Modulation of rapid eye movement sleep in humans by drugs that modify monoaminergic and purinergic transmission

Effects of Vitamin B6 (Pyridoxine) and a B Complex Preparation on Dreaming and Sleep

Anecdotal evidence indicates that supplementation with vitamin B6 (pyridoxine) before bed can enhance dream vividness and recall. In a single pilot study, Ebben, Lequerica, and Spielman (2002) found that vitamin B6 had a dose-dependent effect of increasing scores on a composite measure of dream vividness, bizarreness, emotionality, and color. The present research replicated this study using a larger and more diverse sample of 100 participants from across Australia. We conducted a randomized, double-blind, placebo-controlled investigation of the effects on dreaming and sleep of ingesting 240 mg vitamin B6 (pyridoxine hydrochloride) before bed for five consecutive days. We also included an exploratory condition involving a B complex preparation containing a range of B vitamins. We found that vitamin B6 significantly increased the amount of dream content participants recalled but did not significantly affect dream vividness, bizarreness, or color, nor did it significantly affect other sleep-related variables. In contrast, participants in the B complex group showed significantly lower self-rated sleep quality and significantly higher tiredness on waking. We discuss the potential for using vitamin B6 in research on lucid dreaming.

Duration of activity and mode of action of modafinil: Studies on sleep and wakefulness in humans

The duration of activity of modafinil was investigated in healthy male volunteers in two double-blind crossover studies. Mode of action was explored using a statistical model concerned with the relationship between total sleep duration and that of rapid eye movement (REM) sleep. Nocturnal sleep (23:00-07:00) followed by next-day performance (09:00-17:00) was studied in 12 subjects administered 100, 200, 300 mg modafinil and placebo, 0.5 h before bedtime. Performance overnight (19:00-08:45) followed by sleep (09:15-15:15) was studied in nine subjects administered 100, 200, 300, 400 mg modafinil, 300 mg caffeine and placebo at 22:15. Modafinil dose-dependently reduced sleep duration (nocturnal: 200 mg, p<0.05; 300 mg, p<0.001; morning: 300 and 400 mg, p<0.05) and REM sleep (nocturnal: 300 mg; morning: 400 mg; p<0.05). The statistical model revealed that reduced REM sleep was due to alerting activity, with no evidence of direct suppression of REM sleep, suggesting dopaminergic activity. Enhanced performance with modafinil during overnight work varied with dose (200 mg>100 mg; 300, 400 mg>200, 100 mg, caffeine). However, in the study of next-day performance, the enhancement was attenuated at the highest dose (300 mg) by the greater disturbance of prior sleep. These findings indicate that modafinil has a long duration of action, with alerting properties arising predominantly from dopaminergic activity.

Drug-induced sleep: theoretical and practical considerations

Faithful replication of normal sleep through medications--can it be achieved? Departure from normal sleep with the use of drugs--when is it desired? Answers to these questions depend on accurate understanding of sleep and on concrete criteria upon which to define it. Since these elements are evolving sciences, as yet incompletely known, one might take a nihilistic approach that we simply cannot judge whether we have successfully replicated sleep, since we do not fully grasp what sleep is or what it does. To address these potential obstacles, our article is written in two sections. The first addresses theoretical considerations for how medications might be seen in the larger framework of sleep. The purpose of this section is to inform readers about key issues in evaluating whether a drug has sufficient data to persuasively argue it is re-creating sleep. (We hope that researchers interested in conducting studies, or critical readers of the drug-study literature, might find this section particularly useful.) The second section of this article approaches exemplary, current concepts of pharmacologic manipulation of sleep, organized by disorders as articulated by the International Classification of Sleep Disorders (2005). This second section will combine practical knowledge of clinical sleep medicine, with emphasis on contemporary knowledge about molecular mechanisms that are felt to underlie some of these phenomena. We recognize that our collective knowledge about sleep will advance in the coming years. We hope that this article serves to facilitate that advance.

Cognitive neuroscience of sleep

Mechanism is at the heart of understanding, and this chapter addresses underlying brain mechanisms and pathways of cognition and the impact of sleep on these processes, especially those serving learning and memory. This chapter reviews the current understanding of the relationship between sleep/waking states and cognition from the perspective afforded by basic neurophysiological investigations. The extensive overlap between sleep mechanisms and the neurophysiology of learning and memory processes provide a foundation for theories of a functional link between the sleep and learning systems. Each of the sleep states, with its attendant alterations in neurophysiology, is associated with facilitation of important functional learning and memory processes. For rapid eye movement (REM) sleep, salient features such as PGO waves, theta synchrony, increased acetylcholine, reduced levels of monoamines and, within the neuron, increased transcription of plasticity-related genes, cumulatively allow for freely occurring bidirectional plasticity, long-term potentiation (LTP) and its reversal, depotentiation. Thus, REM sleep provides a novel neural environment in which the synaptic remodelling essential to learning and cognition can occur, at least within the hippocampal complex. During non-REM sleep Stage 2 spindles, the cessation and subsequent strong bursting of noradrenergic cells and coincident reactivation of hippocampal and cortical targets would also increase synaptic plasticity, allowing targeted bidirectional plasticity in the neocortex as well. In delta non-REM sleep, orderly neuronal reactivation events in phase with slow wave delta activity, together with high protein synthesis levels, would facilitate the events that convert early LTP to long-lasting LTP. Conversely, delta sleep does not activate immediate early genes associated with de novo LTP. This non-REM sleep-unique genetic environment combined with low acetylcholine levels may serve to reduce the strength of cortical circuits that activate in the ~50% of delta-coincident reactivation events that do not appear in their waking firing sequence. The chapter reviews the results of manipulation studies, typically total sleep or REM sleep deprivation, that serve to underscore the functional significance of the phenomenological associations. Finally, the implications of sleep neurophysiology for learning and memory will be considered from a larger perspective in which the association of specific sleep states with both potentiation or depotentiation is integrated into mechanistic models of cognition.

[18F]fluorodopa uptake in the upper brainstem measured with positron emission tomography correlates with decreased REM sleep duration in early Parkinson's disease

Sleep disturbances are common in patients with Parkinson's disease (PD). Previous studies have shown alterations of polysomnographic sleep parameters in PD, such as overall diminution of slow-wave and REM sleep duration, absence of muscle atonia during REM and increased occurrence of periodic leg movements during sleep. The pathogenesis of sleep dysregulation in PD is unknown. The aim of this study was to determine relations of abnormal polysomnographic sleep parameters and the dopaminergic function of the striatum and the upper brainstem measured with the use of positron emission and magnetic resonance tomography in 10 early-stage PD patients with a history of sleep disturbances. Our data demonstrated a significant inverse correlation of absolute and percentage REM sleep duration with the mesopontine [18F]6-fluorodopa (FDOPA) uptake in PD patients. Therefore, the results point to a REM inhibiting effect of increased monaminergic transmission within the upper brainstem in early-stage PD. This finding emphasises the pathophysiological significance of a disturbed neurotransmitter equilibrium in the rostral brainstem for REM sleep alterations in PD.

Is the nonREM-REM sleep cycle reset by forced awakenings from REM sleep?

In selective REM sleep deprivation (SRSD), the occurrence of stage REM is repeatedly interrupted by short awakenings. Typically, the interventions aggregate in clusters resembling the REM episodes in undisturbed sleep. This salient phenomenon can easily be explained if the nonREM-REM sleep process is continued during the periods of forced wakefulness. However, earlier studies have alternatively suggested that awakenings from sleep might rather discontinue and reset the ultradian process. Theoretically, the two explanations predict a different distribution of REM episode duration. We evaluated 117 SRSD treatment nights recorded from 14 depressive inpatients receiving low dosages of Trimipramine. The alarms were triggered by an automatic mechanism for the detection of REM sleep and had to be canceled by the subjects themselves. The REM episodes were determined as in undisturbed sleep-they had to include the remaining REM activity and were separated by 30 min without REM epochs. The frequency histogram of REM episodes declined exponentially with episode duration for each of the first four sleep cycles. The duration of nonREM intervals revealed bimodal distributions. These results were found consistent with the model assuming a reset of the ultradian cycle upon awakening. Whether REM or nonREM activity is resumed on return to sleep can be modeled by a random decision whereby the probability for REM sleep might depend on the momentary REM pressure.

Sleep and depression--results from psychobiological studies: an overview

Disturbances of sleep are typical for most depressed patients and belong to the core symptoms of the disorder. Polysomnographic sleep research has demonstrated that besides disturbances of sleep continuity, in depression sleep is characterized by a reduction of slow wave sleep and a disinhibition of REM sleep, with a shortening of REM latency, a prolongation of the first REM period and increased REM density. These findings have stimulated many sleep studies in depressive patients and patients with other psychiatric disorders. In the meantime, several theoretical models, originating from basic research, have been developed to explain sleep abnormalities of depression, like the two-process-model of sleep and sleep regulation, the GRF/CRF imbalance model and the reciprocal interaction model of non-REM and REM sleep regulation. Interestingly, most of the effective antidepressant agents suppress REM sleep. Furthermore, manipulations of the sleep-wake cycle, like sleep deprivation or a phase advance of the sleep period, alleviate depressive symptoms. These data indicate a strong bi-directional relationship between sleep, sleep alterations and depression.

The neuropsychology of REM sleep dreaming

Recent PET imaging and brain lesion studies in humans are integrated with new basic research findings at the cellular level in animals to explain how the formal cognitive features of dreaming may be the combined product of a shift in neuromodulatory balance of the brain and a related redistribution of regional blood flow. The human PET data indicate a preferential activation in REM of the pontine brain stem and of limbic and paralimbic cortical structures involved in mediating emotion and a corresponding deactivation of dorsolateral prefrontal cortical structures involved in the executive and mnemonic aspects of cognition. The pontine brainstem mechanisms controlling the neuromodulatory balance of the brain in rats and cats include noradrenergic and serotonergic influences which enhance waking and impede REM via anticholinergic mechanisms and cholinergic mechanisms which are essential to REM sleep and only come into full play when the serotonergic and noradrenergic systems are inhibited. In REM, the brain thus becomes activated but processes its internally generated data in a manner quite different from that of waking.

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.

Effects of four antiepileptic drugs on sleep and waking in the rat under both light and dark phases

Sedation is a common side effect of anticonvulsant drug therapy. To find out whether the new antiepileptic drugs, felbamate and lamotrigine, are able to produce sedation, we carried out electroencephalographic (EEG) studies in the rat to measure drug effects on sleep-wake patterns, during both light and dark phases. For comparison, the reference drugs, carbamazepine and phenobarbital, were also studied. EEG activity was recorded for 6 h after oral (PO) administration of drugs or vehicle, and the stages of wakefulness, rapid eye movements (REM) sleep and non-REM sleep were classified thereafter. In the light phase, felbamate (30-300 mg/kg) did not produce sedative effects, while lamotrigine (3-30 mg/kg) increased wakefulness at each dose tested. Carbamazepine (10-100 mg/kg) did not produce sleep-wake alterations, and phenobarbital (100 mg/kg) markedly suppressed REM. In the dark phase, felbamate (300 mg/kg), lamotrigine (30 mg/kg), and carbamazepine (100 mg/kg) reduced REM but did not change the total amount of sleep. Phenobarbital, at 100 mg/kg, markedly increased total sleep and greatly reduced REM. This study shows that the anticonvulsant drugs examined have different effects on the states of sleep and wakefulness in the rat. The data are discussed on the basis of the mechanism of action that characterizes each individual drug.

Effects of zopiclone on sleep and symptoms in schizophrenia: comparison with benzodiazepine hypnotics

Sleep variables and psychiatric symptoms were investigated in 6 male chronic schizophrenic outpatients. The patients were being treated with benzodiazepine (BZD) hypnotics for more than 8 weeks, and BZDs were replaced with zopiclone (ZPC) 15 mg/day. Polysomnographic examinations, subjective sleep assessments and BPRS scoring were performed during BZD therapy and at the end of 8 weeks of ZPC therapy. The doses of neuroleptics and anticholinergic agents remained fixed throughout the study. The amount of slow-wave sleep (SWS) was markedly small and that of stage 1 sleep was moderately large during BZD therapy. The amount of stage 1 was smaller and that of stage 2 was larger during treatment with ZPC than BZDs. There were no significant change in the amount of SWS between the treatment. Half of the patients exhibited a sleep-onset REM period (SOREMP) during ZPC therapy. Both total BPRS score and negative symptom score were lower during treatment with ZPC than BZDs. These results suggest that ZPC may be more beneficial in treating schizophrenic insomnia than BZD hypnotics and that reduced SWS and SOREMP may be partly involved in the pathophysiology of schizophrenia.

Drugs and the sleep-wakefulness continuum

The circadian cycle of sleep and wakefulness in humans is controlled by the activity of many neurotransmitters. Studies of the effects of drugs on the central nervous system have elucidated some of the mechanisms that may be involved. Some transmitters are concerned with the basic control of sleep and wakefulness, influencing both alertness during the day and the pattern of nocturnal sleep. On the other hand, there are other transmitters that appear to be concerned primarily with the manifestation of wakefulness and vigilance, without a direct role in the process of sleep.

Symposium: Normal and abnormal REM sleep regulation: REM sleep in depression-an overview

Abnormalities of REM sleep, i.e. shortening of REM latency, lengthening of the duration of the first REM period and heightening of REM density, which are frequently observed in patients with a major depressive disorder (MDD), have attracted considerable interest. Initial hopes that these aberrant patterns of sleep constitute specific markers for the primary/endogenous sub-type of depression have not been fulfilled. The specificity of REM sleep disinhibition for depression in comparison with other psychopathological groups is challenged as well. Demographic variables like age and sex exert strong influences on sleep physiology and must be controlled when searching for specific markers of depressed sleep. It is still an open question whether abnormalities of sleep are state- or trait-markers of depression. Beyond baseline studies, the cholinergic REM induction test (CRIT) indicated a heightened responsitivity of the REM sleep system to cholinergic challenge in depression compared with healthy controls and other psychopathological groups, with the exception of schizophrenia. A special role for REM sleep in depression is supported by the well-known REM sleep suppressing effect of most antidepressants. The antidepressant effect of selective REM deprivation by awakenings stresses the importance of mechanisms involved in REM sleep regulation for the understanding of the pathophysiology of depressive disorders. The positive effect of total sleep deprivation on depressive mood which can be reversed by daytime naps, furthermore emphasizes relationships between sleep and depression. Experimental evidence as described above instigated several theories like the REM deprivation hypothesis, the 2-process model and the reciprocal interaction model of nonREM-REM sleep regulation to explain the deviant sleep pattern of depression. The different models will be discussed with reference to empirical data gathered in the field.

The effects of fenfluramine on sleep and prolactin in depressed inpatients: a comparison of potential indices of brain serotonergic responsivity

The effects of fenfluramine, an indirect serotonergic agonist, on electroencephalographic sleep and prolactin secretion were assessed in 12 unmedicated inpatients with a primary diagnosis of major depressive episode. Compared to prefenfluramine profiles, sleep studies performed following fenfluramine administration showed a statistically significant reduction of slow-wave sleep (SWS) (p < 0.001) and a corresponding increase in percentage of stage-2 sleep (p < 0.007). Automated delta wave counts per min decreased significantly during the first nonrapid eye movement (NREM) period (p = 0.04), and automated rapid-eye movement (REM) counts were also decreased in the second REM period (p = 0.02). These effects on sleep electroencephalogram (EEG) did not correlate significantly with another measure of serotonergic responsivity, namely peak prolactin level following fenfluramine, nor with the severity of depression. The reductions in SWS and REM counts are proposed to be the result of time-dependent changes in serotonergic neurotransmission following the administration of fenfluramine. These findings are consistent with earlier work suggesting a role for serotonin in initiation and regulation of SWS and REM sleep.

Neuropsychological function and REM sleep in schizophrenic patients

To test the hypothesis that rapid eye movement (REM) sleep in schizophrenic patients is associated with cognitive function, we studied 18 schizophrenic inpatients by means of electroencephalograms taken during sleep in their own hospital beds after a minimum 2-wk medication withdrawal period. Patients underwent neuropsychological tests to measure memory function and other aspects of cognitive performance. REM sleep measures demonstrated positive and negative correlations with cognition and memory measures, depending on when REM occurred after sleep onset. Minutes of REM sleep and REM density in the first period correlated negatively with performance, while REM minutes occurring after the first REM period correlated positively with neuropsychological performance. Further work should test whether phasic REM sleep regulation at the beginning of the night plays a compensatory role for neuropsychological dysfunction in schizophrenics.

The duration of REM sleep epic, odes in normal sleep

The distributions of the durations of the first 3 REM sleep episodes have been analysed using a total of 134 overnight sleep recordings from 10 subjects. From investigation of the length of uninterrupted episodes of stage REM, it is shown that arousals to stage 0/1 could play an important part in the process of REM exit, and that by the middle of the sleep period, these arousals probably occur according to a Poisson process. During the first and second REM episodes a more complex process appears to be at work, which could reflect increased pressure for slow wave sleep. These findings suggest that the duration of a REM episode is determined by a process that has a large stochastic element, which is not necessarily tied to REM entry.

Effects of remoxipride, a dopamine D-2 antagonist antipsychotic, on sleep-waking patterns and EEG activity in rats and rabbits

The antipsychotic remoxipride, a selective dopamine D-2 receptor antagonist, was studied for its effects on sleep-waking patterns in the rat and electroencephalographic (EEG) activity in the rabbit. Haloperidol, which has lesser selectivity for D-2 receptors, was used for comparison. In the rat, remoxipride (1-10 mg/kg SC) did not affect either total sleep or non-rapid eye movement (non-REM) sleep. Only REM was slightly reduced by the high dose of 10 mg/kg. Haloperidol (0.1-1 mg/kg PO) enhanced duration of both total sleep and non-REM sleep. In the rabbit, remoxipride (3 and 10 mg/kg IV) induced no significant changes of the EEG power spectrum over 0.1-38.5 Hz or individual frequency bands. In both cortex and hippocampus the drug did not alter the arousal response to acoustic sensory stimuli. Plasma concentration of remoxipride 10 mg/kg IV in rabbits declined biexponentially and was 4 and 2 mumol/l at 30 min and 1 h, respectively. Haloperidol (0.3 and 1 mg/kg) slowed down the EEG activity, enhanced the power spectrum of the cortical and hippocampal activity, and significantly reduced the duration of arousal induced by sensory stimuli. The results indicate that, unlike haloperidol, remoxipride has weak or no sedative effects. The data also provide support to the notion that D-2 receptors are not involved in the regulation of states of sleep and sedation.

Modulation of sleep and waking states by D-1 receptors

This review describes pharmacological studies showing that the dopamine D-1 receptor subtype is involved in the modulation of states of sleep and wakefulness. Stimulation of D-1 receptors by SKF 38393 produces electro encephalographic (EEG) arousal, enhances duration of wakefulness and markedly reduces the stage of rapid eye movement sleep (REM). Importantly, all these effects occur in the absence of the most typical dopamine- mediated behaviours such as stereotyped movements or hyperactivity. On the contrary, studies with the selective D-1 receptor antagonists, especially with the drug SCH 23390, have shown that these compounds increase duration of total sleep including both components, non-REM and REM. Likewise, they produce sedation in different animal species. An important distinguishing feature of the action of D-1 antagonists, compared with non-selective or D-2-selective antagonists, is their ability to enhance the amount of REM. The effect appears to be specifically mediated by D-1 receptors, whereas the interaction of SCH 23390 or its derivatives with the serotonin receptor subtype 5-HT(2) may contribute to an increase of total sleep, but does not seem to influence REM changes. The overall findings indicate that D-1 receptors are involved in mediating the sedation-arousal continuum and the states of sleep-wakefulness. The REM-enhancing action of D-1 antagonists appears to be a unique response, which, considering that sleep disorder is a prominent feature in psychiatric illness, may have clinical relevance. The involvement of D-1 receptors in the modulation of REM stimulates further research aimed at gaining insights into both the complex process of sleep and the function of the D-1 receptor within the central nervous system.

Effect of neuroleptic treatment on polysomnographic measures in schizophrenia

To study the effects of neuroleptic therapy on sleep EEG variables in schizophrenia, as well as the clinical correlates of these variables, we performed polysomnographic (PSG) studies on 14 schizophrenic inpatients before and during neuroleptic therapy. Sleep continuity measures improved after 3 weeks of neuroleptic therapy, showing decreased sleep latency and improved sleep efficiency. REM latency increased with treatment, although half the patients continued to exhibit REM latencies less than 60 min. Other sleep stages and measures of REM sleep (density, activity, number of periods) did not appear to change with neuroleptic treatment. At baseline, REM latency had strong negative correlations with BPRS and SANS scores, but with 3 weeks of such treatment, this association disappeared. Further work is needed to distinguish direct medication effects from the effects of the changing clinical state on PSG measures.

Presynaptic alpha 2-adrenoceptor function and sleep in man: studies with clonidine and idazoxan

The effects of an alpha 2-adrenoceptor agonist, clonidine and an antagonist, idazoxan, were studied on nocturnal sleep in man. Clonidine increased non-rapid eye movement sleep and idazoxan reduced slow wave sleep and increased awake activity. Changes in the continuity of sleep with clonidine were similar to, and those with idazoxan opposite to, the effects of maprotiline, an inhibitor of the uptake of noradrenaline, used as an active control. These findings support the previous conclusion that raised levels of noradrenaline in the synapse, after inhibition of uptake, lead to increased presynaptic inhibition of release of transmitter in man. However, all three drugs decreased rapid eye movement (REM) sleep and the ratio of REM to nonREM sleep and this is believed to be due to a non-specific upset of the balance of influences which control the appearance of REM sleep.

Sleep, depression, and suicide

In a retrospective study of the electroencephalographic (EEG) sleep of major depressives with and without a history of suicide attempts, suicide attempters had longer sleep latency, lower sleep efficiency, and fewer late-night delta wave counts than normal controls. Nonattempters, compared to attempters, had less rapid eye movement (REM) time and activity in period 2, but more delta wave counts in non-REM period 4. Although both attempters and nonattempters were like controls in regard to REM period 2, patients with suicide attempts had altered intranight temporal distribution of phasic REM activity, with increased REM activity (by both visual and automated scoring) in REM sleep period 2 (significant group x period interaction). These findings, which may be more traitlike or persistent than state-related, are discussed in the context of current theories on the role of serotonin in the regulation of sleep and in suicidal behavior.

Fluvoxamine versus desipramine: comparative polysomnographic effects

Electroencephalogram sleep measures over a 4-week period were obtained on 35 inpatients with major depression (unipolar) who received either fluvoxamine or desipramine in a randomized double-blind trial. Fluvoxamine showed immediate rapid eye movement (REM) sleep suppression and an alerting effect on sleep continuity measures. In contrast, desipramine administration was associated with REM suppression and sleep continuity improvement. The "alerting" quality of fluvoxamine, similar to other serotonergic antidepressants, appears to be unrelated to a lack of clinical efficacy, but may be related to persistent REM sleep suppression. However, it is premature to comment on the serotonin specificity for REM sleep.

Sleep polygraphy in schizophrenia: methodological issues

The findings of sleep studies in schizophrenia have remained inconsistent in the literature as exemplified by the recent controversy regarding reduced rapid eye movements (REM) latency in these patients. These inconsistencies can partly be explained by major methodological shortcomings in studies evaluating sleep in schizophrenia. Lack of standardized scoring and diagnostic methods in the earlier studies and more recently, the effect of neuroleptic treatment or its withdrawal, have confounded the sleep results. Data are presented to illustrate the effect of the presence of tardive dyskinesia or active psychotic symptoms that further skew the sleep polygraphic measurements in these patients. Studies in drug-naive patients can circumvent some of these confounds but then these studies are weakened by sampling bias. Available data suggest that previous duration of neuroleptic treatment, duration of neuroleptic withdrawal, presence of tardive dyskinesia, and severity of psychotic symptoms should be considered when interpreting REM sleep measures in schizophrenic patients.

Dopaminergic transmission and the sleep-wakefulness continuum in man

Modulation of dopaminergic transmission on daytime alertness and performance and on nocturnal sleep were studied in man using 30, 60 and 90 mg pemoline, a dopamimetic drug, and 2, 4 and 6 mg pimozide, a dopamine receptor antagonist. Pemoline lengthened daytime sleep latencies and improved attention, and increased wakefulness during nocturnal sleep. Rapid eye movement (REM) sleep was reduced with 90 mg pemoline, but this was due entirely to increased wakefulness. Pimozide had little effect on overnight sleep, but increased the tendency to fall asleep and impaired performance during the day. These studies suggest that the effects of certain drugs which modulate the activity of neurotransmitters, involved in the control of sleep and wakefulness, may be related to the inherent level of activity of the central nervous system. Modulation of the dopaminergic system can have a profound influence on the manifestation of wakefulness and vigilance, but is unlikely to modify directly the elaboration of REM sleep in man.