Gamma-hydroxybutyric acid (GHB) and gamma-aminobutyric acidB receptor (GABABR) binding sites are distinctive from one another: molecular evidence.
gamma-Hydroxybutyric Acid (GHB) is thought to be a weak partial agonist at the gamma-aminobutyric acid(B) Receptor (GABA(B)R), but the precise relationship of the GHB receptor (GHBR) to the GABA(B)R remains unclear. In order to test the hypothesis that the GHBR is not identical to the GABA(B)R, we conducted two groups of experiments. First, GABA(B)R subtype 1 (R1) and/or subtype 2 (R2) were over expressed in HEK 293 cells and membrane binding studies on the transfected cells done using [(3)H]GHB and [(3)H] (2E)-(5-hydroxy-5,7,8,9-tetrahydro-6H-benzo[a][7]annulen-6-ylidene) ethanoic acid ([(3)H]NCS-382). The latter is a specific antagonist at the GHB binding site. Second, [(3)H]GHB and [(3)H]NCS-382 autoradiographic binding studies were done on the brains of mice in which the gene for GABA(B)R1a was deleted. Such mice do not have a functioning GABA(B)R. There was no detectable specific [(3)H]GHB or [(3)H]NCS-382 binding in HEK 293 cells transfected with GABA(B)R1, R2, or R1/R2. Binding to [(3)H]CGP54626A, a high affinity GABA(B)R antagonist, was absent in GABA(B)R1a(-/-) mice. There was no difference in [(3)H]NCS-382 binding observed in the brains of GABA(B)R1a(-/-), GABA(B)R1a(+/-) or GABA(B)R1a(+/+) mice. Specific [(3)H]GHB binding was observed in the brain of GABA(B)R1a(-/-) mice but was significantly lower than in wild type mice. These data support the hypothesis that the GHB binding site is separate and distinct from the GABA(B)R.
Wu
Ying
Y
Brain and Behavior Program, Hospital for Sick Children, University of Toronto, Toronto, ON, Canada M5G 1X8.
Ali
Saima
S
Ahmadian
Gholamreza
G
Liu
Chun Che
CC
Wang
Yu Tian
YT
Gibson
K Michael
KM
Calver
Andrew R
AR
Francis
Joseph
J
Pangalos
Menelas N
MN
Carter Snead
O
O
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism*; D018080:Receptors, GABA-B / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D012978:Sodium Oxybate / Q000378:metabolism
C039403:4-hydroxybutyric acid receptor; D011956:Receptors, Cell Surface; D018080:Receptors, GABA-B; D012978:Sodium Oxybate