Premium
Effect of Guanosine 5′‐ O ‐(3‐Thiotriphosphate) and Calcium on γ‐Aminobutyric Acid B Binding as a Function of Postnatal Development
Author(s) -
AlDahan Muna I.,
Thalmann Robert H.
Publication year - 1989
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1989.tb10933.x
Subject(s) - guanosine , aminobutyric acid , calcium , chemistry , biochemistry , stereochemistry , receptor , organic chemistry
Abstract: We have examined the development of γ‐aminobutyric acid B (GABA B ) receptors in rat cerebrum using a binding assay that has achieved specific binding levels of ∼50% with the GABA B ligand (–)‐[ 3 H]baclofen. As early as postnatal day 1, GABA B receptors are present and are linked to both calcium‐ and guanosine triphosphate‐binding protein (G protein)‐regulatory sites, as indicated by the stimulation of binding by calcium and the inhibition of binding by the guanine nucleotide guanosine 5′‐ O ‐(3‐thiotriphosphate) (GTPγS). However, whereas the EC 50 for the calcium effect was at a mature value in the neonate, the IC 50 for the inhibition of binding by GTPγS was not, and declined more than two orders of magnitude by adulthood. Moreover, while many previous studies had shown that manipulation of G proteins by guanine nucleotides affects receptor affinity rather than density, our saturation analysis of binding suggests that calcium affected GABA B receptor density rather than affinity. The results therefore suggest that calcium and the manipulation of G proteins by GTPγS may affect the GABA B receptor by different mechanisms.