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5‐HT 1D binding sites in porcine brain can be sub‐divided by GR43175
Author(s) -
Sumner M.J.,
Humphrey P.P.A.
Publication year - 1989
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.1476-5381.1989.tb16856.x
Subject(s) - binding site , 5 ht receptor , population , receptor , serotonin , chemistry , stereochemistry , biology , medicine , biophysics , biochemistry , environmental health
We have examined the binding of 5‐carboxamidotryptamine (5‐CT) and GR43175 (3‐(2‐dimethylamino)ethyl‐N‐methyl‐1H‐indole‐5‐methane sulphonamide) to 5‐HT 1D sites labelled with [ 3 H]‐5‐hydroxytryptamine ([ 3 H]‐5‐HT) in neonatal porcine caudate membranes. In competition studies, 5‐CT produced shallow inhibition curves ( K i 138 nM, slope 0.31), indicating binding site heterogeneity, while GR43175 interacted with a single population of binding sites ( K i 251 nM, slope 0.98), producing a maximum of only 52% inhibition of [ 3 H]‐5‐HT binding compared to 100% for 5‐HT or 5‐CT. In the presence of excess GR43175 (10 μ m ), 5‐CT produced a monophasic inhibition curve with a K i value of 800 nM for the remaining sites (slope 0.89). These preliminary data suggest that under the conditions employed, GR43175, and to a lesser extent 5‐CT, may discriminate between two sub‐populations of 5‐HT 1D binding sites in porcine brain.