0000000000459992
AUTHOR
Saku T. Sinkkonen
Altered receptor subtypes in the forebrain of GABAA receptor δ subunit-deficient mice: recruitment of γ2 subunits
A GABA(A) receptor delta subunit-deficient mouse line was created by homologous recombination in embryonic stem cells to investigate the role of the subunit in the brain GABA(A) receptors. High-affinity [(3)H]muscimol binding to GABA sites as studied by ligand autoradiography was reduced in various brain regions of delta(-/-) animals. [(3)H]Ro 15-4513 binding to benzodiazepine sites was increased in delta(-/-) animals, partly due to an increment of diazepam-insensitive receptors, indicating an augmented forebrain assembly of gamma 2 subunits with alpha 4 subunits. In the western blots of forebrain membranes of delta(-/-) animals, the level of gamma 2 subunit was increased and that of alpha …
Autoradiographic imaging of altered synaptic αβγ2 and extrasynaptic αβ GABAA receptors in a genetic mouse model of anxiety
Abstract To image the possible alterations in brain regional GABAA receptor subtype properties in a genetic animal model of human anxiety, mice heterozygous for the deletion of GABAA receptor γ2 subunit (γ2+/−) were studied using ligand autoradiographic assays on brain cryostat sections. The [ 35 S ]TBPS binding assay was designed to reveal impaired GABA and channel site coupling shown to be more prominent in recombinant α1/6β3 than in α1/2β3γ2 or β2 subunit-containing GABAA receptors expressed in HEK 293 cells. Increased GABA-insensitive [ 35 S ]TBPS binding in the γ2+/− mouse brains was evident in the cerebral cortex and in subcortical regions, the alterations being regionally similar to …
Characterization of γ-aminobutyrate type A receptors with atypical coupling between agonist and convulsant binding sites in discrete brain regions
Abstract γ-Aminobutyric acid type A (GABA A ) receptor ionophore ligand t -[ 35 S]butylbicyclophosphorothionate ([ 35 S]TBPS) was used in an autoradiographic assay on brain cryostat sections to visualize and characterize atypical GABA-insensitive [ 35 S]TBPS binding previously described in certain recombinant GABA A receptors and the cerebellar granule cell layer. Picrotoxinin-sensitive but 1-mM GABA-insensitive [ 35 S]TBPS binding was present in the rat cerebellar granule cell layer, many thalamic nuclei, subiculum and the internal rim of the cerebral cortex, amounting in these regions up to 6% of the basal binding determined in the absence of exogenous GABA. Similar binding properties wer…
Multiple actions of fenamates and other nonsteroidal anti-inflammatory drugs on GABAA receptors
The nonsteroidal anti-inflammatory drug (NSAID) niflumic acid, a fenamate in structure, has many molecular targets, one of them being specific subtypes of the main inhibitory ligand-gated anion channel, the GABA(A) receptor. Here, we report on the effects of other fenamates and other classes of NSAIDs on brain picrotoxinin-sensitive GABA A receptors, using an autoradiographic assay with [S-35]TBPS as a ligand on mouse brain sections. We found that the other fenamates studied (flufenamic acid, meclofenamic acid, mefenamic acid and tolfenamic acid) affected the autoradiographic signal at low micromolar concentrations in a facilitatory-like allosteric fashion, i.e., without having affinity to …
Altered atypical coupling of γ-aminobutyrate type A receptor agonist and convulsant binding sites in subunit-deficient mouse lines
We searched for subunit correlations for GABA(A) receptor-associated atypically GABA-insensitive [35S]TBPS binding. The homomeric beta3 subunit receptors could be excluded, as GABA-insensitive [35S]TBPS binding was present in beta3-/- mice. Localization of GABA-insensitive [35S]TBPS binding correlated best with those of delta, alpha4 and alpha6 subunit mRNAs. The amounts of GABA-insensitive [35S]TBPS binding components were increased in delta-/- mice, but dramatically reduced in alpha6-/- mice, suggesting a role for alpha6 but excluding delta subunits.