[3H](-)Baclofen: an improved ligand for GABAB sites.
[3H](-)Baclofen, the radiolabelled form of the active isomer of baclofen, has been used as a ligand for GABAB (gamma-aminobutyric acid) receptors on synaptic membranes from whole brain of rat. The pharmacological profile for displacement of this ligand was observed to be identical with that for the racemic ligand [3H](+/-)baclofen and [3H]GABA under conditions where GABAB, but not GABAA sites, were labelled. The displaceable (specific) portion of membrane-bound [3H](-)baclofen was 47.5 +/- 2.3% of the total which was twice that obtained previously with [3H](+/-)baclofen. Two binding components were observed with affinities of 19 and 304 nM and binding capacities of 0.37 and 1.58 pmol/mg protein respectively. It is suggested that [3H](-)baclofen is an improvement over the labelled racemic form and binds to the same sites. It should provide a more reliable tool for studying GABAB receptors.
Bowery
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NG
Hill
D R
DR
Hudson
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AL
D000818:Animals; D001418:Baclofen; D001667:Binding, Competitive / Q000187:drug effects; D001921:Brain / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D051381:Rats; D011963:Receptors, GABA-A / Q000187:drug effects*; D013237:Stereoisomerism; D013570:Synaptic Membranes / Q000378:metabolism
D008024:Ligands; D011963:Receptors, GABA-A; D001418:Baclofen