Abstract: Levels of mRNA for the major subunits of the GABAA receptor were assayed in the rat pituitary anterior and neurointermediate lobes by ribonuclease protection assay. α1, β1, β2, β3, and γ2s were found to be the predominant subunits in the anterior lobe, whereas α2, α3, β1, β3, γ2s, and γ1 were the predominant subunits expressed in the neurointermediate lobe. α5, α6, and δ subunits were not detectable. Hill and Scatchard analysis of [3H]muscimol binding to anterior and neurointermediate lobe membranes showed high‐affinity binding sites with dissociation constants of 5.6 and 4.5 nM, respectively, and Hill coefficients near 1. Muscimol sites were present at a maximum of 126 fmol/mg in the anterior lobe and 138 fmol/mg in the neurointermediate lobe. The central‐type benzodiazepine antagonist [3H]Ro 15‐1788 bound to a high‐affinity site with a dissociation constant of 1.5 nM in both tissues, at a maximum of 60 fmol/mg in anterior pituitary and 72 fmol/mg in neurointermediate lobe. A Hill coefficient of 1 was measured for this site in both tissues. Assays of CL 218 872 displacement of Ro 15‐1788 were consistent with a pure type I benzodiazepine site in the anterior lobe and a pure type II site in the intermediate lobe. These results are consistent with both tissue‐specific expression of particular GABAA receptor subunits and receptor heterogeneity within individual cells in the pituitary.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of neurochemistry|
|State||Published - Nov 1994|
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience