high s p e c i f i c a c t i v i t y (769 Ci/mmol) for the positron emission tomography of peripheral benzodiazepine receptors in heart, kidney and brain. The precursor used was the N-desmethyl MPCI (PCI). The radioactive reagent was the ( l k ) methyl iodide obtained from nuclear reaction 14N ( p , a ) 11C vit: 11CO2 and 11CH30H. The chemical p u r i t y of the end-product was checked, a f t e r HPLC p u r i f ication, by chemical ionisation mass spectrometry i n the para1 l e l synthesis of cold MPCI. The methylation, reversed phase HPLC p u r i f i c a t i o n , evaporation times were 10, 6 min respectively so t h a t s t e r i l e and i s o t o n i c i n j e c t a b l e solution o f ( l k ) MPCI ready f o r use may be obtained, i n l e s s t h a n 45 min a f t e r the end of nuclear bombardment.

No abstract