GABA binding in mammalian brain: Inhibition by endogenous GABA

Napias, Christian; Bergman, Margalit; Ness, Paul C. Van; Greenlee, Donald V.; Olsen, Richard W.

doi:10.1016/0024-3205(80)90111-3

Cited by 80 publications

(21 citation statements)

References 17 publications

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“…These normally impair the binding of [3H]-GABA. GABA itself could account for a portion of the inhibitory factor (Napias, Bergman, Van Ness, Greenlee & Olsen, 1980;Gardner, Klein & Grove, 1981). Replacement of the supernatant obtained during the freezing and thawing procedures into the incubation mixture reduces the amount bound suggesting that an inhibitory material can be extracted (Johnston & Kennedy, 1978).…”

Section: Discussionmentioning

confidence: 99%

Characteristics of GABA_B receptor binding sites on rat whole brain synaptic membranes

Bowery

Hill

Hudson

1983

British J Pharmacology

391

116

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Saturable binding of (±)‐[3H]‐baclofen and [3H]‐γ‐aminobutyric acid ([3H]‐GABA) to rat brain crude synaptic membranes has been examined by means of a centrifugation assay. The binding of [3H]‐baclofen could be detected in fresh or previously frozen tissue and was dependent on the presence of physiological concentrations of Ca2+ or Mg2+ although a lower affinity Na+‐dependent component could also be observed. Both components probably reflect binding to receptor recognition sites. The saturable portion of bound [3H]‐baclofen formed 20.3 ± 6.9% of total bound ligand. This could be displaced by GABA (IC50 =.0.04 μm), (−)‐baclofen (0.04 μm) and to a much lesser extent by (+)‐baclofen (33 μm). Isoguvacine, piperidine‐4‐sulphonic acid and bicuculline methobromide were inactive (up to 100 μm) and muscimol was only weakly active (IC50 = 12.3 μm). Saturable binding of [3H]‐GABA increased on adding CaCl2 or MgSO4 (up to 2.5 mm and 5.0 mm respectively) to the Tris‐HCl incubation solution. This binding (GABAB site binding) was additional to the bicuculline‐sensitive binding of GABA (GABAA site binding) and could be completely displaced by (−)‐baclofen (IC50 = 0.13 μm). Increasing the Ca2+ concentration (0 to 2.5 mm) increased the binding capacity of the membranes without changing their affinity for the ligand. The binding of [3H]‐GABA to GABAB sites could be demonstrated in fresh as well as previously frozen membranes with a doubling of the affinity being produced by freezing. Further incubation with the non‐ionic detergent Triton‐X‐100 (0.05% v/v) reduced the binding capacity by 50%. The pharmacological profile of displacers of [3H]‐GABA from GABAB sites correlated well with that for [3H]‐baclofen displacement. A correlation with data previously obtained in isolated preparations of rat atria and mouse vas deferens was also apparent. It is concluded that [3H]‐baclofen or [3H]‐GABA are both ligands for the same bicuculline‐insensitive, divalent cation‐dependent binding sites in the rat brain.

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Section: Discussionmentioning

confidence: 99%

Characteristics of GABA_B receptor binding sites on rat whole brain synaptic membranes

Bowery

Hill

Hudson

1983

British J Pharmacology

391

116

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“…6]. It appears, however, that this interaction be tween GABA and the postsynaptic mem brane is rather complex since receptors with different affinities for GABA have been re ported for membranes prepared from differ ent brain areas [1,12,13,29,30,43,45]. This heterogeneity of the GABA receptor seems to be present not only in the adult brain but also at early ontogenetic stages, at least in the cerebral cortex [1].…”

Section: Introductionmentioning

confidence: 99%

Differences between GABA Receptor Binding to Membranes from Cerebellum during Postnatal Development and from Cultured Cerebellar Granule Cells

Meier

Schousboe²

1982

Dev Neurosci

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GABA receptor binding sites were determined in membranes from cerebella of 7-, 15- and 60-day-old rats and cerebellar granule cells derived from 7-day-old rats and cultured for 8 days using [³H]GABA as the ligand and nonradioactive GABA to measure non-specific binding. Membranes from cerebellum at all postnatal stages exhibited at least two binding sites for GABA with binding constants around 7–9 and 150–750 nM, respectively. The total number of binding sites expressed on the basis of total protein increased 10 times between 7 and 60 days of age and 2 times between 15 and 60 days. The latter increase could be quantitatively accounted for by an increase in the number of low affinity sites. In contrast to this, membranes from cultured granule cells only exhibited the high affinity binding site (K_D 7.1±0.5 nM) and the number of binding sites was comparable to that of cerebellar membranes from rats of the corresponding age (15 days old). GABA analogues such as muscimol, piperidine-4-sulphonic acid, homo-β-proline, THIP, and isoguvacine were potent displacers of GABA binding to cultured granule cells, whereas nipecotic acid and guvacine had no effect.

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“…been difficult because of the presence of various materials interfering with GABA binding, including GABA (8) itself, and because of enzymatic degradation of GABA-modulin. This report describes the isolation, purification to homogeneity, and amino acid composition of GABA-modulin isolated from rat brain.…”

mentioning

confidence: 99%

Isolation, characterization, and purification to homogeneity of a rat brain protein (GABA-modulin).

Guidotti¹,

Konkel²,

Ebstein³

et al. 1982

Proc. Natl. Acad. Sci. U.S.A.

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y-Aminobutyric acid (GABA)-modulin is a brain neuropeptide that appears to modulate specific high-affinity (20 nM) GABA recognition sites in brain. When added to crude synaptic membranes this peptide inhibits binding of [3H]GABA to the high-affinity site and prevents facilitation of [H]diazepam binding elicited by GABA. GABA-modulin has been purified to homogeneity by ammonium sulfate precipitation, gel chromatography, and reverse-phase HPLC. Homogeneity was confirmed by a variety of means, including chromatography under four different HPLC conditions, two different polyacrylamide gel electrophoreses, and end group analysis. Purified GABA-modulin contains approximately 126 amino acids and has a molecular weight of 16,500. The GABA-modulin molecule contains an abundance of hydrophilic basic residues, and neither cysteine nor GABA is present. End group analyses of GABA-modulin showed that histidine is the free COOH terminus and the NH2 terminus is blocked.

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GABA binding in mammalian brain: Inhibition by endogenous GABA

Cited by 80 publications

References 17 publications

Characteristics of GABA_B receptor binding sites on rat whole brain synaptic membranes

Characteristics of GABA_B receptor binding sites on rat whole brain synaptic membranes

Differences between GABA Receptor Binding to Membranes from Cerebellum during Postnatal Development and from Cultured Cerebellar Granule Cells

Isolation, characterization, and purification to homogeneity of a rat brain protein (GABA-modulin).

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GABA binding in mammalian brain: Inhibition by endogenous GABA

Cited by 80 publications

References 17 publications

Characteristics of GABAB receptor binding sites on rat whole brain synaptic membranes

Characteristics of GABAB receptor binding sites on rat whole brain synaptic membranes

Differences between GABA Receptor Binding to Membranes from Cerebellum during Postnatal Development and from Cultured Cerebellar Granule Cells

Isolation, characterization, and purification to homogeneity of a rat brain protein (GABA-modulin).

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Characteristics of GABA_B receptor binding sites on rat whole brain synaptic membranes

Characteristics of GABA_B receptor binding sites on rat whole brain synaptic membranes