In vivo autoradiography of radioiodinated (R)-3-quinuclidinyl (S)-4-iodobenzilate [(R, S)-IQNB] and (R)-3-quinuclidinyl (R)-4-iodobenzilate [(R,R)-IQNB]. Comparison of the radiolabelled products of a novel tributylstannyl precursor with those of the established triazene and exchange methods.
Radioiodinated (R,S)-IQNB and (R,R)-IQNB are prepared either from a triazene precursor or using an exchange reaction. In both cases the radiochemical yield is low. The product of the exchange reaction also suffers from having a fairly low specific activity. A new method for preparing radioiodinated (R,S)-IQNB and (R,R)-IQNB from a tributylstannyl precursor has recently been developed. This method is more convenient and much faster than the triazene and exchange methods, and it reliably results in a high radiochemical yield of a high specific activity product. In rat brain, the in vivo properties of the radioiodinated products of the tributylstannyl method are identical to those of the corresponding radioiodinated (R,S)-IQNB and (R,R)-IQNB prepared using the triazene and exchange methods. Dissection studies of selected brain regions show that at 3 h post injection (R,S)-[125I]IQNB prepared by all three methods have indistinguishable % dose g-1 values in all brain regions studied. Autoradiographic comparison of coronal slices through the anteroventral nucleus of the thalamus, through the hippocampus and through the pons at 2 h post injection shows that (R,S)-[125I]IQNB prepared by the triazene and tributylstannyl methods have indistinguishable patterns of binding.
Sood
V K
VK
Department of Radiology, George Washington University Medical Center, Washington, DC 20037, USA.
Lee
K S
KS
Boulay
S F
SF
Rayeq
M R
MR
McRee
R C
RC
Cohen
E I
EI
Zeeberg
B R
BR
He
X S
XS
Weinberger
D R
DR
Rice
K
K
Reba
R C
RC
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism; D007457:Iodine Radioisotopes; D008297:Male; D011813:Quinuclidinyl Benzilate / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism; D014018:Tissue Distribution
D007457:Iodine Radioisotopes; D011813:Quinuclidinyl Benzilate; C040062:3-quinuclidinyl-4-iodobenzilate