Rapid-acting antidepressant strategies: mechanisms of action

Recent Progress in Biosensors for Depression Monitoring-Advancing Personalized Treatment

Depression is currently a major contributor to unnatural deaths and the healthcare burden globally, and a patient's battle with depression is often a long one. Because the causes, symptoms, and effects of medications are complex and highly individualized, early identification and personalized treatment of depression are key to improving treatment outcomes. The development of wearable electronics, machine learning, and other technologies in recent years has provided more possibilities for the realization of this goal. Conducting regular monitoring through biosensing technology allows for a more comprehensive and objective analysis than previous self-evaluations. This includes identifying depressive episodes, distinguishing somatization symptoms, analyzing etiology, and evaluating the effectiveness of treatment programs. This review summarizes recent research on biosensing technologies for depression. Special attention is given to technologies that can be portable or wearable, with the potential to enable patient use outside of the hospital, for long periods.

Temporal pathways between circadian rhythm, depression and anxiety in the transition from adolescence to early adulthood

BACKGROUND

Sleep and circadian rhythm problems intertwine with affective disorders. Adolescents are particularly vulnerable to developing sleep and affective problems. Yet, the temporal pathways between circadian rhythm, depression and anxiety in the transition phase from adolescence to early adulthood are not fully understood.

METHODS

233 adolescents (76 % females) participated at two time points (T1 and T2) at an interval of 19-months (aged 16.8 and 18.4 years). We used The Beck Depression Inventory-II, Generalized Anxiety Disorder Assessment, GENEActiv actigraphy across 8 days (delayed sleep phase (DSP), sleep duration, midpoint, and regularity), and iButton 1922L thermologgers across 3 days (intrinsic circadian period length, amplitude, and mesor).

RESULTS

A shorter sleep duration at T1 associated with an increase in affective problems at T2, and affective problems at T1 associated with an increase in sleep irregularity at T2. A longer circadian period at T1 associated with an increase in males' affective problems at T2. Moderate to severe depression and anxiety at T1 associated with a 2.69-fold risk (95 % CI 1.38-5.26, p = 0.004) and 2.11-fold risk (95 % CI 1.04-4.25, p = 0.038) of poor sleep quality at T2. Moderate to severe generalized anxiety associated with a 3.17-fold risk (95 % CI 1.35-7.41, p = 0.008) of DSP at T2.

LIMITATIONS

The follow-up period is short.

CONCLUSIONS

The results revealed bidirectional temporal links between sleep and affective problems. Novel observations include a heightened risk of future DSP following a current anxiety disorder and a heightened risk of affective problems following a longer circadian period measured from the 24-hour temperature variation in males.

Recommendations for selection and adaptation of rating scales for clinical studies of rapid-acting antidepressants

The novel mechanisms of action (MOA) derived from some recently introduced molecular targets have led to regulatory approvals for rapid acting antidepressants (RAADs) that can generate responses within hours or days, rather than weeks or months. These novel targets include the N-methyl-D-glutamate receptor antagonist ketamine, along with its enantiomers and various derivatives, and the allosteric modulators of gamma-aminobutyric acid (GABA) receptors. There has also been a strong resurgence in interest in psychedelic compounds that impact a range of receptor sites including D1, 5-HT7, KOR, 5-HT5A, Sigma-1, NMDA, and BDNF. The RAADs developed from these novel targets have enabled successful treatment for difficult to treat depressed individuals and has generated a new wave of innovation in research and treatment. Despite the advances in the neurobiology and clinical treatment of mood disorders, we are still using rating instruments that were created decades ago for drugs from a different era (e.g., The Hamilton and Montgomery-Åsberg depression rating scales, HDRS, and MADRS) continue to be used. These rating instruments were designed to assess mood symptoms over a 7-day time frame. Consequently, the use of these rating instruments often requires modifications to address items that cannot be assessed in short time frames, such as the sleep and appetite items. This review describes the adaptative approaches that have been made with the existing scales to meet this need and examines additional domains such as daily activities, side effects, suicidal ideation and behavior, and role functioning. Recommendations for future studies are described, including the challenges related to implementation of these adapted measures and approaches to mitigation.

A Pattern to Link Adenosine Signaling, Circadian System, and Potential Final Common Pathway in the Pathogenesis of Major Depressive Disorder

Several studies have reported separate roles of adenosine receptors and circadian clockwork in major depressive disorder. While less evidence exists for regulation of the circadian clock by adenosine signaling, a small number of studies have linked the adenosinergic system, the molecular circadian clock, and mood regulation. In this article, we review relevant advances and propose that adenosine receptor signaling, including canonical and other alternative downstream cellular pathways, regulates circadian gene expression, which in turn may underlie the pathogenesis of mood disorders. Moreover, we summarize the convergent point of these signaling pathways and put forward a pattern by which Homer1a expression, regulated by both cAMP-response element binding protein (CREB) and circadian clock genes, may be the final common pathogenetic mechanism in depression.

Neurobiological and behavioral mechanisms of circadian rhythm disruption in bipolar disorder: A critical multi-disciplinary literature review and agenda for future research from the ISBD task force on chronobiology

AIM

Symptoms of bipolar disorder (BD) include changes in mood, activity, energy, sleep, and appetite. Since many of these processes are regulated by circadian function, circadian rhythm disturbance has been examined as a biological feature underlying BD. The International Society for Bipolar Disorders Chronobiology Task Force (CTF) was commissioned to review evidence for neurobiological and behavioral mechanisms pertinent to BD.

METHOD

Drawing upon expertise in animal models, biomarkers, physiology, and behavior, CTF analyzed the relevant cross-disciplinary literature to precisely frame the discussion around circadian rhythm disruption in BD, highlight key findings, and for the first time integrate findings across levels of analysis to develop an internally consistent, coherent theoretical framework.

RESULTS

Evidence from multiple sources implicates the circadian system in mood regulation, with corresponding associations with BD diagnoses and mood-related traits reported across genetic, cellular, physiological, and behavioral domains. However, circadian disruption does not appear to be specific to BD and is present across a variety of high-risk, prodromal, and syndromic psychiatric disorders. Substantial variability and ambiguity among the definitions, concepts and assumptions underlying the research have limited replication and the emergence of consensus findings.

CONCLUSIONS

Future research in circadian rhythms and its role in BD is warranted. Well-powered studies that carefully define associations between BD-related and chronobiologically-related constructs, and integrate across levels of analysis will be most illuminating.

An Epigenetic Perspective on Lifestyle Medicine for Depression: Implications for Primary Care Practice

Depression is the most common presenting mental health disorder in primary care. It is also a major contributor to somatic complaints, worsening of chronic medical conditions, poor quality of life, and suicide. Current pharmacologic and psychotherapeutic approaches avert less than half of depression's cumulative burden on society. However, there is a growing body of research describing both how maladaptive lifestyle choices contribute to the development and worsening of depression and how lifestyle-oriented medical interventions can reduce the incidence and severity of depression. This research, largely derived from an emerging field called epigenetics, elucidates the interactions between our lifestyle choices and those epigenetic factors which mediate our tendencies toward either health, or the onset, if not worsening of disease. The present review highlights how lifestyle choices involving diet, physical activity, sleep, social relationships, and stress influence epigenetic processes positively or negatively, and thereby play a significant role in determining whether one does or does not suffer from depression. The authors propose that medical training programs consider and adopt lifestyle medicine oriented instructional initiatives that will enable tomorrow's primary care providers to more effectively identify and therapeutically intervene in the maladaptive choices contributing to their patients' depression.

Circadian rhythm sleep-wake disturbances and depression in young people: implications for prevention and early intervention

A rate-limiting step in the prevention and early intervention of depressive disorders in young people is our insufficient understanding of causal mechanisms. One plausible pathophysiological pathway is disturbance in the 24 h sleep-wake cycle and the underlying circadian system. Abnormalities in circadian rhythms are well documented in adults with various depressive disorders and have been linked to core clinical features, including unstable mood, daytime fatigue, non-restorative sleep, reduced motor activity, somatic symptoms, and appetite and weight change. In this Review, we summarise four areas of research: basic circadian biology and animal models of circadian disturbances; developmental changes in circadian rhythms during adolescence and implications for the emergence of adolescent-onset depressive syndromes; community and clinical studies linking 24 h sleep-wake cycle disturbances and depressive disorders; and clinical trials of circadian-based treatments. We present recommendations based on a highly personalised, early intervention model for circadian-linked depression in young people.

Melatonin serum level, sleep functions, and depression level after bilateral anodal transcranial direct current stimulation in patients with Parkinson's disease: a feasibility study

Objective

Parkinson's disease (PD) is associated with non-motor complications such as sleep disturbance and depression. Transcranial direct current stimulation (tDCS) showed therapeutic effects on the motor dysfunctions. However, the potential effects of tDCS therapy on melatonin hormone, sleep dysfunctions, and depression in patients with PD still unclear. This feasibility study aimed to identify any potential changes in melatonin serum level, sleep functions and depression after the bilateral anodal tDCS in patients with PD.

Material and Methods

Tensessions of bilateral anodal tDCS stimulation applied over left and right prefrontal and motor areas were given to twenty-five patients with PD. Melatonin serum level, Pittsburgh sleep quality index, and geriatric depression scale examined before and after tDCS stimulation.

Results

After bilateral anodal tDCS, there was a significant reduction in melatonin serum level, improvement in depression, improvements in overall sleep quality, and sleep latency. Correlations test showed significant associations between melatonin serum level reduction and changes in subjective sleep quality, and sleep duration, as well as between improvements in depression and overall sleep quality, sleep latency, and sleep disturbance.

Conclusion

Bilateral anodal tDCS therapy was a feasible and safe tool that showed potential therapeutic effects on melatonin serum level, sleep quality, and depression level in patients with PD. Although the further large scale and randomized-control trial studies are crucially needed, there is still a need for such a feasibility study to be established before such trials can be implemented as is recommended in the new medical research council guidelines.

Time is of the essence: Coupling sleep-wake and circadian neurobiology to the antidepressant effects of ketamine

Several studies have demonstrated the effectiveness of ketamine in rapidly alleviating depression and suicidal ideation. Intense research efforts have been undertaken to expose the precise mechanism underlying the antidepressant action of ketamine; however, the translation of findings into new clinical treatments has been slow. This translational gap is partially explained by a lack of understanding of the function of time and circadian timing in the complex neurobiology around ketamine. Indeed, the acute pharmacological effects of a single ketamine treatment last for only a few hours, whereas the antidepressant effects peak at around 24 hours and are sustained for the following few days. Numerous studies have investigated the acute and long-lasting neurobiological changes induced by ketamine; however, the most dramatic and fundamental change that the brain undergoes each day is rarely taken into consideration. Here, we explore the link between sleep and circadian regulation and rapid-acting antidepressant effects and summarize how diverse phenomena associated with ketamine's antidepressant actions - such as cortical excitation, synaptogenesis, and involved molecular determinants - are intimately connected with the neurobiology of wake, sleep, and circadian rhythms. We review several recently proposed hypotheses about rapid antidepressant actions, which focus on sleep or circadian regulation, and discuss their implications for ongoing research. Considering these aspects may be the last piece of the puzzle necessary to gain a more comprehensive understanding of the effects of rapid-acting antidepressants on the brain.

Ketamine as an antidepressant: overview of its mechanisms of action and potential predictive biomarkers

Ketamine, a drug introduced in the 1960s as an anesthetic agent and still used for that purpose, has garnered marked interest over the past two decades as an emerging treatment for major depressive disorder. With increasing evidence of its efficacy in treatment-resistant depression and its potential anti-suicidal action, a great deal of investigation has been conducted on elucidating ketamine's effects on the brain. Of particular interest and therapeutic potential is the ability of ketamine to exert rapid antidepressant properties as early as several hours after administration. This is in stark contrast to the delayed effects observed with traditional antidepressants, often requiring several weeks of therapy for a clinical response. Furthermore, ketamine appears to have a unique mechanism of action involving glutamate modulation via actions at the N-methyl-D-aspartate (NMDA) and α -amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, as well as downstream activation of brain-derived neurotrophic factor (BDNF) and mechanistic target of rapamycin (mTOR) signaling pathways to potentiate synaptic plasticity. This paper provides a brief overview of ketamine with regard to pharmacology/pharmacokinetics, toxicology, the current state of clinical trials on depression, postulated antidepressant mechanisms and potential biomarkers (biochemical, inflammatory, metabolic, neuroimaging sleep-related and cognitive) for predicting response to and/or monitoring of therapeutic outcome with ketamine.

Circadian skin temperature rhythms, circadian activity rhythms and sleep in individuals with self-reported depressive symptoms

BACKGROUND

Disturbed circadian rhythms have been associated with depression. New body-worn devices allow the objective recording of circadian parameters such as physical activity, skin temperature and sleep. The objective of this study was to investigate whether circadian skin temperature and circadian activity rhythms are altered in depressed individuals.

METHODS

Data on skin temperature, physical activity and sleep were available for 1610 subjects from a population-based cohort study. In a matching process two groups were formed for analysis: 121 participants with pronounced depression symptoms (CES-D Score > 21) and n = 121 matched non-depressed controls (CES-D Score < 15). Circadian rhythms were investigated by analyzing non-parametric rhythm indicators of 24-h skin temperature and physical activity data. Sleep timing, continuity and quantity were calculated from actigraphy.

RESULTS

No differences between the groups were found when all participants were considered. After excluding antidepressant medicated participants, the depression group was found to have a lower skin temperature amplitude t(208) = 2.45, p = .015 and a less stable skin temperature rhythm t(208) = 2.40, p = .017. The amplitude predicted the group status (beta = -5.529, p = .016). No effects were found for activity or sleep.

CONCLUSION

The results indicate that skin-temperature rhythms are blunted in unmedicated depressed individuals. This could be a promising non-invasive marker for further analysis.

Sleep Quality, Depression, and Quality of Life After Bilateral Anodal Transcranial Direct Current Stimulation in Patients with Parkinson's Disease

Background

Sleep dysfunctions impose a large burden on quality of life for patients with Parkinson’s disease (PD). Several studies on PD reported potential therapeutic effects of transcranial direct current stimulation (tDCS) on motor and non-motor functions, but not related to sleep quality. Therefore, the present study examined sleep quality, depression perception, and quality of life changes after bilateral anodal tDCS in patients with PD.

Material/Methods

Twenty-one patients (n=21) with PD underwent 10 sessions (20 min each, 5 per week) of bilateral anodal tDCS stimulation applied simultaneously over the left and right prefrontal and motor areas. The Pittsburgh Sleep Quality Index (PSQI) total score and sub-scores, Geriatric Depression Scale (GDS), and Health-related quality of life questionnaire (SF-36) were measured pre/post bilateral tDCS anodal stimulation.

Results

PSQI total score (P=0.045), sleep latency sub-score (P=0.02), and GDS total score (P=0.016) significantly decreased, and physical and mental components scores of SF-36 (P=0.018 and P=0.001, respectively) significantly increased after bilateral anodal tDCS stimulation. The GDS score decrease was directly correlated with decrease in PSQI total score (P=0.01), sleep latency sub-score (P=0.002), and sleep disturbance sub-score (P=0.003). In addition, the GDS score decrease was inversely correlated with increasing mental component score of SF-36 (P=0.001), which was directly correlated with an increase in sleep efficiency sub-score (P=0.03) and the physical component score of SF-36 (P=0.0001).

Conclusions

Bilateral anodal tDCS stimulation showed potential therapeutic effects in patients with PD in terms of sleep quality and depression level improvement, which together improved mental and physical quality of life in patients with PD.

Are Type 2 Diabetes Mellitus and Depression Part of a Common Clock Genes Network?

In recent years, there has been an increased prevalence of type 2 diabetes mellitus (T2DM) and depression across the world. This growing public health problem has produced an increasing socioeconomic burden to the populations of all affected countries. Despite an awareness by public health officials and medical researchers of the costs associated with these diseases, there still remain many aspects of how they develop that are not understood. In this article, we propose that the circadian clock could be a factor that coordinates both the neurobehavioral and metabolic processes that underlie depression and T2DM. We propose further that this perspective, one which emphasizes the regulatory effects of clock gene activity, may provide insights into how T2DM and depression interact with one another, and may thus open a new pathway for managing and treating these disorders.

Are 24-hour motor activity patterns associated with continued rapid response to ketamine?

PURPOSE

This study examined the links between 24-hour activity patterns (specifically, amplitude and timing of wrist activity) and the persisting qualities of clinical antidepressant response to the glutamatergic modulator ketamine.

METHODS

Twenty-four-hour activity patterns were compared across 5 days of 24-hour activity rhythms in patients with major depressive disorder who displayed either a brief antidepressant response (24-48 hours), a continued antidepressant response (>72 hours), or no antidepressant response to ketamine. These postinfusion-response profiles were then used retrospectively to examine cohort-specific fitted parameters at baseline, postinfusion day 1 (D1), and postinfusion D3.

RESULTS

Relative to the nonresponders, the cohort experiencing a brief antidepressant response had blunted 24-hour amplitude that extended from baseline through D3 and postketamine phase advance of activity on D1 that reverted to baseline on D3. Relative to the nonresponders, the cohort experiencing a continued antidepressant response to ketamine had phase-advanced activity at both baseline and D1, as well as increased amplitude on D1 and D3.

CONCLUSION

Taken together, the results suggest that the time course of antidepressant response to ketamine is influenced by underlying biological differences in motor activity timekeeping. These differences may provide clues that link durable mood response with the molecular machinery of the circadian system, thus leading to more effective interventions. In addition, biomarkers of preinfusion motor activity (eg, amplitude, timing) may be useful for recommending future individualized treatment interventions, to the extent that they help identify patients who may relapse quickly after treatment.

Neural Plasticity Is Involved in Physiological Sleep, Depressive Sleep Disturbances, and Antidepressant Treatments

Depression, which is characterized by a pervasive and persistent low mood and anhedonia, greatly impacts patients, their families, and society. The associated and recurring sleep disturbances further reduce patient's quality of life. However, therapeutic sleep deprivation has been regarded as a rapid and robust antidepressant treatment for several decades, which suggests a complicated role of sleep in development of depression. Changes in neural plasticity are observed during physiological sleep, therapeutic sleep deprivation, and depression. This correlation might help us to understand better the mechanism underlying development of depression and the role of sleep. In this review, we first introduce the structure of sleep and the facilitated neural plasticity caused by physiological sleep. Then, we introduce sleep disturbances and changes in plasticity in patients with depression. Finally, the effects and mechanisms of antidepressants and therapeutic sleep deprivation on neural plasticity are discussed.

A Circadian Genomic Signature Common to Ketamine and Sleep Deprivation in the Anterior Cingulate Cortex

BACKGROUND

Conventional antidepressants usually require several weeks to achieve a full clinical response in patients with major depressive disorder, an illness associated with dysregulated circadian rhythms and a high incidence of suicidality. Two rapid-acting antidepressant strategies, low-dose ketamine (KT) and sleep deprivation (SD) therapies, dramatically reduce depressive symptoms within 24 hours in a subset of major depressive disorder patients. However, it is unknown whether they exert their actions through shared regulatory mechanisms. To address this question, we performed comparative transcriptomics analyses to identify candidate genes and relevant pathways common to KT and SD.

METHODS

We used the forced swim test, a standardized behavioral approach to measure antidepressant-like activity of KT and SD. We investigated gene expression changes using high-density microarrays and pathway analyses (Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, Gene Set Enrichment Analysis) in KT- and SD-treated mice compared with saline-treated control male mice.

RESULTS

We show that KT and SD elicit common transcriptional responses implicating distinct elements of the circadian clock and processes involved in neuronal plasticity. There is an overlap of 64 genes whose expression is common in KT and SD. Specifically, there is downregulation of clock genes including Ciart, Per2, Npas4, Dbp, and Rorb in both KT- and SD-treated mice.

CONCLUSIONS

We demonstrate a potential involvement of the circadian clock in rapid antidepressant responses. These findings could open new research avenues to help design chronopharmacological strategies to treat major depressive disorder.

Recovery sleep after extended wakefulness restores elevated A1 adenosine receptor availability in the human brain

Adenosine and functional A₁ adenosine receptor (A₁AR) availability are supposed to mediate sleep-wake regulation and cognitive performance. We hypothesized that cerebral A₁AR availability after an extended wake period decreases to a well-rested state after recovery sleep. [¹⁸F]CPFPX positron emission tomography was used to quantify A₁AR availability in 15 healthy male adults after 52 h of sleep deprivation and following 14 h of recovery sleep. Data were additionally compared with A₁AR values after 8 h of baseline sleep from an earlier dataset. Polysomnography, cognitive performance, and sleepiness were monitored. Recovery from sleep deprivation was associated with a decrease in A₁AR availability in several brain regions, ranging from 11% (insula) to 14% (striatum). A₁AR availabilities after recovery did not differ from baseline sleep in the control group. The degree of performance impairment, sleepiness, and homeostatic sleep-pressure response to sleep deprivation correlated negatively with the decrease in A₁AR availability. Sleep deprivation resulted in a higher A₁AR availability in the human brain. The increase that was observed after 52 h of wakefulness was restored to control levels during a 14-h recovery sleep episode. Individuals with a large increase in A₁AR availability were more resilient to sleep-loss effects than those with a subtle increase. This pattern implies that differences in endogenous adenosine and A₁AR availability might be causal for individual responses to sleep loss.

Ketamine-Induced Glutamatergic Mechanisms of Sleep and Wakefulness: Insights for Developing Novel Treatments for Disturbed Sleep and Mood

Ketamine, a drug with rapid antidepressant effects and well-described effects on slow wave sleep (SWS), is a useful intervention for investigating sleep-wake mechanisms involved in novel therapeutics. The drug rapidly (within minutes to hours) reduces depressive symptoms in individuals with major depressive disorder (MDD) or bipolar disorder (BD), including those with treatment-resistant depression. Ketamine treatment elevates extracellular glutamate in the prefrontal cortex. Glutamate, in turn, plays a critical role as a proximal element in a ketamine-initiated molecular cascade that increases synaptic strength and plasticity, which ultimately results in rapidly improved mood. In MDD, rapid antidepressant response to ketamine is related to decreased waking as well as increased total sleep, SWS, slow wave activity (SWA), and rapid eye movement (REM) sleep. Ketamine also increases brain-derived neurotrophic factor (BDNF) levels. In individuals with MDD, clinical response to ketamine is predicted by low baseline delta sleep ratio, a measure of deficient early night production of SWS. Notably, there are important differences between MDD and BD that may be related to the effects of diagnosis or of mood stabilizers. Consistent with its effects on clock-associated molecules, ketamine alters the timing and amplitude of circadian activity patterns in rapid responders versus non-responders with MDD, suggesting that it affects mood-dependent central neural circuits. Molecular interactions between sleep homeostasis and clock genes may mediate the rapid and durable elements of clinical response to ketamine and its active metabolite.

Circuits Regulating Pleasure and Happiness-Mechanisms of Depression

According to our model of the regulation of appetitive-searching vs. distress-avoiding behaviors, the motivation to display these essential conducts is regulated by two parallel cortico-striato-thalamo-cortical, re-entry circuits, including the core and the shell parts of the nucleus accumbens, respectively. An entire series of basal ganglia, running from the caudate nucleus on one side, to the centromedial amygdala on the other side, controls the intensity of these reward-seeking and misery-fleeing behaviors by stimulating the activity of the (pre)frontal and limbic cortices. Hyperactive motivation to display behavior that potentially results in reward induces feelings of hankering (relief leads to pleasure). Hyperactive motivation to exhibit behavior related to avoidance of misery results in dysphoria (relief leads to happiness). These two systems collaborate in a reciprocal fashion. In clinical depression, a mismatch exists between the activities of these two circuits: the balance is shifted to the misery-avoiding side. Five theories have been developed to explain the mechanism of depressive mood disorders, including the monoamine, biorhythm, neuro-endocrine, neuro-immune, and kindling/neuroplasticity theories. This paper describes these theories in relationship to the model (described above) of the regulation of reward-seeking vs. misery-avoiding behaviors. Chronic stress that leads to structural changes may induce the mismatch between the two systems. This mismatch leads to lack of pleasure, low energy, and indecisiveness, on one hand, and dysphoria, continuous worrying, and negative expectations on the other hand. The neuroplastic effects of monoamines, cortisol, and cytokines may mediate the induction of these structural alterations. Long-term exposure to stressful situations (particularly experienced during childhood) may lead to increased susceptibility for developing this condition. This hypothesis opens up the possibility of treating depression with psychotherapy. Genetic and other biological factors (toxic, infectious, or traumatic) may increase sensitivity to the induction of relevant neuroplastic changes. Reversal or compensation of these neuroplastic adjustments may explain the effects of biological therapies in treating depression.

Canadian Network for Mood and Anxiety Treatments (CANMAT) 2016 Clinical Guidelines for the Management of Adults with Major Depressive Disorder: Section 5. Complementary and Alternative Medicine Treatments

BACKGROUND

The Canadian Network for Mood and Anxiety Treatments (CANMAT) conducted a revision of the 2009 guidelines by updating the evidence and recommendations. The scope of the 2016 guidelines remains the management of major depressive disorder (MDD) in adults, with a target audience of psychiatrists and other mental health professionals.

METHODS

Using the question-answer format, we conducted a systematic literature search focusing on systematic reviews and meta-analyses. Evidence was graded using CANMAT-defined criteria for level of evidence. Recommendations for lines of treatment were based on the quality of evidence and clinical expert consensus. "Complementary and Alternative Medicine Treatments" is the fifth of six sections of the 2016 guidelines.

RESULTS

Evidence-informed responses were developed for 12 questions for 2 broad categories of complementary and alternative medicine (CAM) interventions: 1) physical and meditative treatments (light therapy, sleep deprivation, exercise, yoga, and acupuncture) and 2) natural health products (St. John's wort, omega-3 fatty acids; S-adenosyl-L-methionine [SAM-e], dehydroepiandrosterone, folate, Crocus sativus, and others). Recommendations were based on available data on efficacy, tolerability, and safety.

CONCLUSIONS

For MDD of mild to moderate severity, exercise, light therapy, St. John's wort, omega-3 fatty acids, SAM-e, and yoga are recommended as first- or second-line treatments. Adjunctive exercise and adjunctive St. John's wort are second-line recommendations for moderate to severe MDD. Other physical treatments and natural health products have less evidence but may be considered as third-line treatments. CAM treatments are generally well tolerated. Caveats include methodological limitations of studies and paucity of data on long-term outcomes and drug interactions.

BDNF in sleep, insomnia, and sleep deprivation

The protein brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family of growth factors involved in plasticity of neurons in several brain regions. There are numerous evidence that BDNF expression is decreased by experiencing psychological stress and that, accordingly, a lack of neurotrophic support causes major depression. Furthermore, disruption in sleep homeostatic processes results in higher stress vulnerability and is often associated with stress-related mental disorders. Recently, we reported, for the first time, a relationship between BDNF and insomnia and sleep deprivation (SD). Using a biphasic stress model as explanation approach, we discuss here the hypothesis that chronic stress might induce a deregulation of the hypothalamic-pituitary-adrenal system. In the long-term it leads to sleep disturbance and depression as well as decreased BDNF levels, whereas acute stress like SD can be used as therapeutic intervention in some insomniac or depressed patients as compensatory process to normalize BDNF levels. Indeed, partial SD (PSD) induced a fast increase in BDNF serum levels within hours after PSD which is similar to effects seen after ketamine infusion, another fast-acting antidepressant intervention, while traditional antidepressants are characterized by a major delay until treatment response as well as delayed BDNF level increase. Key messages Brain-derived neurotrophic factor (BDNF) plays a key role in the pathophysiology of stress-related mood disorders. The interplay of stress and sleep impacts on BDNF level. Partial sleep deprivation (PSD) shows a fast action on BDNF level increase.

Evidence for alterations of the glial syncytial function in major depressive disorder

BACKGROUND

Glial cells are essential in maintaining synaptic function. In glutamatergic synapses astrocytes remove the products of neural activity, (i.e. potassium, glutamate and excess water) from the synaptic cleft and redistribute them across the glial network; these products of neural activity can then be recycled for neuronal use or released into the vascular compartment. This type of highly coupled cell network -or syncytium-maintains the balance of synaptic activity by restoring the basal levels of such molecules in the synaptic cleft. Previous studies have reported alterations of glia related genes in Major Depressive Disorder, including some genes related to syncytial function.

METHODS

We used RNA isolated from hippocampal tissues of 13 MDD subjects and 10 healthy controls to broadly examine gene expression using microarrays. Hippocampal RNA samples were isolated by laser capture microdissection from human tissue sections carefully avoiding contamination from neighboring structures. Once RNA quality was validated RNA was labeled and hybridized to microarrays.

RESULTS

Analysis of microarray data identified mRNA transcripts involved in glial syncytial function that were downregulated in MDD subjects compared to controls, including potassium and water channels (KCNJ10, AQP4), gap junction proteins (GJA1) and glutamate transporters (SLC1A2, SLC1A3). These gene expression differences were confirmed by qPCR.

CONCLUSIONS

The downregulation of these genes related to the syncytial network activity of glial cells is consistent with the hypothesis that synaptic homeostasis is disrupted thereby disrupting hippocampal synaptic function in MDD patients. Such glial gene expression changes could contribute either to the onset or perpetuation of depressive symptoms and hence, represent targets for novel therapeutics.

Neuronal correlates of depression

Major depressive disorder (MDD) is a common psychiatric disorder effecting approximately 121 million people worldwide and recent reports from the World Health Organization (WHO) suggest that it will be the leading contributor to the global burden of diseases. At present, the most commonly used treatment strategies are still based on the monoamine hypothesis that has been the predominant theory in the last 60 years. Clinical observations show that only a subset of depressed patients exhibits full remission when treated with classical monoamine-based antidepressants together with the fact that patients exhibit multiple symptoms suggest that the pathophysiology leading to mood disorders may differ between patients. Accumulating evidence indicates that depression is a neural circuit disorder and that onset of depression may be located at different regions of the brain involving different transmitter systems and molecular mechanisms. This review synthesises findings from rodent studies from which emerges a role for different, yet interconnected, molecular systems and associated neural circuits to the aetiology of depression.

Synaptic plasticity model of therapeutic sleep deprivation in major depression

Therapeutic sleep deprivation (SD) is a rapid acting treatment for major depressive disorder (MDD). Within hours, SD leads to a dramatic decrease in depressive symptoms in 50-60% of patients with MDD. Scientifically, therapeutic SD presents a unique paradigm to study the neurobiology of MDD. Yet, up to now, the neurobiological basis of the antidepressant effect, which is most likely different from today's first-line treatments, is not sufficiently understood. This article puts the idea forward that sleep/wake-dependent shifts in synaptic plasticity, i.e., the neural basis of adaptive network function and behavior, represent a critical mechanism of therapeutic SD in MDD. Particularly, this article centers on two major hypotheses of MDD and sleep, the synaptic plasticity hypothesis of MDD and the synaptic homeostasis hypothesis of sleep-wake regulation, and on how they can be integrated into a novel synaptic plasticity model of therapeutic SD in MDD. As a major component, the model proposes that therapeutic SD, by homeostatically enhancing cortical synaptic strength, shifts the initially deficient inducibility of associative synaptic long-term potentiation (LTP) in patients with MDD in a more favorable window of associative plasticity. Research on the molecular effects of SD in animals and humans, including observations in the neurotrophic, adenosinergic, monoaminergic, and glutamatergic system, provides some support for the hypothesis of associative synaptic plasticity facilitation after therapeutic SD in MDD. The model proposes a novel framework for a mechanism of action of therapeutic SD that can be further tested in humans based on non-invasive indices and in animals based on direct studies of synaptic plasticity. Further determining the mechanisms of action of SD might contribute to the development of novel fast acting treatments for MDD, one of the major health problems worldwide.

The effects of n-acetylcysteine and/or deferoxamine on manic-like behavior and brain oxidative damage in mice submitted to the paradoxal sleep deprivation model of mania

Bipolar disorder (BD) is a severe psychiatric disorder associated with social and functional impairment. Some studies have strongly suggested the involvement of oxidative stress in the pathophysiology of BD. Paradoxal sleep deprivation (PSD) in mice has been considered a good animal model of mania because it induces similar manic-like behavior, as well as producing the neurochemical alterations which have been observed in bipolar patients. Thus, the objective of the present study was to evaluate the effects of the antioxidant agent's n-acetylcysteine (Nac) and/or deferoxamine (DFX) on behavior and the oxidative stress parameters in the brains of mice submitted to the animal model of mania induced by PSD. The mice were treated for a period of seven days with saline solution (SAL), Nac, DFX or Nac plus DFX. The animals were subject to the PSD protocol for 36 h. Locomotor activity was then evaluated using the open-field test, and the oxidative stress parameters were subsequently evaluated in the hippocampus and frontal cortex of mice. The results showed PSD induced hyperactivity in mice, which is considered a manic-like behavior. In addition to this, PSD increased lipid peroxidation and oxidative damage to proteins, as well as causing alterations to antioxidant enzymes in the frontal cortex and hippocampus of mice. The Nac plus DFX adjunctive treatment prevented both the manic-like behavior and oxidative damage induced by PSD. Improving our understanding relating to oxidative damage in biomolecules, and the antioxidant mechanisms presented in the animal models of mania are important in helping to improve our knowledge concerning the pathophysiology and development of new therapeutical treatments for BD.

Circadian dysregulation of clock genes: clues to rapid treatments in major depressive disorder

Conventional antidepressants require 2-8 weeks for a full clinical response. In contrast, two rapidly acting antidepressant interventions, low-dose ketamine and sleep deprivation (SD) therapy, act within hours to robustly decrease depressive symptoms in a subgroup of major depressive disorder (MDD) patients. Evidence that MDD may be a circadian-related illness is based, in part, on a large set of clinical data showing that diurnal rhythmicity (sleep, temperature, mood and hormone secretion) is altered during depressive episodes. In a microarray study, we observed widespread changes in cyclic gene expression in six regions of postmortem brain tissue of depressed patients matched with controls for time-of-death (TOD). We screened 12 000 transcripts and observed that the core clock genes, essential for controlling virtually all rhythms in the body, showed robust 24-h sinusoidal expression patterns in six brain regions in control subjects. In MDD patients matched for TOD with controls, the expression patterns of the clock genes in brain were significantly dysregulated. Some of the most robust changes were seen in anterior cingulate (ACC). These findings suggest that in addition to structural abnormalities, lesion studies, and the large body of functional brain imaging studies reporting increased activation in the ACC of depressed patients who respond to a wide range of therapies, there may be a circadian dysregulation in clock gene expression in a subgroup of MDDs. Here, we review human, animal and neuronal cell culture data suggesting that both low-dose ketamine and SD can modulate circadian rhythms. We hypothesize that the rapid antidepressant actions of ketamine and SD may act, in part, to reset abnormal clock genes in MDD to restore and stabilize circadian rhythmicity. Conversely, clinical relapse may reflect a desynchronization of the clock, indicative of a reactivation of abnormal clock gene function. Future work could involve identifying specific small molecules capable of resetting and stabilizing clock genes to evaluate if they can rapidly relieve symptoms and sustain improvement.

Faster, better, stronger: towards new antidepressant therapeutic strategies

Major depression is a highly prevalent disorder and is predicted to be the second leading cause of disease burden by 2020. Although many antidepressant drugs are currently available, they are far from optimal. Approximately 50% of patients do not respond to initial first line antidepressant treatment, while approximately one third fail to achieve remission following several pharmacological interventions. Furthermore, several weeks or months of treatment are often required before clinical improvement, if any, is reported. Moreover, most of the commonly used antidepressants have been primarily designed to increase synaptic availability of serotonin and/or noradrenaline and although they are of therapeutic benefit to many patients, it is clear that other therapeutic targets are required if we are going to improve the response and remission rates. It is clear that more effective, rapid-acting antidepressants with novel mechanisms of action are required. The purpose of this review is to outline the current strategies that are being taken in both preclinical and clinical settings for identifying superior antidepressant drugs. The realisation that ketamine has rapid antidepressant-like effects in treatment resistant patients has reenergised the field. Further, developing an understanding of the mechanisms underlying the rapid antidepressant effects in treatment-resistant patients by drugs such as ketamine may uncover novel therapeutic targets that can be exploited to meet the Olympian challenge of developing faster, better and stronger antidepressant drugs.

On 'polypharmacy' and multi-target agents, complementary strategies for improving the treatment of depression: a comparative appraisal

Major depression is a heterogeneous disorder, both in terms of symptoms, ranging from anhedonia to cognitive impairment, and in terms of pathogenesis, with many interacting genetic, epigenetic, developmental and environmental causes. Accordingly, it seems unlikely that depressive states could be fully controlled by a drug possessing one discrete mechanism of action and, in the wake of disappointing results with several classes of highly selective agent, multi-modal treatment concepts are attracting attention. As concerns pharmacotherapy, there are essentially two core strategies. First, multi-target antidepressants that act via two or more complementary mechanisms and, second, polypharmacy, which refers to co-administration of two distinct drugs, usually in separate pills. Both multi-target agents and polypharmacy ideally couple a therapeutically unexploited action to a clinically established mechanism in order to enhance efficacy, moderate side-effects, accelerate onset of action and treat a broader range of symptoms. The melatonin MT1/MT2 agonist and 5-HT(2C) antagonist, agomelatine, which is effective in the short- and long-term treatment of depression, exemplifies the former approach, while evidence-based polypharmacy is illustrated by the adjunctive use of second-generation antipsychotics with serotonin reuptake inhibitors for treatment of resistant depression. Histone acetylation and methylation, ghrelin signalling, inflammatory modulators, metabotropic glutamate-7 receptors and trace amine-associated-1 receptors comprise attractive substrates for new multi-target and polypharmaceutical strategies. The present article outlines the rationale underpinning multi-modal approaches for treating depression, and critically compares and contrasts the pros and cons of established and potentially novel multi-target vs. polypharmaceutical treatments. On balance, the former appear the most promising for the elaboration, development and clinical implementation of innovative concepts for the more effective management of depression.

Quantification of interactions among circadian clock proteins via surface plasmon resonance

Circadian clock is an internal time keeping system recurring 24 h daily rhythm in physiology and behavior of organisms. Circadian clock contains transcription and translation feedback loop involving CLOCK/NPAS2, BMAL1, Cry1/2, and Per1/2. In common, heterodimer of CLOCK/NPAS2 and BMAL1 binds to EBOX element in the promoter of Per and Cry genes in order to activate their transcription. CRY and PER making heterodimeric complexes enter the nucleus in order to inhibit their own BMAL1-CLOCK-activated transcription. The aim of this study was to investigate and quantify real-time binding affinities of clock proteins among each other on and off DNA modes using surface plasmon resonance. The pairwise interaction coefficients among clock proteins, as well as interaction of PER2, CRY2, and PER2 : CRY2 proteins with BMAL1 : CLOCK complex in the presence and absence of EBOX motif have been investigated via analysis of surface plasmon resonance data with pseudo first-order reaction kinetics approximation and via nonlinear regression curve fitting. The results indicated that CRY2 and PER2, BMAL1, and CLOCK proteins form complexes in vitro and that PER2, CRY2 and PER2 : CRY2 complex have similar affinities toward BMAL1 : CLOCK complex. CRY2 protein had the highest affinity toward EBOX complex, whereas PER2 and CRY2 : PER2 complexes displayed low affinity toward EBOX complex. The quantification of the interaction between clock proteins is critical to understand the operation mechanism of the biological clock and to address the behavioral and physiological disorders, and it will be useful for the design of new drugs toward clock-related diseases.

Bright light therapy for depression: a review of its effects on chronobiology and the autonomic nervous system

Bright light therapy (BLT) is considered among the first-line treatments for seasonal affective disorder (SAD), yet a growing body of literature supports its use in other neuropsychiatric conditions including non-seasonal depression. Despite evidence of its antidepressant efficacy, clinical use of BLT remains highly variable internationally. In this article, we explore the autonomic effects of BLT and suggest that such effects may play a role in its antidepressant and chronotherapeutic properties. After providing a brief introduction on the clinical application of BLT, we review the chronobiological effects of BLT on depression and on the autonomic nervous system in depressed and non-depressed individuals with an emphasis on non-seasonal depression. Such a theory of autonomic modulation via BLT could serve to integrate aspects of recent work centered on alleviating allostatic load, the polyvagal theory, the neurovisceral integration model and emerging evidence on the roles of glutamate and gamma-hydroxybutyric acid (GABA).

Endocannabinoid signaling in the etiology and treatment of major depressive illness

The purpose of this review is to examine human and preclinical data that are relevant to the following hypotheses. The first hypothesis is that deficient CB1R-mediated signaling results in symptoms that mimic those seen in depression. The second hypothesis is that activation of CB1R-mediated signaling results in behavioral, endocrine and other effects that are similar to those produced by currently used antidepressants. The third hypothesis is that conventional antidepressant therapies act through enhanced CB1R mediated signaling. Together the available data indicate that activators of CB1R signaling, particularly inhibitors of fatty acid amide hydrolase, should be considered for clinical trials for the treatment of depression.

Mechanism of action of dextromethorphan/quinidine:comparison with ketamine

Reports of rapid-onset but short-duration antidepressant effects in patients with treatment-resistant mood disorders after intravenous administration of ketamine have prompted efforts to find an agent with ketamine's properties that can be administered orally in repeated doses in order to sustain that action. One candidate for this dextromethorphan, and here the pharmacologic mechanism of action is compared and contrasted with that of ketamine.

Glutamate transporters: a key piece in the glutamate puzzle of major depressive disorder

Glutamatergic therapies are emerging as the new path for the treatment of Major Depression Disorder. Recent reports reviewing the use of glutamate activity modulators in the treatment of resistant depression advocate the importance of understanding the alterations of the diverse components of this complex system in mood disorders. In this postmortem study we used in situ hybridization and microarray analysis to evaluate the gene expression of the membrane transporters SLC1A2 and SLCA3 and the vesicular transporter SLCA17A7 in the hippocampus of Major Depressive Disorder (MDD) and Bipolar Disorder (BPD) subjects. Samples from 8 controls, 11 MDD and 6 BPD subjects were processed for in situ hybridization using cRNA probes for SLC1A2, SLC1A3 and SLC17A7. Laser capture microdissection was used to collect tissue from adjacent sections for microarray analysis. The results showed that the expression of the membrane transporters SLC1A2 and SLC1A3 was diminished in the MDD group compared to controls. The expression of the vesicular glutamate transporter SLC17A7 on the other hand was increased in MDD subjects. As for the BPD group, all three transporters showed trends similar to those observed in MDD, but the changes observed did not reach significance. We hypothesize that the decreased expression of the membrane glutamate transporters and the increased expression of the vesicular transporter in the hippocampus would affect the balance of the glutamatergic circuitry of the hippocampus, and that this effect may be a major contributor to depressive symptoms.

Ketamine, sleep, and depression: current status and new questions

Ketamine, an N-methyl-D-aspartate (NMDA) receptor antagonist, has well-described rapid antidepressant effects in clinical studies of individuals with treatment-resistant major depressive disorder (MDD). Preclinical studies investigating the effects of ketamine on brain-derived neurotrophic factor (BDNF) and on sleep slow wave activity (SWA) support its use as a prototype for investigating the neuroplastic mechanisms presumably involved in the mechanism of rapidly acting antidepressants. This review discusses human EEG slow wave sleep parameters and plasma BDNF as central and peripheral surrogate markers of plasticity, and their use in assessing ketamine's effects. Acutely, ketamine elevates BDNF levels, as well as early night SWA and high-amplitude slow waves; each of these measures correlates with change in mood in depressed patients who respond to ketamine. The slow wave effects are limited to the first night post-infusion, suggesting that their increase is part of an early cascade of events triggering improved mood. Increased total sleep and decreased waking occur during the first and second night post infusion, suggesting that these measures are associated with the enduring treatment response observed with ketamine.

Synaptic abnormalities in the infralimbic cortex of a model of congenital depression

Multiple lines of evidence suggest that disturbances in excitatory transmission contribute to depression. Whether these defects involve the number, size, or composition of glutamatergic contacts is unclear. This study used recently introduced procedures for fluorescence deconvolution tomography in a well-studied rat model of congenital depression to characterize excitatory synapses in layer I of infralimbic cortex, a region involved in mood disorders, and of primary somatosensory cortex. Three groups were studied: (1) rats bred for learned helplessness (cLH); (2) rats resistant to learned helplessness (cNLH); and (3) control Sprague Dawley rats. In fields within infralimbic cortex, cLH rats had the same numerical density of synapses, immunolabeled for either the postsynaptic density (PSD) marker PSD95 or the presynaptic protein synaptophysin, as controls. However, PSD95 immunolabeling intensities were substantially lower in cLH rats, as were numerical densities of synapse-sized clusters of the AMPA receptor subunit GluA1. Similar but less pronounced differences (comparable numerical densities but reduced immunolabeling intensity for PSD95) were found in the somatosensory cortex. In contrast, non-helpless rats had 25% more PSDs than either cLH or control rats without any increase in synaptophysin-labeled terminal frequency. Compared with controls, both cLH and cNLH rats had fewer GABAergic contacts. These results indicate that congenital tendencies that increase or decrease depression-like behavior differentially affect excitatory synapses.

Rapid antidepressant effects: moving right along

Available treatments for depression have significant limitations, including low response rates and substantial lag times for response. Reports of rapid antidepressant effects of a number of compounds, including the glutamate N-methyl-D-aspartate receptor antagonist ketamine, have spurred renewed translational neuroscience efforts aimed at elucidating the molecular and cellular mechanisms of action that result in rapid therapeutic response. This perspective provides an overview of recent advances utilizing compounds with rapid-acting antidepressant effects, discusses potential mechanism of action and provides a framework for future research directions aimed at developing safe, efficacious antidepressants that achieve satisfactory remission not only by working rapidly but also by providing a sustained response.

Mechanism of action of ketamine

Ketamine induces rapid-onset and short-duration improvement in depressive and suicidal symptoms in both treatment-resistant unipolar depression and bipolar depression, and also reduces chronic pain after short intravenous infusions. In order to develop long-acting oral agents with the same clinical effects, the pharmacologic mechanism of action must be understood, and the leading hypotheses are discussed here.

Mechanisms of rapid antidepressant effects of sleep deprivation therapy: clock genes and circadian rhythms

A significant subset of both major depressive disorder and bipolar disorder patients rapidly (within 24 hours) and robustly improves with the chronotherapeutic intervention of sleep deprivation therapy (SDT). Major mood disorder patients are reported to have abnormal circadian rhythms including temperature, hormonal secretion, mood, and particularly sleep. These rhythms are modulated by the clock gene machinery and its products. It is hypothesized that SDT resets abnormal clock gene machinery, that relapse of depressive symptoms during recovery night sleep reactivates abnormal clock gene machinery, and that supplemental chronotherapies and medications can block relapse and help stabilize circadian-related improvement. The central circadian clock genes, BMAL1/CLOCK (NPAS2), bind to Enhancer Boxes to initiate the transcription of circadian genes, including the period genes (per1, per2, per3). It is suggested that a defect in BMAL1/CLOCK (NPAS2) or in the Enhancer Box binding contributes to altered circadian function associated, in part, with the period genes. The fact that chronotherapies, including SDT and sleep phase advance, are dramatically effective suggests that altered clock gene machinery may represent a core pathophysiological defect in a subset of mood disorder patients.

Circadian patterns of gene expression in the human brain and disruption in major depressive disorder

A cardinal symptom of major depressive disorder (MDD) is the disruption of circadian patterns. However, to date, there is no direct evidence of circadian clock dysregulation in the brains of patients who have MDD. Circadian rhythmicity of gene expression has been observed in animals and peripheral human tissues, but its presence and variability in the human brain were difficult to characterize. Here, we applied time-of-death analysis to gene expression data from high-quality postmortem brains, examining 24-h cyclic patterns in six cortical and limbic regions of 55 subjects with no history of psychiatric or neurological illnesses ("controls") and 34 patients with MDD. Our dataset covered ~12,000 transcripts in the dorsolateral prefrontal cortex, anterior cingulate cortex, hippocampus, amygdala, nucleus accumbens, and cerebellum. Several hundred transcripts in each region showed 24-h cyclic patterns in controls, and >100 transcripts exhibited consistent rhythmicity and phase synchrony across regions. Among the top-ranked rhythmic genes were the canonical clock genes BMAL1(ARNTL), PER1-2-3, NR1D1(REV-ERBa), DBP, BHLHE40 (DEC1), and BHLHE41(DEC2). The phasing of known circadian genes was consistent with data derived from other diurnal mammals. Cyclic patterns were much weaker in the brains of patients with MDD due to shifted peak timing and potentially disrupted phase relationships between individual circadian genes. This transcriptome-wide analysis of the human brain demonstrates a rhythmic rise and fall of gene expression in regions outside of the suprachiasmatic nucleus in control subjects. The description of its breakdown in MDD suggests potentially important molecular targets for treatment of mood disorders.

Symmetrical serotonin release during asymmetrical slow-wave sleep: implications for the neurochemistry of sleep-waking states

On land, fur seals predominately display bilaterally synchronized electroencephalogram (EEG) activity during slow-wave sleep (SWS), similar to that observed in all terrestrial mammals. In water, however, fur seals exhibit asymmetric slow-wave sleep (ASWS), resembling the unihemispheric slow-wave sleep of odontocetes (toothed whales). The unique sleeping pattern of fur seals allows us to distinguish neuronal mechanisms mediating EEG changes from those mediating behavioral quiescence. In a prior study we found that cortical acetylcholine release is lateralized during ASWS in the northern fur seal, with greater release in the hemisphere displaying low-voltage (waking) EEG activity, linking acetylcholine release to hemispheric EEG activation (Lapierre et al. 2007). In contrast to acetylcholine, we now report that cortical serotonin release is not lateralized during ASWS. Our data demonstrate that bilaterally symmetric levels of serotonin are compatible with interhemispheric EEG asymmetry in the fur seal. We also find greatly elevated levels during eating and hosing the animals with water, suggesting that serotonin is more closely linked to bilateral variables, such as axial motor and autonomic control, than to the lateralized cortical activation manifested in asymmetrical sleep.

Manipulating the sleep-wake cycle and circadian rhythms to improve clinical management of major depression

BACKGROUND

Clinical psychiatry has always been limited by the lack of objective tests to substantiate diagnoses and a lack of specific treatments that target underlying pathophysiology. One area in which these twin failures has been most frustrating is major depression. Due to very considerable progress in the basic and clinical neurosciences of sleep-wake cycles and underlying circadian systems this situation is now rapidly changing.

DISCUSSION

The development of specific behavioral or pharmacological strategies that target these basic regulatory systems is driving renewed clinical interest. Here, we explore the extent to which objective tests of sleep-wake cycles and circadian function - namely, those that measure timing or synchrony of circadian-dependent physiology as well as daytime activity and nighttime sleep patterns - can be used to identify a sub-class of patients with major depression who have disturbed circadian profiles.

SUMMARY

Once this unique pathophysiology is characterized, a highly personalized treatment plan can be proposed and monitored. New treatments will now be designed and old treatments re-evaluated on the basis of their effects on objective measures of sleep-wake cycles, circadian rhythms and related metabolic systems.

Single treatments that have lasting effects: some thoughts on the antidepressant effects of ketamine and botulinum toxin and the anxiolytic effect of psilocybin

Recent clinical trials suggest that 3 single biological treatments have effects that persist. Based on research showing that the muscles involved in facial expressions can feed back to influence mood, a single trial diminishing glabella frown lines with botulinum toxin demonstrated a significant antidepressant effect for 16 weeks. Based primarily on research with animal models of depression suggesting that glutamate may be involved in depression, the N-methyl-D-aspartate antagonist ketamine has been tested in several trials. A single dose decreased depression for up to a week. The reported effects of the use of mushrooms containing psilocybin by a number of cultures around the world has stimulated several trials showing beneficial effects of a single dose of psilocybin for over a year in healthy people, and for up to 3 months in patients with anxiety disorders who have advanced cancer. This article discusses these studies, their rationale, their possible mechanisms of action, the future clinical research required to establish these therapies and the basic research required to optimize single treatments that have lasting effects.

Concomitant BDNF and sleep slow wave changes indicate ketamine-induced plasticity in major depressive disorder

The N-methyl-d-aspartate (NMDA) receptor antagonist ketamine has rapid antidepressant effects in treatment-resistant major depressive disorder (MDD). In rats, ketamine selectively increased electroencephalogram (EEG) slow wave activity (SWA) during non-rapid eye movement (REM) sleep and altered central brain-derived neurotrophic factor (BDNF) expression. Taken together, these findings suggest that higher SWA and BDNF levels may respectively represent electrophysiological and molecular correlates of mood improvement following ketamine treatment. This study investigated the acute effects of a single ketamine infusion on depressive symptoms, EEG SWA, individual slow wave parameters (surrogate markers of central synaptic plasticity) and plasma BDNF (a peripheral marker of plasticity) in 30 patients with treatment-resistant MDD. Montgomery-Åsberg Depression Rating Scale scores rapidly decreased following ketamine. Compared to baseline, BDNF levels and early sleep SWA (during the first non-REM episode) increased after ketamine. The occurrence of high amplitude waves increased during early sleep, accompanied by an increase in slow wave slope, consistent with increased synaptic strength. Changes in BDNF levels were proportional to changes in EEG parameters. Intriguingly, this link was present only in patients who responded to ketamine treatment, suggesting that enhanced synaptic plasticity - as reflected by increased SWA, individual slow wave parameters and plasma BDNF - is part of the physiological mechanism underlying the rapid antidepressant effects of NMDA antagonists. Further studies are required to confirm the link found here between behavioural and synaptic changes, as well as to test the reliability of these central and peripheral biomarkers of rapid antidepressant response.