New insights into the mechanism of action of hypnotics

Abrupt Withdrawal From Chronic High-Dose Zolpidem Use: A Case Report of Resulting Delirium

We report the case of a male in his twenties who was prescribed 10 mg of zolpidem daily for sleep disturbances. Within one month, he self-augmented the dose to 30 mg daily. Unable to secure an authorized refill, he sought unauthorized suppliers and increased his daily intake to 70 mg over eight months. One day after his medication supply was depleted, he presented to the emergency department with symptoms indicative of acute delirium. Delirium was successfully alleviated within six hours using lorazepam. This was followed by a five-day lorazepam tapering regimen during the patient's hospital stay and then a subsequent four-day taper in an outpatient setting. This case highlights the dangers associated with zolpidem misuse, the swift onset of withdrawal symptoms following abrupt discontinuation, and the crucial importance of rigorous prescription monitoring and patient education regarding the risks of unguided dosage modifications and the sudden cessation of zolpidem.

Cannabinoids, Endocannabinoids and Sleep

Sleep is a vital function of the nervous system that contributes to brain and bodily homeostasis, energy levels, cognitive ability, and other key functions of a variety of organisms. Dysfunctional sleep induces neural problems and is a key part of almost all human psychiatric disorders including substance abuse disorders. The hypnotic effects of cannabis have long been known and there is increasing use of phytocannabinoids and other formulations as sleep aids. Thus, it is crucial to gain a better understanding of the neurobiological basis of cannabis drug effects on sleep, as well as the role of the endogenous cannabinoid system in sleep physiology. In this review article, we summarize the current state of knowledge concerning sleep-related endogenous cannabinoid function derived from research on humans and rodent models. We also review information on acute and chronic cannabinoid drug effects on sleep in these organisms, and molecular mechanisms that may contribute to these effects. We point out the potential benefits of acute cannabinoids for sleep improvement, but also the potential sleep-disruptive effects of withdrawal following chronic cannabinoid drug use. Prescriptions for future research in this burgeoning field are also provided.

Approaches to the Pharmacological Management of Jet Lag

For many years now a treatment mitigating the debilitating effects of jet lag has been sought. Rapid travel across time zones leads, in most people, to temporary symptoms, in particular poor sleep, daytime alertness and poor performance. Mis-timed circadian rhythms are considered to be the main factor underlying jet-lag symptoms, together with the sleep deprivation from long haul flights. Virtually all aspects of physiology are rhythmic, from cells to systems, and circadian rhythms are coordinated by a central pacemaker or clock in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN adapts slowly to changes in time zone, and peripheral clocks or oscillators adapt at different rates, such that the organism is in a state of desynchrony from the external environment and internally. Light exposure is the main factor controlling the circadian system and needs to be considered together with any pharmacological interventions. This review covers the relatively new chronobiotic drugs, which can hasten adaptation of the circadian system, together with drugs directly affecting alertness and sleep propensity. No current treatment can instantly shift circadian phase to a new time zone; however, adaptation can be hastened. The melatoninergic drugs are promising but larger trials in real-life situations are needed. For short stopovers it is recommended to preserve sleep and alertness without necessarily modifying the circadian system. New research suggests that modification of clock function via genetic manipulation may one day have clinical applications.

Altered ultradian cortisol rhythmicity as a potential neurobiologic substrate for chronic insomnia

Chronic insomnia is highly prevalent and associated with significant morbidity (i.e., confers risk for multiple psychiatric and medical disorders, such as depression and hypertension). Therefore, it is essential to identify factors that perpetuate this disorder. One candidate factor in the neurobiology of chronic insomnia is hypothalamic-pituitary-adrenal-axis dysregulation, and in particular, alterations in circadian cortisol rhythmicity. Cortisol secretory patterns, however, fluctuate with both a circadian and an ultradian rhythm (i.e., pulses every 60-120 min). Ultradian cortisol pulses are thought to be involved in the maintenance of wakefulness during the day and their relative absence at night may allow for the consolidation of sleep and/or shorter nocturnal awakenings. It is possible that the wakefulness that occurs in chronic insomnia may be associated with the aberrant occurrence of cortisol pulses at night. While cortisol pulses naturally occur with transient awakenings, it may also be the case that cortisol pulsatility becomes a conditioned phenomenon that predisposes one to awaken and/or experience prolonged nocturnal awakenings. The current review summarizes the literature on cortisol rhythmicity in subjects with chronic insomnia, and proffers the suggestion that it may be abnormalities in the ultradian rather than circadian cortisol that is associated with the pathophysiology of insomnia.

Zolpidem reduces hippocampal neuronal activity in freely behaving mice: a large scale calcium imaging study with miniaturized fluorescence microscope

Therapeutic drugs for cognitive and psychiatric disorders are often characterized by their molecular mechanism of action. Here we demonstrate a new approach to elucidate drug action on large-scale neuronal activity by tracking somatic calcium dynamics in hundreds of CA1 hippocampal neurons of pharmacologically manipulated behaving mice. We used an adeno-associated viral vector to express the calcium sensor GCaMP3 in CA1 pyramidal cells under control of the CaMKII promoter and a miniaturized microscope to observe cellular dynamics. We visualized these dynamics with and without a systemic administration of Zolpidem, a GABAA agonist that is the most commonly prescribed drug for the treatment of insomnia in the United States. Despite growing concerns about the potential adverse effects of Zolpidem on memory and cognition, it remained unclear whether Zolpidem alters neuronal activity in the hippocampus, a brain area critical for cognition and memory. Zolpidem, when delivered at a dose known to induce and prolong sleep, strongly suppressed CA1 calcium signaling. The rate of calcium transients after Zolpidem administration was significantly lower compared to vehicle treatment. To factor out the contribution of changes in locomotor or physiological conditions following Zolpidem treatment, we compared the cellular activity across comparable epochs matched by locomotor and physiological assessments. This analysis revealed significantly depressive effects of Zolpidem regardless of the animal's state. Individual hippocampal CA1 pyramidal cells differed in their responses to Zolpidem with the majority (∼ 65%) significantly decreasing the rate of calcium transients, and a small subset (3%) showing an unexpected and significant increase. By linking molecular mechanisms with the dynamics of neural circuitry and behavioral states, this approach has the potential to contribute substantially to the development of new therapeutics for the treatment of CNS disorders.

The effect of two benzodiazepine receptor agonist hypnotics on sleep-dependent memory consolidation

INTRODUCTION

Numerous studies have demonstrated that sleep promotes memory consolidation, but there is little research on the effect of hypnotics on sleep-dependent memory consolidation. We compared bedtime administration of zolpidem-ER 12.5 mg (6- to 8-h duration of action), middle-of-the-night administration of zaleplon 10 mg (3- to 4-h duration of action), and placebo to examine the effect of different durations of hypnotic drug exposure on memory consolidation during sleep.

METHODS

Twenty-two participants with no sleep complaints underwent 3 conditions in a counterbalanced crossover study: (1) zolpidem-ER 12.5 mg (bedtime dosing), (2) zaleplon 10 mg (middle-of-the-night dosing), and (3) placebo. Memory testing was conducted before and after an 8-h sleep period, using a word pair association task (WPT; declarative memory) and a finger-tapping task (FTT; procedural memory).

RESULTS

ANOVA revealed a significant condition effect for the WPT (p = 0.025) and a trend for the FTT (p = 0.067), which was significant when sex was added to the model (p = 0.014). Improvement in memory performance following sleep was lower with bedtime dosing of zolpidem-ER compared to placebo and middle-of-the-night dosing of zaleplon. There were no differences between placebo and zaleplon.

CONCLUSIONS

The results suggest that in some circumstances hypnotics may have the potential to reduce the degree of sleep-dependent memory consolidation and that drug-free sleep early in the night may ameliorate this effect.

Clinical evaluation of zaleplon in the treatment of insomnia

Zaleplon is a pyrazolopyrimidine hypnotic used for the treatment of insomnia. Zaleplon binds preferentially at the α1β2γ2 subunit of gamma aminobutyric acid type A (GABAA) receptors in the central nervous system, and has a half-life of about one hour. Efficacy studies show that zaleplon is a suitable hypnotic for sleep initiation purposes. However, because of its short half-life, zaleplon is less effective in sleep maintenance when compared with other hypnotics. Nevertheless, zaleplon does increase total sleep time. No rebound effects are observed after treatment discontinuation. The use of zaleplon is relatively safe. Adverse effects are mild and of short duration. No important interactions have been reported, and there is no evidence of abuse potential. Relative to benzodiazepine hypnotics, the biggest advantage of zaleplon is that current evidence suggests it does not produce residual next-day effects. As early as four hours after intake of zaleplon, no effects on cognitive, memory, psychomotor performance, and the ability to drive a car have been reported. Future studies should confirm these findings, and comparisons with new nonbenzodiazepine hypnotics should determine the importance of zaleplon in the future treatment of insomnia.

Translocator protein (18 kDa) mediates the pro-growth effects of diazepam on Ehrlich tumor cells in vivo

The Translocator Protein (TSPO), previously known as the peripheral-type benzodiazepine receptor, is a ubiquitous drug- and cholesterol-binding protein that is up regulated in several types of cancer cells. TSPO drug ligands (e.g., diazepam) induce or inhibit tumor cell proliferation, depending on the dose and tissue origin. We have previously shown that TSPO is expressed in Ehrlich tumor cells and that diazepam increases proliferation of these cells in vitro. Here, we investigated the in vivo effects of diazepam on Ehrlich tumor growth and the role of TSPO in mediating this process. Oral administration of diazepam to mice (3.0mg/kg/day for 7 days) produced plasma and ascitic fluid drug concentrations of 83.83 and 54.12 nM, respectively. Diazepam increased Ehrlich tumor growth, likely due to its ability to increase tumor cell proliferation and Reactive Oxygen Species production. Radioligand binding assays and nucleotide sequencing revealed that Ehrlich tumor cell TSPO had the same pharmacological and biochemical properties as TSPO described in other tumor cells. The estimated K(d) for PK 11195 in Ehrlich tumor cells was 0.44 nM and 8.70 nM (low and high binding site, respectively). Structurally diverse TSPO drug ligands with exclusive affinity for TSPO (i.e., 4-chlordiazepam, Ro5-4864, and isoquinoline-carboxamide PK 11195) also increased Ehrlich tumor growth. However, clonazepam, a GABA(A)-specific ligand with no affinity for TSPO, failed to do so. Taken together, these data suggest that diazepam induces in vivo Ehrlich tumor growth in a TSPO-dependent manner.

Focal decreases of cortical GABAA receptor binding remote from the primary seizure focus: what do they indicate?

PURPOSE

To determine the electroclinical significance and histopathological correlates of cortical gamma-aminobutyric acid(A)(GABA(A)) receptor abnormalities detected in and remote from human neocortical epileptic foci.

METHODS

Cortical areas with decreased(11)C-flumazenil (FMZ) binding were objectively identified on positron emission tomography (PET) images and correlated to intracranial electroencephalography (EEG) findings, clinical seizure variables, histology findings, and surgical outcome in 20 patients (mean age, 9.9 years) with intractable partial epilepsy of neocortical origin and nonlocalizing magnetic resonance imaging (MRI).

RESULTS

Focal decrease of cortical FMZ binding was detected in the lobe of seizure onset in 17 (85%) patients. Eleven patients (55%) had 17 remote cortical areas with decreased FMZ binding outside the lobe of seizure onset. Thirteen of those 16 (81%) of the 17 remote cortical regions that were covered by subdural EEG were around cortex showing rapid seizure spread on intracranial EEG. Remote FMZ PET abnormalities were associated with high seizure frequency and, when resected, showed gliosis in all six cases where material was available. Higher number of unresected cortical regions with decreased FMZ binding was associated with poorer surgical outcome.

CONCLUSIONS

Focal decreases of cortical GABA(A) receptor binding on PET may include cortical regions remote from the primary focus, particularly in patients with high seizure frequency, and these regions are commonly involved in rapid seizure propagation. Although these regions may not always need to be resected to achieve seizure freedom, a careful evaluation of cortex with decreased GABA(A) receptor binding prior to resection using intracranial EEG may facilitate optimal surgical outcome in patients with intractable neocortical epilepsy.

Abuse and dependence liability of benzodiazepine-type drugs: GABA(A) receptor modulation and beyond

Over the past several decades, benzodiazepines and the newer non-benzodiazepines have become the anxiolytic/hypnotics of choice over the more readily abused barbiturates. While all drugs from this class act at the GABA(A) receptor, benzodiazepine-type drugs offer the clear advantage of being safer and better tolerated. However, there is still potential for these drugs to be abused, and significant evidence exists to suggest that this is a growing problem. This review examines the behavioral determinants of the abuse and dependence liability of benzodiazepine-type drugs. Moreover, the pharmacological and putative biochemical basis of the abuse-related behavior is discussed.

New perspectives for the treatment of disorders of sleep and arousal

A variety of molecules with novel mechanisms of action are currently being evaluated for their potential as treatments for sleep disorders. The GABA-A receptor complex remains an important target for hypnotic drugs (eg gaboxadol, indiplon). However, drugs acting through histamine, calcium channels and serotonin receptors may also be of interest for the treatment of insomnia. In the case of the 5HT2A subtype of serotonin receptors, several molecules which improve sleep maintenance and modify sleep architecture by increasing slow wave sleep are currently being tested (eg eplivanserin). Two new drugs with efficacy in excessive sleepiness (modafinil, sodium oxybate) have improved the treatment of this condition. However, the mechanisms of action of these agents are poorly understood. The recent discovery of the hypocretin arousal system in the hypothalamus may aid the identification of additional new drugs. An agonist at receptors for the pineal hormone melatonin is available in some countries (ramelteon) but is currently used only for the treatment of insomnia associated with difficulties of sleep onset. Additional melatonin receptor agonists are being developed and may have potential for treating several conditions including circadian rhythm disorders and depression.

Benzodiazepine receptor ligands. 8: synthesis and pharmacological evaluation of new pyrazolo[5,1-c] [1,2,4]benzotriazine 5-oxide 3- and 8-disubstituted: high affinity ligands endowed with inverse-agonist pharmacological efficacy

The synthesis and the binding study of new 3-arylesters and 3-heteroarylpyrazolo[5,1-c][1,2,4]benzotriazine 5-oxide 8-substituted are reported. The nature of these substituents (in terms of lipophilic and electronic features) seems to influence the binding affinity. High-affinity ligands were studied in mice in vivo for their pharmacological effects, considering six potential benzodiazepine actions: anxiolytic-like effects, muscle relaxant effects, motor coordination, anticonvulsant action, spontaneous motor activity, and ethanol-potentiating action. Compounds 4d and 6d showed an inverse-agonist profile. These compounds were evaluated also for their binding at benzodiazepine site on GABAA receptor complex (GABAA/BzR complex) subtype to evaluate their subtype selectivity.

Efficacy and safety of eszopiclone across 6-weeks of treatment for primary insomnia

OBJECTIVE

Eszopiclone is a new, single-isomer, non-benzodiazepine, cyclopyrrolone agent under investigation for the treatment of insomnia. The present study was a randomized, double-blind, multicenter, placebo-controlled trial conducted to assess the efficacy and safety of eszopiclone in adults with chronic primary insomnia.

RESEARCH DESIGN AND METHODS

Patients (n = 308) were randomized to receive placebo or eszopiclone (2 mg or 3 mg) for 44 consecutive nights, followed by 2 nights of single-blind placebo. Efficacy was evaluated with polysomnography (Nights 1, 15 and 29) and patient-reports (Nights 1, 15, 29 and 43/44). Next-day residual effects were evaluated using the Digit-Symbol Substitution Test (DSST).

RESULTS

Eszopiclone 3 mg had significantly less time to sleep onset (p < or = 0.0001), more total sleep time and sleep efficiency (p < or = 0.0001), better sleep maintenance (p < or = 0.01), and enhanced quality and depth of sleep (p < 0.05) across the double-blind period compared with placebo. Eszopiclone 2 mg had significantly less time to sleep onset (p < or = 0.001), more total sleep time (p < or = 0.01) and sleep efficiency (p < or = 0.001), and enhanced quality and depth of sleep (p < 0.05) compared with placebo, but did not significantly improve sleep maintenance. There was no evidence of tolerance or rebound insomnia after therapy discontinuation. Median DSST scores showed no decrement in psychomotor performance relative to baseline and did not differ from placebo in either eszopiclone group. Treatment was well tolerated; the most common adverse event related to eszopiclone was unpleasant taste.

CONCLUSIONS

Patients treated with nightly eszopiclone 3 mg had better polysomnographic (through Night 29) and patient-reported measures (through Night 44) of sleep over the 6-week trial. There was no evidence of tolerance or rebound insomnia and no detrimental effects on next-day psychomotor performance using the DSST.

The pharmacology and mechanisms of action of new generation, non-benzodiazepine hypnotic agents

The new generation hypnotic drugs, zolpidem, zopiclone and zaleplon, are at least as efficacious in the clinic as benzodiazepines and may offer advantages in terms of safety. These drugs act through the BZ binding sites associated with GABAA receptors, but show some differences from benzodiazepines in pharmacological effects and mechanisms of action. Of particular interest is the finding that zolpidem shows a wide separation between doses producing sedative effects and those giving rise to other behavioural actions, and induces less tolerance and dependence than benzodiazepines. Zolpidem also demonstrates selectivity for GABAA receptors containing alpha1 subunits. Recent studies using genetically modified mice have confirmed that receptors containing alpha1 subunits play a particularly important role in mediating sedative activity, thus providing an explanation for the pharmacological profile of zolpidem.

Zolpidem is not superior to temazepam with respect to rebound insomnia: a controlled study

This randomised controlled trial was conducted to compare zolpidem to an equivalent dose of temazepam with respect to subjective rebound insomnia after cessation of 4 weeks of treatment in chronic insomnia (zolpidem 10 mg, n=79; temazepam 20 mg, n=84). Both agents improved total sleep time (TST) as well as sleep onset latency (SOL) significantly during the 4 treatment weeks. Prevalence rates for rebound insomnia, defined as a worsening of TST or SOL of more than 40% compared to baseline, were 27% for TST and 53% for SOL in the Zolpidem condition and 26% and 58%, respectively, in the temazepam condition. No significant differences were found between both agents with respect to rebound insomnia, nor with respect to their efficacy or safety. We conclude that in clinical practice zolpidem has no advantages over temazepam with respect to rebound insomnia.

GABAergic function in Alzheimer's disease: evidence for dysfunction and potential as a therapeutic target for the treatment of behavioural and psychological symptoms of dementia

Alzheimer's disease (AD) is characterized by disruptions in multiple major neurotransmitters. While many studies have attempted to establish whether GABA is disrupted in AD patients, findings have varied. We review evidence for disruptions in GABA among patients with AD and suggest that the variable findings reflect subtypes of the disease that are possibly manifested clinically by differing behavioural symptoms. GABA, the major inhibitory neurotransmitter, has long been a target for anxiolytics, hypnotic sedatives, and anticonvulsants. We review the clinical use of GABAergic agents in treating persons with AD symptoms. While newer generation GABAergic medications are now available, they have yet to be evaluated among patients with AD.

Detoxification from High-Dose Zolpidem Using Diazepam

OBJECTIVE

To report a rare case of physical and psychological addiction to an excessive dose of zolpidem and subsequent completed detoxification using diazepam.

CASE SUMMARY

A 46-year-old white man with a history of polysubstance abuse received a prescription for zolpidem 2 years prior to his hospital detoxification. During that time, he gradually escalated the total dosage to an amount of 400 mg/day in divided doses. Upon hospitalization, he was detoxified using a standard benzodiazepine 7-day diazepam tapering regimen.

DISCUSSION

Zolpidem is a nonbenzodiazepine medication approved for the short-term treatment of insomnia. Its mechanism is a selective benzodiazepine type 1 receptor agonist. The selectivity of the drug for the type 1 receptor may not be absolute and is inversely dose dependent. Compared with the benzodiazepines, zolpidem addiction is rare. However, at higher than recommended doses for extended periods of time, its addictive potential may be similar to that of the benzodiazepines.

CONCLUSIONS

Given the similarities in receptor binding and pharmacologic activities of zolpidem and the benzodiazepines, we chose to use a standard benzodiazepine detoxification protocol to treat zolpidem withdrawal. Confirmation of this has been evidenced by successful zolpidem detoxification using a standard 7-day benzodiazepine/diazepam taper regimen.

Encapsulation and release of the hypnotic agent zolpidem from biodegradable polymer microparticles containing hydroxypropyl-beta-cyclodextrin

The goal of this study was to design a prolonged release system of the hypnotic agent zolpidem (ZP) useful for the treatment of insomnia. In this work, ZP alone or in the presence of HP-beta-CD was encapsulated in microparticles constituted by poly(DL-lactide) (PDLLA) and poly(DL-lactide-co-glycolide) (PLGA) and the drug release from these systems was evaluated. ZP alone-loaded microparticles were prepared by the classical O/W emulsion-solvent evaporation method. Conversely, ZP/HP-beta-CD containing microparticles were prepared by the W/O/W emulsion-solvent evaporation method following two different procedures (i.e. A and B). Following procedure A, the previously produced ZP/HP-beta-CD solid complex was added to the water phase of primary emulsion. In the procedure B, HP-beta-CD was added to the aqueous phase and ZP to the organic phase. The resulting microparticles were characterized about morphology, size, encapsulation efficiency and release rates. FT-IR, X-ray, and DSC results suggest the drug is in an essentially amorphous state within the microparticles. The release profiles of ZP from microparticles were in general biphasic, being characterized by an initial burst effect and a subsequent slow ZP release. It resulted that co-encapsulating ZP with or without HP-beta-CD in PDLLA and PLGA the drug release from the corresponding microparticles was protracted. Moreover, in a preliminary pharmacological screening, the ataxic activity in rats was investigated and it was found that intragastric administration of the ZP/HP-beta-CD/PLGA microparticles prepared according to procedure B produced the same ataxic induction time as the one induced by the currently used formulation Stilnox. Interestingly moreover, there was a longer ataxic lasting and a lower intensity of ataxia produced by the ZP/HP-beta-CD/PLGA-B-formulation already after 60 min following the administration. However, a need for further pharmacokinetic and pharmacodynamic studies resulted to fully evaluate the utility of this last formulation for the sustained delivery of ZP.

SB242084, flumazenil, and CRA1000 block ethanol withdrawal-induced anxiety in rats

Anxiety-like behaviors are integral features of withdrawal from chronic ethanol exposure. In the experiments in the current study, we tested the hypothesis that anxiety can be regulated independently of other withdrawal signs and thus may be responsive to selective pharmacological agents. For 17 days, rats were fed ethanol (8-12 g/kg/day) in a liquid diet. Between 5 and 6 h after cessation of ethanol treatment, rats were tested in either the social interaction or plus-maze test of anxiety-like behavior after treatment with drugs hypothesized to have anxiolytic action. SB242084, flumazenil, and CRA1000-antagonists for 5-hydroxytryptamine (serotonin) (5-HT) 2C (5-HT(2C)), benzodiazepine, and corticotropin-releasing factor type 1 (CRF(1)) receptors, respectively-attenuated decreased social interaction without concomitant effects on activity measures. In contrast, ifenprodil, MDL 72222, and zolpidem-antagonists for N-methyl-d-aspartate (NMDA) and 5-HT(3) receptors, and agonist for benzodiazepine type 1 receptors, respectively-did not share this effect. Results for SB242084, flumazenil, and ifenprodil in the elevated plus-maze test were comparable to those in the social interaction test. These results support the suggestion that multiple neuronal systems (CRF(1), 5-HT(2C), and benzodiazepine receptors) contribute to the ethanol withdrawal sign of decreased social interaction. Furthermore, the selective effects of pharmacological agents on social interaction seem to indicate that this behavior can be dissociated from other signs. Because anxiety may be a complicating factor in alcohol withdrawal and relapse, future studies of this type are needed to provide focus for the effort to define selective and novel antianxiety agents for these disorders.

Differential actions of diazepam and zolpidem in basolateral and central amygdala nuclei

Benzodiazepines are among the most widely prescribed therapeutic agents, having anxiolytic, anticonvulsant, sedative/hypnotic, and amnestic properties (Mehta and Ticku, Brain Res. Rev. 29 (1999) 196). Recent research indicates that these disparate actions are dissociable (Nature 401 (1999) 796; Science 290 (2000) 131; Kralic et al., Neuropharmacology 43 (2002) 685). Behavioral studies indicate that the amygdala plays a critical role in the anxiolytic effect of benzodiazepines (Nagy et al., Neuropharmacology 18 (1979) 573; The amygdala: anxiety and benzodiazepines. The Amygdala: a Functional Analysis. p. 195). However, the neuronal substrates of this anxiolytic effect remain unclear. Our study characterizes the physiological response to acute application of the benzodiazepine diazepam and the non-benzodiazepine sedative zolpidem using whole cell patch recording in two discrete amygdala subnuclei. We found that acute application of diazepam enhances GABA(A) receptor-mediated inhibitory postsynaptic currents (IPSCs) with equal potency in the basolateral (BL) and central (Ce) amygdala subnuclei. However, zolpidem enhanced IPSCs with similar potency only in the BL, and was effective in the Ce only at high concentrations. This finding is in agreement with histochemical data regarding the localization of GABA(A) receptor isoforms in the amygdala (J. Comp. Neurol. 359 (1995) 154; Brain Res. 964 (2003) 91) and suggests that anxiolytic effects of allosteric modulators of the GABA(A) receptor may be further dissociated from their hypnotic/sedative effects.

Clinical pharmacology, clinical efficacy, and behavioral toxicity of alprazolam: a review of the literature

Alprazolam is a benzodiazepine derivative that is currently used in the treatment of generalized anxiety, panic attacks with or without agoraphobia, and depression. Alprazolam has a fast onset of symptom relief (within the first week); it is unlikely to produce dependency or abuse. No tolerance to its therapeutic effect has been reported. At discontinuation of alprazolam treatment, withdrawal and rebound symptoms are common. Hence, alprazolam discontinuation must be tapered. An exhaustive review of the literature showed that alprazolam is significantly superior to placebo, and is at least equally effective in the relief of symptoms as tricyclic antidepressants (TCAs), such as imipramine. However, although alprazolam and imipramine are significantly more effective than placebo in the treatment of panic attacks, Selective Serotonin Reuptake Inhibitors (SSRIs) appear to be superior to either of the two drugs. Therefore, alprazolam is recommended as a second line treatment option, when SSRIs are not effective or well tolerated. In addition to its therapeutic effects, alprazolam produces adverse effects, such as drowsiness and sedation. Since alprazolam is widely used, many clinical studies investigated its cognitive and psychomotor effects. It is evident from these studies that alprazolam may impair performance in a variety of skills in healthy volunteers as well as in patients. Since the majority of alprazolam users are outpatients, this behavioral impairment limits the safe use of alprazolam in patients routinely engaged in potentially dangerous daily activities, such as driving a car.

The neurobiology and control of anxious states

Fear is an adaptive component of the acute "stress" response to potentially-dangerous (external and internal) stimuli which threaten to perturb homeostasis. However, when disproportional in intensity, chronic and/or irreversible, or not associated with any genuine risk, it may be symptomatic of a debilitating anxious state: for example, social phobia, panic attacks or generalized anxiety disorder. In view of the importance of guaranteeing an appropriate emotional response to aversive events, it is not surprising that a diversity of mechanisms are involved in the induction and inhibition of anxious states. Apart from conventional neurotransmitters, such as monoamines, gamma-amino-butyric acid (GABA) and glutamate, many other modulators have been implicated, including: adenosine, cannabinoids, numerous neuropeptides, hormones, neurotrophins, cytokines and several cellular mediators. Accordingly, though benzodiazepines (which reinforce transmission at GABA(A) receptors), serotonin (5-HT)(1A) receptor agonists and 5-HT reuptake inhibitors are currently the principle drugs employed in the management of anxiety disorders, there is considerable scope for the development of alternative therapies. In addition to cellular, anatomical and neurochemical strategies, behavioral models are indispensable for the characterization of anxious states and their modulation. Amongst diverse paradigms, conflict procedures--in which subjects experience opposing impulses of desire and fear--are of especial conceptual and therapeutic pertinence. For example, in the Vogel Conflict Test (VCT), the ability of drugs to release punishment-suppressed drinking behavior is evaluated. In reviewing the neurobiology of anxious states, the present article focuses in particular upon: the multifarious and complex roles of individual modulators, often as a function of the specific receptor type and neuronal substrate involved in their actions; novel targets for the management of anxiety disorders; the influence of neurotransmitters and other agents upon performance in the VCT; data acquired from complementary pharmacological and genetic strategies and, finally, several open questions likely to orientate future experimental- and clinical-research. In view of the recent proliferation of mechanisms implicated in the pathogenesis, modulation and, potentially, treatment of anxiety disorders, this is an opportune moment to survey their functional and pathophysiological significance, and to assess their influence upon performance in the VCT and other models of potential anxiolytic properties.

The Vogel conflict test: procedural aspects, gamma-aminobutyric acid, glutamate and monoamines

A multitude of mechanisms are involved in the control of emotion and in the response to stress. These incorporate mediators/targets as diverse as gamma-aminobutyric acid (GABA), excitatory amino acids, monoamines, hormones, neurotrophins and various neuropeptides. Behavioural models are indispensable for characterization of the neuronal substrates underlying their implication in the etiology of anxiety, and of their potential therapeutic pertinence to its management. Of considerable significance in this regard are conflict paradigms in which the influence of drugs upon conditioned (trained) behaviours is examined. For example, the Vogel conflict test, which was introduced some 30 years ago, measures the ability of drugs to release the drinking behaviour of water-deprived rats exposed to a mild aversive stimulus ("punishment"). This model, of which numerous procedural variants are discussed herein, has been widely used in the evaluation of potential anxiolytic agents. In particular, it has been exploited in the characterization of drugs interacting with GABAergic, glutamatergic and monoaminergic networks, the actions of which in the Vogel conflict test are summarized in this article. More recently, the effects of drugs acting at neuropeptide receptors have been examined with this model. It is concluded that the Vogel conflict test is of considerable utility for rapid exploration of the actions of anxiolytic (and anxiogenic) drugs. Indeed, in view of its clinical relevance, broader exploitation of the Vogel conflict test in the identification of novel classes of anxiolytic agents, and in the determination of their mechanisms of action, would prove instructive.

A cognitive model of insomnia

Insomnia is one of the most prevalent psychological disorders, causing sufferers severe distress as well as social, interpersonal, and occupational impairment. Drawing on well-validated cognitive models of the anxiety disorders as well as on theoretical and empirical work highlighting the contribution of cognitive processes to insomnia, this paper presents a new cognitive model of the maintenance of insomnia. It is suggested that individuals who suffer from insomnia tend to be overly worried about their sleep and about the daytime consequences of not getting enough sleep. This excessive negatively toned cognitive activity triggers both autonomic arousal and emotional distress. It is proposed that this anxious state triggers selective attention towards and monitoring of internal and external sleep-related threat cues. Together, the anxious state and the attentional processes triggered by it tricks the individual into overestimating the extent of the perceived deficit in sleep and daytime performance. It is suggested that the excessive negatively toned cognitive activity will be fuelled if a sleep-related threat is detected or a deficit perceived. Counterproductive safety behaviours (including thought control, imagery control, emotional inhibition, and difficulty problem solving) and erroneous beliefs about sleep and the benefits of worry are highlighted as exacerbating factors. The unfortunate consequence of this sequence of events is that the excessive and escalating anxiety may culminate in a real deficit in sleep and daytime functioning. The literature providing preliminary support for the model is reviewed and the clinical implications and limitations discussed.

Changes in GABA(A) receptor gene expression induced by withdrawal of, but not by long-term exposure to, zaleplon or zolpidem

The effects of long-term treatment with and subsequent withdrawal of the two hypnotic drugs zaleplon and zolpidem on the abundance of gamma-aminobutyric acid type A (GABA(A)) receptor subunit mRNAs in cultured rat cerebellar granule cells were investigated. Incubation of neurons with either drug at a concentration of 10 microM for 5 days did not significantly affect the amounts of mRNAs encoding the alpha(1), alpha(4), beta(1), beta(2), beta(3), gamma(2)L, or gamma(2)S subunits. As expected, similar treatment with the nonselective benzodiazepine diazepam resulted in a decrease in the abundance of alpha(1), beta(2), gamma(2)L, and gamma(2)S subunit mRNAs as well as an increase in that of the beta(1) subunit mRNA. Withdrawal of zaleplon or zolpidem, like that of diazepam, induced a marked increase in the amount of the alpha(4) subunit mRNA. In addition, discontinuation of treatment with either hypnotic drug resulted in a decrease in the amounts of alpha(1), beta(2), gamma(2)L, and gamma(2)S subunit mRNAs as well as an increase in that of the beta(1) subunit mRNA. These effects of zaleplon and zolpidem on GABA(A) receptor gene expression are consistent with the reduced tolerance liability of these drugs, compared with that of diazepam, as well as with their ability to induce both physical dependence and withdrawal syndrome.

New insights into the role of the GABA(A)-benzodiazepine receptor in psychiatric disorder

BACKGROUND

In the 40 years since the first benzodiazepine was brought into clinical use there has been a substantial growth in understanding the molecular basis of action of these drugs and the role of their receptors in disease states.

AIMS

To present current knowledge about the role of the GABA(A)-benzodiazepine receptor in anxiety disorders, new insights into the molecular biology of the receptor complex and neuroimaging studies suggesting involvement of these receptors in disease states.

METHOD

An overview of published literature, including some recent data.

RESULTS

The molecular biology of this receptor is detailed. Molecular genetic studies suggesting involvement of the GABA(A)-benzodiazepine receptor in animal behaviour and learning are outlined; possible parallels with human psychopathology are discussed.

CONCLUSIONS

Current insights into the role of the GABA(A)-benzodiazepine receptor in the action of benzodiazepines and as a factor in disease states, in both animals and humans, may lead to new, more sophisticated interventions at this receptor complex and potentially significant therapeutic gains.

High-dose flumazenil potentiates the hypnotic activity of propofol, but not that of thiopental, in ddY mice

BACKGROUND

Flumazenil is a specific benzodiazepine agonist, which is reported to have a partial benzodiazepine agonist-like effect at a high dose. This study investigated the effects of flumazenil and midazolam on the hypnotic dose of propofol and thiopental in ddY mice, using a behavioral model.

METHODS

Mice were given either propofol or thiopental intravenously to induce hypnosis, which was defined as a loss of the righting reflex. The mice were pre-treated with flumazenil (0.05, 0.1, or 0.2 mg kg(-1)) or midazolam (0.1 or 0.2 mg kg(-1)), and given propofol or thiopental after a 30-s delay.

RESULTS

Pre-treatment with flumazenil (0.1 or 0.2 mg kg(-1)) significantly decreased the hypnotic dose of propofol compared to the control group (9.3+/-0.39 [8.5-10.0] or 9.0+/-0.28 [8.5-9.6] vs. 10.8+/-0.42 [9.9-11.6] mg kg(-1) (ED50+/-SEM and [95% confidence interval]) P<0.05), but not that of thiopental (9.1+/-0.30 [8.5-9.7] with 0.2 mg kg(-1) flumazenil vs. 9.3+/-0.42 [8.4-10.1] mg kg(-1) with saline). Midazolam reduced the hypnotic dose of both propofol and thiopental. Flumazenil antagonized the potentiating effect of midazolam (0.2 mg kg(-1)) on the hypnotic activity of propofol.

CONCLUSIONS

These results suggest that the hypnotic activity of propofol is potentiated by the partial agonist activity of flumazenil in ddY mice.

A double-blind comparative study of zolpidem versus zopiclone in the treatment of chronic primary insomnia

Zolpidem (10 mg/day) and zopiclone (7.5 mg/day), administered at night, were compared in a 14-day, double-blind, equivalence trial on 479 chronic primary insomniacs (zolpidem, 231; zopiclone, 248) throughout Japan, with a 1-week follow-up to assess rebound. The primary endpoint was the investigators' rating of global improvement of sleep disorders. A total of 32 patients in the zolpidem group (13.9%) and 45 patients in the zopiclone group (18.1%) withdrew from the study before the end of the treatment. In the zolpidem group, 67.9% (142/209) of patients were rated at least 'moderately improved' versus 61.6% (135/219) with zopiclone, zolpidem being at least as effective as zopiclone (90% confidence interval: -1.7, 14.3). With zolpidem, sleep onset latency improved in significantly more patients (85.8% versus 77.5%) and significantly fewer patients showed aggravated sleep onset latency relative to baseline at follow-up (4.5% versus 15.4%). Significantly fewer patients receiving zolpidem experienced drug-related adverse events (31.3% versus 45.3%), with bitter taste representing 5.8% (six of 104) of such complaints with zolpidem compared with 39.9% (69/173) with zopiclone. In conclusion, zolpidem was at least as effective as zopiclone, showed significantly less rebound on discontinuation and was better tolerated.