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[ 3 H]‐5‐carboxamidotryptamine labels 5‐HT 1D binding sites in bovine substantia nigra
Author(s) -
Nowak Henry P.,
Mahle Cathy D.,
Yocca Frank D.
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb13750.x
Subject(s) - substantia nigra , radioligand , binding site , radioligand assay , 5 ht receptor , chemistry , receptor , stereochemistry , serotonin , biochemistry , biophysics , microbiology and biotechnology , biology , endocrinology , dopamine , dopaminergic
1 [ 3 H]‐5‐hydroxytryptamine (5‐HT) has been shown to radiolabel at least five types of 5‐HT binding sites in mammalian brain tissue, 5‐HT 1A , 5‐HT 1B , 5‐HT 1C , 5‐HT 1D and 5‐HT 1E (Frazer et al. , 1990). Selective masking of 5‐HT 1A and 5‐HT 1C receptors, has uncovered binding sites which display both high (5‐HT 1D ) and low (5‐HT 1E ) affinity for 5‐carboxamidotryptamine (5‐CT). By utilizing [ 3 H]‐5‐CT we have eliminated a portion of the complex binding (5‐HT 1E ) seen when [ 3 H]‐5‐HT is used as a radioligand. 2 [ 3 H]‐5‐CT binding to 5‐HT 1D sites in bovine substantia nigra was rapid, reversible and saturable, displaying high affinity ( K d = 0.38 ± 0.04 n m ) and low non‐specific binding (> 90% specific binding). 3 In bovine substantia nigra, [ 3 H]‐5‐CT labelled an equivalent number of binding sites to [ 3 H]‐5‐CT (403 ± 18 and 362 ± 20 fmol mg −1 protein, respectively) and binding was sensitive to guanine nucleotides. 4 A linear correlation ( r 2 = 0.99) existed between the potency of compounds to displace [ 3 H]‐5‐HT and [ 3 H]‐5‐CT in bovine substantia nigra. 5 Therefore, [ 3 H]‐5‐CT is a novel radioligand for the examination of 5‐HT 1 ‐like binding sites, which under proper experimental conditions can be used to radiolabel selectively 5‐HT 1D ‐like binding sites.