Differential effects of short- and long-term zolpidem treatment on recombinant α1β2γ2s subtype of GABA(A) receptors in vitro.

Aim: Zolpidem is a non-benzodiazepine agonist at benzodiazepine binding site in GABA(A) receptors, which is increasingly prescribed. Recent studies suggest that prolonged zolpidem treatment induces tolerance. The aim of this study was to explore the adaptive changes in GABA(A) receptors following short and long-term exposure to zolpidem in vitro.

The effects of zolpidem treatment on GABA(A) receptors in cultured cerebellar granule cells: changes in functional coupling.

Aims: Hypnotic zolpidem is a positive allosteric modulator of γ-aminobutyric acid (GABA) action, with preferential although not exclusive binding for α1 subunit-containing GABA(A) receptors. The pharmacological profile of this drug is different from that of classical benzodiazepines, although it acts through benzodiazepine binding sites at GABA(A) receptors. The aim of this study was to further explore the molecular mechanisms of GABA(A) receptor induction by zolpidem.

Modulation of recombinant GABA(A) receptors by neurosteroid dehydroepiandrosterone sulfate.

Aim: To investigate whether long-term exposure to the neurosteroid dehydroepiandrosterone sulfate (DHEAS) induces adaptive changes of GABA(A) receptors related to the development of tolerance and dependence.

Methods: We compared the parameters of [(3)H]DHEAS binding and the effects of DHEAS on [(3)H]flunitrazepam binding in the membranes of HEK 293 cells, nontransfected or stably transfected with recombinant α(1)β(2)γ(2S) GABA(A) receptors. In HEK 293 cells expressing α(1)β(2)γ(2S) GABA(A) receptors, we investigated the effects of long-term DHEAS treatment on the [(3)H]flunitrazepam and [(3)H]t-butylbicycloorthobenzoate ([(3)H]TBOB) binding and on their modulation with GABA.

The effects of zolpidem treatment and withdrawal on the in vitro expression of recombinant alpha1beta2gamma2s GABA(A) receptors expressed in HEK 293 cells.

Zolpidem, a widely used hypnotic drug which acts through benzodiazepine binding sites, is a positive allosteric modulator of gamma-aminobutyric acid (GABA) action with preferential affinity for GABA(A) receptors containing alpha1 subunit. The pharmacological profile of zolpidem is different from that of classical benzodiazepines. The aim of this study was to find out whether zolpidem treatment triggers adaptive changes in the recombinant alpha1 subunit-containing GABA(A) receptors other than those observed following treatment with classical benzodiazepine-diazepam.

Zolpidem is a potent anticonvulsant in adult and aged mice.

Zolpidem is a widely used hypnotic drug acting via benzodiazepine binding sites on GABA(A) receptors. Several studies suggested that zolpidem might have better anticonvulsant potency than previously thought. To compare the sedative and anticonvulsant potency of this drug, we studied in male mice the influence of zolpidem (0.

Effects of acute and repeated zolpidem treatment on pentylenetetrazole-induced seizure threshold and on locomotor activity: comparison with diazepam.

Zolpidem and diazepam are widely used drugs acting via benzodiazepine binding sites on GABA(A) receptors. While diazepam is non-selective, zolpidem has a high affinity for alpha1-, and no affinity for alpha5-containing receptors. Several studies suggested that behavioral effects of zolpidem might be more similar to classical benzodiazepines than previously thought.

Differential effects of diazepam treatment and withdrawal on recombinant GABAA receptor expression and functional coupling.

Prolonged exposure to benzodiazepines, drugs known to produce tolerance and dependence and also to be abused, leads to adaptive changes in GABA(A) receptors. To further explore the mechanisms responsible for these phenomena, we studied the effects of prolonged diazepam treatment on the recombinant alpha(1)beta(2)gamma(2S) GABA(A) receptors, stably expressed in human embryonic kidney (HEK) 293 cells. The results demonstrating that long-term (48 and 72 h) exposure of cells to a high concentration of diazepam (50 microM) enhanced the maximum number (B(max)) of [(3)H]flunitrazepam, [(3)H]muscimol and [(3)H]t-butylbicycloorthobenzoate ([(3)H]TBOB) binding sites, without changing their affinity (K(d)), suggested the up-regulation of GABA(A) receptors.

The role of transcriptional and translational mechanisms in flumazenil-induced up-regulation of recombinant GABA(A) receptors.

The aim of this study was to further elucidate the mechanisms involved in adaptive changes of GABA(A) receptors following prolonged exposure to flumazenil, the antagonist of benzodiazepine binding sites on GABA(A) receptors. The effects of prolonged flumazenil treatment were studied on recombinant alpha(1)beta(2)gamma(2S) GABA(A) receptors stably expressed in human embryonic kidney (HEK 293) cells. Using radioligand binding experiments we found enhancement in the maximum number of [(3)H]muscimol labeled binding sites in different preparations of HEK 293 cells.

Sedative and anticonvulsant effects of zolpidem in adult and aged mice.

To evaluate the possible age-related differences in the behavioral effects of zolpidem, a widely used hypnotic, we compared the effects of zolpidem on the locomotor activity and on the seizure threshold for pentylenetetrazole (PTZ) and picrotoxin (given by i.v. infusion) between adult (3 months) and aged (13 months) mice.

Interaction of diazepam and swim stress.

Many people take diazepam to prevent or counteract the consequences of exposure to different stressors. However, the interaction of diazepam and stress is not clear. Several studies have suggested that swim stress alters the properties of benzodiazepines.

Allosteric uncoupling and up-regulation of benzodiazepine and GABA recognition sites following chronic diazepam treatment of HEK 293 cells stably transfected with alpha1beta2gamma2S subunits of GABA (A) receptors.

Benzodiazepines are drugs known to produce tolerance and dependence and also to be abused and co-abused. The aim of this study was to further explore the mechanisms that underlie adaptive changes in GABA(A) receptors following prolonged exposure to these drugs. Human embryonic kidney (HEK 293) cells stably expressing recombinant alpha1beta2gamma2s GABA(A) receptors were exposed for 72 h to a high concentration of diazepam (50 microM) in the absence or presence of other drugs.

The role of 5-HT(7) receptors in the control of seizures.

Serotonin exerts its effects via at least 14 different receptor subtypes, but the role of only a few of them has been studied in relation to the control of seizures. A negative role of 5-HT(7) receptors has recently been proposed. To evaluate further in unstressed and stressed animals the possible role of this receptor subtype in the control of brain excitability, we treated mice with antagonists and agonists of these receptors prior to exposure to swim stress and the intravenous infusion of picrotoxin, a non-competitive GABA(A) receptor antagonist.

Zimelidine decreases seizure susceptibility in stressed mice.

To further evaluate whether selective serotonin reuptake inhibitors (SSRIs) have pro- or anticonvulsant properties and whether these properties will be modified by stress, we studied the effect of zimelidine on the convulsions produced by picrotoxin, a GABA(A) receptor antagonist, in unstressed and swim stressed mice. Zimelidine potentiated the ability of swim stress to enhance the threshold doses of intravenously administered picrotoxin producing convulsant signs and death, without having an effect in unstressed mice. The anticonvulsant effect of zimelidine was counteracted with mianserin, the antagonist of 5-HT(2A/2C), and diminished with WAY-100635, a selective antagonist of 5-HT(1A) receptors.

Stimulation of 5-HT 1A receptors increases the seizure threshold for picrotoxin in mice.

To evaluate the possible role of 5-HT 1A and 5-HT 2A receptors in the anticonvulsant effect of swim stress, mice were pre-treated with agonists and antagonists of these receptors prior to exposure to stress and the intravenous infusion of picrotoxin. 8-OH-DPAT ((+/-)-8-hydroxy-2-(di-n-propylamino) tetralin) and WAY-100635 (a selective agonist and antagonist of 5-HT 1A receptors), DOI (1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane) and ketanserin (a 5-HT 2A/2C receptor agonist and antagonist) were used. Results demonstrated that 1 and 3 mg/kg of 8-OH-DPAT increased the doses of picrotoxin producing running/bouncing clonus, tonic hindlimb extension and death in stressed and unstressed mice, respectively.

Chronic treatment with flumazenil enhances binding sites for convulsants at recombinant alpha(1)beta(2)gamma(2S) GABA(A) receptors.

GABA(A) receptors mediate most of the fast inhibitory neurotransmission in the brain. Prolonged occupancy of these receptors by ligands leads to regulatory changes often resulting in reduction of receptor function. The mechanism of these changes is still unknown.

Anticonvulsant effects of acute and repeated fluoxetine treatment in unstressed and stressed mice.

Comorbidity of epilepsy and depression is not rare. Stress can affect both depression and seizures. Therefore, it is important to know whether an antidepressant drug has pro- or anticonvulsant properties and whether these properties will be modified by stress.

Enhancement of benzodiazepine binding sites following chronic treatment with flumazenil.

The aim of this study was to improve our knowledge of the mechanisms leading to adaptive changes in gamma-aminobutyric acid(A) (GABA(A)) receptors following chronic drug treatment. Exposure (48 h) of human embryonic kidney (HEK 293) cells stably expressing recombinant alpha1beta2gamma2S GABA(A) receptors to the antagonist of benzodiazepine binding sites, flumazenil (5 microM), enhanced the maximum number (B(max)) and the equilibrium dissociation constant (K(d)) of [3H]flunitrazepam binding sites. The flumazenil-induced enhancement in B(max) was potentiated by GABA (50 microM) and reduced by the GABA(A) receptor antagonist, bicuculline (100 microM).

Chronic exposure of cells expressing recombinant GABAA receptors to benzodiazepine antagonist flumazenil enhances the maximum number of benzodiazepine binding sites.

The aim of this study was to better understand the mechanisms that underlie adaptive changes in GABAA receptors following their prolonged exposure to drugs. Exposure (48 h) of human embryonic kidney (HEK) 293 cells stably expressing recombinant alpha1beta2gamma2S GABAA receptors to flumazenil (1 or 5 microM) in the presence of GABA (1 microM) enhanced the maximum number (Bmax) of [3H]flunitrazepam binding sites without affecting their affinity (Kd). The flumazenil-induced enhancement in Bmax was not counteracted by diazepam (1 microM).

Prolonged exposure to gamma-aminobutyric acid up-regulates stably expressed recombinant alpha 1 beta 2 gamma 2s GABAA receptors.

The aim of this study was to better understand the mechanisms that underlie adaptive changes in GABA(A) receptors following their prolonged exposure to drugs. Exposure (48 and/or 96 h) of human embryonic kidney (HEK 293) cells stably expressing recombinant alpha1beta2gamma2s GABA(A) receptors for gamma-aminobutyric (GABA, 1 mM) and muscimol (100 microM), but not for diazepam (1 microM), enhanced the maximum number (B(max)) of [3H]flunitrazepam binding sites without affecting their affinity (K(d)). The GABA-induced enhancement in B(max) was reduced by the GABA receptor antagonist, bicuculline (100 microM), and by cycloheximide (10 microl/ml), a protein synthesis inhibitor.

Effect of ergot alkaloids on 3H-flunitrazepam binding to mouse brain GABAA receptors.

In vitro effects of dihydroergotoxine, dihydroergosine, dihydroergotamine, alpha-dihydroergocriptine (ergot alkaloids), diazepam, methyl-beta-Carboline-3-carboxilate (beta-CCM), flumazenil (benzodiazepines), gamma-amino butyric acid (GABA) and thiopental (barbiturate) were studied on mouse brain (cerebrum minus cerebral cortex) benzodiazepine binding sites labeled with 3H-flunitrazepam. Specific, high affinity (affinity constant, Kd = 57.7 8.

Swim stress inhibits 5-HT2A receptor-mediated head twitch behaviour in mice.

Rationale: Several studies have shown that swim stress lowers the convulsant potency of different convulsants. The involvement of alpha(2)-()adrenoceptors has been proposed. Drugs active at alpha(2)-adrenoceptors are known to modulate the head twitch response, the behaviour supposedly mediated by 5-HT(2A) receptors.

Interaction of stress and noradrenergic drugs in the control of picrotoxin-induced seizures.

To evaluate the possible role of noradrenergic system in the anticonvulsant effect of swim stress, the mice were prior to exposure to swim stress and the i.v. infusion of picrotoxin, pre-treated with desipramine (a noradrenaline reuptake inhibitor), N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4, a neurotoxin which destructs noradrenergic axons) or alpha-methyl-p-tyrosine (alpha-MPT, an inhibitor of catecholamine synthesis) and the latency to the onset of two convulsant signs and death was registered.

The involvement of alpha2-adrenoceptors in the anticonvulsive effect of swim stress in mice.

Rationale: Various studies have shown that stressful manipulations in rats and mice lower the convulsant potency of GABA-related, but also some GABA-unrelated convulsants. The mechanism of this anticonvulsive effect of stress is still unknown.

Objectives: We tested the possible involvement of alpha2-adrenoceptors in the previously observed anticonvulsive effect of swim stress.

[3H]Flunitrazepam binding to recombinant alpha1beta2gamma2S GABAA receptors stably expressed in HEK 293 cells.

The interaction of selected compounds with the binding of the benzodiazepine [3H]flunitrazepam to membranes isolated from human embryonic kidney (HEK) 293 cells, stably transfected with the aI( 2 2S subtype of GABAA receptors, was studied. This subtype of GABAA receptors is the most common type of GABAA receptor found in the brain, and benzodiazepines are drugs known to enhance the effects of the inhibitory neurotransmitter gamma-amino butyric acid (GABA) by binding to the benzodiazepine binding sites which are part of the GABAA receptor complex. Scatchard analysis of binding data revealed the existence of a single type of binding site for [3H]flunitrazepam.

Swim stress alters the behavioural response of mice to GABA-related and some GABA-unrelated convulsants.

To elucidate the relationship between stress and seizures, the effect of a single swim stress on the convulsive signs and death produced by several GABA-related and GABA-unrelated convulsants, and the effect of repeated swim stress on picrotoxin-induced convulsions was studied. Mice were subjected to swim stress (10 min swimming at 18-19 degrees C), and the i.v.