0000000000010907
AUTHOR
M. Jüptner
Effects of ovariectomy and steroid replacement on GABAA receptor binding in female rat brain.
Abstract The specific binding of tritiated muscimol to γ-aminobutyric acid (GABA) receptor sites was studied in distinct brain areas of female rats during different endocrine states. In diestrous rats with intact ovaries the highest receptor densities were found in the cortex (10.24 pmol/mg protein) and the lowest concentrations in the mediobasal hypothalamus (3.29 pmol/mg protein). Four weeks after removal of the ovaries, the number of binding sites was enhanced up to 2.4-fold in all brain areas investigated: the preoptic brain area, mediobasal hypothalamus, corticomedial amygdala, and cerebral cortex. The affinity of the binding sites remained unchanged. Substitution of estradiol and prog…
Evidence that 3 alpha-hydroxy-5 alpha-pregnan-20-one is a physiologically relevant modulator of GABA-ergic neurotransmission.
Abstract 3α-Hydroxy-5α-pregnan-20-one (HPO) is a progesterone metabolite which exhibits narcotic properties at high concentrations by interactions with the receptor for gamma-aminobutyric acid (GABA). The present investigation characterized low-dose effects of HPO on GABA A receptor binding, by determining the allosteric properties of HPO on the in vitro binding of 3 H-muscimol to membrane fractions from the cerebella of ovariectomized rats. A newly developed method for tissue preparation was used to wash out endogenous ligands interfering with the assay. HPO reduced the affinity of 3 H-muscimol to GABA A receptor sites by 52% and enhanced the number of accessible binding sites from 5.5±0.5…