Melatonin ameliorates chronic mild stress induced behavioral dysfunctions in mice

Melatonin effects on animal behavior: circadian rhythm, stress response, and modulation of behavioral patterns

Melatonin plays a crucial role in various behavioral and physiological aspects of animals, including regulating their circadian rhythms. This review provides a comprehensive evaluation of the multifaceted effects of melatonin on animal behavior, such as temperament, stress, and aggression regulation. The focus is on the complex interactions between melatonin and the hormonal and neurotransmitter systems, highlighting how melatonin interacts with cortisol, serotonin, and dopamine to influence behavior. Additionally, it investigates the effects of melatonin on the hypothalamic-pituitary-gonada (HPG) axis and stress responses, emphasizing its potential to improve stress management and social interactions, thereby enhancing animal welfare. The review also examines the seasonal variations of melatonin and its impact on aggression and reproductive activities related to photoperiods, as well as its effects on learning and memory to suggest improvements in animal training methods and practices. Furthermore, it discusses the influence of melatonin on appetite and physical activity regulation, implying its involvement in metabolic processes. In conclusion, further research is needed to elucidate the complex mechanisms underlying the extensive influence of melatonin on animal behavior. Through this review, the aim is to integrate the overall knowledge about melatonin and animal behavioral temperament and to propose new research areas for animal management based on behavioral and hormonal regulation.

'The effect of neuropeptide Y1 receptor agonist on hypothalamic neurogenesis in rat experimental depression model'

Depression is responsible for neuropathies such as decreased neurogenesis and increased dendritic atrophy. There is information that antidepressant treatments have an effect by increasing hippocampal neurogenesis and neurotrophic factor expression. The neuropeptide Y1 (NPY1R) receptor agonist has been suggested to have anxiolytic effects. Based on this information, it was aimed to investigate the effect of NPY1R agonist on depression in rats with depression using the CMS model and to determine how depression affects cell proliferation in the hypothalamus and hypothalamic peptide levels. Forty-eight adult, male Wistar albino rats were divided into groups as Control, Depression (D), Depression + NPY1R and NPY1R. Various stressors were applied to D for 30 days. An open field test (OFT) and forced swim test (FST) were performed to check whether the animals were depressed. On the 16th day, an osmotic mini pump was placed under the skin and NPY1R (130 ul/kg/day) was applied for 15 days. Behavioral tests were performed, hypothalamic peptide gene expression levels were analyzed by quantitative RT-PCR and statistical evaluations were made using ANOVA. A decrease in the percentage of movement in the D and control groups were noted in the OFT, an increase in the immobility time in the D group in the FST, and an increase in swimming behavior in the DNPY1R group. The animals did not display any anxiety behavior based on the elevated plus maze test results. It caused a decrease in IGF1R, FGF2, POMC, NPY and GLUT2 gene expression in the hypothalamus of depression group animals, and an increase in NPY gene expression in NPY1R treatment. This study compellingly demonstrated that exposure to chronic mild stress simultaneously downregulates gene expression in the hypothalamus; we observed that NPY receptor NPY1R treatment increased the effect of NPY. Therefore, adjunctive treatments with appropriate molecules such as NPY, Y1 receptor agonists or pharmacological derivatives may have significant potential in the treatment of depression.

Intestinal melatonin levels and gut microbiota homeostasis are independent of the pineal gland in pigs

Introduction

Melatonin (MEL) is a crucial neuroendocrine hormone primarily produced by the pineal gland. Pinealectomy (PINX) has been performed on an endogenous MEL deficiency model to investigate the functions of pineal MEL and its relationship with various diseases. However, the effect of PINX on the gastrointestinal tract (GIT) MEL levels and gut microbiome in pigs has not been previously reported.

Methods

By using a newly established pig PINX model, we detected the levels of MEL in the GIT by liquid chromatography-tandem mass spectrometry. In addition, we examined the effects of PINX on the expression of MEL synthesis enzymes, intestinal histomorphology, and the intestinal barrier. Furthermore, 16S rRNA sequencing was performed to analyze the colonic microbiome.

Results

PINX reduced serum MEL levels but did not affect GIT MEL levels. Conversely, MEL supplementation increased MEL levels in the GIT and intestinal contents. Neither PINX nor MEL supplementation had any effect on weight gain, organ coefficient, serum biochemical indexes, or MEL synthetase arylalkylamine N-acetyltransferase (AANAT) expression in the duodenum, ileum, and colon. Furthermore, no significant differences were observed in the intestinal morphology or intestinal mucosal barrier function due to the treatments. Additionally, 16S rRNA sequencing revealed that PINX had no significant impact on the composition of the intestinal microbiota. Nevertheless, MEL supplementation decreased the abundance of Fibrobacterota and increased the abundance of Actinobacteriota, Desulfobacterota, and Chloroflexi.

Conclusion

We demonstrated that synthesis of MEL in the GIT is independent of the pineal gland. PINX had no influence on intestinal MEL level and microbiota composition in pigs, while exogenous MEL alters the structure of the gut microbiota.

Melatonin treatment improves cognitive deficits by altering inflammatory and neurotrophic factors in the hippocampus of obese mice

Overweight and obesity are associated with an increased risk of developing dementia and cognitive deficits. Neuroinflammation is one of the most important mechanisms behind cognitive impairment in obese patients. In recent years, the neuroendocrine hormone melatonin has been suggested to have therapeutic effects for memory decline in several neuropsychiatric and neurological conditions. However, the effects of melatonin on cognitive function under obesity conditions still need to be clarified. The purpose of this study was to determine whether melatonin treatment can improve cognitive impairment in obese mice. To this end, male C57BL6 mice were treated with a high-fat diet (HFD) for 20 weeks to induce obesity. The animal received melatonin for 8 weeks. Cognitive functions were evaluated using the Y maze, object recognition test, and the Morris water maze. We measured inflammatory cytokines including tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-17A, and brain-derived neurotrophic factor (BDNF) in the hippocampus of obese mice. Our results show that HFD-induced obesity significantly impaired working, spatial and recognition memory by increasing IFN-γ and IL-17A and decreasing BDNF levels in the hippocampus of mice. On the other hand, melatonin treatment effectively improved all cognitive impairments and reduced TNF-α, IFN-γ, and IL-17A and elevated BDNF levels in the hippocampus of obese mice. Taken together, this study suggests that melatonin treatment could have a beneficial role in the treatment of cognitive impairment in obesity.

Redox Regulatory Changes of Circadian Rhythm by the Environmental Risk Factors Traffic Noise and Air Pollution

Significance: Risk factors in the environment such as air pollution and traffic noise contribute to the development of chronic noncommunicable diseases. Recent Advances: Epidemiological data suggest that air pollution and traffic noise are associated with a higher risk for cardiovascular, metabolic, and mental disease, including hypertension, heart failure, myocardial infarction, diabetes, arrhythmia, stroke, neurodegeneration, depression, and anxiety disorders, mainly by activation of stress hormone signaling, inflammation, and oxidative stress. Critical Issues: We here provide an in-depth review on the impact of the environmental risk factors air pollution and traffic noise exposure (components of the external exposome) on cardiovascular health, with special emphasis on the role of environmentally triggered oxidative stress and dysregulation of the circadian clock. Also, a general introduction on the contribution of circadian rhythms to cardiovascular health and disease as well as a detailed mechanistic discussion of redox regulatory pathways of the circadian clock system is provided. Future Directions: Finally, we discuss the potential of preventive strategies or "chrono" therapy for cardioprotection. Antioxid. Redox Signal. 37, 679-703.

Encore: Behavioural animal models of stress, depression and mood disorders

Animal studies over the past two decades have led to extensive advances in our understanding of pathogenesis of depressive and mood disorders. Among these, rodent behavioural models proved to be of highest informative value. Here, we present a comprehensive overview of the most popular behavioural models with respect to physiological, circuit, and molecular biological correlates. Behavioural stress paradigms and behavioural tests are assessed in terms of outcomes, strengths, weaknesses, and translational value, especially in the domain of pharmacological studies.

Maternal separation induced resilience to depression and spatial memory deficit despite intensifying hippocampal inflammatory responses to chronic social defeat stress in young adult male rats

Early life adversity has been suggested to affect neuroendocrine responses to subsequent stressors and accordingly vulnerability for behavioral disorders. This is the first work to study the effects of maternal separation (MS) stress on the co-occurrence of depression and cognitive impairments along with hippocampal inflammatory response under chronic social defeat stress (CSDS) in young adult male rats. During the first two postnatal weeks, the male pups were either exposed to MS or left undisturbed with their mothers (Std). Subsequently, starting on postnatal day 50, the animals of each group were either left undisturbed in the standard group housing (Con) or underwent CSDS for three weeks. Totally, there were four groups (n = 10/group), namely Std-Con, Ms-Con, Std-CSDS, and MS-CSDS. Pup retrieval test was performed on daily basis from PND1 to PND14. During the last week of the CSDS exposure, in the light phase, the behavioral tests and the retro-orbital blood sampling were performed to assess basal plasma corticosterone levels. Afterwards, the hippocampus of the animals was removed to measure the interleukin 1β (IL-1β) content. Exposure to CSDS increased the plasma corticosterone levels and induced social avoidance along with memory deficit. Maternal separation intensified hippocampal IL-1β contents as well as the plasma corticosterone levels in response to CSDS. Meanwhile, it facilitated the spatial learning and potentiated resilience to social avoidance and memory deficit. In conclusion, although maternal separation increased the basal plasma corticosterone levels, it could facilitate the learning process and induce resilience to the onset of depression and memory deficit in response to CSDS, probably through the compensatory increase in maternal care and the induction of mild hippocampal inflammatory response.

Evolution of an increased performance under acute challenge does not exacerbate vulnerability to chronic stress

An adequate stress response plays a vital role in coping with challenges. However, if selection for improved coping with an acute challenge affects the entire stress response system, susceptibility to adverse effects of chronic stressors can be deepened. Here, we used bank voles from lines selected for high swim-induced aerobic metabolism (A) and unselected control (C), and asked if the selection affected sensitivity to chronic mild stress (CMS). The voles were first habituated to daily weighing and feces collection for three weeks, and then for two weeks were exposed to CMS or remained undisturbed. The habituation itself resulted in an increased swim-induced oxygen consumption in both line types, and a decreased body mass. The CMS treatment caused reduction of food consumption in the second week of the experiment, and, in males, a decline in the metabolic rate. Paradoxically, fecal corticosterone metabolites decreased in the CMS-treated group. The response to CMS did not differ between the line types. Thus, the selection for increased performance was not traded off by increased vulnerability to chronic stress. The counter-intuitive results may even lead to a speculation that bank voles—and perhaps also other animals—prefer experiencing unpredictable, unpleasant stressors over the monotony of standard laboratory housing.

Does Sertraline Affect Hypothalamic Food Intake Peptides in the Rat Experimental Model of Chronic Mild Stress-Induced Depression?

Depression is a chronic, recurrent and life-threatening disease affecting approximately 15% of the world population. Depression is responsible for neuropathologies like decreased neurogenesis and increased dendritic atrophy. Antidepressant treatments increase hippocampal neurogenesis and neurotrophic factor expression. Based on this information, it was aimed to investigate effect of sertraline on depression in rats with chronic mild stress (CMS) model and to determine how it affects cell proliferation and hypothalamic peptide levels in hypothalamus. 56 adult male Wistar albino; control, depression(D), depression + sertraline, sertraline were divided into groups. Various stressors were applied to D for 30 days. Open field test (OFT) and forced swimming test (FST) were conducted to check whether the animals were depressed. On the 16th day osmotic minipump was placed subcutaneously and sertraline (10 mg/kg/day) was administered for 15 days. Behavior tests were done. Hypothalamic peptide gene expression levels were analyzed by quantitative RT-PCR. Statistical evaluations were made using ANOVA. It caused a decrease in the percentage of movement in the D and control groups in the OFT, an increase in the immobility time in the D group in the FST, and an increase in the swimming behavior in the DS group. Animals did not show any anxiological behavior based on the elevated plus maze test results. CMS caused a decrease in GLUT2 and NPY gene expression in the hypothalamus of animals, an increase in POMC and FGFR2, and an increase in IGFIR and GLUT2 gene expression in the DS group. Sertraline has been shown to ameliorate the effects of CMS-induced depression. Sertraline is thought to have a positive regulatory effect on both the formation of neural precursor cells and the survival of newly formed neurons in the hypothalamus. Newly formed neurons in the hypothalamus express food intake-related NPY, POMC, GLUT2 neurons, and thus hypothalamic tanycytes may play a key role in the control of energy metabolism.

Melatonin improves learning and memory of mice with chronic social isolation stress via an interaction between microglia polarization and BDNF/TrkB/CREB signaling pathway

Chronic social isolation stress (SIS) could impair learning and memory-related behaviors. Herein, we investigated the efficacy of Melatonin in treatment of memory despair and also its possible underlying mechanism of action in an animal model of SIS. For this purpose, mice were allocated to two opposing conditions, including social condition (SC) and isolated condition (IC), for five weeks. The study consisted of three groups, including saline-treated SC, saline-treated IC, Melatonin-treated IC (10 mg/kg/day for five successive days). At the end of the isolation period, mice underwent three neurobehavioral tests: passive avoidance (PA), Morris water maze (MWM), and Y maze (YM) tests. Hippocampus samples were obtained and the expressions of BDNF, TrkB, phosphorylated TrkB (pTrkB), CREB, phosphorylated CREB (pCREB), as well as M1 and M2 microglia were assessed. Interpreting the behavioral tests, we found that isolated mice showed lower freezing response in the PA test, lower number of novel arm visits in the YM, and higher escape latency and less time spent in the target quadrant in the MWM, when compared to SC rodents (P values < 0.001). The isolated group had higher M1/M2 relative ratio (P < 0.001), as well as lower concentrations of BDNF mRNA (p < 0.001) and protein (P < 0.001), TrkB protein (P = 0.035), CREB mRNA (P < 0.001) and protein (P = 0.012), pTrkB (P < 0.001), and pCREB (P = 0.035). However, Melatonin relatively reversed the behavioral, cellular, and molecular effects of SIS. Taken together, melatonin therapy could alleviate memory impairment through switching microglial polarization from M1 to M2 phenotype along with altered expression and function in the BDNF/TrkB/CREB signaling pathway.

Intranasal Ketamine for Acute Pain: Behavioral and Neurophysiological Safety Analysis in Mice

Background

Subanesthetic ketamine has been used for treatment-resistant depression and is popular as an opioid-sparing agent.

Objective

The present study aimed to investigate the dose-dependent antinociceptive effect of intranasal ketamine (INK) along with behavioral and neurophysiological safety in mice.

Methods

Antinociceptive efficacy was evaluated in the terms of thermal nociceptive response and formalin test. The safety studies were carried out separately in healthy mice using telemetry-based cortical electroencephalography, hemodynamic changes, and spontaneous behavioral functions, including anxiety, stereotypic movement, and locomotor functions.

Results

INK administration significantly augmented the thermal nociceptive threshold and alleviated the pain response in the tonic phase of the formalin test. The results showed the dose-independent effectiveness of ketamine for thermal nociceptive responses because there were no significant differences among different INK dose groups. Behavioral safety analysis using the open field exploratory test revealed no significant effect of INK on anxiety-like functions in healthy mice. However, INK mice showed significantly more stereotypic movement but slower locomotor activities. The electroencephalography signal power spectrum density analysis revealed no significant changes by INK administration except a lower value in the α range. No significant changes were reported in heart rate, diastolic blood pressure, or systolic blood pressure at the higher dose equivalent used in the pain model.

Conclusions

The study demonstrated the behavioral and neurophysiological safety of INK, although it had a mild sedative effect. Therefore, INK is suggested as a potentially safe candidate for the management of acute pain. (Curr Ther Res Clin Exp. 2021; 82:XXX–XXX)

© 2021 Elsevier HS Journals, Inc.

MT2 melatonin receptors expressed in the olfactory bulb modulate depressive-like behavior and olfaction in the 6-OHDA model of Parkinson's disease

Melatonin MT1 and MT2 receptors are expressed in the glomerular layer of the olfactory bulb (OB); however, the role of these receptors has not been evaluated until now. Considering the association of the OB with olfactory and depressive disorders in Parkinson's disease (PD), we sought to investigate the involvement of melatonin receptors in these non-motor disturbances in an intranigral 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD. We demonstrate the presence of functional melatonin receptors in dopaminergic neurons of the glomerular layer. Local administration of melatonin (MLT, 1 μg/μl), luzindole (LUZ, 5 μg/μl) or the MT2-selective receptor drug 4-P-PDOT (5 μg/μl) reversed the depressive-like behavior elicited by 6-OHDA. Sequential administration of 4-P-PDOT and MLT (5 μg/μl, 1 μg/μl) promoted additive antidepressant-like effects. In the evaluation of olfactory discrimination, LUZ induced an olfactory impairment when associated with the nigral lesion-induced impairment. Thus, our results suggest that melatonin MT2 receptors expressed in the glomerular layer are involved in depressive-like behaviors and in olfactory function associated with PD.

Effect of mesoporous silica nanoparticles-based nano-fragrance on the central nervous system

Fragrances are widely used in our daily lives and can make us feel happy. However, traditional aromatic products release fragrance quickly and have a strong aroma. This not only worsens our scenting experience, but also severely shortens the useful life of fragrance products. In this study, nano-fragrances based on mesoporous silica nanoparticles with great encapsulation efficiency and slow-release function were designed and prepared. In addition, this nano-fragrances are applied to wallpapers. Open field tests showed that this nano-fragrance had significant stress relief and anti-depressant effects.

Melatonin Reverses the Depression-associated Behaviour and Regulates Microglia, Fractalkine Expression and Neurogenesis in Adult Mice Exposed to Chronic Mild Stress

Depression may be precipitated by the negative impact of chronic stress, which is considered to play a key role in this neuropsychiatric disorder. Interestingly, depressed patients show decreased levels of melatonin. This hormone acts pro-neurogenic and exhibits anti-depressant effects in rodent models of predictive antidepressant-like effects. However, the benefits of melatonin in reversing the deleterious effects of chronic mild stress on the alterations in behaviour and in the neurogenic niche of the hippocampus in male BALB/c mice are unknown. In this study, we compared the effects of melatonin (2.5 mg/kg) and citalopram (5 mg/kg), an antidepressant drug belonging to the selective serotonin reuptake inhibitors, in male BALB/c mice exposed to chronic mild stress (CMS). We also investigated the potential effects of melatonin and citalopram on microglial cells, hippocampal neurogenesis and peripheral cytokine profiles. Melatonin and citalopram induced similar antidepressant-like activities that occurred with some of the the following findings: (1) reversal of the morphological alterations in microglia; (2) reversal of the decreased immunoreactivity to CX3CL1 and CX3CR1 in the dentate gyrus; (3) positive regulation of cell proliferation, survival and complexity of the dendritic trees of doublecortin-cells; and (4) modifications of peripheral CX3CL1 expression. This outcome is consistent with the hypothesis about the antidepressant-like effect of melatonin and supports its relevance as a modulator of the niche in the dentate gyrus.

Melatonin Modulates Dendrite Maturation and Complexity in the Dorsal- and Ventral- Dentate Gyrus Concomitantly with Its Antidepressant-Like Effect in Male Balb/C Mice

Adult neurogenesis occurs in the dentate gyrus (DG) of the hippocampus. New neurons help to counteract the effects of stress and several interventions including antidepressant drugs, environmental modifications and internal factors act pro-neurogenic with consequences in the dorsal and ventral DG. Melatonin, the main product synthesized by the pineal gland, induces antidepressant-like effects and modulates several events of the neurogenic process. However, the information related to the capability of melatonin to modulate dendrite maturation and complexity in the dorsal and ventral regions of the DG and their correlation with its antidepressant-like effect is absent. Thus, in this study, we analyzed the impact of melatonin (0, 0.5, 1, 2.5, 5 or 10 mg/kg) administered daily for fourteen days on the number, dendrite complexity and distribution of doublecortin (DCX)-cells in the dorsal-ventral regions of the DG in male Balb/C mice. Doublecortin is a microtubule-associated protein that is expressed during the course of dendritic maturation of newborn neurons. Also, we analyzed the impact of melatonin on despair-like behavior in the forced swim test. We first found a significant increase in the number and higher dendrite complexity, mainly with the doses of 2.5, 5 and 10 mg/kg of melatonin (81%, 122%, 78%). These cells showed more complex dendritic trees in the ventral- and the dorsal- DG. Concomitantly, the doses of 5 and 10 mg/kg of melatonin decreased depressant-like behavior (76%, 82%). Finally, the data corroborate the antidepressant-like effect of melatonin and the increasing number of doublecortin-associated cells. Besides, the data indicate that melatonin favors the number and dendrite complexity of DCX-cells in the dorsal- and ventral- region of the DG, which may explain part of the antidepressant-like effect of melatonin.

Melatonin attenuates 5-fluorouracil-induced spatial memory and hippocampal neurogenesis impairment in adult rats

AIMS

Treatment with 5-fluorouracil (5-FU) can cause impairment to adult hippocampal neurogenesis, resulting in cognitive deficits. As melatonin has been shown to enhance memory and hippocampal neurogenesis in animal models, this research investigated the neuroprotective effects of melatonin against spatial memory and hippocampal neurogenesis impairment in 5-fluorouracil (5-FU)-treated rats.

MATERIALS AND METHODS

Four-Five weeks old male Spraque-Dawley rats weighing between 180 and 200 g were used. Animals were maintained under standard laboratory conditions with 25 °C and 12 h light/dark cycle. Animal were administered intravenous (i.v.) injections of 5-FU (25 mg/kg) 5 times every 3 days starting on day 9 of the experiment. The rats were divided into preventive, recovery, and throughout groups and co-treated with melatonin (8 mg/kg, i.p.) once daily (at 7.00 pm) for 21 days prior to, after, and throughout 5-FU treatment, respectively. Spatial memory was assessed using a novel object location (NOL) test. Hippocampal neurogenesis was then examined using Ki67, bromodeoxyuridine (BrdU), and doublecortin (DCX) immunohistochemistry staining.

KEY FINDINGS

Melatonin administration was able to both protect the subjects from and reverse spatial memory deficits. 5-FU was also found to reduce the generation of hippocampal newborn neurons. However, co-treatment with melatonin ameliorated the reductions in neurogenesis caused by 5-FU.

SIGNIFICANCE

These findings suggest that melatonin administration was able to ameliorate the 5-FU-induced spatial memory deficits associated with neurogenesis. The present work will be valuable for patients who suffer memory deficits from 5-FU chemotherapy.

Melatonin mitigates hippocampal and cognitive impairments caused by prenatal irradiation

Formation of new neurons and glial cells in the brain is taking place in mammals not only during prenatal embryogenesis but also during adult life. As an enhancer of oxidative stress, ionizing radiation represents a potent inhibitor of neurogenesis and gliogenesis in the brain. It is known that the pineal hormone melatonin is a potent free radical scavenger and counteracts inflammation and apoptosis in brain injuries. The aim of our study was to establish the effects of melatonin on cells in the hippocampus and selected forms of behaviour in prenatally irradiated rats. The male progeny of irradiated (1 Gy of gamma rays; n = 38) and sham-irradiated mothers (n = 19), aged 3 weeks or 2 months, were used in the experiment. Melatonin was administered daily in drinking water (4 mg/kg b. w.) to a subset of animals from each age group. Prenatal irradiation markedly suppressed proliferative activity in the dentate gyrus in both age groups. Melatonin significantly increased the number of proliferative BrdU-positive cells in hilus of young irradiated animals, and the number of mature NeuN-positive neurons in hilus and granular cell layer of the dentate gyrus in these rats and in CA1 region of adult irradiated rats. Moreover, melatonin significantly improved the spatial memory impaired by irradiation, assessed in Morris water maze. A significant correlation between the number of proliferative cells and cognitive performances was found, too. Our study indicates that melatonin may decrease the loss of hippocampal neurons in the CA1 region and improve cognitive abilities after irradiation.

Evaluating the Memory Enhancing Effects of Angelica gigas in Mouse Models of Mild Cognitive Impairments

(1) Background: By 2050, it is estimated that 130 million people will be diagnosed with dementia, and currently approved medicines only slow the progression. So preventive intervention is important to treat dementia. Mild cognitive impairment is a condition characterized by some deterioration in cognitive function and increased risk of progressing to dementia. Therefore, the treatment of mild cognitive impairment (MCI) is a possible way to prevent dementia. Angelica gigas reduces neuroinflammation, improves circulation, and inhibits cholinesterase, which can be effective in the prevention of Alzheimer’s disease and vascular dementia and the progression of mild cognitive impairment. (2) Methods: Angelica gigas (AG) extract 1 mg/kg was administered to mildly cognitive impaired mice, models based on mild traumatic brain injury and chronic mild stress. Then, spatial, working, and object recognition and fear memory were measured. (3) Result: Angelica gigas improved spatial learning, working memory, and suppressed fear memory in the mild traumatic brain injury model. It also improved spatial learning and suppressed cued fear memory in the chronic mild stress model animals. (4) Conclusions: Angelica gigas can improve cognitive symptoms in mild cognitive impairment model mice.

Deficiency in Androgen Receptor Aggravates the Depressive-Like Behaviors in Chronic Mild Stress Model of Depression

While androgen receptor (AR) and stress may influence the development of the major depressive disorder (MDD), the detailed relationship, however, remains unclear. Here we found loss of AR accelerated development of depressive-like behaviors in mice under chronic mild stress (CMS). Mechanism dissection indicated that AR might function via altering the expression of miR-204-5p to modulate the brain-derived neurotrophic factor (BDNF) expression to influence the depressive-like behaviors in the mice under the CMS. Adding the antiandrogen flutamide with the stress hormone corticosterone can additively decrease BDNF mRNA in mouse hippocampus mHippoE-14 cells, which can then be reversed via down-regulating the miR-204-5p expression. Importantly, targeting this newly identified AR-mediated miR-204-5p/BDNF/AKT/MAPK signaling with small molecules including 7,8-DHF and fluoxetine, all led to alter the depressive-like behavior in AR knockout mice under CMS exposure. Together, results from these preclinical studies conclude that decreased AR may accelerate the stress-induced MDD via altering miR-204-5p/BDNF/AKT/MAPK signaling, and targeting this newly identified signaling may help in the development of better therapeutic approaches to reduce the development of MDD.

Melatonin treatment affects changes in adrenal gene expression of catecholamine biosynthesizing enzymes and norepinephrine transporter in the rat model of chronic-stress-induced depression

This study investigated the effects of melatonin treatment on adrenal catecholamine content, synthesis, uptake, and vesicular transport induced by the chronic unpredictable mild stress (CUMS) model of depression in rats. This entailed quantifying the norepinephrine, epinephrine, mRNA, and protein levels of tyrosine hydroxylase (TH), dopamine-β-hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT), norepinephrine transporter (NET), and vesicular monoamine transporter 2 (VMAT2) in the adrenal medulla. CUMS caused a significant depletion of norepinephrine stores and protein levels of TH, DBH, and NET, whereas the gene expression of PNMT was increased. It was observed that melatonin treatment in the CUMS rats prevented the stress-induced decrease in norepinephrine content and the protein expression of TH, DBH, and NET in the adrenal medulla of chronically stressed rats. The present study demonstrates the stimulatory effect of melatonin on adrenomedullary synthesis, the uptake and content of catecholamine in the rat model of chronic stress-induced depression.

Is chronodisruption a vulnerability factor to stress?

Since the circadian system seems to modulate stress responses, this study aimed to evaluate if the combination of circadian strain and stress amplifies changes expected from each factor alone. Control Balb/c mice (12:12-NS) kept in standard 12:12 light:dark cycles (LD) and submitted to no stress procedures (NS) were compared to groups submitted to shortened LD (10:10-NS), chronic mild stress (CMS) but no circadian strain (12:12-CMS), or shortened LD followed by CMS (10:10-CMS). Rest-activity/temperature rhythms and body weight were assessed throughout the experiments. In Experiment 1 mice were submitted to 3 weeks of CMS; in Experiment 2 sucrose preference and light-dark tests were performed. Also, blood samples were collected at the end of Experiment 2 to assess metabolic parameters. Relative amplitude of temperature after CMS was increased only in the 10:10-CMS group, while body weight change was reduced during CMS regardless of LD intervention. During the CMS, the relative amplitude of temperature was negatively correlated with body weight gain. No differences in behavior and metabolic parameters were seen among groups. Identifying suitable research designs to investigate our hypothesis that circadian disturbances may increase vulnerability to stress-induced depression and anxiety is warranted.

Melatonin alleviates weanling stress in mice: Involvement of intestinal microbiota

Melatonin influences intestinal microbiota and the pathogenesis of various diseases. This study was conducted to explore whether melatonin alleviates weanling stress through intestinal microbiota in a weanling mouse model. Melatonin supplementation in weanling mice (provided in the drinking water at a dosage of 0.2 mg/mL for 2 weeks) significantly improved body weight gain (1.4 ± 0.03 g/day in melatonin group vs 1.2 ± 0.06 g/day in control group) and intestinal morphology (ie, villus length, crypt depth, and villus to crypt ratio), but had little effect on the proliferation or apoptosis of intestinal cells, the numbers of Paneth cells and goblet cells, as well as the expression of makers related to enterocytes (sucrase) and endocrine cells (chromogranin A and peptide YY) in the ileum. Melatonin supplementation had little effect on serum levels of amino acids or stress-related parameters (eg, SOD, TNF-α, and angiotensin I). 16S rRNA sequencing suggested that melatonin supplementation increased the richness indices of intestinal microbiota (observed species, Chao 1, and ACE) and shaped the composition of intestinal microbiota (eg, increase in the abundance of Lactobacillus [19 ± 3% in melatonin group vs 6 ± 2% in control group]), which was demonstrated using an ex vivo proliferation assay and colonic loop proliferation assay. Melatonin supplementation also significantly influenced the metabolism of intestinal microbiota, such as amino acid metabolism and drug metabolism. More importantly, in antibiotic-treated weanling mice and germ-free weanling mice, melatonin failed to affect body weight gain or intestinal morphology. Melatonin significantly reduced (by about 60%) the bacterial load in enterotoxigenic Escherichia coli (ETEC)-infected weanling mice, but had little effect on ETEC load in antibiotic-pretreated animals. In conclusion, melatonin affects body weight gain, intestinal morphology, and intestinal ETEC infection through intestinal microbiota in weanling mice. The findings highlight the importance of intestinal microbiota in mediating the various physiological functions of melatonin in the host.

Cytokine alterations and cognitive impairment in major depressive disorder: From putative mechanisms to novel treatment targets

Overwhelming evidence indicates the involvement of immune-inflammatory processes in the pathophysiology of major depressive disorder (MDD). Peripheral cytokine alterations serve as one of most consistently reported indices of subthreshold inflammatory state observed in MDD. Although cytokines cannot pass directly through the blood-brain barrier, a number of transport mechanisms have been reported. In addition, peripheral cytokines may impact central nervous system via downstream effectors of their biological activity. Animal model studies have provided evidence that cytokines might impact cognitive performance through direct and indirect effects on long-term potentiation, neurogenesis and synaptic plasticity. Therefore, it has been hypothesized that cytokine alterations might contribute to cognitive impairment that is widely observed in MDD and persists beyond episodes of acute relapse in the majority of patients. Although several studies have provided that peripheral cytokine alterations might be related to cognitive deficits in patients with MDD, the quality of evidence still leaves much to be desired due to methodological heterogeneity and limitations. In this article, we provide an overview of studies investigating the association between peripheral cytokine alterations and cognitive performance in MDD, discuss underlying mechanisms and neural substrates. Finally, we propose possible treatment targets related to cytokine alterations taking into account existing evidence for antidepressant efficacy of anti-inflammatory pharmacological treatment modalities.

Unpredictable chronic mild stress differentially impairs social and contextual discrimination learning in two inbred mouse strains

Alterations in the social and cognitive domain are considered important indicators for increased disability in many stress-related disorders. Similar impairments have been observed in rodents chronically exposed to stress, mimicking potential endophenotypes of stress-related psychopathologies such as major depression disorder (MDD), anxiety, conduct disorder, and posttraumatic stress disorder (PTSD). Data from numerous studies suggest that deficient plasticity mechanisms in hippocampus (HC) and prefrontal cortex (PFC) might underlie these social and cognitive deficits. Specifically, stress-induced deficiencies in neural plasticity have been associated with a hypodopaminergic state and reduced neural plasticity persistence. Here we assessed the effects of unpredictable chronic mild stress (UCMS) on exploratory, social and cognitive behavior of females of two inbred mouse strains (C57BL/6J and DBA/2J) that differ in their dopaminergic profile. Exposure to chronic stress resulted in impaired circadian rhythmicity, sociability and social cognition in both inbred strains, but differentially affected activity patterns and contextual discrimination performance. These stress-induced behavioral impairments were accompanied by reduced expression levels of brain derived neurotrophic factor (BDNF) in the prefrontal cortex. The strain-specific cognitive impairment was coexistent with enhanced plasma corticosterone levels and reduced expression of genes related to dopamine signaling in hippocampus. These results underline the importance of assessing different strains with multiple test batteries to elucidate the neural and genetic basis of social and cognitive impairments related to chronic stress.

Circadian Rhythm Disturbances in Mood Disorders: Insights into the Role of the Suprachiasmatic Nucleus

Circadian rhythm disturbances are a common symptom among individuals with mood disorders. The suprachiasmatic nucleus (SCN), in the ventral part of the anterior hypothalamus, orchestrates physiological and behavioral circadian rhythms. The SCN consists of self-sustaining oscillators and receives photic and nonphotic cues, which entrain the SCN to the external environment. In turn, through synaptic and hormonal mechanisms, the SCN can drive and synchronize circadian rhythms in extra-SCN brain regions and peripheral tissues. Thus, genetic or environmental perturbations of SCN rhythms could disrupt brain regions more closely related to mood regulation and cause mood disturbances. Here, we review clinical and preclinical studies that provide evidence both for and against a causal role for the SCN in mood disorders.

Depressive-like behavior is elevated among offspring of parents exposed to dim light at night prior to mating

Rates of major depressive disorder (MDD) have steadily increased over the past 50 years. Many factors have been implicated in the etiology of depressive disorders and environmental influences are being increasingly recognized. The increase in depression rates has coincided with increased artificial nighttime lighting. Exposure to light at night (LAN) has been associated with increased depressive-like behavior in rodents and decreased mood in humans. However, relatively little is known on the multigenerational effects of dLAN on affect. In this study, we exposed adult male and female Siberian hamsters (Phodopus sungorus) to either DARK (0lx) or dim LAN (5lx) for 9 weeks, then paired animals in a full factorial design; all animals were thereafter housed in dark nights. Offspring were gestated and reared in dark nights, then tested in adulthood for depressive-like behaviors and hippocampal expression of glucocorticoid (GR) and melatonin (MT1) receptor expression. Maternal exposure to dLAN decreased sucrose preference, time to first float bout in the Porsolt swim test, and GR expression in the hippocampus. Paternal exposure to dLAN increased time spent floating, and increased hippocampal GR expression. Overall, our results suggest that chronic exposure of parents to light at night has multigenerational effects on offspring depressive-like behavior. If these results pertain to humans, then our data suggest that LAN may contribute to the rapidly rising rates of major depressive disorder in industrialized and developing countries.

The antidepressant effect of melatonin and fluoxetine in diabetic rats is associated with a reduction of the oxidative stress in the prefrontal and hippocampal cortices

In the past few years possible mechanisms that link diabetes and depression have been found. One of these mechanisms is the increase in lipid peroxidation and decrease in antioxidant activity in the hippocampal and prefrontal cortices, which are brain areas involved in mood. The goal of the present study was to evaluate the effect of an antidepressant and of an antioxidant on behavior and oxidative activity in brains of diabetic rats. Rats rendered diabetic after a treatment with streptozotocin (STZ) (60mg/kg) were treated with fluoxetine (15mg/kg), melatonin (10mg/kg), or vehicle for 4 weeks. All animals were tested for signs of depression and anxiety using the elevated plus maze (EPM), open field test (OFT) and the forced swim test (FST). Four groups were compared: (1) normoglycemic, (2) hyperglycemic vehicle treated, and hyperglycemic (3) fluoxetine or (4) melatonin treated rats. On the last day of the study, blood samples were obtained to determine the levels of hemoglobin A1c (HbA1c). Also, brain samples were collected to measure the oxidative stress in the hippocampal and prefrontal cortices using the thiobarbituric acid reactive substances (TBARS) assay. The activity of the antioxidant enzymes catalase (CAT), glutathione peroxidase (GPx), and glutathione S-transferase (GST) were also measured on the brain samples. The results show that both fluoxetine and melatonin decrease the signs of depression and anxiety in all tests. Concomitantly, the levels of HbA1c were reduced in drug treated rats, and to a greater degree in the fluoxetine group. In the cerebral cortex of diabetic rats, TBARS was increased, while the activity of CAT, GPx and GST were decreased. Fluoxetine and melatonin treatments decreased TBARS in both cortices. In the prefrontal cortex, fluoxetine and melatonin restored the activity of CAT, while only melatonin improved the activity of GPx and GST. In the hippocampus, the activity of GPx alone was restored by melatonin, while fluoxetine had no effect. These results suggest that antidepressants and antioxidants can counter the mood and oxidative disorders associated with diabetes. While these effects could result from a decreased production of reactive oxygen species (ROS) remains to be established.

The chronic mild stress (CMS) model of depression: History, evaluation and usage

Now 30 years old, the chronic mild stress (CMS) model of depression has been used in >1300 published studies, with a year-on-year increase rising to >200 papers in 2015. Data from a survey of users show that while a variety of names are in use (chronic mild/unpredictable/varied stress), these describe essentially the same procedure. This paper provides an update on the validity and reliability of the CMS model, and reviews recent data on the neurobiological basis of CMS effects and the mechanisms of antidepressant action: the volume of this research may be unique in providing a comprehensive account of antidepressant action within a single model. Also discussed is the use of CMS in drug discovery, with particular reference to hippocampal and extra-hippocampal targets. The high translational potential of the CMS model means that the neurobiological mechanisms described may be of particular relevance to human depression and mechanisms of clinical antidepressant action.

Exogenous daytime melatonin modulates response of adolescent mice in a repeated unpredictable stress paradigm

The immediate and short-term behavioural and physiological implications of exposure to stressful scenarios in the adolescent period are largely unknown; however, increases in occurrence of stress-related physiological and psychological disorders during puberty highlight the need to study substances that may modulate stress reactivity during a crucial stage of maturation. Seven groups of mice (12-15 g each) were administered distilled water (DW) (non-stressed and stressed controls), sertraline (10 mg/kg), diazepam (2 mg/kg) or one of three doses of melatonin (5, 10 and 15 mg/kg). Mice were exposed to 30 min of chronic mild stress (25 min of cage shaking, cage tilting, handling and 5 min of forced swimming in tepid warm water at 25 °C, in a random order) after administration of DW or drugs, daily for 21 days. Behavioural assessments were conducted on day 1 and day 21 (after which mice were sacrificed, blood taken for estimation of corticosterone levels and brain homogenates used for estimation of antioxidant activities). Administration of melatonin resulted in an increase in horizontal locomotion and self-grooming, while rearing showed a time-dependent increase, compared to non-stress and stress controls. Working memory improved with increasing doses of melatonin (compared to controls and diazepam); in comparison to setraline however, working memory decreased. A dose-related anxiolytic effect is seen when melatonin is compared to non-stressed and stressed controls. Melatonin administration reduced the systemic/oxidant response to repeated stress. Administration of melatonin in repeatedly stressed adolescent mice was associated with improved central excitation, enhancement of working memory, anxiolysis and reduced systemic response to stress.

Chronic activation of NPFFR2 stimulates the stress-related depressive behaviors through HPA axis modulation

Neuropeptide FF (NPFF) is a morphine-modulating peptide that regulates the analgesic effect of opioids, and also controls food consumption and cardiovascular function through its interaction with two cognate receptors, NPFFR1 and NPFFR2. In the present study, we explore a novel modulatory role for NPFF-NPFFR2 in stress-related depressive behaviors. In a mouse model of chronic mild stress (CMS)-induced depression, the expression of NPFF significantly increased in the hypothalamus, hippocampus, medial prefrontal cortex (mPFC) and amygdala. In addition, transgenic (Tg) mice over-expressing NPFFR2 displayed clear depression and anxiety-like behaviors with hyperactivity in the hypothalamic-pituitary-adrenal (HPA) axis, reduced expression of glucocorticoid receptor (GR) and neurogenesis in the hippocampus. Furthermore, acute treatment of NPFFR2 agonists in wild-type (WT) mice enhanced the activity of the HPA axis, and chronic administration resulted in depressive and anxiety-like behaviors. Chronic stimulation of NPFFR2 also decreased the expression of hippocampal GR and led to persistent activation of the HPA axis. Strikingly, bilateral intra-paraventricular nucleus (PVN) injection of NPFFR2 shRNA predominately inhibits the depressive-like behavior in CMS-exposed mice. Antidepressants, fluoxetine and ketamine, effectively relieved the depressive behaviors of NPFFR2-Tg mice. We speculate that persistent NPFFR2 activation, in particular in the hypothalamus, up-regulates the HPA axis and results in long-lasting increases in circulating corticosterone (CORT), consequently damaging hippocampal function. This novel role of NPFFR2 in regulating the HPA axis and hippocampal function provides a new avenue for combating depression and anxiety-like disorder.

Therapeutic Prospective of Infused Allogenic Cultured Mesenchymal Stem Cells in Traumatic Brain Injury Mice: A Longitudinal Proton Magnetic Resonance Spectroscopy Assessment

Improved therapeutic assessment of experimental traumatic brain injury (TBI), using mesenchymal stem cells (MSCs), would immensely benefit its therapeutic management. Neurometabolite patterns at injury site, measured with proton magnetic resonance spectroscopy (1H‐MRS) after MSCs transplantation, may serve as a bio‐indicator of the recovery mechanism. This study used in vivo magnetic resonance imaging and 1H‐MRS to evaluate the therapeutic prospects of implanted MSCs at injury site in experimental mice longitudinally up to 21 days. Negative tissue contrast and cytotoxic edema formation were observed in susceptibility‐based contrast (T2*) and an apparent diffusion coefficient map, respectively. Lesion site showed decreased N‐acetylaspartate, total choline, myo‐inositol, total creatine, glutamate‐glutamine complex, and taurine neurometabolic concentrations by 1H‐MRS investigation. There was a considerable decrease in locomotor activity, depression index, and cognitive index after TBI. It may, therefore, be inferred that MSC transplantation prompted recovery by decreasing negative signals and edema, restoring metabolites to baseline concentrations, and enhancing behavioral activity. Overall findings support the potential of MSC transplantation for the enhancement of endogenous neuroprotective responses, which may provide future clinical applications for translating laboratory research into therapeutic clinical advances. Stem Cells Translational Medicine2017;6:316–329

Prophylactic Role of Oral Melatonin Administration on Neurogenesis in Adult Balb/C Mice during REM Sleep Deprivation

Purpose. The aim of this study was to assess the effect of melatonin in the proliferation of neural progenitors, melatonin concentration, and antiapoptotic proteins in the hippocampus of adult mice exposed to 96 h REM sleep deprivation (REMSD) prophylactic administration of melatonin for 14 days. Material and Methods. Five groups of Balb/C mice were used: (1) control, (2) REMSD, (3) melatonin (10 mg/kg) plus REMSD, (4) melatonin and intraperitoneal luzindole (once a day at 5 mg/kg) plus REMSD, and (5) luzindole plus REMSD. To measure melatonin content in hippocampal tissue we used HPLC. Bcl-2 and Bcl-xL proteins were measured by Western Blot and neurogenesis was determined by injecting 5-bromo-2-deoxyuridine (BrdU) and BrdU/nestin expressing cells in the subgranular zone of the dentate gyrus were quantified by epifluorescence. Results. The melatonin-treated REMSD group showed an increased neural precursor in 44% with respect to the REMSD group and in 28% when contrasted with the control group (P < 0.021). The melatonin-treated REMSD group also showed the highest expression of Bcl-2 and Bcl-xL as compared to the rest of the groups. Conclusion. The exogenous administration of melatonin restores the tissue levels of sleep-deprived group and appears to be an efficient neuroprotective agent against the deleterious effects of REMSD.

Potential pleiotropic beneficial effects of adjuvant melatonergic treatment in posttraumatic stress disorder

Loss of circadian rhythmicity fundamentally affects the neuroendocrine, immune, and autonomic system, similar to chronic stress and may play a central role in the development of stress-related disorders. Recent articles have focused on the role of sleep and circadian disruption in the pathophysiology of posttraumatic stress disorder (PTSD), suggesting that chronodisruption plays a causal role in PTSD development. Direct and indirect human and animal PTSD research suggests circadian system-linked neuroendocrine, immune, metabolic and autonomic dysregulation, linking circadian misalignment to PTSD pathophysiology. Recent experimental findings also support a specific role of the fundamental synchronizing pineal hormone melatonin in mechanisms of sleep, cognition and memory, metabolism, pain, neuroimmunomodulation, stress endocrinology and physiology, circadian gene expression, oxidative stress and epigenetics, all processes affected in PTSD. In the current paper, we review available literature underpinning a potentially beneficiary role of an add-on melatonergic treatment in PTSD pathophysiology and PTSD-related symptoms. The literature is presented as a narrative review, providing an overview on the most important and clinically relevant publications. We conclude that adjuvant melatonergic treatment could provide a potentially promising treatment strategy in the management of PTSD and especially PTSD-related syndromes and comorbidities. Rigorous preclinical and clinical studies are needed to validate this hypothesis.

Piromelatine ameliorates memory deficits associated with chronic mild stress-induced anhedonia in rats

RATIONALE

Previous studies have demonstrated that piromelatine (a melatonin and serotonin 5-HT1A and 5-HT1D agonist) exerts an antidepressant activity in rodent models of acute stress and improves cognitive impairments in a rat model of Alzheimer's disease (AD). However, the role of piromelatine in chronic stress-induced memory dysfunction remains unclear.

OBJECTIVE

The aim of this study was to determine whether piromelatine ameliorates chronic mild stress (CMS)-induced memory deficits and explore the underlying mechanisms.

METHODS

Rats were exposed randomly to chronic mild stressors for 7 weeks to induce anhedonia (reflected by a significant decrease in sucrose intake), which was used to select rats vulnerable (CMS-anhedonic, CMSA) or resistant (CMS-resistant, CMSR) to stress. Piromelatine (50 mg/kg) was administered daily during the last 2 weeks of CMS. The tail suspension and forced swimming tests were adopted to further characterize vulnerable and resilient rats. The Y-maze and novel object recognition (NOR) tests were used to evaluate memory performance. Brain-derived neurotrophic factor (BDNF), cAMP response element-binding protein (CREB), phosphorylated CREB (pCREB), and cytogenesis were measured in the hippocampus.

RESULTS

We found that only CMSA rats displayed significant increases in immobility time in the tail suspension and forced swimming tests; memory deficits in the Y-maze and NOR tests; significant decreases in hippocampal BDNF, CREB, and pCREB expression; and cytogenesis. All these anhedonia-associated effects were reversed by piromelatine.

CONCLUSIONS

Piromelatine ameliorates memory deficits associated with CMS-induced anhedonia in rats and this effect may be mediated by restoring hippocampal BDNF, CREB, and cytogenesis deficits.

Cognitive Dysfunction in Major Depressive Disorder. A Translational Review in Animal Models of the Disease

Major Depressive Disorder (MDD) is the most common psychiatric disease, affecting millions of people worldwide. In addition to the well-defined depressive symptoms, patients suffering from MDD consistently complain about cognitive disturbances, significantly exacerbating the burden of this illness. Among cognitive symptoms, impairments in attention, working memory, learning and memory or executive functions are often reported. However, available data about the heterogeneity of MDD patients and magnitude of cognitive symptoms through the different phases of MDD remain difficult to summarize. Thus, the first part of this review briefly overviewed clinical studies, focusing on the cognitive dysfunctions depending on the MDD type. As animal models are essential translational tools for underpinning the mechanisms of cognitive deficits in MDD, the second part of this review synthetized preclinical studies observing cognitive deficits in different rodent models of anxiety/depression. For each cognitive domain, we determined whether deficits could be shared across models. Particularly, we established whether specific stress-related procedures or unspecific criteria (such as species, sex or age) could segregate common cognitive alteration across models. Finally, the role of adult hippocampal neurogenesis in rodents in cognitive dysfunctions during MDD state was also discussed.

Melatonin treatment during the incubation of sensitization attenuates methamphetamine-induced locomotor sensitization and MeCP2 expression

Behavior sensitization is a long-lasting enhancement of locomotor activity after exposure to psychostimulants. Incubation of sensitization is a phenomenon of remarkable augmentation of locomotor response after withdrawal and reflects certain aspects of compulsive drug craving. However, the mechanisms underlying these phenomena remain elusive. Here we pay special attention to the incubation of sensitization and suppose that the intervention of this procedure will finally decrease the expression of sensitization. Melatonin is an endogenous hormone secreted mainly by the pineal gland. It is effective in treating sleep disorder, which turns out to be one of the major withdrawal symptoms of methamphetamine (MA) addiction. Furthermore, melatonin can also protect neuronal cells against MA-induced neurotoxicity. In the present experiment, we treated mice with low dose (10mg/kg) of melatonin for 14 consecutive days during the incubation of sensitization. We found that melatonin significantly attenuated the expression of sensitization. In contrast, the vehicle treated mice showed prominent enhancement of locomotor activity after incubation. MeCP2 expression was also elevated in the vehicle treated mice and melatonin attenuated its expression. Surprisingly, correlation analysis suggested significant correlation between MeCP2 expression in the nucleus accumbens (NAc) and locomotion in both saline control and vehicle treated mice, but not in melatonin treated ones. MA also induced MeCP2 over-expression in PC12 cells. However, melatonin failed to reduce MeCP2 expression in vitro. Our results suggest that melatonin treatment during the incubation of sensitization attenuates MA-induced expression of sensitization and decreases MeCP2 expression in vivo.

The Influences of Whole Brain Radiotherapy on Social Cognition and Association with Hippocampal and Frontal Dosimetry

The influence of brain radiotherapy on neurocognition is a major concern. Social cognition is a mental process in the meaning of social interaction and the recognition of facial emotion is a domain of social cognition. Thus, we aimed to investigate the early effect of whole brain radiotherapy on facial emotion recognition ability. Thirteen patients with various brain tumors in the study. Beck depression and anxiety inventory and the facial emotion recognition test by using a set of photographs were performed at the beginning and post radiotherapy. The severity of depression (16.40 ± 12.16 vs 04.00 ± 02.38 points) and anxiety (14.47 ± 11.96 vs 04.54 ± 03.30 points) were significantly higher in patients. The only significance according to facial emotion recognition rate between initial phase of patients and healthy controls was identifying neutral facial em otion (p = 0.002). The patients after brain radiotherapy had significantly better rate of recognizing fear facial emotions (p = 0.039). This study is the first that investigated the effects of cranial irradiation on facial emotion recognition ability and compares this ability with healthy controls. Interestingly, in the early phase the patients seem to be improved in fear facial emotion after brain radiotherapy without sparing cognition specific regions as hippocampus and frontal regions.

Ozone exposure of Flinders Sensitive Line rats is a rodent translational model of neurobiological oxidative stress with relevance for depression and antidepressant response

RATIONALE

Major depression has been associated with higher levels of air pollution that in turn leads to neurodegeneration via increased oxidative stress. There is a need for suitable translational animal models to study the role of oxidative stress in depression and antidepressant action.

OBJECTIVE

Considering the gene X environment hypothesis of depression, the present study investigated the effect of chronic ozone inhalation on depression and anxiety-related behavior, cognition, and brain markers of oxidative stress in the Flinders Sensitive Line (FSL) rat. In addition, response to the antioxidant melatonin, and the antidepressants desipramine or escitalopram, was assessed.

METHODS

Rats were exposed to ozone (0.0 or 0.3 parts per million (ppm)) per inhalation for 4 h daily for a period of 15 days, while simultaneously receiving saline or the above-mentioned drugs.

RESULTS

The data indicate that chronic ozone inhalation induced memory impairment, anxiety and depression-like effects, reduced cortical and hippocampal superoxide dismutase and catalase activity, and compromised central monoamine levels similar to that noted in depression. Moreover, the behavioral and neurochemical effects of melatonin, desipramine, and escitalopram were mostly attenuated in the presence of ozone.

CONCLUSION

Thus, genetically susceptible individuals exposed to high levels of oxidative stress are at higher risk of developing mood and/or an anxiety disorders, showing greater redox imbalance and altered behavior. These animals are also more resistant to contemporary antidepressant treatment. The presented model provides robust face, construct, and predictive validity, suitable for studying neuronal oxidative stress in depression, antidepressant action and mechanisms to prevent neuronal oxidative stress.

Association between toll-like receptors expression and major depressive disorder

Accumulating evidences suggest that Toll-like receptors (TLRs) were involved in the pathophysiology of major depressive disorder. TLR4 was thought to be associated with major depressive disorder in animal model, but the others were still unknown. In order to examine TLR1-9 mRNA expression levels in peripheral blood and their relationships with the psychopathology of major depressive disorder, 30 patients with major depressive disorder were compared with 29 healthy controls. The 17-item Hamilton Depression Rating Scale (HAMD-17) was used to assess the severity of major depression. The mRNA expression levels of TLRs were examined in parallel with a housekeeping gene using real-time polymerase chain reaction (RT-PCR). Analysis of covariance with age and body mass index adjustment revealed a significantly higher expression of TLR3, 4, 5 and 7 mRNA but lower expression of TLR1 and 6 in patients with major depressive disorder as compared with healthy controls. Multiple linear regression analysis revealed that TLR4 was an independent risk factor relating to severity of major depression. These findings suggest that TLRs, especially TLR4, may be involved in the psychopathology of major depression.

Melatonin, noncoding RNAs, messenger RNA stability and epigenetics--evidence, hints, gaps and perspectives

Melatonin is a highly pleiotropic regulator molecule, which influences numerous functions in almost every organ and, thus, up- or down-regulates many genes, frequently in a circadian manner. Our understanding of the mechanisms controlling gene expression is actually now expanding to a previously unforeseen extent. In addition to classic actions of transcription factors, gene expression is induced, suppressed or modulated by a number of RNAs and proteins, such as miRNAs, lncRNAs, piRNAs, antisense transcripts, deadenylases, DNA methyltransferases, histone methylation complexes, histone demethylases, histone acetyltransferases and histone deacetylases. Direct or indirect evidence for involvement of melatonin in this network of players has originated in different fields, including studies on central and peripheral circadian oscillators, shift work, cancer, inflammation, oxidative stress, aging, energy expenditure/obesity, diabetes type 2, neuropsychiatric disorders, and neurogenesis. Some of the novel modulators have also been shown to participate in the control of melatonin biosynthesis and melatonin receptor expression. Future work will need to augment the body of evidence on direct epigenetic actions of melatonin and to systematically investigate its role within the network of oscillating epigenetic factors. Moreover, it will be necessary to discriminate between effects observed under conditions of well-operating and deregulated circadian clocks, and to explore the possibilities of correcting epigenetic malprogramming by melatonin.