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Orensanz LM, Córdoba C, Fernández I. Beta-alanine potentiation of [3H]flunitrazepam binding to rat spinal cord homogenates. Neurosci Lett 1990; 111:241-5. [PMID: 2110638 DOI: 10.1016/0304-3940(90)90268-e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effect of beta-alanine, gamma-aminobutyric acid (GABA), and other functionally related amino acids on [3H]flunitrazepam binding to rat spinal cord homogenates was studied. beta-Alanine potentiated [3H]flunitrazepam binding by 40% and GABA by 88%. Taurine increased the binding by 19%. Hypotaurine produced an 11% increase. No significant effect was seen in glycine, alanine, serine, valine or the dipeptide carnosine. The beta-alanine increase in [3H]flunitrazepam binding was completely inhibited by 10 microM strychnine, whereas the GABA increase required 0.1 mM strychnine to be fully suppressed. Results suggest that beta-alanine specifically potentiates binding of [3H]flunitrazepam in rat spinal cord homogenates.
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Affiliation(s)
- L M Orensanz
- Departamento de Investigación, Hospital Ramón y Cajal, Madrid, Spain
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2
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Abstract
GABAA receptor agonists modulate [3H]diazepam binding in rat cortical membranes with different efficacies. At 23 degrees C, the relative potencies for enhancement of [3H]diazepam binding by agonists parallel their potencies in inhibiting [3H]gamma-aminobutyric acid [( 3H]GABA) binding. The agonist concentrations needed for enhancement of [3H]diazepam binding are up to 35 times higher than for [3H]GABA binding and correspond closely to the concentrations required for displacement of [3H]bicuculline methochloride (BMC) binding. The maximum enhancement of [3H]diazepam varied among agonists: muscimol = GABA greater than isoguvacine greater than 3-aminopropane sulphonic acid (3APS) = imidazoleacetic acid (IAA) greater than 4,5,6,7-tetrahydroisoxazolo (4,5,6)-pyridin-3-ol (THIP) = taurine greater than piperidine 4-sulphonic acid (P4S). At 37 degrees C, the potencies of agonists remained unchanged, but isoguvacine, 3 APS, and THIP acquired efficacies similar to GABA, whereas IAA, taurine, and P4S maintained their partial agonist profiles. At both temperatures the agonist-induced enhancement of [3H]diazepam binding was reversible by bicuculline methobromide and by the steroid GABA antagonist RU 5135. These results stress the importance of studying receptor-receptor interaction under near-physiological conditions and offer an in vitro assay that may predict the agonist status of putative GABA receptor ligands.
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Kryzhanovskii GN, Shandra AA. Use of nicotinamide and pyridoxal-5-phosphate in the treatment of experimental epilepsy. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 1985; 15:111-8. [PMID: 2991809 DOI: 10.1007/bf01186976] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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4
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Tunnicliff G, Welborn KL. The action of structural analogues of ?-aminobutyric acid on binding sites in mouse brain. Drug Dev Res 1984. [DOI: 10.1002/ddr.430040107] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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5
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Wamsley JK, Gee KW, Yamamura HI. Comparison of the distribution of convulsant/barbiturate and benzodiazepine receptors using light microscopic autoradiography. Life Sci 1983; 33:2321-9. [PMID: 6316061 DOI: 10.1016/0024-3205(83)90266-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Some convulsant drugs elicit CNS excitation by blocking neuronal activity at GABAergic synapses whereas depressant compounds may result in the enhancement of GABAergic transmission. These effects are thought to involve drug actions at a multireceptor complex involving a benzodiazepine receptor, GABA receptor, picrotoxin receptor and a chloride ionophore. A radiolabeled convulsant, [35S]t-butylbicyclophosphorothionate [( 35S]-TBT) has been developed and used to characterize the binding to the "picrotoxin" or convulsant/barbiturate site. The microscopic distribution of the convulsant/barbiturate sites are reported in this communication, as demonstrated by receptor autoradiography after labeling tissue sections with [35S]-TBT. Comparison of the distribution of these sites with those of the benzodiazepine receptors show a close regional correlation in many areas. The convulsant/barbiturate sites and the benzodiazepine receptors, however, are unevenly distributed in the rat cerebellum and exist in separate lamina.
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6
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Sherman-Gold R, Dudai Y. Diethylpyrocarbonate modification of benzodiazepine receptors from calf cerebral cortex. Neurochem Res 1983; 8:259-67. [PMID: 6304551 DOI: 10.1007/bf00963925] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Diethylpyrocarbonate (DEP), an amino acid modifying reagent, causes complete inactivation of particulate and deoxycholate-solubilized benzodiazepine-receptors from calf cerebral cortex. No heterogeneity was observed in DEP-sensitivity of the receptors. Protection from DEP-induced inactivation was provided by the centrally active benzodiazepines, diazepam and nitrazepam, but not by the peripherally active Ro5-4864, suggesting that DEP modifies a residue which is essential for the central actions of benzodiazepines. GABA did not protect against inactivation or influence the protection afforded by diazepam, indicating that the DEP-modifiable residue is independent of GABA binding sites, or that GABA binding sites are also sensitive to DEP. DEP-induced inactivation of benzodiazepine-receptors proceeds much faster at pH 10.1 than at pH 8.1 or 6.0, indicating the modification of a high pKa side group, possibly the phenol of a tyrosyl residue. This postulation is in accord with our previous findings with the modifying reagents tetranitromethane and N-acetylimidazole.
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Sherman-Gold R, Dudai Y. Glycoprotein properties of benzodiazepine receptors from calf cerebral cortex. J Neurosci Res 1983; 10:27-33. [PMID: 6310136 DOI: 10.1002/jnr.490100105] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Several lectins (concanavalin A, wheat germ agglutinin, wax bean agglutinin, and phytohemagglutinin) induce aggregation and precipitation of deoxycholate-solubilized benzodiazepine receptors from calf cerebral cortex. These receptors were also retained on columns of immobilized lectins. Photoaffinity labeling of the soluble benzodiazephine receptors prevented their interaction with lectins. Periodate treatment caused inactivation of benzodiazepine receptors which was partially prevented by diazepam and/or gamma-aminobutyric acid. The possible association of the drug-binding site and the carbohydrate moiety is discussed.
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Willow M, Johnston GA. Pharmacology of barbiturates: electrophysiological and neurochemical studies. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1983; 24:15-49. [PMID: 6140244 DOI: 10.1016/s0074-7742(08)60219-6] [Citation(s) in RCA: 76] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Mennini T, Garattini S. Benzodiazepine receptors': correlation with pharmacological responses in living animals. Life Sci 1982; 31:2025-35. [PMID: 6129557 DOI: 10.1016/0024-3205(82)90094-7] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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11
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Sherman-Gold R, Dudai Y. beta-Carboline binding to deoxycholate solubilized benzodiazepine receptors from calf cerebral cortex. Neurosci Lett 1981; 26:325-8. [PMID: 6895661 DOI: 10.1016/0304-3940(81)90153-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The beta-carbolines harmane and norharmane competitively inhibit [3H]flunitrazepam ([3H]FNZ) binding to deoxycholate-solubilized benzodiazepine receptors from calf cerebral cortex, with Ki in the micromolar range [3H]Propyl-beta-carboline-3-carboxylate ([3H]PrCC) binds to the soluble receptors with an affinity similar to its binding to particulate receptors (0.41 nM vs 0.48 nM, respectively). The component that binds [3H]PrCC displays a sedimentation profile on sucrose gradient centrifugation similar to that of [3H]FNZ binding component (sedimentation coefficient about 11S).
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Abstract
The effects of pentobarbitone on the binding of gamma-aminobutyric acid (GABA) to crude synaptosomal rat brain membranes were studied. In extensively washed P2 membranes, pentobarbitone had a biphasic action: at concentrations ranging between 12.5 and 500 microM, pentobarbitone enhanced GABA binding in a concentration-dependent manner; at concentrations greater than 500 microM, this enhancement was progressively reversed towards control levels of GABA binding. The effect of pentobarbitone seen at higher concentrations may reflect a GABA-mimetic action, since similar concentrations enhanced diazepam binding to washed P2 membranes, an effect antagonized by bicuculline methochloride and picrotoxinin. When washed P2 membranes were incubated in 0.5% Triton X-100 (30 min at 37 degrees C), the enhancement of GABA binding by low concentrations of pentobarbitone was abolished, while at higher concentrations GABA binding was progressively inhibited, suggesting that the GABA-mimetic action is retained. When washed P2 membranes were subjected to high-frequency homogenization, the biphasic dose-response relationship for pentobarbitone was markedly shifted to the right. The choice of membrane preparation appears to be a critical factor in examining drug-receptor interactions in vitro, at least for those involving GABA and the barbiturates.
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13
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Olsen RW. The GABA postsynaptic membrane receptor-ionophore complex. Site of action of convulsant and anticonvulsant drugs. Mol Cell Biochem 1981; 39:261-79. [PMID: 6273709 DOI: 10.1007/bf00232579] [Citation(s) in RCA: 188] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The function of the inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), has been implicated in the mode of action of many drugs which excite or depress the central nervous system. Many convulsant agents appear to block GABA action whereas anticonvulsants enhance GABA action. Some of these drug effects involve altered GABA-mediated synaptic transmission at the level of GABA biosynthesis, release from nerve endings, uptake into cells, and metabolic degradation. A greater number of agents of diverse classes appear to affect GABA action at the postsynaptic membrane, as determined from both electrophysiological and biochemical studies. The recently developed in vitro radioactive receptor binding assays have led to a wealth of new information about GABA action and its alteration by drugs. GABA inhibitory transmission involves the regulation, by GABA binding to its receptor site, of chloride ion channels. In this GABA receptor-ionophore system, other drug receptor sites, one for benzodiazepines and one for barbiturates/picrotoxinin (and related agents) appear to form a multicomponent complex. In this complex, the drugs binding to any of the three receptor categories are visualized to have an effect on GABA-associated chloride channel regulation. Available evidence suggests that the complex mediates many of the actions of numerous excitatory and depressant drugs showing a variety of pharmacological effects.
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Kenessey A, Láng T, Gráf L. Demonstration of an endogenous, highly potent, noncompetitive protein inhibitor(s) of 3H-diazepam binding in bovine brain. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1981; 18:103-6. [PMID: 6273343 DOI: 10.1111/j.1399-3011.1981.tb02044.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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16
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Abstract
Primary cultures of dissociated hippocampi from fetal mice examined for the presence of binding sites for [3H]diazepam. The binding assays were done with living cells still attached to the culture dish. The cells contain high affinity binding sites for [3H]diazepam, Kd = 5 nM, which are completely inhibited with 20 nM R05-4864 but only 26% with 20 nM lorazepam. The binding was inhibited by purinergic compounds and by quinidine. The living cell did not exhibit increased binding of [3H]diazepam in the presence of GABA and in fact a slight decrease in binding was found. This was also found when live, intact C6 glial cells were investigated. These observations suggest that the use of living cells to study the benzodiazepine receptor is valuable and maybe necessary to fully characterize this receptor.
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Davis LG, McIntosh H, Reker D. An endogenous ligand to the benzodiazepine receptor: preliminary evaluation of its bioactivity. Pharmacol Biochem Behav 1981; 14:839-44. [PMID: 6265958 DOI: 10.1016/0091-3057(81)90371-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Chromatographic separation of aqueous brain extracts yields a peptide containing fraction which competitively inhibits 3H-diazepam binding to its receptor. An intracerebral-ventricular injection of this isolated fraction results in altered responses in pharmacological and behavioral tests which are similar to those observed when diazepam is administered in the same fashion. The most pronounced effect was obtained in the conflict test. Changes observed in other tests, such as blocking pentylenetetrazole convulsions, altering motility or reducing hyperthermia, were also consistent with the actions of diazepam. At the dose used, neither diazepam nor the brain extract altered muscular co-ordination in two ataxia evaluations. Thus, the animals' performance in the other paradigms would not be adversely influenced by immobilization side-effects. The results reported here support the notion that an endogenous factor does exist in brain which can act like the benzodiazepine drugs when tested for bioactivity in animal studies.
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Supavilai P, Karobath M. Action of pyrazolopyridines as modulators of [3H]flunitrazepam binding to the gaba/benzodiazepine receptor complex of the cerebellum. Eur J Pharmacol 1981; 70:183-93. [PMID: 6114867 DOI: 10.1016/0014-2999(81)90213-2] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The pyrazolopyridines etazolate (SQ 20009) and cartazolate (SQ 65396) have strong modulatory effects on the GABA/benzodiazepine receptor complex of rate cerebellum. Thus, etazolate and cartazolate directly stimulate [3H]flunitrazepam binding (with EC50 values of 1.2 microM and 0.3 microM respectively) by increasing the apparent affinity of [3H]flunitrazepam for its binding sites. Stimulation of [3H]flunitrazepam binding by pyrazolopyridines is dependent on the presence of certain anions like chloride, bromide, iodide, nitrite, nitrate but not fluoride, acetate, formate or sulfate. If is inhibited by bicuculline-methiodide, and by the "chloride channel drugs' picrotoxinin and IPTBO. isoTHAZ, a GABA analogue with GABA antagonist properties in vivo, fails to inhibit binding stimulated by etazolate but antagonizes [3H]flunitrazepam binding stimulated by GABA. The pyrazolopyridines have also indirect effects on benzodiazepine receptor binding since they enhance the apparent sensitivity of those GABA recognition sites which are coupled to benzodiazepine binding sites. Thus, in the presence of 10 microM etazolate, GABA and muscimol enhance [3H]flunitrazepam binding, with EC50 values of 109 nM and 12 nM respectively. This sensitization effect is partially dependent on the presence of chloride ions. The pyrazolopyridines facilitate also the stimulation of benzodiazepine receptor binding by beta-alanine and taurine and by the rigid and flattened GABA analogues THIP and piperidine-4-sulfonic acid. Taken together, these results suggest that the pyrazolopyridines modulate [3H]flunitrazepam binding by acting at a site closely related to GABA receptor-regulated chloride ion channels.
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Karobath M, Drexler G, Supavilai P. Modulation by picrotoxin and IPTBO of 3H-flunitrazepam binding to the GABA/benzodiazepine receptor complex of rat cerebellum. Life Sci 1981; 28:307-13. [PMID: 6111726 DOI: 10.1016/0024-3205(81)90738-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Abstract
A putative benzodiazepine receptor was solubilized from calf cortex by the use of sodium deoxycholate as an 10.9S entity containing subunits of which at least part are of 51 K molecular weight. The solubilized receptor retains its high affinity for [3H]flunitrazepam. The affinity for various other drugs, including benzodiazepines and xanthine derivatives, was also not significantly altered. GABAergic modulation of the receptor affinity for [3H]flunitrazepam was diminished but still detectable.
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Supavilai P, Karobath M. The effect of temperature and chloride ions on the stimulation of [3H]flunitrazepam binding by the muscimol analogues THIP and piperidine-4-sulfonic acid. Neurosci Lett 1980; 19:337-41. [PMID: 6133252 DOI: 10.1016/0304-3940(80)90284-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
THIP and piperidine-4-sulfonic acid (PSA) interact with [3H]GABA binding sites and have GABAmimetic efficacy in vivo, but fail to enhance benzodiazepine receptor binding performed at 0 degree C. However, when [3H]flunitrazepam binding is determined at elevated temperature (30 or 37 degrees C), THIP and PSA display potent chloride ion-dependent stimulatory effects. These results resolve apparent discrepancies between the properties of GABA receptors observed in vivo and in vitro, and they suggest that the modulation of benzodiazepine receptor binding investigated at physiological temperatures can be used as an experimental system for the characterization of GABA receptors.
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Davis LG, Cohen RK. Identification of an endogenous peptide-ligand for the benzodiazepine receptor. Biochem Biophys Res Commun 1980; 92:141-8. [PMID: 7356447 DOI: 10.1016/0006-291x(80)91531-4] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Dudai Y, Yavin Z, Yavin E. Binding of [3H]flunitrazepam to differentiating rat cerebral cells in culture. Brain Res 1979; 177:418-22. [PMID: 40671 DOI: 10.1016/0006-8993(79)90798-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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