Helmut Bittiger

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GABA (gamma-amino-butyric acid), the principal inhibitory neurotransmitter in the brain, signals through ionotropic (GABA(A)/ GABA(c)) and metabotropic (GABA(B)) receptor systems. Here we report the cloning of GABA(B) receptors. Photoaffinity labelling experiments suggest that the cloned receptors correspond to two highly conserved GABA(B) receptor forms(More)
gamma-Aminobutyric acid type B receptors (GABABRs) are involved in the fine tuning of inhibitory synaptic transmission. Presynaptic GABABRs inhibit neurotransmitter release by down-regulating high-voltage activated Ca2+ channels, whereas postsynaptic GABABRs decrease neuronal excitability by activating a prominent inwardly rectifying K+ (Kir) conductance(More)
The biochemical, electrophysiological and pharmacological properties of the new GABAB receptor blocker CGP 35348 are described. In a variety of receptor binding assays CGP 35348 showed affinity for the GABAB receptor only. CGP 35348 had an IC50 of 34 microM at the GABAB receptor. The compound antagonized (100, 300, 1000 microM) the potentiating effect of(More)
The gamma-aminobutyric acid type B (GABAB) receptor is distantly related to the metabotropic glutamate receptor-like family of G-protein-coupled receptors (family 3). Sequence comparison revealed that, like metabotropic glutamate receptors, the extracellular domain of the two GABAB receptor splice variants possesses an identical region homologous to the(More)
Recently, two N-terminal splice variants of the metabotropic receptor for GABA (gamma-amino-butyric acid) were cloned. Here, we describe an antiserum that recognizes the two receptor variants. We demonstrate that these proteins are identical with GABAB receptors that are photoaffinity labeled with [125I]CGP71872 in rat brain. The C-terminal epitopes(More)
CGP 20712 A (1-[2-((3-carbamoyl-4-hydroxy)phenoxy)ethylamino]-3- [4-(1-methyl-4-trifluoromethyl-2-imidazolyl) phenoxy]-2-propanol methanesulfonate), a specific beta 1-adrenoceptor antagonist, was tested for resolution of beta 1- and beta 2-adrenoceptors in an in vitro [3H]dihydroalprenolol ([3H]DHA) binding assay. Competition experiments, using rat(More)
The aim of this study was to reexamine the concept that gamma-hydroxybutyric acid (GHB) is a weak but selective agonist at gamma-aminobutyric acidB (GABAB) receptors, using binding experiments with several radioligands. Ki values of GHB were similar (approximately equal to 100 microM) in three agonist radioligand assays for GABAB receptors, [3H]baclofen(More)
We have investigated whether the pathogenesis of spontaneous generalized non-convulsive seizures in rats with genetic absence epilepsy is due to an increase in the brain levels of gamma-hydroxybutyric acid (GHB) or in the rate of its synthesis. Concentrations of GHB or of its precursor gamma-butyrolactone (GBL) were measured with a new GC/MS technique which(More)
CGP 28014 (N-(2-pyridone-6-yl)-N′,N′-di-n-propylformamidine) or its methanesulfonate salt CGP 28014 A was suspected to be a catechol-O-methyl-transferase (COMT) inhibitor because it was found to reduce the levels of homovanillic acid (HVA) and to increase those of 3,4-dihydroxyphenylacetic acid (DOPAC) in the rat striatum, after oral or intraperitoneal(More)
The existence of DA receptors in the rat hippocampus was demonstrated with an in vivo [3H]spiperone radioreceptor assay. Kinetic studies revealed that maximum binding of [3H]spiperone in hippocampus was much smaller than in striatum and frontal cortex but much higher than in cerebellum. In inhibition studies of [3H]spiperone binding, all neuroleptics tested(More)