up i n t h e b r a i n ( 1 ) . Among t h e s u b s t a n c e s s t u d i e disopropyl-p-iodo-amphetamine was s e l e c t e d t o measure r e g i o n a l c e r e b r a l blood flow i n man (2,3). p-iodo-amphetamine, a m e t a b o l i t e o f isopropyl-p-iodo-amphetamine i s a l s o t a k e n up i n t h e b r a i n with a high index ( 4 ) . I t was n e c e s s a r y t o s y n t h e s i z e t h i s new tracer w i t h a high s p e c i f i c a c t i v i t y i n o r d e r t o t e s t i t s p r o p e r t i e s .The s p e c i f i c a c t i v i t y a f t e r t h e exchange r e a c t i o n between p-iodo-amphetamine and r a d i o a c t i v e i o d i n e i s always low and t h e r e f o r e we p r e f e r e d t o s y n t h e s i z e t h i s molecule d i r e c t l y u s i n g t h e Sandmeyer r e a c t i o n from r a d i o a c t i v e i o d i n e and p-aminoamphetamine (Scheme 1).
Unit6 de Pharmacologie Chimique INSERM 17, r u e du Fer Moulin 75005 P a r i s , France ABSTRACT W e developed a chromatoqraphic s y s t e m which separates catecholamines and' indolamines a s w e l l as-a l a r g e number of t h e i r met a b o l i t e s ( a c i d s , aminoacids and g l y c o l s ) . Waters R a d i a l Pak columns compressed r a d i a l l y t o a v o i d f o r m a t i o n of c a v i t i e s i n t h e p a c k i n g , were used. These columns must be washed w i t h methanol i n o r d e r t o o b t a i n r e p r o d u c i b l e r e s u l t s when a n i o n -p a i r i n g mobile phase i s employed. The c o n d i t i o n i n g o f t h e columns was n o t a f f e ct e d by washing w i t h t r i e t h y l a m i n e o r v a r i a t i o n s i n r a d i a l p r e s s ure. Good r e s o l u t i o n o f 1 3 samples was o b t a i n e d i n 28 m i n u t e s w i t h a mobile phase composed of 0.1 M KH2P04, 0.1 mM EDTA and 5 mM h e p t a n e s u l f o n i c a c i d i n water and M e OH (85:15), pH = 3 . 6 . Prod u c t s were i d e n t i f i e d w i t h t h e u s e o f a Metrohm 641 e l e c t r o c h emical d e t e c t o r . t i o n o f N A , DA, DOPAC, HVA, 5HT and 5HIAA i n d e p r o t e i n a t e d mouse b r a i n samples.The t e c h n i q u e was used f o r r a p i d , s i m u l t a n e o u s d e t e r m i n a -
Rats were injected with iodoamphetamine synthesized and labeled with 125I or with 125I- isopropyliodoamphetamine , a molecule of established value for the determination of local cerebral blood flow. The blood kinetics, tissue distribution, and brain uptake index for each tracer exhibited practically no differences. Autoradiographic quantification of the local cerebral blood flow, calculated according to the microsphere model, produced identical results for both molecules. However, compared with the values reported for other tracers, our values constituted an underestimation of white matter blood flow and a more real estimation of hippocampal flow. It is concluded from the brain uptake of the derivatives of both amphetamines during the first minutes following their injection that these tracers can be used as a chemical microembolus for the measurement of local cerebral blood flow.
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