Pharmacological studies on zopiclone

The efficacy and safety of zolpidem and zopiclone to treat insomnia in Alzheimer's disease: a randomized, triple-blind, placebo-controlled trial

No prior studies have evaluated the efficacy and safety of zolpidem and zopiclone to treat insomnia of demented patients. This randomized, triple-blind, placebo-controlled clinical trial used these drugs to treat patients with probable, late onset Alzheimer's dementia (AD) (DSM V and NINCDS-ADRDA criteria) exhibiting insomnia (DSM V criteria and nocturnal NPI scores ≥ 2). Actigraphic records were performed for 7 days at baseline and for 14 days during the treatment period in 62 patients aged 80.5 years in average and randomized at a 1:1:1 ratio for administration of zolpidem 10 mg/day, zopiclone 7.5 mg/day or placebo. Primary endpoint was the main nocturnal sleep duration (MNSD), whereas secondary outcomes were the proportion of the night time slept, awake time after sleep onset (WASO), nocturnal awakenings, total daytime sleep time and daytime naps. Cognitive and functional domains were tested before and after drug/placebo use. Three participants under zopiclone use had intervention interrupted due to intense daytime sedation and worsened agitation with wandering. Zopiclone produced an 81 min increase in MNSD (95% confidence interval (CI): -0.8, 163.2), a 26 min reduction in WASO (95% CI: -56.2, 4.8) and a 2-episode decrease in awakening per night (95% CI: -4.0, 0.4) in average compared to placebo. Zolpidem yielded no significant difference in MNSD despite a significant 22 min reduction in WASO (95% CI: -52.5, 8.3) and a reduction of 1 awakening each night (95% CI: -3.4, 1.2) in relation to placebo. There was a 1-point reduction in mean performance in the symbols search test among zolpidem users (95% CI: -4.1, 1.5) and an almost eight-point reduction in average scores in the digit-symbol coding test among zopiclone users (95% CI: -21.7, 6.2). In summary, short-term use of zolpidem or zopiclone by older insomniacs with AD appears to be clinically helpful, even though safety and tolerance remain issues to be personalized in healthcare settings and further investigated in subsequent trials. This trial was registered in ClinicalTrials.gov Identifier: NCT03075241.

Zopiclone to treat insomnia in older adults: A systematic review

Considering the global increase in use of Z-drugs to treat insomnia, the study objective was to conduct a systematic review on the efficacy and safety of zopiclone to treat sleep disorders in older adults compared to other sedative-hypnotics, to placebo or to non-pharmacological interventions. The literature search for original reports - clinical trials, cohort studies and cross-sectional, observational investigations - was done in eleven databases and web search engines followed PRISMA guidelines, and methodological quality was assessed using the Risk of Bias tool in the Cochrane Reviewers' Handbook. The search resulted in 12 randomized, placebo-controlled clinical trials along with 2 open studies and 2 observational reports. Overall, the studies suggest that zopiclone is effective to treat insomnia by reducing sleep latency, nocturnal awakenings and wake time after sleep onset while increasing total sleep time, with probable effects on sleep architecture. Zopiclone was found to be fairly tolerated, to induce a low rate of adverse events with non-severe impact on psychomotor or cognitive performance and to produce no major harm to the overall well-being and daily living abilities. However, the quality of most studies was classified as low or unclear. Though the studies available support benefits from zopiclone use, there is still a need for further evidence on long-term effects, tolerability and safety in the treatment of older adults by means of high-quality trials.

Gaboxadol, a selective extrasynaptic GABA(A) agonist, does not generalise to other sleep-enhancing drugs: a rat drug discrimination study

Gaboxadol is a selective extrasynaptic GABA(A) receptor agonist (SEGA) which enhances slow-wave sleep, and may act principally at extrasynaptic GABA(A)alpha4betadelta receptors. Drug discrimination is a very useful approach for exploring in vivo pharmacological similarities and differences between compounds and was therefore used to compare gaboxadol and zolpidem, an established hypnotic drug, against zopiclone, S-zopiclone, indiplon and tiagabine, all of which have been reported to enhance sleep. Gaboxadol generalised to itself, but not to zolpidem, zopiclone, S-zopiclone, R-zopiclone, indiplon or tiagabine. By contrast, zolpidem generalised to itself, zopiclone, S-zopiclone and indiplon, but not to R-zopiclone (the inactive enantiomer of zopiclone), gaboxadol or tiagabine. This suggests that zolpidem, zopiclone, S-zopiclone and indiplon share a discriminative stimulus, which may be mediated by their efficacy at GABA(A)alpha1betagamma receptors. Gaboxadol and tiagabine each have a different discriminative stimulus from all the other drugs tested.

Comparative pharmacokinetics and pharmacodynamics of short-acting hypnosedatives: zaleplon, zolpidem and zopiclone

Benzodiazepines have historically been the mainstay of treatment for sleeping disorders, yet they have many shortcomings. A new group of sedative hypnotic agents has been developed for this purpose. Similar to the benzodiazepines, zaleplon, zolpidem and zopiclone have activity at the GABA receptor complex, yet they appear to have more selectivity for certain subunits of the GABA receptor. This produces a clinical profile that is more efficacious with fewer side effects. Zaleplon, zolpidem and zopiclone are structurally distinct. Due to variation in binding to the GABA receptor subunits, these three compounds show subtle differences in their effect on sleep stages, and as antiepileptics, anxiolytics and amnestics. The duration of action of zaleplon, zolpidem and zopiclone can be related to their individual pharmacokinetic profile, which subsequently determines the time course of drug effect. Each of these compounds has a unique pharmacokinetic profile with different bioavailability, volume of distribution and elimination half-lives. Zaleplon has a rapid elimination so there are fewer residual side effects after taking a single dose at bedtime. By comparison, zolpidem and zopiclone have a more delayed elimination so there may be a prolonged drug effect. This can result in residual sedation and side effects but may be useful for sustained treatment of insomnia with less waking during the night. There are also differences in potency based on plasma concentrations suggesting that there are differences in binding to the GABA receptor complex. Although zaleplon has a much lower bioavailability (30%), the treatment dose is similar to zolpidem and zopiclone (bioavilaibility of 70%) because of the increased potency of zaleplon. The pharmacokinetics and pharmacodynamics of zaleplon, zolpidem and zopiclone are significantly different from benzodiazepines. The new drugs are sufficiently unique from each other to allow customisation of treatment for various types of insomnia. While zaleplon may be best indicated for the delayed onset of sleep, zolpidem and zopiclone may be better indicated for maintaining a complete night's sleep. Only the patient's symptoms and response to treatment will dictate the best course of treatment.

Stereoselective distribution and stereoconversion of zopiclone enantiomers in plasma and brain tissues in rats

Concentrations of (-)-zopiclone and (+)-zopiclone were determined in plasma and brain after oral administration, to investigate the stereoselectivity of distribution in rats. Zopiclone enantiomers were administered separately to rats and concentrations were determined by chiral HPLC in plasma and brain. In initial experiments, rats were treated with urethane before cannulation for blood sampling but as this drug modified zopiclone pharmacokinetics, it was not used in subsequent studies. This study showed that zopiclone pharmacokinetics after oral gavage in rats are stereoselective. After oral administration of (+)-zopiclone, no stereoconversion was observed in plasma. Conversely, after administration of (-)-zopiclone, both enantiomers were found in plasma and brain with (+)-zopiclone/(-)-zopiclone ratios of 1 and 8.4 in plasma and brain, respectively. Our findings suggest that zopiclone undergoes stereoconversion and that it is stereospecifically distributed to the brain.

Sedative and anxiolytic effects of zopiclone's enantiomers and metabolite

We evaluated racemic zopiclone, its (S)- and (R)-enantiomers and a metabolite, (S)-desmethylzopiclone, for their actions on locomotor activity, rotarod performance, the elevated plus maze and the Vogel conflict test of anxiety, and electroconvulsive shock-induced seizures duration. Zopiclone and its (R)- and (S)-enantiomers reduced locomotor activity, and zopiclone and its (S)-enantiomer disrupted rotarod performance at 10 mg/kg. (S)-desmethylzopiclone did not alter these measures at doses of less than 200 mg/kg. (S)-desmethylzopiclone altered plus maze performance at the lowest dose of all the zopiclone derivatives tested, caused a dose-related effect on the Vogel conflict test and caused a dose-related reduction of electroconvulsive shock-induced seizure durations. The data indicate that (S)-desmethylzopiclone can bring about an anxiolytic effect without a substantial degree of central nervous system depression, and suggest that the agent may be particularly useful clinically in the treatment of anxiety.

Independent sleep EEG slow-wave and spindle band dynamics associated with 4 weeks of continuous application of short-half-life hypnotics in healthy subjects

OBJECTIVES

Habituation and adverse withdrawal reactions after prolonged medication with benzodiazepine (BZ) hypnotics are believed to play a role in dose escalation and the development of dependence.

METHODS

In the current sleep EEG study in 43 healthy male subjects, the known property of BZ- and similar hypnotics to change the NREM sleep EEG spectrum is utilized for a detailed quantitative analysis across 4 weeks of continuous medication and a subsequent two-week withdrawal period. The BZ hypnotic triazolam and the non-BZ hypnotics zopiclone and zolpidem, differing in pharmacological properties and reported adverse effects, were examined in parallel to a placebo group.

RESULTS

Reliably occurring spectral effects in the sleep stage 2 EEG were found in the 3 frequency bands 0.8-5 Hz, 5-10 Hz and 10-15 Hz. All 3 hypnotics showed the typical 'benzodiazepine signature', a 10-15 Hz increase and lower-frequency (<10 Hz) suppression relative to the preceding drug-free night. However, these effects developed differently across the first medication night, across the 4 medication weeks and after withdrawal: While the 5-10 Hz effect covaried with the blood presence of the drugs as estimated from the known plasma half-lifes, showed habituation and a rebound after withdrawal, the 10-15 Hz power increased across medication days and showed no rebound. Effects in the 0.8-5 Hz band in the first medication night correlated with the decrease of sleep efficiency at later withdrawal for triazolam and zolpidem.

Effects of repeated administration of zolpidem on sleep, diurnal and nocturnal respiratory function, vigilance, and physical performance in patients with COPD

STUDY OBJECTIVE

To assess the effects of repeated 10-mg oral doses of zolpidem on diurnal and nocturnal respiratory function, as well as on diurnal vigilance and physical performance in COPD patients with disordered sleep.

DESIGN

Prospective single-blind placebo-controlled clinical study.

SETTING

Outpatients of a respiratory medicine department.

PATIENTS AND METHODS

Patients with stable COPD were enrolled for 10 days (D0 to D10), ie, 9 consecutive nights (N1 to N9). They received placebo on N1 and N9 and zolpidem, 10 mg, from N2 to N8.

MEASUREMENTS

The following parameters were measured: nocturnal polysomnographic recordings with respiratory signals and arterial blood gas values on retiring and awakening on N0, N1, N2, N8, and N9; subjective evaluation of the quality of sleep and of diurnal vigilance by visual analog scales every day from D0 to D10; pulmonary function test, central control of breathing, and walking test on D0 and D9; biological laboratory tests and theophylline level on D0 and D8.

RESULTS

Ten COPD patients (PaO2 = 72.7 +/- 7.6 mm Hg; PaCO2 = 47.7 +/- 5.4 mm Hg; FEV1 = 0.84 +/- 0.3 L; FEV1/vital capacity = 42.5 +/- 12.3%), 56.8 +/- 8.3 years old, were studied. Compared with placebo, no significant change was found for the various sleep architecture parameters, except an increase in the duration of stage 2 during the D8/N8 night (p < 0.05). In contrast, the autoevaluation score for the quality of sleep was significantly improved during the D6/N6 night relative to that with placebo (p < 0.05), with no change in the other subjective criteria. No variable of the nocturnal respiratory parameters, pulmonary function test, central control of breathing, and physical performance was altered by zolpidem. Arterial blood gas values on awakening were not altered. Clinical and biological tolerance of zolpidem was correct with no significant variation of the theophylline level.

CONCLUSION

This study shows that repeated 10-mg oral doses of zolpidem during 8 days does not impair nocturnal respiratory and sleep architecture parameters or diurnal pulmonary function tests, central control of breathing, and physical performances in patients with stable COPD.

Pharmacokinetic-pharmacodynamic modelling of zopiclone effects on human central nervous system

The present data shows the pharmacokinetics and concentration-effect relationship of a single 7.5 mg oral dose of zopiclone in ten healthy volunteers. Plasma concentrations and effects of zopiclone on central nervous system as quantified by changes in saccadic peak velocity and digit symbol substitution test were measured for 17 hr after ingestion of zopiclone. Pharmacokinetics was described with a linear one-compartment open model. Maximum effects preceded peak plasma zopiclone concentrations causing a clockwise hysteresis, i.e. proteresis, in concentration versus effect loops. Therefore, pharmacodynamics was described both with a tolerance model and a model with distributional pseudo-tolerance where the concentration in the blood sampling site is assumed to equilibrate slower with arterial blood than the site of action of zopiclone. Both models related the changes in pharmacodynamics linearly to changes in zopiclone concentrations. The median (range) values for clearance, volume of distribution and elimination half-life were 21 (15-53) L/hr, 132 (58-161) L and 3.4 (1.7-5.7) hr, respectively. Both pharmacodynamic models were able to describe the relationship between zopiclone concentrations and changes in psychomotor performance equally well. However, because the pharmacodynamics of zopiclone were studied in a non-steady-state situation, the mechanism for proteresis, i.e. true tolerance versus distributional pseudotolerance cannot be identified.

The transition from slow-wave sleep to paradoxical sleep: evolving facts and concepts of the neurophysiological processes underlying the intermediate stage of sleep

Paradoxical sleep in rats, cats and mice is usually preceded and sometimes followed by a short-lasting (a few seconds) electroencephalogram (EEG) stage characterized by high-amplitude spindles in the anterior cortex and low-frequency theta rhythm in the dorsal hippocampus. The former is an index of advanced slow-wave sleep; the latter is an index of limbic activation since it occurs during active waking and paradoxical sleep. Barbiturates and benzodiazepines extend this intermediate stage at the expense of paradoxical sleep while concomitantly barbiturates suppress the pontine reticular activation characteristic of this sleep stage. During the intermediate stage, thalamocortical responsiveness and thalamic transmission level, which are controlled by brain stem activating influences, are the lowest of all sleep-waking stages. The unusual EEG pattern of this stage is otherwise only observed in the acute intercollicular-transected preparation. Therefore, forebrain structures may be functionally briefly disconnected from the brain-stem during this short-lasting stage, which could possibly account for the mental content of a similar sleep period in humans. In spite of strong evidence in favour of this forebrain deafferentiation hypothesis, other data indicate that the IS is in some way linked either to slow-wave sleep or to paradoxical sleep.

Tolerance, cross-tolerance and dependence measured by operant responding in rats treated with triazolam via osmotic pumps

Previous research has found that drugs with affinity for omega (benzodiazepine) sites differ in their abilities to produce tolerance and dependence. The present study therefore investigated the effects of ligands of omega (BZ) sites in rats that had been rendered tolerant to a benzodiazepine. Two experiments were carried out in separate groups of rats. Behavioral changes induced by chronic infusion of triazolam (3 mg/kg/day, SC, for 14 days) via osmotic pumps were studied in animals trained on a fixed ratio 10 schedule of food presentation. Control animals were implanted with pumps containing the vehicle. Test drugs were administered IP using cumulative dosing. In one experiment triazolam decreased response rates on days 1, 2 and 3 after implantation of the pumps and tolerance developed to this depressant effect. In the other experiment, vehicle and triazolam treated rats differed in their responding during chronic infusion but differences were not statistically significant on any particular day. Flumazenil (3.0-30 mg/kg) greatly decreased rates of responding on day 11 in triazolam treated rats. This effect may represent a precipitated withdrawal syndrome. However, no withdrawal effects on operant performance were observed upon pump removal. Chronic infusion of triazolam did not affect the sensitivity of rats to alpidem on day 11 (10-100 mg/kg) whereas it abolished the stimulant effect of bretazenil (0.1-1.0 mg/kg). Chronic triazolam treatment produced tolerance to the depressant effects of triazolam (1.0-3.0 mg/kg), lorazepam (0.3-3.0 mg/kg) and zopiclone (10 mg/kg) but no tolerance to those of CL 218,872 (3.0-30 mg/kg) and zolpidem (0.3-3.0 mg/kg) when tested 3-14 days after pump removal.(ABSTRACT TRUNCATED AT 250 WORDS)

Sleep disorders and anxiety: biochemical antecedents and pharmacological consequences

Evidence is presented that the most widely used and effective drugs used in the treatment of anxiety and insomnia act by indirectly activating GABA-A receptors in limbic regions of the brain. Since the discovery of the benzodiazepines, different classes of benzodiazepine receptor ligands (such as the cyclopyrroliones and imidazopyridines) have been developed which alleviate anxiety and insomnia by activating different sites on the benzodiazepine-GABA receptor complex to those activated by the 'classical' benzodiazepines as exemplified by temazepam and diazepam. There is evidence that natural ligands also exist in the mammalian brain which can modulate the benzodiazepine-GABA receptor complex. This raises the possibility that insomnia and anxiety states may arise as a consequence of a deficit in the availability of endogenous ligands that act as agonists at these sites.

Zopiclone in insomniac shiftworkers. Evaluation of its hypnotic properties and its effects on mood and work performance

Fifty adult insomniac shiftworkers (47 males and 3 females) between the ages of 22 and 55 participated in this two-week, double-blind comparative study of the hypnotic properties and effects on mood and work performance of zopiclone 7.5 mg and placebo. All subjects took inactive medication on the first night of the study and then received either zopiclone or placebo for the following 13 nights according to randomization. Pre-study variables included a demographic profile, medical history, physical examination, laboratory data, profile of insomnia and work shift pattern description. A sleep questionnaire along with mood and work performance questionnaires were filled out on Days 1, 2, 4, 9 and 12 of the study; on Days 7 and 14, adverse events were recorded. After the first placebo night, subjects assigned to receive zopiclone showed significantly improved sleep induction; from the second night on, a distinct pharmacological effect over placebo was observed and maintained since statistically significant increases in quantitative sleep induction and sleep soundness (qualitative and quantitative) were noted during the course of zopiclone treatment. Active hypnotic treatment did not interfere with morning awakening and functioning, nor did it affect mood or work performance. Zopiclone treatment produced significantly more taste disturbance and drowsiness. In summary, zopiclone was shown to be an effective, fast-acting hypnotic which maintained its efficacy over a two-week period in our sample of insomniac shiftworkers and did not produce mood changes or influence work performance.

Effects of non-sedative anxiolytic drugs on responses to GABA and on diazepam-induced enhancement of these responses on mouse neurones in cell culture

1. Intracellular microelectrode recording techniques were performed on mouse spinal cord and cerebral hemisphere neurones grown in primary dissociated cell culture. The effects of several anxiolytics applied by local pressure ejection on responses to gamma-aminobutyric acid (GABA) evoked by iontophoresis were investigated. Responses to GABA were depolarizing since intracellular chloride ion concentration was increased by injection from potassium chloride (3M)-filled recording micropipettes and neurones were held at large negative membrane potentials (-70 to -90 mV). The agents studied were six 'non-sedative anxiolytics', CL 218,872 (3-methyl-6-(3-trifluoromethyl-phenyl)1,2,4-triazolo(4,3-b) pyridazine), PK 8165 (2-phenyl-4-(2-(4-piperidinyl)ethyl)-quinoline), PK 9084 (2-phenyl-4-(2-(3-piperidinyl)ethyl)-quinoline), CGS 9896 (2-(4-chlorophenyl)-2,5-dihydropyrazolo(4,3-c)quinoline-3(3H)-one) , ZK 91296 (ethyl 5-benzyloxy-4-methoxymethyl-beta-carboline-3-beta-carboxylate), buspirone (8-4-[4-(2-pyrimidinyl)-1-piperazinyl]butyl-8-azaspiro[4.5]decane- 7,9- dione), and two sedative anxiolytics, diazepam and zopiclone [( 6-(5-chloro-2-pyridyl)-6,7-dihydro-7-oxo-5H-pyrrolo[3,4-b]pyrazin- 5- yl]4-methyl-1-piperazinecarboxylate). 2. Direct effects on responses to GABA were studied for all drugs applied in varying concentrations. For the drugs which significantly altered responses to GABA, the effects of the benzodiazepine receptor antagonists Ro 15-1788 (ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo(1,5a)-(1,4)benzodi azepine - 3-carboxylate) and CGS 8216 (2-phenylpyrazolo(4,3-c)-quinolin-3(5H)-one) were evaluated. For the drugs devoid of significant direct effect on responses to GABA, the influence on diazepam-induced enhancement of responses to GABA was evaluated. 3. Diazepam, zopiclone and CL 218,872 concentration-dependently and reversibly enhanced responses to GABA. Maximal enhancement was 82% for diazepam (500 nM), 64% for zopiclone (10 microM) and 20% for CL 218,872 (10 microM). PK 8165 effects varied with concentration, enhancing responses to GABA (up to 18%) at nM concentrations and reducing responses to GABA (up to 90%) at microM concentrations. CGS 9896, ZK 9126, PK 9084 and buspirone, in concentrations ranging from 1 nM to 10 microM, lacked significant direct effects on responses to GABA. 4. The enhancing effects of diazepam, zopiclone, CL 218,872 and PK 8165 were antagonized by Ro 15-1788. However, the reducing effect on responses to GABA of PK 8165 at microM concentrations was not antagonized by CGS 8216. CGS 9896 and ZK 91296 concentration-dependently blocked the diazepam-induced enhancement of responses to GABA. However, PK 9084 and buspirone did not antagonize the diazepam-induced enhancement of responses to GABA. 5. These results indicate that diazepam and zopiclone may be full agonists, CL 218,872 and PK 8165 are partial agonists, and CGS 9896 and ZK 91296 are pure antagonists at benzodiazepine receptors. On the other hand, PK 9084 and buspirone do not interact with benzodiazepine receptors.

A sleep laboratory evaluation of the long-term efficacy of zopiclone

Six patients between the ages of 25 and 59, with chronic, primary insomnia received the new, non-benzodiazepine, hypnotic zopiclone continuously for 17 weeks after a drug free interval of 12 nights. To qualify for the study, sleep efficiency, determined by a sleep study on two, consecutive, placebo-controlled nights, had to be less than 75%. Patients evaluated their sleep by questionnaire and had sleep studies completed throughout active treatment. Zopiclone (7.5 mg) increased sleep efficiency by decreasing sleep latency, wakefulness after sleep onset and increasing total sleep time. Sleep architecture was minimally affected by zopiclone treatment; no significant changes in delta or REM sleep were observed. The commonest side effect was a bitter or metallic taste. No significant changes in biological functioning were noted throughout the study period. These findings indicate that zopiclone is a safe and effective hypnotic medication which maintains its effectiveness with protracted use.

The effect of agonists at the GABA-benzodiazepine receptor complex on the duration of immobility of mice in the forced swimming test

In the present study, we examined the effect of various agents which affect in a different manner the GABA-benzodiazepine receptor-chloride ionophore complex system in relation to the immobile behavior of mice in the forced swimming test. The benzodiazepines diazepam and flurazepam, the barbiturates pentobarbital and phenobarbital, zopiclone and beta-CCP (propyl-beta-carboline-3-carboxylate) enhanced the immobile behavior in a dose-dependent manner. In the doses used here, these agents produced almost no muscle relaxant action. Ro15-1788 and beta-CCM (methyl-beta-carboline-3-carboxylate) themselves had no effect on the duration of immobility. However, Ro15-1788 and beta-CCM reversed the enhancing effect produced by all 6 drugs. These results indicate that the enhancement of the duration of immobility of mice may be somehow correlated to the anxiolytic action but not to the muscle relaxant action. The effect may be mainly mediated by the benzodiazepine receptor, which forms a part of the GABA-benzodiazepine receptor-chloride ionophore complex. Furthermore it is suggested that there were behavioral similarities in the effects of beta-CCP and benzodiazepines.

Novel benzodiazepine receptor ligands stimulate intake of hypertonic NaCl solution in rehydrating rats

Experiments were conducted to determine the degree of generality of previous findings that anxiolytics increased the ingestion of hypertonic saline in rehydrating rats. Further, potential differential effects amongst recently described benzodiazepine receptor partial agonists were explored. Finally, the hypothesis that benzodiazepine receptor partial inverse agonists would decrease the ingestion of hypertonic NaCl solution was tested. Results indicated that full agonists (midazolam, ZK 93423, zopiclone) produced substantial dose-related increases in hypertonic saline consumption. The putative 5-HT1A agonist, buspirone, produced only a dose-dependent decrease in saline intake. Partial agonists fell into two distinct categories: ZK 91296, CL 218,872 and two novel benzodiazepines, Ro16-6028 and Ro17-1812, also increased saline ingestion. In contrast, two pyrazoloquinolines, CGS 9896 and CGS 9895, had no significant effect on intake. Two compounds, CGS 8216 and FG 7142, described as benzodiazepine partial inverse agonists, did not significantly affect consumption of the hypertonic saline.

Comparative effects of zopiclone, triazolam and placebo on memory and psychomotor performance in healthy volunteers

This study evaluated the effects of acute doses of zopiclone (7.5 mg), triazolam (0.25 mg) and placebo on memory and psychomotor performance of 12 normal volunteers. The subjects received both drugs in a repeated measure, double-blind Latin square design. The tests (CFF, CRT, DSST, memory assessments) were performed before and 2 and 6 hr after treatment. Zopiclone and triazolam induced an anterograde amnesia affecting short-term and long-term memory which lasted less than 6 hr. No retrograde amnesia was observed. Two hr after drug intake of both hypnotics psychomotor performances were significantly altered compared with placebo. The subjects also felt more drowsy, dizzy, clumsy and tired, and less alert and energetic 2 hr after zopiclone and triazolam compared to placebo. There was no difference between the effects of the two hypnotics at the doses studied.

Differential effects of benzodiazepine receptor ligands on isotonic saline and water consumption in water-deprived rats

Water-deprived male rats were adapted to a 30 min test of water or saline drinking in a single-bottle acceptance test. The potent benzodiazepine agonist, clonazepam, produced significant increases in both water and saline consumption. Increases in the consumption of both were also obtained with the non-benzodiazepine agonist, zopiclone (a cyclopyrrolone), but not with the pyrazoloquinoline agonist, CGS 9896. Hence, some, but not all, benzodiazepine receptor agonists enhance drinking responses. The benzodiazepine receptor antagonists, Ro15-1788 and CGS 8216, had no significant effect on the intake of either isotonic saline or water. In contrast, the beta-carboline FG 7142, which has been described as an inverse agonist acting at benzodiazepine receptors, reduced both saline and water drinking at 10 and 20 mg/kg. Although the baseline level of saline drinking was considerably higher than that of water, there was no general indication that any drug effect on consumption interacted with the type of fluid in the drinking test. However, in the case of agonist-induced increases in consumption, peak effects occurred at different doses; they were lower for saline- than for water-drinking.

A new method for screening anxiolytic drugs in rats

In order to evaluate the anxiolytic action of drugs, a simple experimental procedure using a corridor-type runway was designed. In this apparatus, five food pellets were set in a row on a plastic platform. Rats with one day food-deprivation take a food pellet and then usually return to the start box. The time required to take 5 pellets (total time) and the number of returns were recorded. Diazepam (DZP) at 1-3.2 mg/kg and zopiclone (ZOP) at 10 mg/kg caused decreases in both parameters. These effects were blocked by the benzodiazepine receptor blocker, Ro15-1788, at 10 mg/kg. However, tracazolate failed to produce any change in both parameters. Haloperidol and imipramine prolonged the total time while reducing the number of returns. In contrast to DZP and ZOP, pentetrazol, well known to possess an anxiogenic effect, prolonged the total time. These results suggest that decreases in both the total time and the number of returns produced by DZP and ZOP may be related to their anxiolytic action which is mediated by a benzodiazepine receptor. Therefore, this procedure would be a simple and selective method for detecting benzodiazepine-type anxiolytics.

Pharmacological and clinical studies of cyclopyrrolones: zopiclone and suriclone

Among the non-benzodiazepine compounds which have been found to interact with the "GABA receptor-BZ receptor-chloride channel complex," the very chemically original cyclopyrrolone family has a special place. This has been demonstrated using selected pharmacological, biochemical and clinical data obtained with two cyclopyrrolones, zopiclone and suriclone, which, in addition to their capacity of displacing BZ from their sites, simultaneously possess the main pharmacological properties of BZ and well established therapeutic activities, as hypnotic and anxiolytic, respectively. However, although cyclopyrrolones recognize BZ receptor sites, their mechanism of action might not exactly fit with that of BZ. Indeed, using tritiated zopiclone and suriclone, it has been shown that they could act on sites distinct from those of BZ or could induce receptor conformational changes different from those induced by BZ.

Partial chemical characterization of cyclopyrrolones ([3H] suriclone) and benzodiazepines ([3H]flunitrazepam) binding site: differences

Rat hippocampus membranes were treated with several protein modifying reagents (iodoacetamide, N-ethylmaleimide, tetranitromethane and N-acetylimidazole). The effects of these treatments on the binding sites of cyclopyrrolones ([3H] suriclone), a new chemical family of minor tranquilizers, and benzodiazepines ([3H] flunitrazepam) were investigated. Here we show that both ligands are similarly sensitive to cysteine alkylation: [3H] suriclone and [3H] flunitrazepam binding are reduced by iodoacetamide and slightly increased by N-ethylmaleimide. On the contrary they are clearly differenciated by tyrosine modification: [3H] suriclone binding is not changed whereas [3H] flunitrazepam binding is increased by tetranitromethane and decreased by N-acetylimidazole. Our present findings and published evidence suggest cyclopyrrolones and benzodiazepines bind to distinct sites or to different allosteric forms of the benzodiazepine receptor.

Anxiolytic drugs and the acquisition of conditioned fear in mice

Previous studies have shown that, in rodents, chlordiazepoxide and other benzodiazepines can interfere with learning in passive avoidance or conditioned suppression procedures. The most consistent effects are observed when the drugs are administered before the acquisition trial and subjects are re-tested in the non-drugged state. It is not clear, however, whether this effect on learning is associated with the behavioural depressant actions of these drugs. In the present study mice were injected with chloridiazepoxide, diazepam, zopiclone, or CGS 9896 and locomotor activity measured in a two-compartment box. The animals were then enclosed in one of the compartments and received a series of footshocks. On a second trial, 24 h after the first, the mice were returned to the box without injection and locomotion and time spent in each compartment were measured. During trial 1 chlordiazepoxide, diazepam, and zopiclone produced dose-related decreases in locomotor activity. The same doses disrupted fear conditioning. CGS 9896 also interfered with the conditioning of fear but did not reduce exploratory activity during the first trial at any of a wide range of doses, showing that learning can be affected without direct behavioural depressant activity. In a further experiment, chlordiazepoxide and CGS 9896 disrupted fear conditioning when injected before trial 1 but not when injected immediately after this trial. Mice drugged with chlordiazepoxide or CGS 9896 before both trials 1 and 2 also showed disrupted conditioning, demonstrating that the drug effects cannot be interpreted in terms of state dependent learning.

Suriclone, a new anxiolytic of the cyclopyrrolone family: evidence for possible interference with GABAergic systems

The action of suriclone (R.P. 31,264), a new non-benzodiazepine compound of the cyclopyrrolone family with clinical anxiolytic activity was examined using biochemical and electrophysiological models supposed to be capable of revealing central GABAergic activity. Suriclone, which does not act directly on the gamma-aminobutyric acid (GABA) receptor (muscimol binding assay), markedly reduced the increase of striatal HVA level induced in the rat by a neuroleptic and decreased the cerebellar vermis cGMP content. Moreover, in the cat, suriclone was able to enhance dorsal root potential amplitude which reflects an increase of the presynaptic inhibition. In view of these results, a central GABAergic mechanism of action may be proposed for suriclone.