GABAA and GABAB sites in bovine adrenal medulla membranes.
The effect of several ligands and Ca2+ ions on [3H]GABA binding to bovine adrenal medulla membranes was investigated. Without any blockade, the [3H]GABA binding showed two components, one of low affinity (Kd = 139 +/- 22 nM and Bmax = 3.2 +/- 0.4 pmol/mg protein) and the other of high affinity (Kd = 41 +/- 6 nM and Bmax = 0.35 +/- 0.26 pmol/mg protein). Muscimol specifically blocked low-affinity sites, and (-)baclofen blocked high-affinity components. Ca2+ ions were strictly necessary for maximum binding to high-affinity sites, whereas they did not significantly affect sites of the lower affinity. These results show that the bovine adrenal medulla has a GABAA receptor population of low affinity together with a GABAB receptor of high affinity.
Castro
E
E
Instituto de Bioquímica (Centro mixto C.S.I.C.-U.C.M.), Facultad de Farmacia, Madrid, Spain.
Oset-Gasque
M J
MJ
Cañadas
S
S
Gimenez
G
G
González
M P
MP
D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D009118:Muscimol / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000187:drug effects / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D011963:Receptors, GABA-A; D009118:Muscimol; D005680:gamma-Aminobutyric Acid; D001418:Baclofen; D002118:Calcium