Critical analysis of the theories advanced to explain short REM sleep latencies and other sleep anomalies in several psychiatric conditions

Temperament and character in primary insomnia

Recent studies by Cloninger suggest that the temperament dimension of harm avoidance might be related to serotonergic activity. Since serotonergic mechanisms equally play a major role in sleep regulation, we decided to use Cloninger’s psychobiological model of temperament and character to assess whether there is a link between psychophysiologic insomnia and specific personality traits. Chronic insomnia is a common complaint in modern society, and it is still controversial whether insomniacs share specific personality traits. Thirty-two chronic insomniacs (<50 years) were studied. They underwent polysomnography for two consecutive nights and filled out the 226-item self-questionnaire of Temperament and Character Inventory as well as the Hospital Anxiety and Depression scale. (1) Harm avoidance for all subscores was significantly higher in insomniac patients when compared with controls; (2) self-directedness scores were lower in insomniacs; (3) sleep latency was positively correlated to harm avoidance; (4) HA1 (anticipatory worry) was negatively correlated to REM latency. Temperament and Character Inventory is a useful tool in the investigation of chronic insomnia. Serotonergic mechanisms might explain the high incidence of harm avoidance as personality trait in psychophysiologic insomniac patients. Further studies are needed to see whether harm avoidance could be a psychological vulnerability marker for primary insomnia and be used as predictor of SSRI treatment responders.

5-HT7, NEUROGENESIS AND ANTIDEPRESSANTS: A PROMISING THERAPEUTIC AXIS FOR TREATING DEPRESSION

1. There is mounting evidence that a wide range of antidepressants share the common feature of increasing hippocampal neurogenesis. The specificity of this association has suggested that an ability to increase neurogenesis might be a useful paradigm to screen for compounds with antidepressant activity. 2. The hope of developing better antidepressants has stimulated research into the molecular control of neurogenesis and here we summarize some of the recent findings. We also review recent work that highlights 5-HT7 receptor as a promising molecular target in the treatment of depression. 3. In summary, it appears that 5-HT7 antagonism is capable of producing diverse antidepressant-like behavioural effects, alters hippocampal neuronal morphology and synergistically regulates hippocampal neurogenesis.

Major depression in males: effects of age, severity and adaptation on sleep variables

Sleep abnormalities have been repeatedly demonstrated in major depression. However, the respective influences of age, severity, adaptation and gender have never been clearly disentangled. In a retrospective study, full polysomnograms of 67 male depressive patients and 67 carefully age-matched male healthy control subjects were analyzed. The usual differences associated with the sleep of depressed patients were observed. However, in contrast to most reports, REMS was also found to be reduced; although no comparisons between sexes can be made in this all-male study, one interpretation of this finding is that reduction of REMS is a marker of male depression. Age was found to influence most sleep variables, but not the order of their association with depression. Depression severity was found to be associated with Wake After Sleep Onset (WASO), REMS, and Non-REMS (NREMS). No residual adaptation effect was observed. One of the main markers of depression was in fact the absence of sleep, whether observed as long delays prior to entering sleep, or excessive intermittent awakenings. This sleep reduction affected both REMS and NREMS, in comparable percentages. This supports the hypothesis of a hyperarousal possibly linked to stress.

5-HT7 receptor inhibition and inactivation induce antidepressantlike behavior and sleep pattern

BACKGROUND

The 5-hydroxytryptamine7 receptor (5-HT7) is implicated in circadian rhythm phase resetting, and 5-HT7 receptor-selective antagonists alter rapid eye movement (REM) sleep parameters in a pattern opposite from those in patients with clinical depression.

METHODS

As sleep, circadian rhythm, and mood regulation are related, we examined 5-HT7 receptor knockout mice in two behavioral models of depression. The forced swim and tail suspension tests are highly predictive for antidepressant drug activity.

RESULTS

Unmedicated 5-HT7-/- mice showed decreased immobility in both tests, consistent with an antidepressantlike behavior. The selective 5-HT7 receptor antagonist SB-269970 also decreased immobility. The selective serotonin reuptake inhibitor citalopram, a widely used antidepressant, decreased immobility in both 5-HT7+/+ and 5-HT7-/- mice in the tail suspension test, suggesting that it utilizes an independent mechanism. The 5-HT7-/- mice spent less time in and had less frequent episodes of REM sleep, also consistent with an antidepressantlike state.

CONCLUSIONS

The 5-HT7 receptor might have a role in mood disorders and antagonists might have therapeutic value as antidepressants.

Comparative effects of duloxetine and desipramine on sleep EEG in healthy subjects

RATIONALE

Antidepressants are known to modify human sleep patterns.

OBJECTIVES

Duloxetine is a new antidepressant with a mechanism of action involving reuptake inhibition of both serotonin (5-HT) and norepinephrine (NE). In this study, the effects of two dosing regimens of duloxetine on sleep electroencephalography (EEG) were investigated at steady-state plasma concentrations in young, healthy, male subjects.

METHODS

Placebo (n=12), desipramine (50 mg BID; n=12) and two regimens of duloxetine (80 mg QD, n=6; or 60 mg BID, n=6) were compared in a randomized, double-blind, three-period crossover study, each treatment being administered from day 1 to day 7. Sleep polygraphic recordings took place at baseline (day -1) and day 6 of each period. The Leeds sleep evaluation questionnaire (LSEQ) was also administered on the morning of day 7.

RESULTS

Both regimens of duloxetine produced a significant increase in the onset latency of REM sleep as well as a significant mean decrease in total REM sleep duration. Desipramine exhibited comparable effects. When compared to placebo, sleep continuity was significantly reduced with desipramine and duloxetine 60 mg BID whereas a significant improvement was observed with duloxetine 80 mg QD. On the LSEQ, duloxetine 80 mg QD produced a significant improvement in the "getting to sleep" subscale compared to placebo, whereas desipramine demonstrated a significant reduction (worsening) in the "quality of sleep" score versus placebo.

CONCLUSIONS

The two dose regimens of duloxetine (80 mg QD and 60 mg BID) produced a REM sleep pattern comparable to that of most antidepressant medications. Duloxetine 80 mg QD appeared to exhibit less impact upon sleep quality than duloxetine 60 mg BID in healthy subjects.

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.

Effect of SB-243213, a selective 5-HT(2C) receptor antagonist, on the rat sleep profile: a comparison to paroxetine

5-HT(2) receptor antagonists promote slow wave sleep (SWS) in humans and rats, conversely 5-HT(2) agonists inhibit SWS in rats. These alterations are thought to be predominantly mediated via the 5-HT(2C) receptor subtype. It is evident that 5-HT(2) receptor function also plays an important role in depression. Here, we examine the acute effect of the selective 5-HT(2C) receptor antagonist 5-methyl-1-[[-2-[(2-methyl-3-pyridyl)oxy]-5-pyridyl]carbamoyl]-6-triflouromethylindoline hydrochloride (SB-243213-A) on rat sleep in comparison to the selective serotonin reuptake inhibitor (SSRI) paroxetine. Both SB-243213-A (10 mg/kg po) and paroxetine (3 mg/kg po) significantly increased deep SWS (SWS2) quantity (27% and 24%, respectively) and reduced paradoxical sleep (PS) quantity (35%) during the sleep period. Following SB-243213-A, SWS2 occurrence frequency was reduced (24.1%); however, elevated quantity of SWS2 can be attributed to an increase in occurrence duration (81%). Reduced PS quantity results from a decrease in occurrence frequency (46%). In comparison, paroxetine increased SWS2 occurrence frequency (50%), with decreased frequency (27%) and duration (21%) of PS. The data for SB-243213-A in the present study is consistent with that following ritanserin supporting 5-HT(2C) receptor subtype mediation of this response. The similar effect of SB-243213-A to paroxetine with regard to PS quantity provides further evidence that 5-HT(2C) receptor antagonists maybe beneficial in the treatment of depression/anxiety.

Shorter REM latency associated with more sleep cycles of a shorter duration in healthy humans

A significant association between rapid eye movement (REM) sleep latency and the number of non-REM/REM sleep cycles was found 15 years ago in a large retrospective study. The present prospective study further explored this intra-sleep relationship and analyzed the links between these two variables and the mean cycle duration. It was based on a carefully selected group of healthy control subjects whose sleep was polysomnographically recorded at home for 4 sequential nights. The latency of REM sleep was inversely correlated with the number of cycles and positively correlated with the mean cycle duration, both in individual nights and on means of 4 nights. The present study demonstrated that variations in the number of cycles or the mean cycle duration between the nights are far less important than the substantial differences observed between subjects. Present outcomes support the study of sleep cycle periods and frequencies in those psychiatric disorders where REM sleep latencies have been found to be shorter, and they suggest that these variables be included in sleep studies in which cycles are compared with each other.

The first-night effect may last more than one night

The first-night effect in sleep polysomnographic studies is usually considered to last for one night. However, a few observations have indicated that variables associated to rapid eye movement sleep take longer to stabilize. Notwithstanding, current opinion holds that second nights of recording can be used without restriction for research and clinical purposes. The goal of this study was to describe the dynamics of habituation to polysomnography in optimal conditions. Twenty-six young, carefully screened, healthy subjects were recorded in their home for four consecutive full polysomnographies. Repeated measures ANOVA were applied. Between the two first nights, while there were no differences in sleep duration in non-rapid eye movement sleep, marked modifications in corresponding spectral power were observed. The dynamics of adaptation of rapid eye movement sleep appeared to be a process extending up to the fourth night. Similar dynamics in NREMS and REMS homeostasis have been observed in sleep deprivation studies, and it appears that the same mechanisms may be responsible for the FNE. The longer habituation process of REMS in particular has important implications for sleep research in psychiatry.

Characterization of SB-269970-A, a selective 5-HT(7) receptor antagonist

The novel 5-HT(7) receptor antagonist, SB-269970-A, potently displaced [(3)H]-5-CT from human 5-HT(7(a)) (pK(i) 8.9+/-0.1) and 5-HT(7) receptors in guinea-pig cortex (pK(i) 8.3+/-0.2). 5-CT stimulated adenylyl cyclase activity in 5-HT(7(a))/HEK293 membranes (pEC(50) 7.5+/-0.1) and SB-269970-A (0.03 - 1 microM) inhibited the 5-CT concentration-response with no significant alteration in the maximal response. The pA(2) (8.5+/-0.2) for SB-269970-A agreed well with the pK(i) determined from [(3)H]-5-CT binding studies. 5-CT-stimulated adenylyl cyclase activity in guinea-pig hippocampal membranes (pEC(50) of 8.4+/-0.2) was inhibited by SB-269970-A (0.3 microM) with a pK(B) (8.3+/-0.1) in good agreement with its antagonist potency at the human cloned 5-HT(7(a)) receptor and its binding affinity at guinea-pig cortical membranes. 5-HT(7) receptor mRNA was highly expressed in human hypothalamus, amygdala, thalamus, hippocampus and testis. SB-269970-A was CNS penetrant (steady-state brain : blood ratio of ca. 0.83 : 1 in rats) but was rapidly cleared from the blood (CLb=ca. 140 ml min(-1) kg(-1)). Following a single dose (3 mg kg(-1)) SB-269970 was detectable in rat brain at 30 (87 nM) and 60 min (58 nM). In guinea-pigs, brain levels averaged 31 and 51 nM respectively at 30 and 60 min after dosing, although the compound was undetectable in one of the three animals tested. 5-CT (0.3 mg kg(-1) i.p.) induced hypothermia in guinea-pigs was blocked by SB-269970-A (ED(50) 2.96 mg kg(-1) i.p.) and the non-selective 5-HT(7) receptor antagonist metergoline (0.3 - 3 mg kg(-1) s.c.), suggesting a role for 5-HT(7) receptor stimulation in 5-CT induced hypothermia in guinea-pigs. SB-269970-A (30 mg kg(-1)) administered at the start of the sleep period, significantly reduced time spent in Paradoxical Sleep (PS) during the first 3 h of EEG recording in conscious rats.