Dopamine System Dysregulation in Major Depressive Disorders

The stressed synapse 2.0: pathophysiological mechanisms in stress-related neuropsychiatric disorders

Stress is a primary risk factor for several neuropsychiatric disorders. Evidence from preclinical models and clinical studies of depression have revealed an array of structural and functional maladaptive changes, whereby adverse environmental factors shape the brain. These changes, observed from the molecular and transcriptional levels through to large-scale brain networks, to the behaviours reveal a complex matrix of interrelated pathophysiological processes that differ between sexes, providing insight into the potential underpinnings of the sex bias of neuropsychiatric disorders. Although many preclinical studies use chronic stress protocols, long-term changes are also induced by acute exposure to traumatic stress, opening a path to identify determinants of resilient versus susceptible responses to both acute and chronic stress. Epigenetic regulation of gene expression has emerged as a key player underlying the persistent impact of stress on the brain. Indeed, histone modification, DNA methylation and microRNAs are closely involved in many aspects of the stress response and reveal the glutamate system as a key player. The success of ketamine has stimulated a whole line of research and development on drugs directly or indirectly targeting glutamate function. However, the challenge of translating the emerging understanding of stress pathophysiology into effective clinical treatments remains a major challenge.

In utero exposure to antipsychotic medication and psychiatric outcomes in the offspring

Information on neurodevelopmental effects of antenatal exposure to antipsychotics is limited to 10 studies, all examining children up to 5 years of age or less. The paper aimed to investigate the association between in utero exposure to antipsychotics and psychiatric outcomes in children using Danish nationwide registers. In total, 9011 liveborn singletons born 1998-2015 in Denmark whose mothers took antipsychotic medication before pregnancy were identified. Children whose mothers continued to take antipsychotics during pregnancy were compared with children of mothers who discontinued antipsychotics before pregnancy. As a negative control, paternal antipsychotic use in the same window was investigated. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox proportional hazards regression for the primary outcome of psychiatric disorders, as well for subcategories of psychiatric disorders. In total, 9.9% of children in the discontinuation group and 11.0% of children in the continuation group received a psychiatric disorder diagnosis during follow-up. The adjusted HR for psychiatric disorders among offspring in the continuation group compared to the discontinuation group was 1.10 (95% CI 0.93-1.30). For antipsychotic use in the fathers, the HR was 1.05 (95% CI 0.89-1.24). The study does not provide evidence of increased risk of psychiatric disorders among children of women who continue antipsychotic treatment during pregnancy. This was observed after accounting for the underlying risk conferred by maternal psychiatric disorders. This suggests women who need to continue antipsychotic medications during pregnancy can do so without adverse psychiatric outcomes for offspring.

Medicinal plants used in traditional Mayan medicine for the treatment of central nervous system disorders: An overview

ETHNOPHARMACOLOGICAL RELEVANCE

For thousands of years, different cultural groups have used and transformed natural resources for medicinal purposes focused on psychological or neurological conditions. Some of these are recognized as central nervous system (CNS) disorders and diseases, whereas other ethnopsychiatric interpretations are explained in culture-specific terms. In traditional Mayan medicine, several herbs have been part of treatments and rituals focused on cultural and ethnomedical concepts.

AIM OF REVIEW

This study aims to provide a comprehensive overview of the medicinal plants used in Mesoamerica by traditional healers and Mayan groups to CNS disorders and associate the traditional use with demonstrated pharmacological evidence to establish a solid foundation for directing future research.

METHODS

A systematic search for primary sources of plant use reports for traditional CNS-related remedies of Mesoamerica were obtained from library catalogs, thesis and scientific databases (PubMed, Scopus, Google Scholar; and Science Direct), and entered in a database with data analyzed in terms of the usage frequency, use by ethnic groups, plant endemism, and pharmacological investigation.

RESULTS

A total of 155 plants used for ethnopsychiatric conditions in Mesoamerica by Mayan groups were found, encompassing 127 native species. Of these, only 49 native species have reported in vitro or in vivo pharmacological analyses. The most commonly reported ethnopsychiatric conditions are related to anxiety, depression, memory loss, epilepsy, and insomnia. The extent of the scientific evidence available to understand the pharmacological application for their use against CNS disorders varied between different plant species, with the most prominent evidence shown by Annona cherimola, Justicia pectoralis, J. spicigera, Mimosa pudica, Persea americana, Petiveria alliacea, Piper amalago, Psidium guajava, Tagetes erecta and T. lucida.

CONCLUSION

Available pharmacological data suggest that different plant species used in traditional Mayan medicine may target the CNS, mainly related to GABA, serotonin, acetylcholine, or neuroprotective pathways. However, more research is required, given the limited data regarding mechanism of action at the preclinical in vivo level, identification of active compounds, scarce number of clinical studies, and the dearth of peer-reviewed studies.

Optogenetic stimulation of ventral tegmental area dopaminergic neurons in a female rodent model of depression: The effect of different stimulation patterns

Major depressive disorder is one of the most common mental disorders, and more than 300 million of people suffer from depression worldwide. Recent clinical trials indicate that deep brain stimulation of the superolateral medial forebrain bundle (mfb) can have rapid and long-term antidepressant effects in patients with treatment-resistant depression. However, the mechanisms of action are elusive. In this study, using female rats, we demonstrate the antidepressant effects of selective optogenetic stimulation of the ventral tegmental area's dopaminergic (DA) neurons passing through the mfb and compare different stimulation patterns. Chronic mild unpredictable stress (CMUS) induced depressive-like, but not anxiety-like phenotype. Short-term and long-term stimulation demonstrated antidepressant effect (OSST) and improved anxiolytic effect (EPM), while long-term stimulation during CMUS induction prevented depressive-like behavior (OSST and USV) and improved anxiolytic effect (EPM). The results highlight that long-term accumulative stimulation on DA pathways is required for antidepressant and anxiolytic effect.

Association of tobacco and marijuana use with symptoms of depression and anxiety among adolescents and young adults in Texas

INTRODUCTION

Young people with depression and/or anxiety may self-medicate with tobacco or tobacco with marijuana to reduce their symptoms. This study sought to differentiate between the use of tobacco products as intended and tobacco products modified to accommodate marijuana, and to explore their relationships with symptoms of depression and anxiety among youth and young adults.

METHODS

The study is a secondary analysis of Wave 9 (Spring 2019) data from the Texas Adolescent Tobacco and Marketing Surveillance (TATAMS) (n=2439, N=274030). Anxiety and major depressive symptoms were measured by GAD-7 and PHQ-9, respectively.

RESULTS

The odds of reporting current use of e-cigarettes without marijuana (adjusted prevalence odds ratio, APOR=2.34; 95% CI: 1.30-4.21, p=0.005) and current use of combustible tobacco without marijuana (APOR=2.99; 95% CI: 1.26-7.09, p=0.014) were significantly higher among those who reported depression/anxiety comorbidity compared to those who reported no symptoms of major depressive symptoms (MDS), anxiety or comorbidity. The odds of reporting ever use of e-cigarettes with marijuana (APOR=3.68; 95% CI: 1.69- 8.00, p=0.001), current use of e-cigarettes with marijuana (APOR=2.76; 95% CI: 1.28-5.97, p=0.01) and ever use of combustible tobacco with marijuana (APOR=3.99; 95% CI: 1.66-9.58, p=0.002) were significantly higher among those reporting only MDS compared to those who reported no symptoms of MDS, anxiety or comorbidity.

CONCLUSIONS

The study findings can have implications for intervention planning, as interventions need to address marijuana and nicotine use in tobacco products and address anxiety and depression.

Mood Disorders Induced by Maternal Overnutrition: The Role of the Gut-Brain Axis on the Development of Depression and Anxiety

Since the first evidence suggesting that maternal nutrition can impact the development of diseases in the offspring, much has been elucidated about its effects on the offspring’s nervous system. Animal studies demonstrated that maternal obesity can predispose the offspring to greater chances of metabolic and neurodevelopmental diseases. However, the mechanisms underlying these responses are not well established. In recent years, the role of the gut-brain axis in the development of anxiety and depression in people with obesity has emerged. Studies investigating changes in the maternal microbiota during pregnancy and also in the offspring demonstrate that conditions such as maternal obesity can modulate the microbiota, leading to long-term outcomes in the offspring. Considering that maternal obesity has also been linked to the development of psychiatric conditions (anxiety and depression), the gut-brain axis is a promising target to be further explored in these neuropsychiatric contexts. In the present study, we review the relationship between maternal obesity and anxious and depressive features, exploring the gut-brain axis as a potential mechanism underlying this relationship.

Reactive and Regulative Temperament in Relation to Clinical Symptomatology and Personality Disorders in Patients with a Substance Use Disorder

Temperament and personality traits are important factors underlying the vulnerability for both the initiation and continuation of addictive behaviors. We investigated the influence of reactive and regulative temperament and their interaction in relation to clinical symptomatology and personality disorders (PDs) in a sample of 841 inpatients (68.1% males) with a substance use disorder (SUD). To assess reactive temperament we used the Behavioral Inhibition and Behavioral Activation Scales (BISBAS) and to assess regulative temperament we used the Effortful Control Scale. Clinical symptomatology and personality traits were measured by means of the Symptom Checklist-90 (SCL-90) and the Assessment of ADP-IV Personality Disorders (ADP-IV). Hierarchical regression analyses showed that both, clinical symptomatology and PDs were related to low levels of effortful control (EC). None of the two-way interactions (BIS × EC, BAS × EC) however were significantly related to psychopathology. Current findings highlight the role of effortful control (EC) in the expression of psychopathology in an adult sample of inpatients with SUD. Therapeutic interventions aiming at strengthening EC can possibly result in better treatment outcomes for both the addiction and the comorbid psychopathology.

Zoom fatigue and its risk factors in online learning during the COVID-19 pandemic

BACKGROUND Global nations have enforced strict health protocols because of the COVID-19’s high transmission, infectivity, and mortality. As shown by increased online learning and video conferencing, the employment and education sectors are shifting to home-based activities. Video conferencing as a communication medium has subtly led to zoom fatigue. This study aimed to analyze the risk factors of zoom fatigue for early prevention and treatment. METHODS This cross-sectional study was conducted on 335 Indonesian university students selected by purposive sampling in July 2021. Data were collected using a demographic questionnaire including online courses duration during the COVID-19 pandemic; Pittsburgh sleep quality index; depression, anxiety and stress scale-21; and zoom & exhaustion fatigue (ZEF) scale through Google Form (Google LLC, USA) distributed via social media and student forums. Association and correlation tests were used, and the model was developed using linear regression. RESULTS The respondents were aged 21.3 (1.8) years with 12.8 (5.1) months of online courses during the COVID-19 pandemic and a ZEF scale of 2.8 (0.9). Students with higher ZEF had irregular physical exercise, poorer sleep quality, longer video conferencing sessions, longer months of courses during the COVID-19 pandemic, and higher mental illness (i.e., stress, anxiety, and depression). Smoking negatively correlated with fatigue (r = −0.12). The model for ZEF showed good predictability for zoom fatigue (p<0.001, R2 = 0.57). CONCLUSIONS Daily exposure to video conferencing in educational settings throughout the pandemic has drastically increased zoom fatigue. The stakeholders must act immediately to minimize the risks while providing maximum benefits.

Androgens and Their Role in Regulating Sex Differences in the Hypothalamic/Pituitary/Adrenal Axis Stress Response and Stress-Related Behaviors

Androgens play a pivotal role during development. These gonadal hormones and their receptors exert organizational actions that shape brain morphology in regions controlling the stress regulatory systems in a male-specific manner. Specifically, androgens drive sex differences in the hypothalamic/pituitary/adrenal (HPA) axis and corresponding hypothalamic neuropeptides. While studies have examined the role of estradiol and its receptors in sex differences in the HPA axis and associated behaviors, the role of androgens remains far less studied. Androgens are generally thought to modulate the HPA axis through the activation of androgen receptors (ARs). They can also impact the HPA axis through reduction to estrogenic metabolites that can bind estrogen receptors in the brain and periphery. Such regulation of the HPA axis stress response by androgens can often result in sex-biased risk factors for stress-related disorders, such as anxiety and depression. This review focuses on the biosynthesis pathways and molecular actions of androgens and their nuclear receptors. The impact of androgens on hypothalamic neuropeptide systems (corticotropin-releasing hormone, arginine vasopressin, oxytocin, dopamine, and serotonin) that control the stress response and stress-related disorders is discussed. Finally, this review discusses potential therapeutics involving androgens (androgen replacement therapies, selective AR modulator therapies) and ongoing clinical trials.

Drug Use in Night Owls May Increase the Risk for Mental Health Problems

Drugs of abuse are widely known to worsen mental health problems, but this relationship may not be a simple causational one. Whether or not a person is susceptible to the negative effects of drugs of abuse may not only be determined by their addictive properties, but also the users’ chronotype, which determines their daily activity patterns. The present study investigates the relationship between chronotype, drug use and mental health problems in a cross-sectional community sample. Participants (n = 209) completed a selection of questionnaires online, including the Munich Chronotype Questionnaire, the Depression Anxiety Stress Scale, the Alcohol Use Disorder Identification Test, the Cannabis Use Disorder Identification Test and the Fagerström Test for Nicotine Dependence. We conducted multiple regression models to determine relationships between participants’ chronotype and their reported mental health symptoms and then estimated mediation models to investigate the extent to which their drug consumption accounted for the identified associations. Chronotype was significantly associated with participants’ overall mental health (β = 0.16, p = 0.022) and their anxiety levels (β = 0.18, p = 0.009) but not with levels of depression or stress. However, both relationships were fully mediated by participants’ overall drug consumption. Thus, late chronotypes, so-called “night owls”, not only use more drugs but consequently have an increased risk for developing anxiety and deteriorating mental health status. This group may be particularly vulnerable to the negative psychological effects of drugs. Our results point toward the importance of considering chronotype in designing preventative and therapeutic innovations, specifically for anxiety, which at present has been largely neglected.

Precision Medicine in Alzheimer's Disease: Investigating Comorbid Common Biological Substrates in the Rat Model of Amyloid Beta-Induced Toxicity

Alzheimer's disease (AD), one of the most widespread neurodegenerative disorder, is a fatal global burden for the elder population. Although many efforts have been made, the search of a curative therapy is still ongoing. Individuating phenotypic traits that might help in investigating treatment response is of growing interest in AD research. AD is a complex pathology characterized by many comorbidities, such as depression and increased susceptibility to pain perception, leading to postulate that these conditions may rely on common biological substrates yet to be determined. In order to investigate those biological determinants to be associable with phenotypic traits, we used the rat model of amyloid beta-induced toxicity. This established model of early phase of AD is obtained by the intracerebroventricular injection of soluble amyloid beta1-42 (Aβ) peptide 7 days before performing experiments. In this model, we have previously reported increased immobility in the forced swimming test, reduced cortical serotonin levels and subtle alterations in the cognitive domain a depressive-like phenotype associated with subtle alteration in memory processes. In light of evaluating pain perception in this animal model, we performed two different behavioral tests commonly used, such as the paw pressure test and the cold plate test, to analyze mechanical hyperalgesia and thermal allodynia, respectively. Behavioural outcomes confirmed the memory impairment in the social recognition test and, compared to sham, Aβ-injected rats showed an increased selective susceptibility to mechanical but not to thermal stimulus. Behavioural data were then corroborated by neurochemical and biochemical biomarker analyses either at central or peripheral level. Data showed that the peptide injection evoked a significant increase in hypothalamic glutamate, kynurenine and dopamine content, while serotonin levels were reduced. Plasma Cystatin-C, a cysteine protease, was increased while serotonin and melatonin levels were decreased in Aβ-injected rats. Urinary levels paralleled plasma quantifications, indicating that Aβ-induced deficits in pain perception, mood and cognitive domain may also depend on these biomarkers. In conclusion, in the present study, we demonstrated that this animal model can mimic several comorbid conditions typical of the early phase of AD. Therefore, in the perspective of generating novel therapeutic strategies relevant to precision medicine in AD, this animal model and the biomarkers evaluated herein may represent an advantageous approach.

Carbon dots-decorated hydroxyapatite nanowires–lanthanide metal–organic framework composites as fluorescent sensors for the detection of dopamine

A ratiometric composite fluorescent probe (HAPNWs-CDs-Tb/MOF) with hydroxyapatite carrier and the fluorescence ratio of carbon dots and lanthanide metal organic framework as the response signal was prepared for the detection of dopamine.

Pedunculo-pontine tegmentum cholinergic REM-ON neurons modulate ventral tegmental neurons to modulate rapid eye movement sleep in rats

The interaction among the acetylcholine (ACh)-ergic REM-ON neurons in the pedunculo-pontine area (PPT), noradrenergic REM-OFF neurons in locus coeruleus (LC) and GABA-ergic neurons in the regulation of rapid eye movement sleep (REMS) have been studied in relative details; however, many questions including the role of dopamine (DA) remain unanswered. The ventral tegmental area (VTA) is rich in DA-ergic neurons, which have been implicated with schizophrenia and depression, when REMS is significantly affected. Also, some of the symptoms of REMS and these diseases are common. As the ACh-ergic REM-ON neurons in the PPT project to VTA, we proposed that such inputs might affect REMS, dreams and hallucinations. We recorded sleep-wake-REMS in freely moving, chronically prepared rats under three controlled experimental conditions. In different sets of experiments, either the ACh-ergic inputs to the VTA were blocked by local microinjection of Scopolamine (Scop) alone, or, the PPT neurons were bilaterally stimulated by Glutamate (Glut), or, the PPT neurons were stimulated by Glut in presence of Scop into the VTA. It was observed that Glut into PPT and Scop into the VTA significantly increased and decreased REMS, respectively. Additionally, PPT stimulation induced increased REMS was prevented in the presence of Scop into the VTA. Based on these findings we propose that inputs from ACh-ergic REM-ON neurons to VTA increase REMS and it could be a possible circuitry for expressions of hallucinations and dreams.

Different depression: motivational anhedonia governs antidepressant efficacy in Huntington's disease

Depression is more common in neurodegenerative diseases such as Huntington's disease than the general population. Antidepressant efficacy is well-established for depression within the general population: a recent meta-analysis showed serotonin norepinephrine reuptake inhibitors, tricyclic antidepressants and mirtazapine outperformed other antidepressants. Despite the severe morbidity, antidepressant choice in Huntington's disease is based on Class IV evidence. We used complementary approaches to determine treatment choice for depression in Huntington's disease: propensity score analyses of antidepressant treatment outcome using the ENROLL-HD data set, and a dissection of the cognitive mechanisms underlying depression in Huntington's disease using a cognitive battery based on the Research Domain Criteria for Depression. Study 1 included ENROLL-HD 5486 gene-positive adult patients started on an antidepressant medication for depression. Our outcome measures were depression (Hospital Anxiety and Depression Scale or Problem Behaviours Assessment 'Depressed Mood' item) at first follow-up (primary outcome) and all follow-ups (secondary outcome). The intervention was antidepressant class. We used Svyglm&Twang in R to perform propensity scoring, using known variables (disease progression, medical comorbidity, psychiatric morbidity, sedatives, number of antidepressants, demographics and antidepressant contraindications) to determine the probability of receiving different antidepressants (propensity score) and then included the propensity score in a model of treatment efficacy. Study 2 recruited 51 gene-positive adult patients and 26 controls from the South Wales Huntington's Disease Management Service. Participants completed a motor assessment, in addition to measures of depression and apathy, followed by tasks measuring consummatory anhedonia, motivational anhedonia, learning from reward and punishment and reaction to negative outcome. We used generalised linear models to determine the association between task performance and depression scores. Study 1 showed selective serotonin reuptake inhibitors outperformed serotonin norepinephrine reuptake inhibitors on the primary outcome (P = 0.048), whilst both selective serotonin reuptake inhibitors (P = 0.00069) and bupropion (P = 0.0045) were superior to serotonin norepinephrine reuptake inhibitors on the secondary outcome. Study 2 demonstrated an association between depression score and effort for reward that was not explained by apathy. No other mechanisms were associated with depression score. We found that selective serotonin reuptake inhibitors and bupropion outperform serotonin norepinephrine reuptake inhibitors at alleviating depression in Huntington's disease. Moreover, motivational anhedonia appears the most significant mechanism underlying depression in Huntington's disease. Bupropion is improves motivational anhedonia and has a synergistic effect with selective serotonin reuptake inhibitors. This work provides the first large-scale, objective evidence to determine treatment choice for depression in Huntington's disease, and provides a model for determining antidepressant efficacy in other neurodegenerative diseases.

Neurotransmitter and Intestinal Interactions: Focus on the Microbiota-Gut-Brain Axis in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder of unknown etiology. IBS is caused by a disruption in the gut-brain axis. Given the importance of the gut microbiota in maintaining local and systemic homeostasis of immunity, endocrine, and other physiological processes, the microbiota-gut-brain axis has been proposed as a key regulator in IBS. Neurotransmitters have been shown to affect blood flow regulation, intestinal motility, nutrient absorption, the gastrointestinal immune system, and the microbiota in recent studies. It has the potential role to play a function in the pathophysiology of the gastrointestinal and neurological systems. Transmitters and their receptors, including 5-hydroxytryptamine, dopamine, γ-aminobutyric acid, and histamine, play an important role in IBS, especially in visceral sensitivity and gastrointestinal motility. Studies in this field have shed light on revealing the mechanism by which neurotransmitters act in the pathogenesis of IBS and discovering new therapeutic strategies based on traditional pharmacological approaches that target the nervous system or novel therapies that target the microbiota.

Postpartum scarcity-adversity disrupts maternal behavior and induces a hypodopaminergic state in the rat dam and adult female offspring

Postpartum adversity is among the strongest predictors for the emergence of postpartum depression (PPD) in humans and a translational risk factor employed in rodent models. Parental care is disturbed under conditions of environmental adversity, including low resource environments, and in PPD. Nonetheless, the neural changes associated with these adversity-induced maladaptive behavioral states remain poorly understood. Postpartum scarcity-adversity can be modeled in rats by providing the dam with limited bedding and nesting (LBN) materials, which mimics the effects of a stressful low resource environment in potentiating maltreatment/neglect in humans. Indeed, LBN exposure from postpartum days (PD) 2-9 increased adverse maternal behaviors, impaired pup retrieval, and increased passive stress coping responses. Since mesolimbic dopamine (DA) activity is an important mechanism for motivated maternal behavior and is implicated in PPD, we assessed the impact of postpartum scarcity-adversity on in vivo electrophysiological properties of ventral tegmental area (VTA) DA neurons at two timepoints. We found reduced numbers of active VTA DA neurons in LBN dams at PD 9-10 but not PD-21, suggesting a transient impact on VTA population activity in LBN dams. Finally, we assessed the impact of early life scarcity-adversity on VTA DA function by conducting VTA recordings in adult female offspring and found a long-lasting attenuation in DA activity. These findings highlight a link between adversity-induced deficits in DA function and disrupted maternal behavior, suggesting the VTA/mesolimbic DA system as a potential mechanism by which postpartum scarcity-adversity drives aberrant maternal behavior, and early postnatal programming of adult VTA function in the offspring.

Metabolomics Analysis of the Prefrontal Cortex in a Rat Chronic Unpredictable Mild Stress Model of Depression

BACKGROUND

Depressive disorder is the leading cause of disability and suicidality worldwide. Metabolites are considered indicators and regulators of depression. However, the pathophysiology of the prefrontal cortex (PFC) in depression remains unclear.

METHODS

A chronic unpredictable mild stress (CUMS) model and a maturation rodent model of depression was used to investigate metabolic changes in the PFC. Eighteen male Sprague-Dawley rats were randomly divided into CUMS and control groups. The sucrose preference test (SPT) and forced swimming test (FST) were employed to evaluate and record depression-associated behaviors and changes in body weight (BW). High-performance liquid chromatography-tandem mass spectrometry was applied to test metabolites in rat PFC. Furthermore, principal component analysis and orthogonal partial least-squares discriminant analysis were employed to identify differentially abundant metabolites. Metabolic pathways were analyzed using MetaboAnalyst. Finally, a metabolite-protein interaction network was established to illustrate the function of differential metabolites.

RESULTS

SPT and FST results confirmed successful establishment of the CUMS-induced depression-like behavior model in rats. Five metabolites, including 1-methylnicotinamide, 3-methylhistidine, acetylcholine, glycerophospho-N-palmitoyl ethanolamine, α-D-mannose 1-phosphate, were identified as potential biomarkers of depression. Four pathways changed in the CUMS group. Metabolite-protein interaction analysis revealed that 10 pathways play roles in the metabolism of depression.

CONCLUSION

Five potential biomarkers were identified in the PFC and metabolite-protein interactions associated with metabolic pathophysiological processes were explored using the CUMS model. The results of this study will assist physicians and scientists in discovering potential diagnostic markers and novel therapeutic targets for depression.

Histamine and histamine receptors: Roles in major depressive disorder

Although the incidence of major depressive disorder (MDD) is high and its social impact is great, we still know very little about the pathophysiology of depression. The monoamine hypothesis of depression suggests that 5-HT, NE, and DA synergistically affect mood, which is the basis of current drug therapy for depression. However, histamine as a monoamine transmitter is rarely studied. Our review is the first time to illustrate the effect of histaminergic system on depression in order to find the way for the development of new antidepressant drugs. The brain neurotransmitter histamine is involved in MDD, and the brain histaminergic system operates through four receptors. Histamine and its receptors can also regulate the immune response to improve symptoms of depression. In addition, H3R can interact with other depression-related transmitters (including 5-HT, DA, GLU, and MCH); thus, histamine may participate in the occurrence of depression through other neural circuits. Notably, in rodent studies, several H3R and H1R antagonists were found to be safe and effective in alleviating depression-like behavior. To highlight the complex functions of histamine in depression, and reveals that histamine receptors can be used as new targets for antidepressant therapy.

Efficacy of a novel proprietary dietary supplement (TRI 360TM) on psychological symptoms and stress-related quality of life in adult subjects: A randomized controlled clinical trial

Nowadays, diet plays an increasingly important role in normal physiology and mental health. Recently, many studies have shown that more use of dietary supplements in mental and psychological disorders. Study objective was to investigate safety and efficacy of proprietary nutraceutical combination (TRI 360^TM) on psychological symptoms in adult human subjects with one or more psychological symptoms in open-label, single-center, parallel-group, randomized controlled trial. Eighty-four participants aged 20-45 years with psychological symptoms were completed this trial. Participants were randomly assigned to placebo and treatment groups. Treatment group received TRI 360^TM capsules twice a day. TRI 360^TM was well-tolerated and didn't show treatment-related adverse-events upto 180 days. All assessed perception scorings on psychological symptoms like fatigue, mental stress, sleep disturbance, anxiety, depression, emotional trauma, mood changes, self-confidence, willpower, and motivation were very significantly (p ≤ 0.0001) improved in TRI 360^TM participants than placebo control group. Furthermore, significantly (p ≤ 0.001) increased levels of functional biomarkers: vitamin C and D₃ metabolites, neurotransmitters, hormones, antiaging protein (klotho) level; and decreased proinflammatory cytokines and oxidative stress marker, malondialdehyde in TRI 360^TM group than placebo. According to these findings, the use of TRI 360^TM supplementation as a potentially safe therapeutic option for reducing psychological symptoms in healthy adults.

Sedentary behaviors and risk of depression in the Seguimiento Universidad de Navarra cohort: the SUN Project

The study aimed to prospectively examine the association between different sedentary behaviors and the risk of depression. We included 12,691 Spanish university graduates (mean age: 36.7 year; SD: 11.5), participants of the Seguimiento Universidad de Navarra cohort (the SUN Project), initially free of depression who were followed-up for a median of 10.9 years. Based on items presented in our baseline questionnaire, time spent in four sedentary behaviors (hours/day) were evaluated: overall sitting time; TV-viewing; computer use; and driving. Participants were classified as incident cases of depression if they reported a physician diagnosis of depression in at least one of the follow-up assessments conducted after the first two years of follow-up. Cox regression models were used to assess the relationship between sedentary behaviors and depression. A total of 560 incident cases of depression were identified during follow-up. We found no significant association between overall sitting time, TV-viewing or driving and risk of depression. On the other hand, computer use was directly associated with the risk of developing depression during the follow-up (p-value for trend = 0.020), with the participants in the highest quartile of computer use (3.64 to 10 hours/week) having a higher risk of developing depression (HR = 1.33; 95%CI: 1.05-1.70) than those in the lowest quartile (0 to 0.25 hours/week) after adjusting for potential confounders. Prolonged use of computer was independently associated with an increased risk of developing depression among young middle-aged adult university graduates from a Spanish cohort.

The Organization of Somatostatin-Immunoreactive Cells in the Visual Cortex of the Gerbil

Somatostatin (SST) is widely expressed in the brain and plays various, vital roles involved in neuromodulation. The purpose of this study is to characterize the organization of SST neurons in the Mongolian gerbil visual cortex (VC) using immunocytochemistry, quantitative analysis, and confocal microscopy. As a diurnal animal, the Mongolian gerbil provides us with a different perspective to other commonly used nocturnal rodent models. In this study, SST neurons were located in all layers of the VC except in layer I; they were most common in layer V. Most SST neurons were multipolar round/oval or stellate cells. No pyramidal neurons were found. Moreover, 2-color immunofluorescence revealed that only 33.50%, 24.05%, 16.73%, 0%, and 64.57% of SST neurons contained gamma-aminobutyric acid, calbindin-D28K, calretinin, parvalbumin, and calcium/calmodulin-dependent protein kinase II, respectively. In contrast, neuropeptide Y and nitric oxide synthase were abundantly expressed, with 80.07% and 75.41% in SST neurons, respectively. Our immunocytochemical analyses of SST with D₁ and D₂ dopamine receptors and choline acetyltransferase, α₇ and β₂ nicotinic acetylcholine receptors suggest that dopaminergic and cholinergic fibers contact some SST neurons. The results showed some distinguishable features of SST neurons and provided some insight into their afferent circuitry in the gerbil VC. These findings may support future studies investigating the role of SST neurons in visual processing.

Ghrelin mediated regulation of neurosynaptic transmitters in depressive disorders

Ghrelin is a peptide released by the endocrine cells of the stomach and the neurons in the arcuate nucleus of the hypothalamus. It modulates both peripheral and central functions. Although ghrelin has emerged as a potent stimulator of growth hormone release and as an orexigenic neuropeptide, the wealth of literature suggests its involvement in the pathophysiology of affective disorders including depression. Ghrelin exhibits a dual role through the advancement and reduction of depressive behavior with nervousness in the experimental animals. It modulates depression-related signals by forming neuronal networks with various neuropeptides and classical neurotransmitter systems. The present review emphasizes the integration and signaling of ghrelin with other neuromodulatory systems concerning depressive disorders. The role of ghrelin in the regulation of neurosynaptic transmission and depressive illnesses implies that the ghrelin system modulation can yield promising antidepressive therapies.

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Ghrelin is the orexigenic type of neuropeptide.

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It binds with the growth hormone secretagogue receptor (GHSR).

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GHSR is ubiquitously present in the various brain regions.

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Ghrelin is involved in the regulation of depression-related behavior.

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The review focuses on the neurotransmission and signaling of ghrelin in neuropsychiatric and depressive disorders.

Relationship among the quality of cognitive abilities, depression symptoms, and various aspects of handgrip strength in the elderly

Background/Aim. Both the cognitive and physical functioning changes occur within the normal aging, suggesting possible common biological processes. The aging process is often characterized by a reduction of adaptive responses, an increasing vulnerability and functional limitations. The aim of this study was to determine if there were correlations between particular cognitive abilities (verbal ability, spatial ability, processing speed, memory, verbal fluency, divergent thinking, memory, attention, executive functions, conceptualization, orientation, computation), depression symptoms and different dynamometric parameters of muscle contraction, during handgrip (HG) of both hands, in the elderly population. Methods. The sample consisted of 98 participants, 16 males and 82 females, aged from 65 to 85. Neuropsychological assessment included Montreal Cognitive Assessment (MoCA), Frontal Function Test (Go/No-Go), Categorical and Phonemic fluency tests and Geriatric Depression Scale Short Form (GDS-SF). Physical measures were assessed by Handgrip Dynamometry Tests (HG), and included: the maximum force (Fmax), maximal rate of force development (RFDmax), static endurance HG time realized at 50% of maximal HG force (tFmax50%) of dominant (Do) and non-dominant (NDo) hand. Results. Higher MoCA score was followed by higher values of muscle endurance of dominant hands. Higher values of F max of dominant hand were associated with higher values of Alternating Trail Making that is by visuoconstructive abilities (MoCA). The variable Categorical fluency was in a small, positive correlation with Fmax. No correlation of depressive symptoms with HG parameters was found except in the subgroup of female subjects. Conclusion. Better cognitive performance was associated with better HG muscle strength. Therefore, HG strength can be a useful tool in geriatric practice in monitoring not only physical, but also cognitive function status and de-cline. The link between lower cognitive functioning and lower values of HG variables, emphasize the need for in-creased awareness about it in clinical practice.

Exposure to environmental chemicals and perinatal psychopathology

Women are nearly twice as likely to develop mood disorders compared with men, and incidence is greatest during reproductive transitions, including pregnancy and postpartum. Because these periods are characterized by dramatic hormonal and physiologic changes, there is heightened susceptibility to external factors, such as exposure to environmental toxicants, which may play a role in maternal psychopathology. The purpose of this scoping review was to provide an overview of studies conducted in humans and animal models on the effects of nonoccupational exposure to environmental chemicals on maternal psychopathology during the perinatal period. The largest number of studies examined exposure to environmental tobacco smoke and antenatal depression and showed consistently positive findings, although more prospective studies using biomarkers for exposure assessment are needed. The few studies examining persistent organic pollutants such as polybrominated diphenyl ethers and perinatal depression were consistent in showing associations with increased depressive symptoms. Results were mixed for exposure to heavy metals and non-persistent chemicals, but a strong literature in animal models supported an association between bisphenols and phthalates and reduced maternal behavior and care of pups after parturition. Biological mechanisms may include endocrine disruption, neurotransmitter system impairment, alterations in gene expression, and immune activation and inflammation. Additional longitudinal studies that include biospecimen collection are essential to furthering the understanding of how environmental toxicants during pregnancy may affect perinatal psychopathology and the underlying mechanisms of action. Future work should also leverage the parallels between animal and human maternal behavior, thereby highlighting the opportunity for multidisciplinary work in this avenue.

Plasma Neurotrophic Factor Levels are not Associated with the Severity of Depression: Prospective Pilot Study

INTRODUCTION

Depression is one of the most common mental illnesses. Impaired neurogenesis is observed in depression. Biomarkers of impaired neurogenesis in depression can act as a useful objective and diagnostic and prognostic tool to determine the severity of depression.

AIM

To study the concentration of biochemical indicators in the blood that may be involved in the pathogenesis of depression and their intercorrelations, and to determine any associations between the concentrations of biochemical indicators and severity of depressive symptoms.

METHODS

We determined the plasma concentrations of serotonin, dopamine, and neurotrophic factors involved in neurogenesis (BDNF, CDNF and neuropeptide Y) using enzyme immunoassay and mass spectrometry in depressed patients (n=22) and healthy controls (n=16) matched by socio-demographic parameters. All participants were assessed using the Hamilton Depression Scale (HAMD), the Generalized Anxiety Disorder Questionnaire (GAD-7), and the Center for Epidemiologic Studies Depression Scale (CES-D) to enter the study. The standard cut-offs for the CES-D and GAD-7 scales were used to confirm the presence or absence of depression and anxiety.

RESULTS

The concentrations of serotonin, dopamine, BDNF, CDNF, and neuropeptide Y in plasma did not differ between the groups and was not found to be associated with the scores on the scales. Positive correlations were found between the concentration of neuropeptide Y and serotonin, BDNF, and CDNF in blood plasma.

CONCLUSIONS

Plasma concentrations of biomarkers related to the pathophysiology of depression did not correlate with the severity of its symptoms.

Nutritional therapy can reduce the burden of depression management in low income countries: A review

Depression is a serious mental and mood disorder with global health and economic burden. This burden may be overwhelming in low income countries, although there are insufficient data. Most antidepressant formulations are predicated on the monoamine, neuroendocrine and neuro-inflammation hypotheses, with little or no cognizance to other neurochemicals altered in depression. A nutritional strategy with or without conventional antidepressants is recommended, as nutrition plays vital roles in the onset, severity and duration of depression, with poor nutrition contributing to its pathogenesis. This review discusses nutritional potentials of utilizing omega-3 fatty acids, proteins, vitamins, minerals and herbs or their phytochemicals in the management of depression with the aim of reducing depression burden. Literature search of empirical data in books and journals in data bases including but not limited to PubMed, Scopus, Science Direct, Web of Science and Google Scholar that might contain discussions of sampling were sought, their full text obtained, and searched for relevant content to determine eligibility. Omega-3 fatty and amino acids had significant positive anti-depression outcomes, while vitamins and minerals although essential, enhanced omega-3 fatty and amino acids activities. Some herbs either as whole extracts or their phytochemicals/metabolites had significant positive anti-depression efficacy. Nutrition through the application of necessary food classes or herbs as well as their phytochemicals, may go a long way to effectively manage depression. This therefore will provide inexpensive, natural, and non-invasive therapeutic means with reduced adverse effects that can also be applied alongside clinical management. This nutritional strategy should be given more attention in research, assessment and treatment for those with depression and other mental illness in low income countries, especially in Africa.

Integrated Network Pharmacology and GC-MS-Based Metabolomics to Investigate the Effect of Xiang-Su Volatile Oil Against Menopausal Depression

Menopausal depression perplexes a great number of women in later life. Xiangfu-Zisu (Xiang-Su), a traditional Chinese herbal pair composed of rhizomes of Cyperus rotundus L. (Xiangfu) and leaves of Perilla frutescens (L.) Britt. (Zisu), is frequently reported with antidepressant-like effects. The volatile oil from Xiangfu and Zisu has shown good antidepressant action, but its mechanism is still unclear. This study aimed to investigate the pharmacological mechanism of Xiang-Su (XS) volatile oil against menopausal depression through gas chromatography–mass spectrometry (GC-MS)-based network pharmacology and metabolomics. First, ADME screening was performed on actual detected components of XS volatile oil to obtain active constituents, and then duplicates of active constituent–related targets and menopausal depression–related targets were collected. These duplicates were considered as targets for XS volatile oil against menopausal depression, followed by GO and KEGG enrichment analyses. It showed that a total of 64 compounds were identified in XS volatile oil, and 38 active compounds were screened out. 42 overlapping genes between 144 compound-related genes and 780 menopausal depression–related genes were obtained. Results showed that targets of SLC6A4 and SLC6A3, regulation of serotonergic and dopaminergic synapses, were involved in the antidepressant mechanism of XS volatile oil. Next, antidepressant-like effect of XS volatile oil was validated in menopausal rats by ovariectomy (OVX) combined with chronic unpredictable mild stress (CUMS). Behavioral tests, biochemical analysis, and GC-MS–based non-targeted plasma metabolomics were employed to validate the antidepressant effect of XS volatile oil. Experimental evidence demonstrated that XS volatile oil reversed behavioral parameters in the sucrose preference test (SPT), open-field test (OFT), forced swim test (FST), and serum estradiol levels in OVX rats. Furthermore, results of metabolomics indicated that XS volatile oil mainly acts on regulating metabolic pathways of phenylalanine, tyrosine and tryptophan biosynthesis, tyrosine metabolism, and tryptophan metabolism, which were corresponding with the above-predicted results. These data suggest that network pharmacology combined with metabolomics provides deep insight into the antidepressant effect of XS volatile oil, which includes regulating key targets like SLC6A4 and SLC6A3, and pathways of serotonergic and dopaminergic synapses.

A review of effects of calorie restriction and fasting with potential relevance to depression

In recent years, there has been a great deal of interest in the effects of calorie reduction (calorie restriction) and fasting on depression. In the current paper, we have reviewed the literature in this area, with discussion of the possible neurobiological mechanisms involved in calorie restriction and intermittent fasting. Factors which may play a role in the effects of these dietary manipulations on health include changes involving free fatty acids, ketone bodies, neurotransmitters, cyclic adenosine monophosphate response element binding protein (CREB), brain-derived neurotrophic factor (BDNF), cytokines, orexin, ghrelin, leptin, reactive oxygen species and autophagy. Several of these factors are potential contributors to improving symptoms of depression. Challenges encountered in research on calorie restriction and intermittent fasting are also discussed. Although much is now known about the acute effects of calorie restriction and intermittent fasting, further long term clinical studies are warranted.

Dissecting Motor and Cognitive Component Processes of a Finger-Tapping Task With Hybrid Dopamine Positron Emission Tomography and Functional Magnetic Resonance Imaging

Striatal dopamine is involved in facilitation of motor action as well as various cognitive and emotional functions. Positron emission tomography (PET) is the primary imaging method used to investigate dopamine function in humans. Previous PET studies have shown striatal dopamine release during simple finger tapping in both the putamen and the caudate. It is likely that dopamine release in the putamen is related to motor processes while dopamine release in the caudate could signal sustained cognitive component processes of the task, but the poor temporal resolution of PET has hindered firm conclusions. In this study we simultaneously collected [11C]Raclopride PET and functional Magnetic Resonance Imaging (fMRI) data while participants performed finger tapping, with fMRI being able to isolate activations related to individual tapping events. The results revealed fMRI-PET overlap in the bilateral putamen, which is consistent with a motor component process. Selective PET responses in the caudate, ventral striatum, and right posterior putamen, were also observed but did not overlap with fMRI responses to tapping events, suggesting that these reflect non-motor component processes of finger tapping. Our findings suggest an interplay between motor and non-motor-related dopamine release during simple finger tapping and illustrate the potential of hybrid PET-fMRI in revealing distinct component processes of cognitive functions.

Effects of comorbid disorders on reward processing and connectivity in adults with ADHD

ADHD is a neurodevelopmental disorder with a long trajectory into adulthood where it is often comorbid with depression, substance use disorder (SUD) or obesity. Previous studies described a dysregulated dopaminergic system, reflected by abnormal reward processing, both in ADHD as well as in depression, SUD or obesity. No study so far however tested systematically whether pathologies in the brain's reward system explain the frequent comorbidity in adult ADHD. To test this, we acquired MRI scans from 137 participants probing the reward system by a monetary incentive delay task (MIDT) as well as assessing resting-state connectivity with ventral striatum as a seed mask. No differences were found between comorbid disorders, but a significant linear effect pointed toward less left intrastriatal connectivity in patients depending on the number of comorbidities. This points towards a neurobiologically impaired reward- and decision-making ability in patients with more comorbid disorders. This suggests that less intrastriatal connectivity parallels disorder severity but not disorder specificity, while MIDT abnormalities seem mainly to be driven by ADHD.

Glutamate as a Stressoric Factor for the Ex Vivo Release of Catecholamines from the Rabbit Medial Prefrontal Cortex (mPFC)

One of the major roles of glutamic acid (Glu) is to serve as an excitatory neurotransmitter within the central nervous system (CNS). This amino acid influences the activity of several brain areas, including the thalamus, brainstem, spinal cord, basal ganglia, and pons. Catecholamines (CAs) are synthesized in the brain and adrenal medulla and by some sympathetic nerve fibers. CAs, including dopamine (DA), norepinephrine (NE), and epinephrine (E), are the principal neurotransmitters that mediate a variety of CNS functions, such as motor control, cognition, emotion, memory processing, pain, stress, and endocrine modulation. This study aims to investigate the effects of the application of various Glu concentrates (5, 50, and 200 µM) on CAs release from rabbit medial prefrontal cortex (mPFC) slices and compare any resulting correlations with CAs released from the hypothalamus during 90 min of incubation. Medial prefrontal cortex samples were dissected from decapitated, twelve-week-old female rabbits. The results demonstrated that Glu differentially influences the direct release of CAs from the mPFC and the indirect release of CAs from the hypothalamus. When under stress, the hypothalamus, a central brain structure of the HPA axis, induces and adapts such processes. Generally, there was an inhibitory effect of Glu on CAs release from mPFC slices. Our findings show that the effect arises from Glu's action on higher-order motivational structures, which may indicate its contribution to the stress response by modulating the amount of CAs released.

Prenatal Poly I:C Challenge Affects Behaviors and Neurotransmission via Elevated Neuroinflammation Responses in Female Juvenile Rats

BACKGROUND

Exposure to polyriboinosinic-polyribocytidylic acid (Poly I:C) in pregnant rats has been reported to cause schizophrenia-like behaviors and abnormal neurotransmissions in adult, particularly male, offspring. However, what is less well understood are the effects of maternal Poly I:C exposure on adolescent behaviors and neurotransmission in female juvenile rats.

METHODS

Female adolescent Poly I:C offspring were constructed by treating with 5 mg/kg Poly I:C on timed pregnant rats (gestation day 15). A battery of behavioral tests was conducted during postnatal day 35-60. Neurotransmitter receptors and inflammation markers in brain regions were evaluated by RT-qPCR on postnatal day 60.

RESULTS

Open field, elevated plus maze, and forced swimming tests revealed that prenatal Poly I:C exposure led to elevated anxiety-like and depression-like behaviors in female adolescent offspring. Deficits in pre-pulse inhibition and social interaction were also observed. However, the Poly I:C rats had better performance than the controls in the novel object recognition memory test, which demonstrated a behavioral phenotype with improved cognitive function. Prenatal Poly I:C exposure caused brain region-specific elevation of the P2X7 receptor- and NF-κB-NLRP3-IL-1β inflammatory signaling in female juvenile rats. Prenatal Poly I:C exposure decreased expression of GABAA receptor subunits Gabrb3 in the prefrontal cortex and Gabrb1 and dopamine D2 receptor in the hippocampus, but increased NMDA receptor subunit Grin2a in the prefrontal cortex, 5-HT2A in the hippocampus, and Gabrb3 and D2 receptor in the nucleus accumben.

CONCLUSIONS

Prenatal Poly I:C challenge causes behavioral deficits and brain-specific neurotransmission changes via elevated neuroinflammation responses in female adolescent offspring rats.

Differences in the incidence of lurasidone adverse events between depressive disorders and schizophrenia in double-blind, randomized, placebo-controlled trials: a meta-analysis

RATIONALE

We conducted a meta-analysis of double-blind, randomized placebo-controlled trials of lurasidone (LUR) to examine the difference in the risk ratios (RRs) for adverse events (AEs) between depressive disorders (bipolar depression and major depressive disorders) and schizophrenia.

OBJECTIVES

Three trials for depressive disorders (n = 1,239) were used for flexible-dose LUR 20-60 (LUR20-60) and/or 80-120 (LUR80-120) mg/day. Nine schizophrenia trials (n = 2,684) were used for fixed-dose LUR. The RRs of LUR20-60 and LUR80-120 for depressive disorders were compared with those of LUR 40 (LUR40) and LUR 80 (LUR80) mg/day for schizophrenia, respectively, to match LUR dose.

RESULTS

LUR20-60 caused a higher incidence of akathisia (RR = 2.28; p = 0.003) and weight gain (RR = 4.11; p = 0.05) than placebo in patients with depressive disorders, and LUR40 caused a higher incidence of akathisia (RR = 2.39; p = 0.0001), extrapyramidal symptoms (RR = 1.88; p = 0.02), anticholinergic drug use (RR = 1.58; p = 0.005), somnolence (RR = 2.19; p = 0.002), and dizziness (RR = 2.06; p = 0.05) than placebo in patients with schizophrenia. However, no significant differences in the RRs for all outcomes were found between depressive disorders and schizophrenia. LUR80-120 caused a higher incidence of akathisia (RR = 3.90; p < 0.0001), extrapyramidal symptoms (RR = 2.26; p = 0.04), anticholinergic use (RR = 4.70; p < 0.0001), and nausea (RR = 2.15; p = 0.001) than placebo in patients with depressive disorders. LUR80 caused a higher incidence of akathisia (RR = 2.99; p < 0.0001), extrapyramidal symptoms (RR = 2.55; p = 0.01), anticholinergic use (RR = 1.86; p = 0.01), somnolence (RR = 2.46; p = 0.001), and nausea (RR = 1.64; p = 0.04) than placebo in patients with schizophrenia. Depressive disorders had a higher RR for anticholinergic use than schizophrenia (p = 0.04).

CONCLUSIONS

The incidence of AEs did not differ between schizophrenia and depressive disorders.

Astrocytes in depression and Alzheimer's disease

Astrocytes are an abundant subgroup of cells in the central nervous system (CNS) that play a critical role in controlling neuronal circuits involved in emotion, learning, and memory. In clinical cases, multiple chronic brain diseases may cause psychosocial and cognitive impairment, such as depression and Alzheimer's disease (AD). For years, complex pathological conditions driven by depression and AD have been widely perceived to contribute to a high risk of disability, resulting in gradual loss of self-care ability, lower life qualities, and vast burden on human society. Interestingly, correlational research on depression and AD has shown that depression might be a prodrome of progressive degenerative neurological disease. As a kind of multifunctional glial cell in the CNS, astrocytes maintain physiological function via supporting neuronal cells, modulating pathologic niche, and regulating energy metabolism. Mounting evidence has shown that astrocytic dysfunction is involved in the progression of depression and AD. We herein review the current findings on the roles and mechanisms of astrocytes in the development of depression and AD, with an implication of potential therapeutic avenue for these diseases by targeting astrocytes.

MicroRNAs as Critical Biomarkers of Major Depressive Disorder: A Comprehensive Perspective

Major Depressive Disorder (MDD) represents a major global health concern, a body-mind malady of rising prevalence worldwide nowadays. The complex network of mechanisms involved in MDD pathophysiology is subjected to epigenetic changes modulated by microRNAs (miRNAs). Serum free or vesicles loaded miRNAs have starred numerous publications, denoting a key role in cell-cell communication, systematically and in brain structure and neuronal morphogenesis, activity and plasticity. Upregulated or downregulated expression of these signaling molecules may imply the impairment of genes implicated in pathways of MDD etiopathogenesis (neuroinflammation, brain-derived neurotrophic factor (BDNF), neurotransmitters, hypothalamic-pituitary-adrenal (HPA) axis, oxidative stress, circadian rhythms...). In addition, these miRNAs could serve as potential biomarkers with diagnostic, prognostic and predictive value, allowing to classify severity of the disease or to make decisions in clinical management. They have been considered as promising therapy targets as well and may interfere with available antidepressant treatments. As epigenetic malleable regulators, we also conclude emphasizing lifestyle interventions with physical activity, mindfulness and diet, opening the door to new clinical management considerations.

In Search of Digital Dopamine: How Apps Can Motivate Depressed Patients, a Review and Conceptual Analysis

INTRODUCTION

Depression is highly prevalent and causes considerable suffering and disease burden despite the existence of wide-ranging treatment options. Momentary assessment is a promising tool in the management of psychiatric disorders, and particularly depression. It allows for a real-time evaluation of symptoms and an earlier detection of relapse or treatment efficacy. Treating the motivational and hedonic aspects of depression is a key target reported in the literature, but it is time-consuming in terms of human resources. Digital Applications offer a major opportunity to indirectly regulate impaired motivational circuits through dopaminergic pathways.

OBJECTIVE

The main objective of this review was twofold: (1) propose a conceptual and critical review of the literature regarding the theoretical and technical principles of digital applications focused on motivation in depression, activating dopamine, and (2) suggest recommendations on the relevance of using these tools and their potential place in the treatment of depression.

MATERIAL AND METHODS

A search for words related to "dopamine", "depression", "smartphone apps", "digital phenotype" has been conducted on PubMed.

RESULTS

Ecological momentary interventions (EMIs) differ from traditional treatments by providing relevant, useful intervention strategies in the context of people's daily lives. EMIs triggered by ecological momentary assessment (EMA) are called "Smart-EMI". Smart-EMIs can mimic the "dopamine reward system" if the intervention is tailored for motivation or hedonic enhancement, and it has been shown that a simple reward (such as a digital badge) can increase motivation.

DISCUSSION

The various studies presented support the potential interest of digital health in effectively motivating depressed patients to adopt therapeutic activation behaviors. Finding effective ways to integrate EMIs with human-provided therapeutic support may ultimately yield the most efficient and effective intervention method. This approach could be a helpful tool to increase adherence and motivation.

CONCLUSION

Smartphone apps can motivate depressed patients by enhancing dopamine, offering the opportunity to enhance motivation and behavioral changes, although longer term studies are still needed.

Mitophagy in depression: Pathophysiology and treatment targets

Mitochondria, the 'powerhouse' of eukaryotic cells, play a key role in cellular homeostasis. However, defective mitochondria increase mitochondrial ROS (mtROS) production and cell-free mitochondrial DNA (mtDNA) release, leading to increased inflammation. Mitophagy is a vital pathway, which selectively removes defective mitochondria through the process of autophagy. Thus, an impairment in the mitophagy pathway might trigger the gradual accumulation of defective mitochondria. Accumulating evidence suggest that inflammation and mitochondrial dysfunction are linked to the pathogenesis of depression. In this article, we have reviewed the role of impaired mitophagy as a contributing factor in depression pathophysiology. Further, we have discussed the potential therapeutic interventions aimed at modulating mitophagy in depression.

Validation of the Oxford Depression Questionnaire: Sensitivity to change, minimal clinically important difference, and response threshold for the assessment of emotional blunting

BACKGROUND

The Oxford Depression Questionnaire (ODQ) is a patient-reported scale for assessing emotional blunting in patients with major depressive disorder (MDD). This analysis was undertaken to further validate the scale in patients experiencing emotional blunting while receiving antidepressant treatment.

METHODS

Patients with MDD who experienced inadequate depressive-symptom resolution and emotional blunting on selective serotonin reuptake inhibitor or serotonin-noradrenaline reuptake inhibitor monotherapy (adequate dose for ≥6 weeks) were switched to vortioxetine 10-20 mg/day. ODQ total scores were assessed excluding and including the "antidepressant-as-cause" domain (ODQ-20 and ODQ-26, respectively). Anchor- and distribution-based methods were used to determine the minimal clinically important difference in ODQ scores in terms of change from baseline to week 8 of antidepressant treatment.

RESULTS

After 8 weeks of vortioxetine treatment, the mean change in ODQ-20 and ODQ-26 scores from baseline was -24.8 and -30.1 points, respectively. Greater mean changes from baseline in ODQ-20 and ODQ-26 scores were seen in patients reporting no emotional blunting vs those still experiencing emotional blunting after 8 weeks of vortioxetine treatment (ODQ-20: -27.0 vs -22.6 points; ODQ-26: -32.8 vs -27.5 points, respectively). In patients considered clinically minimally improved (Clinical Global Impression-Improvement score, 3) after 8 weeks of vortioxetine treatment, respective mean (standard deviation) change in ODQ-20 and ODQ-26 score from baseline was -15.5 (18.1) and -20.0 (20.5) points.

LIMITATIONS

Short study duration.

CONCLUSIONS

These results provide further validation of the clinical utility of the ODQ for assessing emotional blunting in patients with MDD. The suggested minimal clinically important difference for change in ODQ-20 and ODQ-26 scores is 16 and 20 points, respectively, after 8 weeks of antidepressant treatment.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03835715.

Transcriptome and Metabolome Analyses Reveal Potential Salt Tolerance Mechanisms Contributing to Maintenance of Water Balance by the Halophytic Grass Puccinellia nuttalliana

Elevated soil salinity exacerbated by human activities and global climate change poses serious threats to plant survival. Although halophytes provide many important clues concerning salt tolerance in plants, some unanswered questions remain to be addressed, including the processes of water and solute transport regulation. We performed high-throughput RNA-sequencing in roots and metabolome characterizations in roots and leaves of Puccinellia nuttalliana halophytic grass subjected to 0 (control) and 150 mM NaCl. In RNAseq, a total of 31 Gb clean bases generated were de novo assembled into 941,894 transcripts. The PIP2;2 and HKT1;5 transcript levels increased in response to the NaCl treatment implying their roles in water and ion homeostasis. Several transcription factors, including WRKY39, DEK3, HY5, and ABF2, were also overexpressed in response to NaCl. The metabolomic analysis revealed that proline and dopamine significantly increased due to the upregulation of the pathway genes under salt stress, likely contributing to salt tolerance mechanisms. Several phosphatidylcholines significantly increased in roots suggesting that the alterations of membrane lipid composition may be an important strategy in P. nuttalliana for maintaining cellular homeostasis and membrane integrity under salt stress. In leaves, the TCA cycle was enriched suggesting enhanced energy metabolism to cope with salt stress. Other features contributing to the ability of P. nuttalliana to survive under high salinity conditions include salt secretion by the salt glands and enhanced cell wall lignification of the root cells. While most of the reported transcriptomic, metabolomics, and structural alterations may have consequences to water balance maintenance by plants under salinity stress, the key processes that need to be further addressed include the role of the changes in the aquaporin gene expression profiles in the earlier reported enhancement of the aquaporin-mediated root water transport.

The miRNome of Depression

Depression is an effect of complex interactions between genetic, epigenetic and environmental factors. It is well established that stress responses are associated with multiple modest and often dynamic molecular changes in the homeostatic balance, rather than with a single genetic factor that has a strong phenotypic penetration. As depression is a multifaceted phenotype, it is important to study biochemical pathways that can regulate the overall allostasis of the brain. One such biological system that has the potential to fine-tune a multitude of diverse molecular processes is RNA interference (RNAi). RNAi is an epigenetic process showing a very low level of evolutionary diversity, and relies on the posttranscriptional regulation of gene expression using, in the case of mammals, primarily short (17–23 nucleotides) noncoding RNA transcripts called microRNAs (miRNA). In this review, our objective was to examine, summarize and discuss recent advances in the field of biomedical and clinical research on the role of miRNA-mediated regulation of gene expression in the development of depression. We focused on studies investigating post-mortem brain tissue of individuals with depression, as well as research aiming to elucidate the biomarker potential of miRNAs in depression and antidepressant response.

Early life adversity affecting the attachment bond alters ventral tegmental area transcriptomic patterning and behavior almost exclusively in female mice

Early life experiences that affect the attachment bond formation can alter developmental trajectories and result in pathological outcomes in a sex-related manner. However, the molecular basis of sex differences is quite unknown. The dopaminergic system originating from the ventral tegmental area has been proposed to be a key mediator of this process. Here we exploited a murine model of early adversity (Repeated Cross Fostering, RCF) to test how interfering with the attachment bond formation affects the VTA-related functions in a sex-specific manner. Through a comprehensive behavioral screening, within the NiH RDoC framework, and by next-generation RNA-Seq experiments, we analyzed the long-lasting effect of RCF on behavioral and transcriptional profiles related to the VTA, across two different inbred strains of mouse in both sexes. We found that RCF impacted to an extremely greater extent VTA-related behaviors in females than in males and this result mirrored the transcriptional alterations in the VTA that were almost exclusively observed in females. The sexual dimorphism was conserved across two different inbred strains in spite of their divergent long lasting consequences of RCF exposure. Our data suggest that to be female primes a sub-set of genes to respond to early environmental perturbations. This is, to the best of our knowledge, the first evidence of an almost exclusive effect of early life experiences on females, thus mirroring the extremely stronger impact of precocious aversive events reported in clinical studies in women.

A pair of dopamine neurons mediate chronic stress signals to induce learning deficit in Drosophila melanogaster

Chronic stress could induce severe cognitive impairments. Despite extensive investigations in mammalian models, the underlying mechanisms remain obscure. Here, we show that chronic stress could induce dramatic learning and memory deficits in Drosophila melanogaster The chronic stress-induced learning deficit (CSLD) is long lasting and associated with other depression-like behaviors. We demonstrated that excessive dopaminergic activity provokes susceptibility to CSLD. Remarkably, a pair of PPL1-γ1pedc dopaminergic neurons that project to the mushroom body (MB) γ1pedc compartment play a key role in regulating susceptibility to CSLD so that stress-induced PPL1-γ1pedc hyperactivity facilitates the development of CSLD. Consistently, the mushroom body output neurons (MBON) of the γ1pedc compartment, MBON-γ1pedc>α/β neurons, are important for modulating susceptibility to CSLD. Imaging studies showed that dopaminergic activity is necessary to provoke the development of chronic stress-induced maladaptations in the MB network. Together, our data support that PPL1-γ1pedc mediates chronic stress signals to drive allostatic maladaptations in the MB network that lead to CSLD.

The rostromedial tegmental (RMTg) "brake" on dopamine and behavior: A decade of progress but also much unfinished work

Between 2005 and 2009, several research groups identified a strikingly dense inhibitory input to midbrain dopamine neurons arising from a previously uncharted region posterior to the ventral tegmental area (VTA). This region is now denoted as either the rostromedial tegmental nucleus (RMTg) or the "tail of the VTA" (tVTA), and is recognized to express distinct genetic markers, encode negative "prediction errors" (inverse to dopamine neurons), and play critical roles in behavioral inhibition and punishment learning. RMTg neurons are also influenced by many categories of abused drugs, and may drive some aversive responses to such drugs, particularly cocaine and alcohol. However, despite much progress, many important questions remain about RMTg molecular/genetic properties, diversity of projection targets, and applications to addiction, depression, and other neuropsychiatric disorders. This article is part of the special Issue on 'Neurocircuitry Modulating Drug and Alcohol Abuse'.

Pharmacological Characterization of Toludesvenlafaxine as a Triple Reuptake Inhibitor

Toludesvenlafaxine hydrochloride dihydrate is a novel chemical entity and a potential triple monoamine reuptake inhibitor. This study characterized the in vitro triple reuptake inhibition activity, antidepressant-like activity in animals, and pharmacokinetic profiles in rats of toludesvenlafaxine. Binding affinity was determined using human serotonin transporter (SERT) protein, norepinephrine transporter (NET) protein and dopamine transporter (DAT) protein, and the reuptake inhibition was determined using Chinese hamster ovary cells expressing human SERT, NET and DAT. The antidepressant-like activity was examined in rat chronic unpredictable mild stress model and olfactory bulbectomized model. In rats, the tissue distribution and pharmacokinetic parameters were determined. Toludesvenlafaxine had high binding affinity on SERT, NET and DAT, and significantly inhibited the reuptake of serotonin (IC₅₀ = 31.4 ± 0.4 nM), norepinephrine (IC₅₀ = 586.7 ± 83.6 nM) and dopamine (IC₅₀ = 733.2 ± 10.3 nM) in vitro. Toludesvenlafaxine demonstrated significant antidepressant-like effects in rat models at 8-16 mg/kg. In addition, toludesvenlafaxine significantly reduced serum corticosterone and significantly increased testosterone levels in rats. Toludesvenlafaxine was quickly absorbed and converted to O-desvenlafaxine (ODV) after oral administration, both of which were selectively distributed into the hypothalamus with high concentration. Plasma ODV exposure was proportionally related to the doses after oral dosing. These results suggest that toludesvenlafaxine is a triple reuptake inhibitor with relatively fast-acting antidepressant-like activity and good therapeutic profile including improvement of anhedonia and sexual function.

2-Phenyl-3-(phenylselanyl)benzofuran elicits acute antidepressant-like action in male Swiss mice mediated by modulation of the dopaminergic system and reveals therapeutic efficacy in both sexes

RATIONALE

Depression is a psychiatric disorder that constitutes one of the leading causes of disability worldwide. 2-Phenyl-3-(phenylselanyl)benzofuran (SeBZF1) has been studied as a potential antidepressant drug, but its pharmacological action needs more investigation.

OBJECTIVES AND METHODS

Our aim was to extend information about the antidepressant-like action of SeBZF1 using the mouse tail suspension test (TST). Initial experiments investigated the mechanisms involved in the acute antidepressant-like action of SeBZF1 in male Swiss mice. For this purpose, males received noradrenergic or dopaminergic receptor antagonists before acute SeBZF1 administration (50 mg/kg, per oral). In parallel, effects of combined treatment with SeBZF1 and bupropion at sub-effective doses (1 and 3 mg/kg, respectively) were tested. The next experiments were designed to determine the acute effects of SeBZF1 in females through a dose-response curve (5-50 mg/kg). Lastly, the efficacy of a 7-day repeated treatment with SeBZF1 (1 and 5 mg/kg) in mice of both sexes and its safety were evaluated. TST and the open-field test (OFT) were employed in all behavioral experiments.

RESULTS

Pre-administration of dopaminergic antagonists (SCH23390, a selective D₁R antagonist; sulpiride, a selective D₂/D₃R antagonist; and haloperidol, a non-selective antagonist), but not of adrenergic α₁, α₂, and β-R antagonists, blocked the acute antidepressant-like effects of SeBZF1 in males. Co-administration of sub-effective doses of SeBZF1 and bupropion reduced the depressive phenotype. In addition, acute treatment with SeBZF1 at 50 mg/kg produced a reduction of female immobility. Finally, repeated treatment with SeBZF1 (1 and 5 mg/kg) was effective in causing antidepressant-like effects in both sexes. Locomotor activity, plasma transaminases, and urea levels remained unaltered after SeBZF1 exposure.

CONCLUSION

Our findings provide evidence of the involvement of the dopaminergic system in the acutely antidepressant-like action of SeBZF1 in male mice and reveal the compound efficacy when acute or repeatedly administered in both sexes.

Association of Environmental tobacco smoke exposure with depression among non-smoking adults

Background

Depression is a psychological dysfunction that impairs health and quality of life. However, whether environmental tobacco smoke exposure (ETSE) is associated with depression is poorly understood. This study was designed to evaluate the association of ETSE with depression among non-smoking adults in the United States.

Method

Using the 2015–2016 United States National Health and Nutrition Examination Survey (NHANES), we identified 2623 adults (females – 64.2%, males – 35.8%) who had never smoked and applied multivariable adjusted-logistic regression to determine the adjusted odds ratio (aOR) and 95% confidence interval (CI) at P < 0.05 for the association of ETSE with depression adjusting for relevant confounders.

Results

Mean age of respondents was 46.5 ± 17.9 years, 23.5% reported ETSE, and 4.7% reported depression. Also, aORs for the association of ETSE with depression were 1.992 (1.987, 1.997) among females and 0.674 (0.670, 0.677) among males. When we examined the association by age groups, the aORs were 1.792 (1.787, 1.796) among young adults (< 60 years) and 1.146 (1.140, 1.152) among older adults (≥60 years).

Conclusions

We found that ETSE was associated with higher odds of depression among females but not among males.

Effects of an Adenosine A2A Receptor Antagonist on Striatal Dopamine D2-Type Receptor Availability: A Randomized Control Study Using Positron Emission Tomography

Introduction: Altered dopaminergic neurotransmission, especially in the functioning of dopamine D2-type receptors, is considered central to the etiology of a variety of neuropsychiatric disorders. In particular, individuals with substance use disorders have been consistently observed to exhibit lower D2-type receptor availability (quantified as binding potential; BPND) using positron emission tomography (PET). Upregulation of D2-type receptor density thus may therefore provide a therapeutic effect for substance use disorders. Importantly, in vitro studies reveal that D2 receptors coexist with adenosine 2A (A2A) receptors to form the highest density of heteromers in the whole striatum, and there is a functional interaction between these two receptors. As such, blockade of A2A receptor's function may prevent D2 receptor downregulation, yet no study has currently examined this hypothesis in humans. Methods and Analysis: This double-blind, randomized controlled trial aims to evaluate the effect of the A2A receptor antagonist istradefylline (compared to placebo) on both dopamine D2-type receptor availability in the human brain and on neuropsychological measurements of impulsivity. It is hypothesized that istradefylline will both increase striatal D2-type BPND and improve control of impulsivity more than placebo. Forty healthy participants, aged 20-65 with no history of psychiatric or neurological disorders, will be recruited and randomized into two groups and will undergo [11C]raclopride PET, once before and once after administration of either 40 mg/day istradefylline or placebo for 2 weeks. Neuropsychological measurements will be administered on the same days of the PET scans. Ethics and Dissemination: The study protocol was approved by the Certified Review Boards (CRB) of National Center of Neurology and Psychiatry (CR18-011) and prospectively registered with the Japan Registry of Clinical Trials (jRCTs031180131; https://jrct.niph.go.jp/latest-detail/jRCTs031180131). The findings of this study will be disseminated through peer reviewed scientific journals and conferences. Clinical Trial Registration:www.ClinicalTrials.gov, identifier jRCTs031180131.

Endoplasmic Reticulum Stress Is Associated with the Mesencephalic Dopaminergic Neuron Injury in Stressed Rats

An increasing number of people are in a state of stress due to social and psychological pressures, which may result in mental disorders. Previous studies indicated that mesencephalic dopaminergic neurons are associated with not only reward-related behaviors but also with stress-induced mental disorders. To explore the effect of stress on dopaminergic neuron and potential mechanism, we established stressed rat models of different time durations and observed pathological changes in dopaminergic neurons of the ventral tegmental area (VTA) through HE and thionine staining. Immunohistochemistry coupled with microscopy-based multicolor tissue cytometry (MMTC) was employed to investigate the number changes of dopaminergic neurons. Double immunofluorescence labelling was used to investigate expression changes of endoplasmic reticulum stress (ERS) protein GRP78 and CHOP in dopaminergic neurons. Our results showed that prolonged stress led to pathological alteration in dopaminergic neurons of VTA, such as missing of Nissl bodies and pyknosis in dopaminergic neurons. Immunohistochemistry with MMTC indicated that chronic stress exposure resulted in a significant decrease in dopaminergic neurons. Double immunofluorescence labelling showed that the endoplasmic reticulum stress protein took part in the injury of dopaminergic neurons. Taken together, these results indicated the involvement of ERS in mesencephalic dopaminergic neuron injury induced by stress exposure.

Partial agonists of dopamine receptors: receptor theory and the dopamine hypothesis of psychosis

This article discusses dopamine partial agonism, which is the main mechanism of action of the psychiatric drugs aripiprazole, brexpiprazole and cariprazine. It outlines the principles of receptor theory and the structure of dopamine receptors; characterises agonists, antagonists and partial agonists; and summarises the dopamine hypothesis of psychosis and the role of dopamine and serotonin in depression.

Refractory migraine profile in CGRP-monoclonal antibodies scenario

Objective

Refractory migraine (Ref‐M) represents a conundrum that headache experts have to face with. We aim to investigate whether a peculiar profile may characterize patients with Ref‐M according to 2020 European Headache Federation criteria. Furthermore, to substantiate a dysfunctional dopaminergic pathway involvement in these patients, we explored the effectiveness of olanzapine.

Materials & Methods

Eighty‐four patients (fitting previous Ref‐M criteria of the 2014) were treated with erenumab for six months. Differences between clinical and demographic features of responder (Ref‐M according to 2014 criteria) and not‐responder (Ref‐M according to 2020 criteria) patients to CGRP‐mAbs were investigated and their predictive values assessed. In fifteen patients with Ref‐M not responders to CGRP‐mAbs, olanzapine was administered (5 mg/die) for 3 months and frequency and pain intensity of migraine attacks were estimated.

Results

Patients with Ref‐M not responsive to CGRP‐mAbs (29/84) when compared with Ref‐M responsive to CGRP‐mAbs showed higher baseline frequency of migraine attacks, medication overuse and pain catastrophizing scale (PCS) scores. Logistic regression analyses showed that frequency of attacks, medication overuse and PCS score represent independent negative predictors of CGRP‐mAbs response. A ≥50% reduction of headache days/month was observed after olanzapine treatment in 67% of patients with Ref‐M not responsive to CGRP‐mAbs.

Conclusions

We outline that higher frequency of migraine attacks, medication overuse and pain catastrophizing characterize patients with Ref‐M not responsive to CGRP‐mAbs. In this frame, olanzapine effectiveness on frequency and pain intensity of migraine attacks supports the hypothesis that migraine refractoriness may be subtended by a prominent involvement of the dopaminergic pathway.