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SPECT tracer [ 123 I]IBZM has similar affinity to dopamine D2 and D3 receptors
Author(s) -
Videbæk Charlotte,
Toska Karen,
Scheideler Mark A.,
Paulson Olaf B.,
Moos Knudsen Gitte
Publication year - 2000
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/1098-2396(20001201)38:3<338::aid-syn13>3.0.co;2-n
Subject(s) - radioligand , receptor , dopamine receptor d2 , dopaminergic , dopamine receptor , dopamine , chemistry , dopamine receptor d3 , medicine , neuroscience , biochemistry , biology
Emission tomography investigations of the pathophysiological involvement of the cerebral dopaminergic transmitter system in the living human brain relies heavily on a careful selection of the most suitable radioligand. In recent years, many clinical studies have employed [ 123 I]IBZM in SPECT studies. The aim of the present study was to characterize the binding of IBZM to dopaminergic receptor subtypes as a means of elucidating which receptor subtypes are visualized and examined by [ 123 I]IBZM. The affinity of IBZM for each of the major human dopamine receptors (D1, D2 short , D3, D4 4.2 , and D5 receptor) was determined by competitive radioligand binding assay using membranes prepared from clonal cell lines expressing the different subtypes. Radioligands with high affinity for the D1 A and D5 receptors ([ 3 H]SCH‐23390), dopamine D2 short and D4 4.2 receptors ([ 3 H]Spiroperidol), and dopamine D3 receptor ([ 3 H]7‐OH‐DPAT) were used to measure specific binding. Corresponding unlabeled displacing ligands for determination of nonspecific binding were employed. Assays were performed at 25°C. These experiments show that for IBZM K i values were 1.6 nM for dopamine D2 s receptors and 2.2 nM for dopamine D3 receptors. There was no binding of IBZM to D1 A , D5, or D4 4.2 receptors. In conclusion, when [ 123 I]IBZM is used as SPECT tracer, the studies reflect dopaminergic D2 as well as D3 receptor binding. Synapse 38:338–342, 2000. © 2000 Wiley‐Liss, Inc.