The influence of ipsapirone, a 5-HT1A agonist, on sleep patterns of healthy subjects

Sleep disturbances in autism spectrum disorder: Animal models, neural mechanisms, and therapeutics

Sleep is crucial for brain development. Sleep disturbances are prevalent in children with autism spectrum disorder (ASD). Strikingly, these sleep problems are positively correlated with the severity of ASD core symptoms such as deficits in social skills and stereotypic behavior, indicating that sleep problems and the behavioral characteristics of ASD may be related. In this review, we will discuss sleep disturbances in children with ASD and highlight mouse models to study sleep disturbances and behavioral phenotypes in ASD. In addition, we will review neuromodulators controlling sleep and wakefulness and how these neuromodulatory systems are disrupted in animal models and patients with ASD. Lastly, we will address how the therapeutic interventions for patients with ASD improve various aspects of sleep. Together, gaining mechanistic insights into the neural mechanisms underlying sleep disturbances in children with ASD will help us to develop better therapeutic interventions.

Effect of TAAR1/5-HT1A agonist SEP-363856 on REM sleep in humans

SEP-363856 is a trace amine-associated receptor 1 (TAAR1) and 5-hydroxytryptamine type 1A (5-HT_1A) agonist, currently in Phase 3 clinical trials for the treatment of schizophrenia. Although SEP-363856 activates TAAR1 and 5-HT_1A receptors in vitro, an accessible marker of time- and concentration-dependent effects of SEP-363856 in humans is lacking. In rodents, SEP-363856 has been shown to suppress rapid eye movement (REM) sleep. The aim of the current study was to translate the REM sleep effects to humans and determine pharmacokinetic/pharmacodynamic (PK/PD) relationships of SEP-363856 on a measure of brain activity. The effects of SEP-363856 were evaluated in a randomized, double-blind, placebo-controlled, 2-way crossover study of single oral doses (50 and 10 mg) on REM sleep in healthy male subjects (N = 12 at each dose level). Drug concentrations were sampled during sleep to interpolate individual subject's pharmacokinetic trajectories. SEP-363856 suppressed REM sleep parameters with very large effect sizes (>3) following single doses of 50 mg and plasma concentrations ≥100 ng/mL. Below that effective concentration, the 10 mg dose elicited much smaller effects, increasing only the latency to REM sleep (effect size = 1). The PK/PD relationships demonstrated that REM sleep probability increased as drug concentrations declined below 100 ng/mL over the course of the night. SEP-363856 was generally safe and well tolerated at both doses. The REM sleep-suppressing effects of SEP-363856 provide an accessible marker of brain activity, which can aid in dose selection and help elucidate its therapeutic potential in further clinical trials.

Vortioxetine in management of major depressive disorder - a favorable alternative for elderly patients?

Introduction: Depressive disorders are common in older patients, and their prevalence may reach up to 17.1%. Though for older adults, the initial recommended treatment is either life-review treatment or group cognitive-behavioral therapy, a combination of pharmacotherapy with interpersonal psychotherapy is also an option. There are many classes of antidepressants, and some meta-analyses suggest that the efficacy of different antidepressant groups is similar. Therefore, depression treatment in an elderly patient should consider preference, safety, and tolerability. Most reports suggest that SSRIs, such as citalopram, escitalopram, or sertraline, should be proposed as first-time medications.Areas covered: This article discusses the pharmacokinetic and pharmacodynamic properties of vortioxetine, emphasizing the observed differences, benefits, and risks for older patients. Vortioxetine - a multimodal antidepressant drug - was shown to be effective against major depressive disorders in both double-blinded, placebo-controlled trials and open-label studies.Expert opinion: Compared with commonly used antidepressants, vortioxetine appears to have unique properties that may be beneficial for elderly patients. Not only does it enhance cognitive function, but it also has a favorable safety profile.

Dreamlike effects of LSD on waking imagery in humans depend on serotonin 2A receptor activation

RATIONALE

Accumulating evidence indicates that the mixed serotonin and dopamine receptor agonist lysergic acid diethylamide (LSD) induces an altered state of consciousness that resembles dreaming.

OBJECTIVES

This study aimed to test the hypotheses that LSD produces dreamlike waking imagery and that this imagery depends on 5-HT2A receptor activation and is related to subjective drug effects.

METHODS

Twenty-five healthy subjects performed an audiorecorded guided mental imagery task 7 h after drug administration during three drug conditions: placebo, LSD (100 mcg orally) and LSD together with the 5-HT2A receptor antagonist ketanserin (40 mg orally). Cognitive bizarreness of guided mental imagery reports was quantified as a standardised formal measure of dream mentation. State of consciousness was evaluated using the Altered State of Consciousness (5D-ASC) questionnaire.

RESULTS

LSD, compared with placebo, significantly increased cognitive bizarreness (p < 0.001). The LSD-induced increase in cognitive bizarreness was positively correlated with the LSD-induced loss of self-boundaries and cognitive control (p < 0.05). Both LSD-induced increases in cognitive bizarreness and changes in state of consciousness were fully blocked by ketanserin.

CONCLUSIONS

LSD produced mental imagery similar to dreaming, primarily via activation of the 5-HT2A receptor and in relation to loss of self-boundaries and cognitive control. Future psychopharmacological studies should assess the differential contribution of the D2/D1 and 5-HT1A receptors to cognitive bizarreness.

Differentiated effects of the multimodal antidepressant vortioxetine on sleep architecture: Part 1, a pharmacokinetic/pharmacodynamic comparison with paroxetine in healthy men

We compared the effect of vortioxetine, paroxetine and placebo after three days of dosing on sleep architecture. This was a randomised, double-blind, four-way crossover, placebo-controlled, multiple-dose study in 24 healthy young men. Subjects received 20mg vortioxetine, 40 mg vortioxetine, 20mg paroxetine or placebo for three consecutive days in four different periods with at least three weeks between them. Polysomnography and blood sampling for pharmacokinetic analysis were performed on the pre-dose night and nights 1 and 3 of dosing in each period. Plasma concentrations of vortioxetine and paroxetine during the polysomnography measurement were used to estimate SERT occupancies using published relationships in healthy subjects.All three active treatments significantly increased REM onset latency and decreased time spent in REM sleep. In the pharmacokinetic/pharmacodynamics analysis significant relationships were found between REM onset latency and time spent in REM sleep and vortioxetine/paroxetine exposure. The relation between REM suppression parameters and SERT occupancy was significantly different between vortioxetine and paroxetine, despite the same SERT occupancy. This indicates that vortioxetine has a different clinical pharmacological profile from paroxetine, which may explain the differences in adverse effect profile of the two drugs, for instance the lower incidence of nausea, weight gain and sexual dysfunction with vortioxetine.

Vilazodone for the treatment of major depressive disorder: focusing on its clinical studies and mechanism of action

We tried to review and update clinical and preclinical studies evaluating vilazodone's role as an antidepressant for patients with major depressive disorder (MDD). In terms of its mechanism of actions, we sought to elaborate them mainly through preclinical animal studies. A data search was conducted in November 1, 2013, using the key terms "vilazodone" or "Viibryd," in PubMed and Medline databases. All published and unpublished studies are included and citations from publications were also reviewed for additional references. Five unpublished, phase-II and two pivotal published phase-III clinical trials with nearly identical design (8-week, double-blind, randomized, and placebo-controlled) investigated efficacy of vilazodone, were found for the treatment of patients with MDD. Two post-hoc studies and one long-term open study were also included. Data were thoroughly reviewed to incorporate the pharmacology, action mechanism, efficacy and safety for the vilazodone in the treatment of major depressive disorder. Vilazodone is an antidepressant with novel mechanism of action because its chemical structure is unrelated to conventional antidepressant, and it has a selective serotonin (5-HT) reuptake inhibitor and 5-HT1A receptor partial agonist profile. Vilazodone is an effective and safe treatment option with its novel action mechanisms for patients with depression. Its putative benefits compared with other antidepressants must be thoroughly studied in adequately-powered and well-designed future clinical trials.

A review of current evidence for vilazodone in major depressive disorder

OBJECTIVES

This review is to inform clinicians of currently available data on vilazodone for treating patients with major depressive disorder (MDD), focusing on its differential action mechanism and extended clinical utility.

METHODS

A data search was conducted in June 2012 using the PubMed/ MEDLINE/relevant clinical trial databases with the key terms "vilazodone" or "Viibryd."

RESULTS

The efficacy, safety, and tolerability of vilazodone have been demonstrated in two pivotal 8-week, randomized, double-blinded, placebo-controlled studies. Certain pharmacological characteristics of vilazodone were observed, including early onset of action, fewer sexual side effects, the absence of known cardiac toxicity, and minimal effect on weight gain, that may provide potential clinical advantages compared with currently available antidepressants. However, such possibilities should be replicated and confirmed in more well-designed and adequately powered clinical trials. Vilazodone requires dose titration up to 2 weeks to reach a target dose of 40 mg/d due to high rate of gastrointestinal side effects. No direct comparative studies with other antidepressants are currently available to confirm the aforementioned potential clinical utility.

CONCLUSION

Vilazodone is a newer antidepressant possessing different action mechanisms compared to currently available antidepressants but whether it has superiority to other class of antidepressants in terms of efficacy and safety should still warrant further evaluation through more well-controlled and direct comparison clinical trials.

Daytime Ayahuasca administration modulates REM and slow-wave sleep in healthy volunteers

OBJECTIVES

Ayahuasca is a traditional South American psychoactive beverage and the central sacrament of Brazilian-based religious groups, with followers in Europe and the United States. The tea contains the psychedelic indole N,N-dimethyltryptamine (DMT) and beta-carboline alkaloids with monoamine oxidase-inhibiting properties that render DMT orally active. DMT interacts with serotonergic neurotransmission acting as a partial agonist at 5-HT(1A) and 5-HT(2A/2C) receptor sites. Given the role played by serotonin in the regulation of the sleep/wake cycle, we investigated the effects of daytime ayahuasca consumption in sleep parameters.

MEASUREMENTS AND RESULTS

Subjective sleep quality, polysomnography (PSG), and spectral analysis were assessed in a group of 22 healthy male volunteers after the administration of a placebo, an ayahuasca dose equivalent to 1 mg DMT kg(-1) body weight, and 20 mg d-amphetamine, a proaminergic drug, as a positive control. Results show that ayahuasca did not induce any subjectively perceived deterioration of sleep quality or PSG-measured disruptions of sleep initiation or maintenance, in contrast with d-amphetamine, which delayed sleep initiation, disrupted sleep maintenance, induced a predominance of 'light' vs 'deep' sleep and significantly impaired subjective sleep quality. PSG analysis also showed that similarly to d-amphetamine, ayahuasca inhibits rapid eye movement (REM) sleep, decreasing its duration, both in absolute values and as a percentage of total sleep time, and shows a trend increase in its onset latency. Spectral analysis showed that d-amphetamine and ayahuasca increased power in the high frequency range, mainly during stage 2. Remarkably, whereas slow-wave sleep (SWS) power in the first night cycle, an indicator of sleep pressure, was decreased by d-amphetamine, ayahuasca enhanced power in this frequency band.

CONCLUSIONS

Results show that daytime serotonergic psychedelic drug administration leads to measurable changes in PSG and sleep power spectrum and suggest an interaction between these drugs and brain circuits modulating REM and SWS.

Homeostatic regulation of sleep in a genetic model of depression in the mouse: effects of muscarinic and 5-HT1A receptor activation

In depressed patients, sleep undergoes marked alterations, especially sleep onset insomnia, sleep fragmentation, and disturbances of the Rapid Eye Movement (REM) sleep. Abnormalities of rest-activity rhythms and of hypothalamic-pituitary-adrenocortical function have also been described in these patients. In the present study, we examined the presence of such abnormalities in a recently developed line of mice (Helpless mice-H) that exhibit depression-like behaviors in validated tests, compared to the nonhelpless (NH) line derived from the same colony. Experiments were essentially carried out in females for which previous studies showed marked differences between H and NH lines. Compared to NH mice, the H line exhibited (i) lower basal locomotor activity, (ii) sleep fragmentation, shift towards lighter sleep stages, and facilitation of REM sleep reflected by increased amounts and decreased latency, (iii) larger response to the REM sleep promoting effect of muscarinic receptor stimulation (by arecoline). In contrast, H and NH mice were equally responsive to the REM sleep inhibitory effect of 5-HT1A receptor stimulation (by 8-OH-DPAT). In addition, a deficiency in delta power enhancement after sleep deprivation was observed in the H group, and acute immobilization stress in this group failed to elicit a REM sleep rebound and was associated with a long-lasting raise in serum corticosterone levels. These results further validate H mice as a depression model and suggest they might be of particular interest for investigating the neurobiological mechanisms and possibly genetic substrates underlying sleep alterations associated with depression.

The use of sleep measures to compare a new 5HT1A agonist with buspirone in humans

The partial agonist buspirone has a REM (rapid eye movement) suppressing effect on human sleep probably via a 5HT(1A) receptor in the pontine area. Eptapirone is a new 5HT(1A) agonist with a greater intrinsic effect than buspirone. The objective of this study was to examine the effects of eptapirone on sleep architecture, particularly REM sleep, in normal volunteers and compare it with buspirone and placebo. This was a randomized, double-blind placebo-controlled four-way crossover study in 12 healthy volunteers. Volunteers were screened to ensure that they had normal overnight sleep EEG (electroencephalogram) and were extensive CYP 2D6 metabolizers. Sleep was recorded on pairs of nights on four occasions, with medication being taken before the second night. Treatments were eptapirone 1.5mg at 10 AM, eptapirone 1.5mg at 11 PM, buspirone 20mg at 11 PM and placebo. Standard measures of sleep were derived and compared among the four treatments using ANOVA. REM sleep was significantly suppressed supporting the proposition that activation of post-synaptic 5HT(1A) receptors reduces REM sleep. Sleep fragmentation increased by both drugs. REM sleep suppression was significantly greater with morning eptapirone than with buspirone. Wakefulness in sleep was significantly greatest after morning eptapirone. REM sleep effects were greatest after evening eptapirone, suggesting a greater effect on central serotonin receptors than that of buspirone.

Sleep quality in schizophrenia and the effects of atypical antipsychotic medication

BACKGROUND

Sleep disorders are widespread among patients with schizophrenia and contribute to adverse clinical outcomes. Antipsychotic drugs exert varying effects on sleep, and the effects of atypical agents may differ from those of conventional neuroleptics.

OBJECTIVE

To review the literature on the effects of atypical medication on subjective and objective sleep quality in patients with schizophrenia.

METHODS

A non-systematic literature review of Medline was performed in August 2003 searching the period from January 1985 to August 2003 for studies of the effects of atypical antipsychotics on sleep.

RESULTS

We found published studies of clozapine, olanzapine, and risperidone, but none on quetiapine or ziprasidone. Studies with clozapine showed that it increased total sleep time, sleep efficiency, stage-2 non-rapid eye movement sleep and rapid eye movement (REM) sleep density, and decreased stage-4 sleep, slow wave sleep (SWS) and stage-1 sleep. Single-dose studies with olanzapine have shown that it increases SWS, sleep continuity, total sleeping time, subjective sleep quality, and delta sleep. Long-term studies with risperidone have shown improvements in total sleep, sleep efficiency, sleep continuity, SWS, and stage-2 sleep, and reductions in sleep latency, number of awakenings, and proportion of time awake. These benefits were paralleled by improvements in subjective sleep assessment and psychopathology, and psychosocial functioning.

CONCLUSIONS

The evidence presented in this review suggests that atypical antipsychotics exert favorable effects on sleep profile compared with conventional agents, including improvement of subjective sleep quality and modification of specific sleep stages known to be associated with better clinical outcome.

Involvement of 5-HT1A receptors in homeostatic and stress-induced adaptive regulations of paradoxical sleep: studies in 5-HT1A knock-out mice

For the last two decades, the involvement of 5-HT(1A) receptors in the regulation of vigilance states has been studied extensively thanks to pharmacological tools, but clear-cut conclusion has not been reached yet. By studying mutant mice that do not express this receptor type (5-HT(1A)-/-) and their wild-type 129/Sv counterparts, we herein demonstrate that 5-HT(1A) receptors play key roles in the control of spontaneous sleep-wakefulness cycles, as well as in homeostatic regulation and stress-induced adaptive changes of paradoxical sleep. Both strains of mice exhibited a diurnal sleep-wakefulness rhythm, but 5-HT(1A)-/- animals expressed higher amounts of paradoxical sleep than wild-type mice during both the light and the dark phases. In wild-type mice, pharmacological blockade of 5-HT(1A) receptors by WAY 100635 (0.5 mg/kg, i.p.) promoted paradoxical sleep, whereas the 5-HT(1A) agonist 8-OH-DPAT (0.25-1 mg/kg, s.c.) had an opposite effect. In contrast, none of the 5-HT(1A) receptor ligands affected sleep significantly in 5-HT(1A)-/- mice. However, 5-HT(1B) receptor stimulation by CP 94253 (1-3 mg/kg, i.p.) induced a reduction in paradoxical sleep in both strains, this effect being more pronounced in 5-HT(1A)-/- mutants. Finally, in contrast to wild-type mice, 5-HT(1A)-/- mutants did not exhibit any rebound of paradoxical sleep after either a 9 hr instrumental paradoxical sleep deprivation or a 90 min immobilization stress. Altogether, these data indicate that, in the mouse, 5-HT(1A) receptors participate in the spontaneous and homeostatic regulation, as well as in stress-induced adaptive changes of paradoxical sleep.

Reciprocal autoreceptor and heteroreceptor control of serotonergic, dopaminergic and noradrenergic transmission in the frontal cortex: relevance to the actions of antidepressant agents

The frontal cortex (FCX) plays a key role in processes that control mood, cognition and motor behaviour, functions which are compromised in depression, schizophrenia and other psychiatric disorders. In this regard, there is considerable evidence that a perturbation of monoaminergic input to the FCX is involved in the pathogenesis of these states. Correspondingly, the modulation of monoaminergic transmission in the FCX and other corticolimbic structures plays an important role in the actions of antipsychotic and antidepressant agents. In order to further understand the significance of monoaminergic systems in psychiatric disorders and their treatment, it is essential to characterize mechanisms underlying their modulation. Within this framework, the present commentary focuses on our electrophysiological and dialysis analyses of the complex and reciprocal pattern of auto- and heteroreceptor mediated control of dopaminergic, noradrenergic and serotonergic transmission in the FCX. The delineation of such interactions provides a framework for an interpretation of the influence of diverse classes of antidepressant agent upon extracellular levels of dopamine, noradrenaline and serotonin in FCX. Moreover, it also generates important insights into strategies for the potential improvement in the therapeutic profiles of antidepressant agents.

Role of dorsal raphe nucleus serotonin 5-HT1A receptor in the regulation of REM sleep

Cholinergic neurons in the laterodorsal (LDT) and the pedunculopontine (PPT) tegmental nuclei act to promote REM sleep (REMS). The predominantly glutamatergic neurons of the REMS-induction region of the medial pontine reticular formation are in turn activated by cholinergic cells, which results in the occurrence of tonic and phasic components of REMS. All these neurons are inhibited by serotonergic (5-HT), noradrenergic, and presumably histaminergic (H2 receptor) and dopaminergic (D2 and D3 receptor) cells. 5-Hydroxytryptamine-containing neurons in the dorsal raphe nucleus (DRN) virtually cease firing when an animal starts REMS, consequently decreasing the release of 5-HT during this state. The activation of GABA(A) receptors is apparently responsible for this phenomenon. Systemic administration of the selective 5-HT1A receptor agonist 8-OHDPAT induces dose-dependent effects; i.e. low doses increase slow wave sleep and reduce waking, whereas large doses increase waking and reduce slow wave sleep and REM sleep. Direct injection of 8-OHDPAT or flesinoxan, another 5-HT1A agonist into the DRN, or microdialysis perfusion of 8-OHDPAT into the DRN significantly increases REMS. On the other hand, infusion of 8-OHDPAT into the LDT selectively inhibits REMS, as does direct administration into the DRN of the 5-HT1A receptor antagonists pindolol or WAY 100635. Thus, presently available evidence indicates that selective activation of the somatodendritic 5-HT1A receptor in the DRN induces an increase of REMS. On the other hand, activation of the postsynaptic 5-HT1A receptor at the level of the PPT/LDT nuclei decreases REMS occurrence.

Serotonin and the sleep/wake cycle: special emphasis on microdialysis studies

Several areas in the brainstem and forebrain are important for the modulation and expression of the sleep/wake cycle. Even if the first observations of biochemical events in relation to sleep were made only 40 years ago, it is now well established that several neurotransmitters, neuropeptides, and neurohormones are involved in the modulation of the sleep/wake cycle. Serotonin has been known for many years to play a role in the modulation of sleep, however, it is still very controversial how and where serotonin may operate this modulation. Early studies suggested that serotonin is necessary to obtain and maintain behavioral sleep (permissive role on sleep). However, more recent microdialysis experiments provide evidence that the level of serotonin during W is higher in most cortical and subcortical areas receiving serotonergic projections. In this view the level of extracellular serotonin would be consistent with the pattern of discharge of the DRN serotonergic neurons which show the highest firing rate during W, followed by a decrease in slow wave sleep and by virtual electrical silence during REM sleep. This suggests that during waking serotonin may complement the action of noradrenaline and acetylcholine in promoting cortical responsiveness and participate to the inhibition of REM-sleep effector neurons in the brainstem (inhibitory role on REM sleep). The apparent inconsistency between an inhibitory and a facilitatory role played by serotonin on sleep has at least two possible explanations. On the one hand serotonergic modulation on the sleep/wake cycle takes place through a multitude of post-synaptic receptors which mediate different or even opposite responses; on the other hand the achievement of a behavioral state depends on the complex interaction between the serotonergic and other neurotransmitter systems. The main aim of this commentary is to review the role of brain serotonin in relation to the sleep/wake cycle. In particular we highlight the importance of microdialysis for on-line monitoring of the level of serotonin in different areas of the brain across the sleep/wake cycle.

Changes in sleep and wakefulness following 5-HT1A ligands given systemically and locally in different brain regions

Serotonin (5-HT) has been implicated in the regulation of vigilance, but whether 5-HT is important for sleep or waking processes remains controversial. This review addresses the role of 5-HT1A receptors in sleep and wakefulness. Systemic administration of 5-HT1A agonists consistently increases wakefulness, whereas slow wave sleep (SWS) and REM (rapid-eye movement) sleep are reduced. However, systemic 5-HT1A agonists also produce a delayed increase in deep slow wave sleep, or an increase in slow wave activity. Intrathecal administration of a selective 5-HT1A agonist produces an increase in SWS, whereas wakefulness is reduced, presumably by stimulating 5-HT1A receptors located presynaptically on primary afferents in the spinal cord. Microinjection of serotonin into the region of the cholinergic basalis neurons produces an increase in slow wave activity, presumably by stimulating 5-HT1A receptors. Microdialysis perfusion of a selective 5-HT1A agonist into the dorsal Raphe nucleus causes an increase in REM sleep, whereas the other sleep/wake stages are unaltered. The REM sleep increase is likely due to a decrease in 5-HT neuronal activity, and thereby reduced 5-HT neurotransmission in projection areas, e.g. the laterodorsal and pedunculopontine tegmental nuclei. Direct injection of a selective 5-HT1A agonist into the pedunculopontine tegmental nuclei reduces REM sleep, consistent with such a hypothesis. These complex sleep/wake data of 5-HT1A ligands suggest that 5-HT1A receptor activation may increase waking, increase slow wave sleep or increase REM sleep depending on where the 5-HT1A receptors are located within the central nervous system.

Sleep electroencephalographic response to muscarinic and serotonin1A receptor probes in patients with major depression and in normal controls

BACKGROUND

To test the hypothesis that depression is associated with an increased ratio of cholinergic to serotonergic neurotransmission, we compared the effects of pilocarpine, a muscarinic agonist, and ipsapirone, a serotonin (5-HT)1A agonist, on electroencephalographic (EEG) sleep in depressed and healthy subjects. We hypothesized, adopting the reciprocal interaction model, that the effects on REM sleep of these probes within the same individuals are negatively correlated and unmask neurobiological changes in depression.

METHODS

Polysomnographic recordings were obtained in 12 unmedicated patients with a current major depression and 12 normal controls. They received placebo, pilocarpine 25 mg, or ipsapirone 10 mg (orally, 15 min before bedtime, after premedication with the peripheral anticholinergic probanthine 30 mg, double blind, counterbalanced) on three occasions.

RESULTS

Pilocarpine shortened and ipsapirone prolonged REM latency equally in both groups. These effects were not correlated. Pilocarpine decreased slow-wave sleep and EEG delta power during the first nonREM episode more in controls than in patients, and enhanced EEG sigma power equally in both groups. Ipsapirone had no significant effects on EEG power.

CONCLUSION

These data do not support the postulate of muscarinic receptor up-regulation and 5-HT1A receptor down-regulation in depression. The significance of blunted delta power suppression in patients following pilocarpine warrants further investigations.

Effects of clozapine on sleep: a longitudinal study

Polysomnographic studies on the effects of clozapine, an atypical antipsychotic agent with strong sedative properties, on night sleep report inconsistent results. Most of these studies did not include baseline recordings and were not controlled for clozapine-induced fever, which is known to alter nocturnal sleep. We conducted a 2-week longitudinal polysomnographic investigation in 10 long-term drug-free schizophrenic patients prior to and at the end of the first and second weeks of clozapine treatment. Rectal temperature was measured daily and patients with fever (> 37.9 degrees C) were excluded. Clozapine significantly improved sleep continuity. In addition, non-rapid eye movement (NREM) sleep and in particular stage 2 sleep increased significantly, while the amounts of stage 4 and slow-wave sleep decreased significantly. Clozapine increased significantly REM density, but it did not affect the amount of REM sleep. We conclude that in patients who do not experience clozapine-induced fever, clozapine has strong sleep consolidating effects resulting from an increase in stage 2 NREM sleep.

Human sleep EEG following the 5-HT1A antagonist pindolol: possible disinhibition of raphe neuron activity

The sleep electroencephalogram (EEG) was used to assay central effects of pindolol (10 and 30 mg p.o.), a mixed beta(1/2)-adrenoceptor/5-hydroxytryptamine (5-HT)(1A/1B) receptor blocker, in humans. Compared to placebo, pindolol produced a dose-related suppression of rapid-eye-movement (REM) sleep, including a prolongation of REM latency, and a decrease of REM time and REM density. At the higher dose, it also reduced EEG spectral power during non-REM sleep in portions of the delta, theta, and alpha frequencies (1.125-5.125 Hz, 7.125-9.625 Hz). By contrast, betaxolol (20 mg p.o.), a selective beta1-antagonist devoid of serotonergic affinity, affected neither REM sleep nor EEG power. REM sleep is, in part, under the inhibitory control of serotonergic neurons projecting from the dorsal raphe nucleus to pontine cholinergic/cholinoceptive cells. The EEG power spectrum induced by pindolol tended to be opposite to what has previously been reported for ipsapirone, a 5-HT1A agonist. Therefore, the present data, tentatively, are consistent with the contention that pindolol inhibits, possibly selectively, somatodendritic 5-HT1A autoreceptors in humans and may antagonize self-inhibition of midbrain raphe nuclei 5-HT neurons.

The electroencephalographic sleep pattern in schizophrenic patients treated with clozapine or classical antipsychotic drugs

The effects of antipsychotic agents on sleep were tested by examining the nocturnal electroencephalographic recordings of 14 drug-naïve schizophrenic patients and comparing these with recordings from 12 patients treated with clozapine and 10 treated with classical neuroleptics (haloperidol: n = 7; flupentixol: n = 3). In both of the treated groups, sleep continuity measures and rapid eye movement (REM) density were significantly higher than in the drug-naïve group. Clozapine-treated patients showed significantly more stage two sleep, more stable non-REM sleep (stages two, three and four) and less stage one than patients treated with haloperidol or flupentixol. Clozapine had no effect on the amount of REM sleep. Although mean REM latency was almost twice as long in the clozapine compared with the other two groups, this difference was not statistically significant. The present study suggests considerable differences between the influence of typical and atypical antipsychotic agents on sleep. However, the results of this cross-sectional study should be confirmed using a longitudinal intraindividual approach.

The 5-HT1A agonist ipsapirone enhances EEG slow wave activity in human sleep and produces a power spectrum similar to 5-HT2 blockade

The REM sleep-suppressing effect of postsynaptic 5-HT1A stimulation has been well established. Here we investigate the effects of the 5-HT1A agonist ipsapirone (10 and 20 mg) on sleep EEG power spectra during non-REM sleep in nine healthy humans. At the lower dose, slow wave activity (SWA; EEG power in the delta (1-4.5 Hz) range) was significantly enhanced. At the higher dose, where side-effects occurred, the enhancement in SWA was not significant. The spectral profile was characterized by a bimodal increase of power in the lower delta and in the theta (5-8 Hz) frequencies, and by troughs at 4 Hz and at 11 Hz, a pattern compellingly similar to that reported for a 5-HT2 antagonist (seganserin). We propose that the spectral data following the lower ipsapirone dose reflect a net decrease of neuronal activity at 5-HT2 receptors, mediated through stimulation of somatodendritic autoreceptors in the raphe nuclei (presynaptic) and/or through stimulation of postsynaptic 5-HT1A receptors colocalized with 5-HT2 receptors. The spectral non-REM sleep EEG profile might be used to investigate central 5-HT function in humans.

Sleep deprivation increases brain serotonin turnover in the Djungarian hamster

Djungarian hamsters well adapted to a short photoperiod were subjected to 4 h of total sleep deprivation (SD) by gentle handling. Tissue concentrations of monoamines and of their metabolites were measured from several brain areas using HPLC with electrochemical detection. The 5-hydroxyindoleacetic acid/5-hydroxytryptamine (5-HIAA/5-HT) ratio was significantly increased after SD in the hippocampus, hypothalamus and brain stem, indicating increased serotonin (5-HT) turnover in those areas, while no changes were found in the frontal cortex and olfactory bulb. Dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations were elevated in the hypothalamus, while the noradrenaline concentrations did not change in any of the measured areas. We conclude that a short SD, which has been shown to elevate EEG slow-wave activity during recovery sleep, specifically increases 5-HT turnover in the brain.