PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Etazolate”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1983

Etazolate (SQ20009): electrophysiology and effects on [3H]flunitrazepam binding in cultured cortical neurons.

The actions of etazolate (SQ20009) on cultured cortical neurons have been examined in electrophysiological experiments and in receptor binding studies. Etazolate (0.3 to 100 microM) prolongs the duration of spontaneously occurring IPSPs. Higher concentrations of etazolate produce an increase in membrane chloride conductance, an effect which is picrotoxinin and bicuculline sensitive. Etazolate potentiates the response to exogenously applied GABA and acts synergistically with diazepam to enhance GABA-mediated conductance. Etazolate does not increase glycine-mediated conductance changes. Etazolate increases [3H]flunitrazepam binding and stimulates the GABA enhancement of [3H]flunitrazepam binding. In addition, GABA stimulates the etazolate enhancement of [3H]flunitrazepam binding. The etazolate-mediated increases in binding are Cl- dependent and picrotoxinin and bicuculline sensitive. The dose response relationships for etazolate-mediated effects are similar in physiological experiments and in binding studies. These data suggest that etazolate interacts with the postsynaptic GABA receptor complex at a site distinct from either the GABA recognition site or the benzodiazepine binding site to enhance GABA-mediated inhibition and to increase benzodiazepine binding.

Animals↗
PubMed1982

Molecular interactions of etazolate with benzodiazepine and picrotoxinin binding sites.

Pyrazolopyridines, such as etazolate (SQ 20009), enhance [3H]diazepam binding to a Lubrol-solubilized fraction that has specific binding sites for 3H benzodiazepines, [alpha-3H]dihydropicrotoxinin (DHP) and [3H]muscimol. Etazolate enhancement of [3H]diazepam binding was inhibited by picrotoxinin. Furthermore, etazolate inhibited the [3H]DHP binding in a Lubrol-solubilized fraction with an IC50 value of 6-8 microM. These results provide evidence that etazolate, like pentobarbital, modulates benzodiazepine binding via the DHP-sensitive site of the benzodiazepine-GABA receptor-ionophore complex.

Animals↗
PubMed1978

Hydrolysis and subsequent cyclization of etazolate hydrochloride and related compounds in aqueous solutions: application of PMR and mass spectrometry in accelerated stability studies.

The hydrolysis of etazolate hydrochloride, an inhibitor of cyclic nucleotide 3',5'-monophosphate phosphodiesterase that degrades cyclic adenosine 3',5'-monophosphate (cyclic AMP) to adenosine 5'-monophosphate, and related compounds was studied by PMR and mass spectrometry. The compounds underwent reversible acid-catalyzed hydrolysis in aqueous solutions at 60 degrees, followed by cyclization to a major and a minor product formed by independent pathways. Under the experimental conditions, the minor product was stable. The formation rate of the major product, 6-ethyl-1,6-dihydrodipyrazolo [3,4-b:3',4'-d] pyridin-3(2H)-one, was considerably greater than that of the minor component, 3-ethoxy-6-ethyl-1,6-dihydrodipyrazolo [3,4-b:3',4'-d] pyridine. For the 6-methyl analog of etazolate, the rate of methyl deuteration was considerably slower than the rate of cyclization.

Cyclization↗
PubMed1983

Differential modulation of etazolate or pentobarbital enhanced [3H] muscimol binding by benzodiazepine agonists and inverse agonists.

Flunitrazepam, a benzodiazepine agonist increases, and DMCM, an inverse agonist decreases the stimulation by etazolate or pentobarbital of [3H] muscimol binding to membranes of rat cerebral cortex. Ro 15-1788 has no marked effects but antagonizes the action of both flunitrazepam and DMCM. The investigation of several drugs acting on benzodiazepine receptors on etazolate enhancement of [3H] muscimol binding suggests that their receptor interaction reflects a spectrum from agonists to inverse agonists.

Animals↗
PubMed1984

In vitro characterization of benzodiazepine receptor agonists, antagonists, inverse agonists and agonist/antagonists.

Using an extensively washed membrane preparation and standardized incubation conditions, the actions of benzodiazepine (BZ) receptor ligands were evaluated on [3H]flunitrazepam [+/- 10 microM gamma-aminobutyric acid (GABA)], [3H]muscimol (+/- 2.5 microM etazolate) and [35S]butyl bicyclophosphorothionate (TBPS) binding. Classical BZ receptor agonists stimulated [35S]TBPS binding and [3H]muscimol binding in the presence of etazolate. These agents also possessed ratios for [3H]flunitrazepam binding in the absence and presence of GABA (GABA ratio) of 2 to 5. BZ antagonists and inverse agonists had GABA ratios less than 1 and did not alter, or reduced, both [35S]TBPS and [3H]muscimol (+etazolate) binding. The nonsedating BZ agonist/antagonist agents CGS 9896, CL 218872, PK 8165 and PK 9084 all possessed GABA ratios between 1.1 and 1.4 and only stimulated [35S]TBPS and [3H]muscimol (+etazolate) binding to approximately 50% of the level of classical BZ agonists. The BZ partial agonists CGS 9895 and RU 39419 both were unique in that they possessed GABA ratios of 1 or less, stimulated [35S]TBPS binding and had no effect on [3H]muscimol binding (+etazolate). Therefore, by monitoring the major components of the BZ receptor complex (BZ receptor, GABA receptor and chloride channel), we were able to distinguish between different BZ drugs and to support suggestions that these drugs act via unique BZ receptor populations which possess differential couplings to the GABA receptor and chloride channel.

Animals↗
PubMed1981

Action of pyrazolopyridines as modulators of [3H]flunitrazepam binding to the gaba/benzodiazepine receptor complex of the cerebellum.

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.

Animals↗
PubMed1985

Avermectin B1a modulation of gamma-aminobutyric acid/benzodiazepine receptor binding in mammalian brain.

The anthelminthic natural product avermectin B1a (AVM) modulates the binding of gamma-aminobutyric acid (GABA) and benzodiazepine (BZ) receptor ligands to membrane homogenates of mammalian brain. The potent (EC50 = 40 nM) enhancement by AVM of [3H]diazepam binding to rat or bovine brain membranes resembled that of barbiturates and pyrazolopyridines in being inhibited (partially) by the convulsants picrotoxin, bicuculline, and strychnine, and by the anticonvulsants phenobarbital and chlormethiazole. The maximal effect of AVM was not increased by pentobarbital or etazolate. However, AVM affected BZ receptor subpopulations or conformational states in a manner different from pentobarbital. Further, unlike pentobarbital and etazolate, AVM did not inhibit allosterically the binding of the BZ receptor inverse agonist [3H]beta-carboline-3-carboxylate methyl ester, nor did it inhibit, but rather enhanced, the binding of the cage convulsant [35S]t-butyl bicyclophosphorothionate to picrotoxin receptor sites. AVM at submicromolar concentrations had the opposite effect of pentobarbital and etazolate on GABA receptor binding, decreasing by half the high-affinity binding of [3H]GABA and related agonist ligands, and increasing by over twofold the binding of the antagonist [3H]bicuculline methochloride, an effect that was potentiated by picrotoxin. AVM also reversed the enhancement of GABA agonists and inhibition of GABA antagonist binding by barbiturates and pyrazolopyridines. These overall effects of AVM are unique and require the presence of another separate drug receptor site on the GABA/BZ receptor complex.

Animals↗
PubMed1981

Interaction of anticonvulsants with the barbiturate-benzodiazepine-GABA receptor complex.

Unlike the anesthetic barbiturate pentobarbital and the anxiolytic pyrazolopyridine etazolate, which enhance [3H]diazepam binding to rat brain membranes, the anticonvulsant barbiturates phenobarbital and metharbital, and also chlormethiazole, at therapeutic concentrations (10-1000 muM), do not stimulate [3H]diazepam binding, but instead block the enhancement by both pentobarbital and etazolate. The same anticonvulsants at similar concentrations inhibit [3H]alpha-dihydropicrotoxinin (DHP) binding suggesting that these anticonvulsants compete for the same receptor sites as pentobarbital and etazolate, designated the barbiturate-picrotoxinin receptor component of the benzodiazepine-GABA receptor complex.

Animals↗
PubMed1987

Effects of pyrazolopyridines and a triazolopyridazine on the pentobarbital discriminative stimulus.

Rats were trained to discriminate injections of racemic pentobarbital (5.0 mg/kg) from saline in a two-lever drug discrimination task. After stable discrimination performance was attained, stimulus generalization studies were conducted with another barbiturate (barbital), benzodiazepine derivatives (diazepam and chlordiazepoxide), pyrazolopyridine derivatives (etazolate, cartazolate, and tracazolate), and a triazolopyridazine (CL 218, 872). The pentobarbital stimulus generalized to all of these compounds, except cartazolate. In addition, the administration of the benzodiazepine receptor antagonist flumazepil prior to benzodiazepine or triazolopyridazine administration produced a dose-related antagonism of each generalization. In contrast, the administration of flumazepil before barbiturate or pyrazolopyridine (i.e., etazolate or tracazolate) injection resulted in no attenuation of these generalizations. The results indicate that while certain barbiturates, benzodiazepines, pyrazolopyridines and triazolopyridazines are capable of producing similar stimulus effects, the behavioral actions of these agents can be differentiated on the basis of their susceptibility to antagonism by flumazepil.

Animals↗
PubMed1984

Differential interactions of GABA agonists, depressant and convulsant drugs with [35S]-t-butylbicyclophosphorothionate binding sites in cortex and cerebellum.

Effects of three GABA agonists, four GABA antagonists and convulsants (picrotoxinin, alpha-dihydropicrotoxinin [DHP], pentamethylenetetrazole [PTZ] and isopropylbicyclophosphate ester) and three depressant drugs (pentobarbital, (+)etomidate and etazolate) were investigated on [35S]t-butylbicyclophosphorothionate (TBPT) in cortex and cerebellum. All the convulsants tested were equipotent in inhibiting [35S]TBPT binding in cortex and cerebellum. Convulsants like picrotoxinin inhibited [35S]-TBPT binding competitively in both cortex and cerebellum. In contrast, gamma-aminobutyric acid (GABA) agonists (muscimol, GABA and 4,5,6,7-tetrahydroisoxazol[5,4-C]pyridine-3-ol [THIP]), and depressants like etazolate, (+)etomidate and pentobarbital were more potent inhibitors of [35S]TBPT binding in cerebellum than in cortex. GABA inhibition of [35S]TBPT binding appears to be mediated through a low-affinity site. GABA and pentobarbital inhibited [35S]TBPT binding in cortex and cerebellum noncompetitively. Depressants like pentobarbital appear to interact with the TBPT sites allosterically. These results suggest that depressant and convulsant drugs that modulate GABAergic transmission interact differently with the TBPT binding sites in cortex and cerebellum.

Animals↗
PubMed1995

Allosteric modulation of [3H]flunitrazepam binding to recombinant GABAA receptors.

The allosteric modulation of [3H]flunitrazepam binding by gamma-aminobutyric acid (GABA), pentobarbital, (+)-etomidate, etazolate, alphaxalone, propofol and chlormethiazole was investigated in cerebellar membranes and membranes from human embryonic kidney (HEK) 193 cells transfected with alpha 1 beta 3 gamma 2 or alpha 1 gamma 2 subunits. Results obtained indicate that [3H]flunitrazepam binding to recombinant GABAA receptors consisting of alpha 1 beta 3 gamma 2 subunits could be modulated by these compounds in a way and with a potency similar to that observed in cerebellar membranes. In addition, it was demonstrated that not only receptors consisting of alpha 1 beta 3 gamma 3, but also those consisting of alpha 1 gamma 2 subunits exhibited [3H]flunitrazepam binding which could be stimulated by GABA. In contrast to alpha 1 beta 3 gamma 2 receptors, however, [3H]flunitrazepam binding to recombinant alpha 1 gamma 2 receptors was inhibited by pentobarbital, (+)-etomidate, etazolate, alphaxalone, propofol and chlormethiazole. This seems to indicate that binding sites for these compounds are present on alpha 1 gamma 2 receptors, but that their allosteric interaction with [3H]flunitrazepam binding sites is different from that of alpha 1 beta 3 gamma 2 receptors.

Allosteric Regulation↗
PubMed1984

Ivermectin interactions with benzodiazepine receptors in rat cortex and cerebellum in vitro.

The anthelmintic macrolide, ivermectin, enhances the binding of benzodiazepine agonist ( [3H]-diazepam) and antagonist ( [3H] beta-carboline ethyl ester) ligands to rat cortical and cerebellar membrane preparations. Enhancement of benzodiazepine agonist binding is partially additive with that of gamma-aminobutyric acid (GABA) and is inhibited by etazolate, bicuculline, and the steroid GABA antagonist R5135. Ivermectin-stimulated benzodiazepine antagonist binding is enhanced by bicuculline and inhibited by GABA and etazolate. The modulatory effects of bicuculline are chloride-dependent. The stimulatory effects of ivermectin, while quantitatively different in cortex and cerebellum, are qualitatively similar in both brain regions and are reduced in the presence of chloride. Ivermectin effects on benzodiazepine ligand binding to the benzodiazepine receptor complex and the differences in the effects of GABA, bicuculline, and R5135 on ivermectin-stimulated agonist and antagonist binding may provide evidence for distinct differences in the recognition sites for the two classes of benzodiazepine receptor ligand and their interactions with other components of the receptor complex.

Animals↗
PubMed1995

Rat beta 3 subunits expressed in human embryonic kidney 293 cells form high affinity [35S]t-butylbicyclophosphorothionate binding sites modulated by several allosteric ligands of gamma-aminobutyric acid type A receptors.

Human embryonic kidney 293 cells transiently transfected with beta 3 subunits of gamma-aminobutyric acid type A receptors from the rat exhibited a specific high affinity binding for [35S]t-butylbicyclophosphorothionate (TBPS) that could be inhibited by pentobarbital, etazolate, (+)-etomidate, alphaxalone, propofol, chlormethiazole, and Ro 5-4864. The potency of these compounds for inhibition of [35S]TBPS binding was similar in membranes from beta 3 subunit-transfected human embryonic kidney 293 cells and in cerebellar membranes. In contrast to maximally inhibiting concentrations of unlabeled TBPS or picrotoxin, which caused a monophasic and rather slow dissociation of [35S]TBPS, maximally inhibiting concentrations of pentobarbital, etazolate, alphaxalone, propofol, chlormethiazole, and Ro 5-4864 accelerated the dissociation of [35S]TBPS from beta 3 subunit-containing membranes. Immunoaffinity chromatography and Western blot analysis with subunit-specific antibodies indicated that other endogenous subunits possibly present in these cells were not associated with beta 3 subunits. These results appear to indicate that most of the allosteric binding sites present on gamma-aminobutyric acid type A receptors can be formed by the beta subunit of these receptors. Homo-oligomeric beta 3 receptors therefore are an excellent model system for the structural investigation of gamma-aminobutyric acid type A receptors.

Allosteric Site↗
PubMed1996

Pharmacological modulation of myocardial tumor necrosis factor alpha production by phosphodiesterase inhibitors.

Phosphodiesterase (PDE) inhibitors are used as therapeutic agents for management of congestive heart failure. PDE inhibitors are potent inotropic and vasodilator drugs, which have also been shown to inhibit tumor necrosis factor alpha (TNF-alpha) production. TNF-alpha is a pleiotropic cytokine that has the ability to produce cardiac depressant and other cardiovascular effects in many disease conditions. TNF-alpha levels are elevated in patients with chronic congestive heart failure, and it is possible that TNF-alpha may play a role in this condition. The effects of PDE inhibitors on TNF-alpha secretion from rat heart were evaluated in this study. Rat left ventricle was minced and incubated for 4 hr with various PDE inhibitors, and the amount of TNF-alpha secretion was evaluated by cytotoxicity assay. Ro-20, 1724, etazolate, amrinone, milrinone and pentoxifylline inhibited unstimulated TNF-alpha production, with IC50 values of 1.87, 2.07, 13.9, 153 and 201 microM, respectively. Lipopolysaccharide-induced TNF-alpha secretion from rat left ventricle was also evaluated in this study. Amrinone, milrinone and pentoxifylline inhibited lipopolysaccharide-induced TNF-alpha secretion, with IC50 values of 14.8, 81.6 and 748 microM, respectively, whereas Ro-2D, 1724 and etazolate had no effect on lipopolysaccharide-induced TNF-alpha secretion. These results demonstrated that TNF-alpha was secreted from rat left ventricle after 4 hr and different pharmacological manipulations were able to inhibit the secretion of TNF-alpha from left ventricle. These initial pharmacological results may provide an important tool for further investigation into the beneficial effects of PDE inhibitors in congestive heart failure or other conditions where TNF-alpha levels are elevated.

Animals↗