The forced swim test: Historical, conceptual and methodological considerations and its relationship with individual behavioral traits

Non-neuronal brain biology and its relevance to animal welfare

Non-neuronal cells constitute a significant portion of brain tissue and are seen as having key roles in brain homeostasis and responses to challenges. This review illustrates how non-neuronal biology can bring new perspectives to animal welfare through understanding mechanisms that determine welfare outcomes and highlighting interventions to improve welfare. Most obvious in this respect is the largely unrecognised relevance of neuroinflammation to animal welfare which is increasingly found to have roles in determining how animals respond to challenges. We start by introducing non-neuronal cells and review their involvement in affective states and cognition often seen as core psychological elements of animal welfare. We find that the evidence for a causal involvement of glia in cognition is currently more advanced than the corresponding evidence for affective states. We propose that translational research on affective disorders could usefully apply welfare science derived approaches for assessing affective states. Using evidence from translational research, we illustrate the involvement of non-neuronal cells and neuroinflammatory processes as mechanisms modulating resilience to welfare challenges including disease, pain, and social stress. We review research on impoverished environments and environmental enrichment which suggests that environmental conditions which improve animal welfare also improve resilience to challenges through balancing pro- and anti-inflammatory non-neuronal processes. We speculate that non-neuronal biology has relevance to animal welfare beyond neuro-inflammation including facilitating positive affective states. We acknowledge the relevance of neuronal biology to animal welfare whilst proposing that non-neuronal biology provides additional and relevant insights to improve animals' lives.

Hippocampal overexpression of tissue-type plasminogen activator "tPA" attenuates social defeat-induced depression and ethanol related behavior in mice

Depression and anxiety disorders are often exacerbated by social stress, necessitating the exploration of molecular mechanisms underlying stress resilience. Tissue plasminogen activator (tPA), a serine protease with pleiotropic effects in the brain, plays a critical role in modulating neuroplasticity and stress responses. This study investigates the behavioral and molecular effects of tPA gain-of-function in a social stress paradigm in male C57BL/6 mice using lentiviral vectors. Behaviorally, hippocampal tPA gain-of-function mitigated depression-like responses in the novelty-suppressed feeding, sucrose splash, tail suspension, and forced swim tests following exposure to chronic social stress. Additionally, in a two-bottle choice drinking paradigm, tPA overexpression reduced social stress-induced ethanol intake and preference, suggesting a role in dampening maladaptive coping behaviors. However, analysis of tastants' intake and preference revealed no significant effects of tPA overexpression, indicating that it does not influence hedonic responses under stress conditions. Molecularly, tPA overexpression preserved hippocampal tPA mRNA expression and maintained levels of mature brain-derived neurotrophic factor in the hippocampus despite chronic stress exposure. These findings highlight the potential neuroprotective effects of tPA in maintaining hippocampal plasticity and mitigating stress-induced dysregulation of critical neurotrophic pathways. Collectively, this study underscores the potential of tPA as a therapeutic target for stress-induced mood and substance use disorders by modulating behavioral and neurobiological responses to chronic social stress.

Elucidating the Antidepressant-Like Effect of Tannic Acid in Mice: Modulation of Serotonergic System and Pro-Inflammatory Mediators

This study aimed to evaluate the therapeutic action of tannic acid (TA) in male Swiss mice by investigating: i) the involvement of the serotonergic system in the acute TA antidepressant-like action per se using pharmacological tools, and ii) the neuroprotective activity of TA in a lipopolysaccharide (LPS)-induced depressive-like behavior. For mechanistic investigation of the acute TA antidepressant-like action, mice received i.p. the serotoninergic receptor antagonists: WAY-100135 (5-HT1 A antagonist), ketanserin (5-HT2 A/2 C antagonist), or ondansetron (5-HT3 antagonist); 15 min later, TA or water was given by gavage. After 1 h, mice were subjected to a tail suspension test (TST). TA in different doses was tested in acute open field test (OFT), TST, and forced swimming test (FST). In the LPS protocol, animals were pretreated once daily with TA (60 or 120 mg/kg), fluoxetine (20 mg/kg) or vehicle for 7 days. On the 7th day, mice received a single injection of LPS (830 μg/kg, i.p.). After 24 h, OFT and TST were assessed. Behavioral data concerning the acute antidepressant-like effects of TA demonstrated that this tannin acts via 5-HT1 A and 5-HT2 A/2 C receptors. Besides, monoamine oxidase A (MAO-A) in vitro activity was determined in total brain; the polyphenol action was able to decrease enzyme activity. In the LPS-induced depression model, TA prevented the increase in LPS-induced immobility time in the TST, downregulated the expression of NF-κB and IL-1β, and modulated MAO-A activity in the cerebral cortex. In conclusion, TA exhibited neuroprotective and antidepressant-like activities in mice, positioning it as a promising candidate for depression therapeutics.

Qifuyin alleviates anxiety and depression in 3×Tg-AD mice by modulating neuroendocrine function

Background

Alzheimer's disease (AD) is frequently accompanied by behavioral and psychological symptoms of dementia (BPSD). Studies have shown that 3×Tg-AD mice, a classical animal model of AD, exhibit anxiety and depression-like behaviors characteristic of BPSD.

Objective

This study investigated the effects of Qifuyin on anxiety and depression-like behaviors in 3×Tg-AD mice.

Methods

The 20 male and female C57BL/6 mice at 10.3 months of age were used as the control group, while the 82 male and female 3×Tg-AD mice of the same age were divided into five groups. The control and model groups were gavaged with solvent, the positive medicine group received a combination of donepezil and memantine, and the Qifuyin (QFY) groups were divided into three doses: low, medium, and high. The effects of QFY on anxiety-like behaviors in mice were assessed using the open field test (OFT) and elevated plus maze (EPM) test, while depression-like behaviors were evaluated through the forced swim test (FST) and sucrose splash test (ST). Plasma levels of corticosterone (CORT), testosterone (T), and estradiol (E2) were measured using ELISA, while adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), corticotropin-releasing hormone (CRH), and gonadotropin-releasing hormone (GnRH) were quantified via radioimmunoassay. Differences in plasma hormone levels among groups were analyzed using principal component analysis (PCA). Pearson correlation analysis was conducted to explore the relationships between plasma hormones and behavioral phenotypes, and multiple linear regression was employed to identify the hormones most strongly correlated with anxiety and depression-like behaviors in mice following QFY treatment.

Results

In 3×Tg-AD mice, anxiety-like behaviors were characterized by reduced the duration, number of visits, and total distances in central area during the OFT. The EPM revealed reduced the duration and frequency in the open arms for both sexes. Depression-like behaviors were evident in the FST, with increased immobility, and in the ST, with prolonged grooming latency in both sexes and reduced grooming frequency in females. The treatment of QFY alleviated these behaviors. In males, In the model group, plasma ACTH, GnRH, and FSH levels were significantly decreased. In the QFY-treated group, plasma CRH levels were significantly reduced, while GnRH levels were significantly increased. In the model group of females, plasma ACTH levels were significantly elevated, while FSH and LH levels were markedly reduced. In the QFY-treated group, plasma CORT levels were significantly decreased, whereas FSH and LH levels were significantly increased. Multiple linear regression indicated QFY mainly mitigates anxiety and depression-like symptoms through modulating GnRH in males and T and ACTH in females.

Conclusions

The administration of QFY alleviates anxiety and depression in 3×Tg-AD mice by regulating the HPA, HPT and HPO axes.

Administration of chiglitazar reverses chronic stress-induced depressive-like symptoms in mice via activation of hippocampal PPARα and BDNF

Background

Developing non-monoamine based novel antidepressants is now popular and necessary. Peroxisome proliferator-activated receptor α (PPARα) has been demonstrated to play a role in the pathophysiology of depression, and several PPARα agonists including WY14643, fenofibrate, and gemfibrozil, have all been reported to possess antidepressant-like efficacy in rodents. Chiglitazar is a novel pan agonist of PPARs, and this study aims to investigate whether this agonist has beneficial effects against depression.

Methods

Chronic unpredictable mild stress (CUMS), chronic restraint stress (CRS), forced swim test (FST), tail suspension test (TST), sucrose preference test (SPT), western blotting, and adeno-associated virus (AAV)-mediated gene transfer were adopted together in the present study.

Results

It was found that repeated intraperitoneal (i.p.) injection of chiglitazar significantly reversed both CUMS-induced and CRS-induced depressive-like behaviors in mice in the FST, TST, and SPT. Chiglitazar treatment also fully reversed both CUMS-induced and CRS-induced downregulation in the expression of hippocampal PPARα and brain-derived neurotrophic factor (BDNF) signaling in mice. Furthermore, pharmacological blockade of hippocampal PPARα and BDNF signaling attenuated the antidepressant-like effects of chiglitazar in mice. Genetic knockdown of hippocampal PPARα and BDNF also abolished the antidepressant-like actions of chiglitazar in mice.

Conclusion

In summary, administration of chiglitazar reverses chronic stress-induced depressive-like symptoms in mice via activation of hippocampal PPARα and BDNF.

Pharmacological agents and injection stress, but not social isolation, alter cognitive judgement bias in the mouse touchscreen operant chamber

Cognitive judgement bias (CJB) refers to the interpretation of ambiguous stimuli in a negative (pessimistic) or positive (optimistic) way. Negative CJB is observed in depression and anxiety, conditions that burden affected individuals and their caregivers. Pre-clinical animal research is key to understanding CJB and developing therapies for affective and anxiety disorders, so a translationally relevant CJB test would be a useful addition to the existing pre-clinical rodent touchscreen test battery. Here, a CJB task in mouse touchscreen operant chambers was adapted and validated using pharmacological agents, bupropion and tetrabenazine, known to induce positive and negative CJB, respectively. Further, negative shifts in CJB were observed following an injection procedure (handling and intraperitoneal injection with a saline solution), demonstrating the sensitivity of the task. Interestingly, whereas social isolation has been linked to changes in affective state in humans, 8 weeks of single-housing in mice did not alter CJB but did induce anxiety-like behaviour in an open field. Collectively, these results present a validated task to assess CJB in mice, which will facilitate future explorations into the underlying neurobiology and potential treatment of affective and anxiety disorders.

GABAergic antidepressant effect of daidzin: in vivo approach with in silico receptor binding affinities

Daidzin (DZN: 7-(β-D-Glucopyranosyloxy)-4-hydroxyisoflavone) is a soy plant-derived isoflavone. It has diverse biological activities, including nephroprotective effects. To date, its anxiolytic, memory-enhancing, and antiepileptic properties have been discovered. However, its antidepressant activity has not yet been investigated.This study aimed to investigate DZN's antidepressant activity through animal and in silico studies. Male Swiss albino mice were randomly divided into nine groups consisting of control (vehicle), DZN 5, 10, and 20mg/kg, diazepam (GABAA agonist), flumazenil (GABAA antagonist), and a combination of DZN-10 with diazepam and/or flumazenil. Additionally, in silico studies were also performed to understand the possible molecular mechanisms behind this neurological activity. Findings suggest that DZN dose-dependently and significantly (p < 0.05) enhanced immobility time (IMT) in animals. DZN-10 also increased diazepam's effects significantly (p < 0.05), possibly by raising its IMT values. However, DZN significantly (p < 0.05) declined flumazenil's effect in their combination. In silico findings suggest that DZN has a strong binding affinity against GABAA receptor subtypes. We suppose DZN exerts its antidepressant effect, possibly by interacting with GABAA receptors. It exerts a synergistic effect with the GABA agonist drug diazepam. Further studies are required to determine the exact molecular mechanism behind this neurological activity.

Effects of tea polyphenols and tea polysaccharides on improving nonylphenol-induced depression-like behavior, monoamine neurotransmitter disorder, and neuronal pyroptosis

BACKGROUND

Exposure to nonylphenol (NP) has been linked to depressive-like behaviors, while tea consumption is associated with a reduced risk of depression. This study investigates and compares the effects of tea polyphenols (TPs) and tea polysaccharides (TPSs) in alleviating NP-induced depressive-like behaviors, focusing on neuronal apoptosis and disrupted monoamine neurotransmitter secretion.

METHODS

Thirty-two specific-pathogen-free male, Sprague-Dawley rats (age: 4 weeks) were randomly assigned to four groups: control (5 mL/kg corn oil), NP (40 mg/kg NP), NP+TPS (25 mg/kg TPS), and NP+TP (50 mg/kg TP) groups.

RESULTS

The NP+TP group exhibited a shorter latency period in the feeding test than the NP group. Both NP+TP and NP+TPS groups showed reduced immobility time in the tail suspension and forced swimming tests. NP accumulation in the midbrain and cortical tissues was lower in these two groups. Additionally, these groups showed an increased number of "pear-shaped" neurons and higher serum neurotransmitter levels. The NP+TP and NP+TPS groups also demonstrated increased expression of estrogen receptor β (ERβ), tryptophan hydroxylase (TPH1), tryptophan hydroxylase-2 (TPH2), 5-hydroxytryptamine (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA) at both protein and gene levels. These two groups also showed a progressive increase in neuron counts, a more organized arrangement, and reduced nuclear staining intensity compared with the NP group. Moreover, their IL-1β and IL-18 levels were lower, along with a reduction in Iba-1-positive microglia. The neuronal apoptosis rate, number of apoptotic cells, and expression of apoptosis-related inflammatory proteins (NLRP3, GSDMD, and Caspase-1) were also decreased in the NP+TP and NP+TPS groups.

CONCLUSION

TP and TPS mitigate NP-induced depressive-like behaviors by significantly reducing neuronal apoptosis, normalizing monoamine neurotransmitter secretion, and alleviating neuroinflammation. These findings highlight the potential of these tea components as neuroprotective agents against environmental endocrine disruptor-induced depression.

Improved recognition memory and reduced inflammation following β-caryophyllene treatment in the Wistar-Kyoto rodent model of treatment-resistant depression

Persistent low mood, anxiety and cognitive deficits are common symptoms of depression and highly efficacious treatments that address symptoms including cognitive dysfunction are still required. β-caryophyllene (BCP) is a terpene with anti-inflammatory and pro-cognitive properties; however, its efficacy on cognition in depression remains unclear. This study aimed to investigate acute and chronic BCP treatment effects on cognitive, depressive- and anxiety-like behaviours, and inflammation in male and female Wistar-Kyoto (WKY) rats, a rodent model of treatment-resistant depression. Rats were administered either BCP (50 mg/kg) or vehicle (control). Open field (OFT), social interaction, sucrose preference, novel object recognition (NOR) and elevated plus maze (EPM) tests were conducted after acute (1 h) and chronic (2 weeks) treatment. Peripheral plasma inflammatory cytokine levels were examined. BCP acutely increased locomotor activity in the OFT but did not improve social interaction, whereas chronic BCP prevented increased latency to first interaction in females (not males). BCP did not improve sucrose preference or prevent anxiety-like behaviours in the EPM. BCP significantly increased novel object discrimination in the NOR test in male and female WKY rats and reduced cytokine levels after chronic treatment. This study shows for the first time that chronic BCP treatment improved recognition memory and exerted anti-inflammatory properties in a rodent model of depressive-like behaviours. BCP did not significantly improve anxiety-like behaviours, social interaction or anhedonia in WKY rats of either sex. These findings demonstrate the pro-cognitive effects of BCP in a rodent model of treatment-resistant depression worthy of further investigation.

Does Measuring Social Attention Lead to Changes in Behavior? A Preliminary Investigation into the Implications of Attention Bias Trials on Behavior in Rhesus Macaques

A welfare assessment tool in development must satisfy several criteria before it is considered ready for general use. Some tools that meet many of these criteria have been criticized for their negative effect on welfare. We conducted a preliminary assessment of the impact of attention bias (AB) trials using threat-neutral conspecific face pairs followed by presumed neutral-positive filler stimuli on the behavior of 21 rhesus macaques (Macaca mulatta; 15 female). Behavioral observations were conducted following AB trials and repeated two weeks later when no AB trials had occurred (no trial: NT). The association between observation period and behavior was assessed using linear mixed-effects models in R. Trials did not impact any observed behavior except for fear, which was displayed by five monkeys over six trials (four NT). For this sample, there was a significant reduction in fear behavior following AB trials. We, therefore, found no evidence suggesting that AB trials negatively affect behaviour. AB protocols may be suitable for continued development for primate welfare assessment and we encourage researchers to include assessing test impact on welfare in their AB protocols.

Decreased gut microbiome-derived indole-3-propionic acid mediates the exacerbation of myocardial ischemia/reperfusion injury following depression via the brain-gut-heart axis

Despite the increasing recognition of the interplay between depression and cardiovascular disease (CVD), the precise mechanisms by which depression contributes to the pathogenesis of cardiovascular disease remain inadequately understood. The involvement of gut microbiota and their metabolites to health and disease susceptibility has been gaining increasing attention. In this study, it was found that depression exacerbated cardiac injury, impaired cardiac function (EF%: P < 0.01; FS%: P < 0.05), hindered long-term survival (P < 0.01), and intensified adverse cardiac remodeling (WGA: P < 0.01; MASSON: P < 0.0001) after myocardial ischemia/reperfusion (MI/R) in mice. Then we found that mice receiving microbiota transplants from chronic social defeat stress (CSDS) mice exhibited worse cardiac function (EF%: P < 0.01; FS%: P < 0.01) than those receiving microbiota transplants from non-CSDS mice after MI/R injury. Moreover, impaired tryptophan metabolism due to alterations in gut microbiota composition and structure was observed in the CSDS mice. Mechanistically, we analyzed the metabolomics of fecal and serum samples from CSDS mice and identified indole-3-propionic acid (IPA) as a protective agent for cardiomyocytes against ferroptosis after MI/R via NRF2/System xc-/GPX4 axis, played a role in mediating the detrimental influence of depression on MI/R. Our findings provide new insights into the role of the gut microbiota and IPA in depression and CVD, forming the basis of intervention strategies aimed at mitigating the deterioration of cardiac function following MI/R in patients experiencing depression.

Serum KNG and FVIII may serve as potential biomarkers for depression

BACKGROUND

The global burden of major depressive disorder (MDD) is rising, with current diagnostic methods hindered by significant subjectivity and low inter-rater reliability. Several studies have implied underlying link between coagulation-related proteins, such as kininogen (KNG) and coagulation factor VIII (FVIII), and depressive symptoms, offering new insights into the exploration of depression biomarkers. This study aims to elucidate the roles of KNG and FVIII in depression, potentially providing a foundational basis for biomarker research in this field.

METHODS

A three-part experiment was conducted: (1) we measured serum levels of KNG and FVIII in the chronic unpredictable mild stress (CUMS) model; (2) KNG adeno-associated-virus overexpression (KNG-AAV-OE) model was constructed to further investigate the roles of KNG and FVIII. Meanwhile, quantity PCR, western blotting and immunofluorescence staining detected the KNG-FVIII pathway. (3) Peripheral blood samples were gathered from healthy control (HC, N = 21), as well as first-episode drug-naive patients with MDD (FEDN-MDD, N = 21), to further confirm the association between KNG, FVIII and depression.

RESULTS

Firstly, serum KNG and FVIII levels were significantly elevated in the CUMS model. Then, the rats exhibited pronounced depressive-like behaviors in the KNG-AAV-OE model, with corresponding increases in serum KNG and FVIII. Lastly, clinical data showed increased KNG and FVIII levels in FEDN-MDD compared to HC. Furthermore, KNG and FVIII levels exhibited a strong positive correlation with the scores of the 24-item Hamilton Depression Scale and the 14-item Hamilton Anxiety Scale.

CONCLUSION

To sum up, this study highlights critical roles of serum KNG and FVIII in depression and the KNG-AAV-OE may lead the augment of FVIII in serum. Consequently, our research may offer new evidence and foundation for depression biomarkers research in the future.

The impact and mechanisms of YL-IPA08, a potent ligand for the translocator protein (18 kDa) on protection against LPS-induced depression and cognitive dysfunction in rodents

Translocator protein (18 kDa) (TSPO) has been implicated in the development of depression and cognitive dysfunction. This study aimed to investigate the anti-depression/anti-anxiety and cognitive enhancing impacts and potential mechanisms of TSPO ligand YL-IPA08 in lipopolysaccharide (LPS)-induced inflammatory model. The effects of YL-IPA08 in LPS induced mice were identified by behavioral tests, and the target of YL-IPA08 was validated using the TSPO antagonist PK11195. The microglia in PFC were analyzed by immunofluorescence, and the inflammatory cytokines (IL-6, IL-1β and TNF-α) and anti-inflammatory factors (IL-4, IL-10, TGF-β1) in PFC was detected by ELISA or WB. Effect of TGF-β1 inhibitor Repsox on the actions of YL-IPA08 in LPS-treated mice was further verified. We found that YL-IPA08 administration ameliorated LPS-induced depression/anxiety-like behaviors and cognitive impairment, which were blocked by PK11195. YL-IPA08 reversed the increased number and inflammatory morphological changes of microglia in PFC of LPS mice by targeting TSPO. YL-IPA08 reversed the increased inflammatory cytokines (IL-6, IL-1β and TNF-α) and decreased anti-inflammatory factors (IL-4, IL-10) in the PFC of LPS mice by TSPO activation. In addition, YL-IPA08 elevated the suppressed levels of TGF-β1 and smad3 (member of TGF-β1 pathway) in PFC of LPS mice by TSPO activation. TGF-β1 inhibitor Repsox blocked the anti-depression/anxiety and cognition enhancing effects of YL-IPA08 in LPS mice. Our data implicated that central inflammation regulation and TSPO-TGF-β1/Smad pathway activation contributed to the anti-depressant/anxiety and cognitive promoting impacts of YL-IPA08.

Tilianin obtained from Agastache mexicana inhibits monoamine oxidase and modifies depressive behavior in rats

BACKGROUND

Agastache mexicana is used in traditional medicine to treat anxiety, insomnia, pain, among others. In a previous study, the methanolic extract exerted anxiolytic and sedative effects, as observed behaviorally, associated with one of its major components, tilianin.

OBJECTIVE

To assess the effect produced by the extracts and tilianin obtained from Agastache mexicana on depressive-induced behavior model and on the activity of monoamine oxidases (MAOs).

METHODS

The depression experimental model consisted of the forced swimming test in rats. MAOs activity was evaluated in cortex and hippocampus from the tilianin and Agastache extracts treated rats using specific inhibitors for each isoform. The quantification of monoamines was carried out using an High Performance Liquid Chromatography method.

RESULTS

An increase in the swimming time was observed in rodents treated with doses of 16 (226.6 ± 5.5 seconds) and 50 mg/kg (237.8 ± 5.7 seconds) of tilianin, methanolic (260.4 ± 3 seconds), and hydroalcoholic extracts (249.6 ± 2.6 seconds) at 100 mg/kg. MAOs activity was significantly decreased in brain tissue from animals treated with 16 and 50 mg/kg of tilianin, methanolic, and hydroalcoholic extracts at 100 mg/kg.

CONCLUSIONS

The tilianin effect on monoamine oxidases inhibition is confirmed, suggesting its potential use in the treatment of certain neurological disorders.

Pituitary adenylate cyclase-activating polypeptide (PACAP)overexpression in the paraventricular nucleus of the thalamus alters motivated and affective behavior in female rats

BACKGROUND

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been found to be involved in a wide range of motivated and affective behaviors. While the PACAP-38 isoform is more densely expressed than PACAP-27 in most of the brain, PACAP-27 is more highly expressed in the rodent paraventricular nucleus of the thalamus (PVT), where females also have greater expression than males. Notably, the role of PACAP-27 expression in cells of the PVT has not been explored.

METHODS

Adult, female Long-Evans rats were injected in the PVT with an adeno-associated virus (AAV) to increase expression of PACAP or a control AAV. They were then investigated for subsequent ethanol drinking and preference; sucrose drinking and preference; or locomotor activity in a novel chamber, behavior in a light-dark box, behavior in a novelty suppression of feeding test, locomotor activity in a familiar activity chamber, and behavior in a forced swim test.

RESULTS

Injection with the PACAP AAV resulted in a specific increase in levels of PACAP-27. Rats injected with the PACAP AAV demonstrated reduced drinking and preference for ethanol under the intermittent-access procedure compared to those injected with the control AAV. In contrast, rats injected with the PACAP AAV showed no significant difference in drinking or preference for sucrose, or in any affective behavior tested, except that they spent less time swimming in the forced swim test.

CONCLUSIONS

In light of the low overall level of expression of PACAP-27 in the brain, the ability of PACAP-27 in the PVT to control ethanol drinking, with minimal effects on other motivated or affective behaviors, supports the idea that compounds related to PACAP-27 should be investigated as potential therapeutics for the treatment of alcohol use disorder.

Maternal Resveratrol Supplementation Attenuates Prenatal Stress Impacts on Anxiety- and Depressive-like Behaviors by Regulating Bdnf Transcripts Expression in the Brains of Adult Male Offspring Rats

BACKGROUND

Prenatal stress has been reported to harm the physiological and biochemical functions of the brain of the offspring, potentially resulting in anxiety- and depression-like behaviors later in life. Trans-Resveratrol (RESV) is known for its anti-inflammatory, anxiolytic, and antidepressant properties. However, whether administering RESV during pregnancy can counteract the anxiety- and depression-like behaviors induced by maternal stress is unknown.

OBJECTIVE

This study aimed to assess the protective potential of RESV against molecular and behavioral changes induced by prenatal stress.

METHODS

During pregnancy, the dams received 50 mg/kg BW/day of RESV orally. They underwent a movement restriction for forty-five minutes, three times a day, in addition to being exposed to artificial light 24 h before delivery. The male offspring were left undisturbed until early adulthood, at which point they underwent behavioral assessments, including the open field test, elevated plus maze, and forced swim test. Subsequently, they were euthanized, and the hippocampus and prefrontal cortex were extracted for RT-qPCR analysis to measure Bdnf mRNA expression.

RESULTS

By weaning, results showed that prenatal stress led to reduced weight gain and, in adulthood, increased anxiety- and depression-like behaviors and changes in Bdnf mRNA expression. However, these effects were attenuated by maternal RESV supplementation.

CONCLUSIONS

The findings suggest that RESV can prevent anxiety- and depression-like behaviors induced by prenatal stress by modulating Bdnf mRNA expression.

Escitalopram reverses anxiety-like and despair behavior and affects endocannabinoid-related genes expression in the brain of adolescent male rats subjected to early life stress

Due to the increasing prevalence of depressive and anxiety disorders in youth, a growing interest in the endocannabinoid system (ECS) as a potential alternative target point for treatment arised. This study aimed to investigate whether chronic administration of escitalopram reverses behavioral changes induced by maternal separation in male adolescent Wistar rats and explore the corresponding neurochemical changes in the ECS. The pups were separated from their dams for 360 min daily from postnatal day (PND) 2 until PND 15. Later, male rats were administered escitalopram (10 mg/kg i.p.) during their adolescent period (PND 35 - PND 55). Behavioral assessments were conducted in late adolescence (PND 54 - PND 57) in one group, and brain structures were dissected for biochemical analysis in the subsequent group of rats on PND 56. Expression of genes encoding: CB1 receptor, enzyme that catalyzes synthesis (NAPE-PLD) and degradation (FAAH) of anandamide (a full agonist of CB1 receptor) was evaluated using qRT-PCR. The corresponding protein levels were estimated via Western blot analysis. Our study revealed that maternal separation induced anxiety and despair-like behavior in adolescent rats. Escitalopram reversed anxiety-like behavior and attenuated signs of despair behavior. The escitalopram administration has been followed by a decrease in the studied genes expression in the amygdala, the hypothalamus, and the hippocampus, what might suggest that the endocannabinoid system is involved in the mechanism of its action in adolescents. However Western blot analysis did not indicate significant alterations in the protein levels, so more detailed studies are needed to verify this hypothesis.

Dopaminergic receptors involvement in the antidepressant-like effect of N-(3-((3-(trifluoromethyl)phenyl)selanyl)prop-2-yn-1-yl) benzamide in mice

Major Depressive Disorder (MDD) directly impacts the lives of countless individuals worldwide, yet its causes remain incompletely understood. However, it is recognized that a deficiency in monoamines, including dopamine, may contribute to this disorder. N-(3-((3-(trifluoromethyl)phenyl)selenyl)prop-2-yn-1-yl) (CF3SePB) is an organoselenium compound that presented antidepressant-like effect in mice related to modulation of serotonergic, but not noradrenergic system. To expand the knowledge about CF3SePB mechanisms of action, this study aimed to evaluate the involvement of dopaminergic system in its antidepressant-like effect. Male Swiss mice were pre-treated with the haloperidol (0.05 mg/kg, i.p., a non-selective D2 receptor antagonist), SCH 23390 (0.01 mg/kg, s.c., a D1 receptor antagonist), and sulpiride (50 mg/kg, i.p., a D2 receptor antagonist) 15 min before CF3SePB (50 mg/kg, i.g.), and after 30 min of CF3SePB administration the forced swimming test (FST) was performed. CF3SePB presented an anti-immobility effect in the FST, demonstrated by increase in the latency to first episode of immobility and reduction of total immobility of mice, and the pre-treatment of mice with haloperidol, SCH 23390 and sulpiride prevented these effects, showing that the antidepressant-like effect of CF3SePB is related to the modulation of the dopaminergic system, specifically the D1 and D2 receptors. In addition, in silico pharmacokinetic profiling of CF3SePB predicted its low likelihood of inducing adverse effects and potential to cross the blood-brain barrier. These results expand the understanding of CF3SePB mechanisms for its antidepressant-like effect, reinforcing the potential of this organonoselenium compound for developing new antidepressants.

Chronic treatment of mixture of two iridoids proportional to prescriptional dose of Yueju improves hippocampal PACAP-related neuroinflammation and neuroplasticity signaling in the LPS-induced depression model

ETHNOPHARMACOLOGICAL RELEVANCE

Geniposide (GP) and shanzhiside methyl ester (SM) are the two important bioactive compounds in the classical traditional Chinese herbal medicine Yueju Pill, which is currently used as an over-the-counter (OTC) medicine in China. Yueju has been demonstrated with antidepressant-like effects with the prescriptional dose. As GP and SM both have antidepressant potential, the synergism of them could be crucial to the function of Yueju.

OBJECTIVES

The neuropeptide pituitary adenylyl cyclase-activating polypeptide (PACAP) has been implicated in the onset of antidepressant-like response. Here we investigated the synergism of the chronic treatment with GP and SM, at proportional doses to Yueju, on antidepressant-like effects, and underlying mechanism of PACAP-related signaling in a neuroinflammation-based depression model.

MATERIALS AND METHODS

Depression-related behaviors were tested in the lipopolysaccharide (LPS)-induced depression model. The molecular signaling of neuroinflammation and neuroplasticity was investigated using Western blot analysis, immunofluorescence and pharmacological inhibition of mTOR signaling.

RESULTS

Chronic treatment of GP and SM (GS) at the dose which is proportional to the prescriptional dose of Yueju synergistically elicited antidepressant-like effects. Chronic treatment of the GS or the conventional antidepressant fluoxetine (FLX) showed antidepressant-like effects in LPS-injected mice. In vitro analysis indicated the synergism of GS on PACAP expression. In the hippocampus of LPS-injected mice, both GS and FLX enhanced PACAP expression, downregulated the inflammatory signaling of Iba-1/NF-кB/IL-1β and NLRP3, and upregulated the neuroplasticity signaling of mTOR-BDNF/PSD95. Additionally, both treatments reduced microglia activation indicated by Iba-1 immunofluorescent staining. Rapamycin, an mTOR inhibitor, blunted the antidepressant-like effects and the upregulation of BDNF expression induced by chronic GS.

CONCLUSION

The antidepressant-like effects elicited by chronic fluoxetine or by synergistic doses of GS were involved in the upregulation of hippocampal PACAP levels, in association with ameliorated neuroinflammation and neuroplasticity signaling in LPS-injected mice. GS synergism may play a key part in the antidepressant-like effects of the prescriptional dose of Yueju.

PACAP regulates neuroendocrine and behavioral stress responses via CRF-containing neurons of the rat hypothalamic paraventricular nucleus

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide widely distributed in the brain including the hypothalamic paraventricular nucleus (PVN) implying a regulatory role in stress function. Recent evidence indicates that one of the main targets of PACAP within the PVN are corticotropin-releasing factor (CRF) neurons, which are key regulators of the hypothalamic-pituitary-adrenal (HPA) axis. However, the neural correlates that mediate PACAP effects on stress function are not fully understood. In the present study, we characterized the neuronal mechanism by which PACAP regulates neuroendocrine and behavioral stress responses in rats. We found that intracerebroventricular administration of PACAP increased the swim stress-induced c-Fos expression in distinct brain areas of the stress and anxiety circuitry including the parvocellular part of the PVN and changed behavioral stress coping during forced swimming to a more passive coping style (i.e., indicated by increased floating and reduced struggling behavior). Subsequently, PACAP administration directly into the PVN mimicked these behavioral effects and potentiated the plasma ACTH response to forced swim stress suggesting an excitatory role of PACAP on HPA stress axis reactivity. In addition, immunohistochemical analysis revealed a considerable portion of stress-activated CRF neurons in the medial parvocellular part of the PVN that co-localized PAC1 receptors suggesting that PACAP-induced effects on stress function are likely mediated directly by activation of CRF neurons in the PVN. Thus, these findings suggest that the PVN may represent one of the key areas where PACAP regulates the neuroendocrine and behavioral stress response.

Sugemule-7 alleviates oxidative stress, neuroinflammation, and cell death, promoting synaptic plasticity recovery in mice with postpartum depression

Postpartum depression (PPD) profoundly impacts the mental and physical health of women globally and is an incurable psychological disorder. Traditional pharmacological treatments often have strong side effects and may adversely affect infant health through breastfeeding, underscoring the critical need for natural and gentle treatment strategies. Sugemule-7, a traditional Chinese medicine comprising multiple natural plant ingredients, represents a potentially safer and more effective alternative. To investigate its preventive effects on PPD, we established an animal model and administered the drug Sugemule-7. Our study demonstrated that varying doses of Sugemule-7 effectively alleviated depressive and anxiety-like behaviors in PPD mice, as assessed through a battery of tests, including the open field test, tail suspension test, sucrose preference test, forced swim test, novelty-suppressed feeding test, and elevated plus maze test. Furthermore, Sugemule-7 significantly improved oxidative stress levels in the serum, prefrontal cortex, and hippocampus of PPD-induced mice while also suppressing inflammatory responses and abnormal neuronal death in these brain regions. Transcriptomic sequencing of hippocampal and prefrontal cortex tissues supported our findings, revealing that differential gene expression is primarily involved in regulating synaptic plasticity. Overall, our study confirms the efficacy of Sugemule-7 in treating PPD at different concentrations, potentially alleviating depressive behaviors by enhancing synaptic plasticity, mitigating oxidative stress, reducing inflammation, and protecting neurons.

Characterizing the therapeutical use of ketamine for adolescent rats of both sexes: Antidepressant-like efficacy and safety profile

While ketamine was approved for treatment-resistant depression in adult patients, its efficacy and safety profile for adolescence still requires further characterization. In this context, prior preclinical studies have shown that sub-anesthetic doses of ketamine during adolescence exert antidepressant-like effects in rodents in a dose- and sex-dependent manner. However, additional studies evaluating the short- and long-term safety profile of ketamine at the doses necessary to induce antidepressant-like effects are needed. The present study aimed at validating the dose- and sex-dependent antidepressant-like responses of adolescent ketamine while evaluated its safety profile in rats of both sexes. To do so, ketamine was administered (1, 5 or 10 mg/kg; vs. vehicle; 1 vs. 7 days) during adolescence in naïve or early-life stressed (i.e., maternal deprivation) rats of both sexes. Antidepressant-like responses were scored in the forced-swim or novelty-suppressed feeding tests, and safety was evaluated by measuring psychomotor- and reinforcing-like responses induced by ketamine. In addition, long-term safety was assessed in adulthood through cognitive performance, or addiction liability (induced by ketamine re-exposure in rats treated with ketamine in adolescence). The main results validated the potential use of ketamine as an antidepressant for adolescence, but at different dose ranges for each sex. However, some safety concerns emerged in adolescent female rats (i.e., signs of sensitization at the dose used as antidepressant) or adult male rats (i.e., addiction liability when re-exposed to ketamine in adulthood), suggesting that caution and further research are needed before ketamine could be safely used in the clinic as an antidepressant for adolescents.

Myelin Transcription Factor 1 (MyT1) overexpression mitigates social isolation-induced behavioral deficits: Insights into cortical synaptotagmin 1 regulation and antidepressant-like effects

Social isolation (SI) stress is increasingly recognized as a concern, associated with detrimental effects on mood and emotional well-being. Myelin Transcription Factor 1 (MyT1) is known for its pivotal role in nervous system development and mood regulation. This study delves into the potential of MyT1 to mitigate SI-induced behavioral abnormalities in mice. Utilizing a chronic SI model involving neonatal and post-weaning SI, male and female mice were subjected to lentiviral overexpression of MyT1 specifically in the medial prefrontal cortex (mPFC). A battery of behavioral assessments, including novelty-suppressed feeding, sucrose preference, sucrose splash, tape grooming, tail suspension, and forced swim tests, revealed notable antidepressant-like effects in both sexes upon MyT1 overexpression. Enhanced MyT1 expression corresponded with increased feeding initiation, sucrose preference, and self-grooming, alongside decreased immobility time. Importantly, the upregulation of MyT1 was accompanied by a significant reduction in cortical synaptotagmin 1 (Syt1) level. These findings underscore the involvement of MyT1 in mitigating SI-induced depression-like behavior. Moreover, the observed alterations in behavior are closely associated with changes in cortical Syt1 expression, suggesting its potential role as a target for unraveling the molecular mechanisms underlying mood disorders induced by SI. This study sheds light on the intricate interplay between MyT1 and cortical function in modulating responses to SI, paving the way for potential therapeutic interventions targeting these pathways.

Genetic ablation of the isoform γ of PI3K decreases antidepressant efficacy of ketamine in male mice

About one-third of major depressive disorder (MDD) patients demonstrate unresponsiveness to classic antidepressants, and even the clinical efficacy of fast-acting drugs such as ketamine varies significantly among patients with treatment-resistant depression. Nevertheless, the lack of suitable animal models that mimic a possible ketamine-resistant phenotype challenges the understanding of resistance to drug treatment. In this study, we showed that PI3Kγ knock-out (KO) mice do not respond to classical doses of ketamine and classical antidepressants. PI3Kγ KO mice were unresponsive to both the rapid and sustained antidepressant-like effects of a single dose of ketamine in the forced swimming test. Additionally, they were unresponsive to the antidepressant-like effects induced by the tricyclic antidepressant imipramine and the selective serotonin reuptake inhibitor fluoxetine. However, acute pharmacological inhibition of PI3Kγ did not block the antidepressant-like effect of ketamine, showing that a chronic deficiency of the PI3Kγ-mediated pathway is necessary for the effects of classic doses of ketamine and antidepressants. Therefore, we propose that PI3Kγ participates in the antidepressant activity and is likely implicated in the neurobiology and phenotype observed in patients with MDD who demonstrate treatment resistance.

Alpha-synuclein Fibrils Inhibit Activation of the BDNF/ERK Signaling Loop in the mPFC to Induce Parkinson's Disease-like Alterations with Depression

Depression (Dep) is one of the most common concomitant symptoms of Parkinson's disease (PD), but there is a lack of detailed pathologic evidence for the occurrence of PD-Dep. Currently, the management of symptoms from both conditions using conventional pharmacological interventions remains a formidable task. In this study, we found impaired activation of extracellular signal-related kinase (ERK), reduced levels of transcription and translation, and decreased expression of brain-derived neurotrophic factor (BDNF) in the medial prefrontal cortex (mPFC) of PD-Dep rats. We demonstrated that the abnormal phosphorylation of α-synuclein (pS129) induced tropomyosin-related kinase receptor type B (TrkB) retention at the neuronal cell membrane, leading to BDNF/TrkB signaling dysfunction. We chose SEW2871 as an ameliorator to upregulate ERK phosphorylation. The results showed that PD-Dep rats exhibited improvement in behavioral manifestations of PD and depression. In addition, a reduction in pS129 was accompanied by a restoration of the function of the BDNF/ERK signaling loop in the mPFC of PD-Dep rats.

Noradrenergic Projections from the Locus Coeruleus to the Medial Prefrontal Cortex Enhances Stress Coping Behavior in Mice Following Long-Term Intermittent Fasting

Intermittent fasting has been shown to alleviate stress, anxiety, and depressive symptoms. Although noradrenaline, also known as norepinephrine (NE), is implicated in stress regulation, the dynamics of NE release and the associated neural pathways during stress coping behaviors in fasting mice remain poorly understood. In this study, we employed the forced swimming test (FST) to evaluate the effects of intermittent fasting on stress coping behavior in mice. Our results demonstrate that mice subjected to long-term intermittent fasting exhibited significantly more active coping behaviors in the FST compared to control mice. In contrast, acute fasting did not produce similar effects. Using the fluorescent GRAB-NE sensor to measure NE release with sub-second temporal resolution during the FST, we found that intermittent fasting modulates the locus coeruleus-medial prefrontal cortex (LC-mPFC) pathway, which underlies these behavioral adaptations. Moreover, chemogenetic activation of LC-mPFC projections strongly promoted active coping in the FST. These findings suggest that enhanced LC-mPFC activity mediates the increased active coping behavior observed in fasting mice. This study provides new insights into the neural mechanisms through which intermittent fasting may ameliorate depressive-like behaviors, offering potential therapeutic targets for stress-related disorders.

Genipin 1-O-β-D-gentiobioside ameliorates CUMS-induced prefrontal cortex neuron neuronal apoptosis by modulating HIPK2 SUMOylation

BACKGROUND

Depression is a common mental illness with more than 280 million sufferers worldwide. Inflammation, particularly the c-Jun amino-terminal kinase (JNK) pathway, contributes to depression development and neuronal apoptosis. Gardenia is a herb with therapeutic effects on depression that has been shown to inhibit neuronal apoptosis. However, one of the components in gardenia, Genipin 1-O-β-D-gentiobioside(GG), has been less studied for its mechanism on depression. Thus, in the current study, we investigate how Genipin 1-O-β-D-gentiobioside improves depression and elucidate its possible mechanism of action.

METHODS

In this investigation, we utilize a chronic unpredictable mild stress (CUMS) mouse model and corticosterone-induced primary cortical neurons to examine the role of GG in ameliorating depressive symptoms and neuronal apoptosis. TUNEL staining and flow cytometry assessed the effects of GG on neuronal apoptosis. Western Blot analyses and immunofluorescence assays apoptosis-related proteins in the prefrontal cortex and primary neurons. The site of action of GG in regulating homeodomain interacting protein kinase 2 (HIPK2) SUMOylation was further explored in primary neurons. We constructed siRNA-SUMO1 vectors to transfect primary neuronal cells with intracellular SUMO1 knockdown. Proximity ligation assay (PLA) experiments were performed on primary neurons according to the instructions of the assay kit to observe the physical relationship between HIPK2 and SUMO1. We predicted the HIPK2 SUMOylation modification site by an online database and constructed vectors to target and site-directed mutagenesis, then to transfected primary neuronal cells.

RESULTS

The results showed that GG effectively alleviated depressive-like behaviours, down-regulated apoptosis-related proteins (p-JNK, Bax, Cleaved-Caspase-3), and inhibited neuronal apoptosis in CUMS-induced depressed mice and corticosterone-induced primary cortical neurons. We reveal a complex mechanism underlying the link between GG, SUMOylation of HIPK2, and complex pathways of neuronal apoptosis regulation. K326 and K1189 are the key SUMOylation sites regulated by GG in intricate interactions of apoptosis-related proteins.

CONCLUSION

Our study demonstrated that GG exerts antidepressant-like actions through neuroprotective effects by inhibiting the apoptosis of prefrontal cortex neurons, revealing the mechanism of GG inhibition of JNK phosphorylation by enhancing HIPK2 SUMOylation.

Perinatal bisphenol A exposure has an age- and dose-dependent association with thyroid allostasis adaptive response, as well as anxiogenic-depressive-like and asocial behaviors in juvenile and adult male rats

Thyroid hormones are essential for brain development, and a shortage throughout the fetal and postnatal periods can result in mood disorders. Perinatal exposure to bisphenol A (BPA) affects thyroid activity and dependent processes indirectly during pregnancy or early postnatal life. This is particularly important because it may cause changes in tissue ontogeny, increasing the risk of developing disorders later in life. The study aimed to investigate the consequences of thyroid hormone deficiency on anxiety, social, and depressive behaviors, as well as disruption in thyroid peroxidase (TPO) gene expression, which influences the NF-κB/Nrf-2/HO-1/iNOS signaling pathway, leading to oxidative stress, inflammation, and DNA fragmentation in perinatal BPA exposure (PND18), and whether these effects can be observed in juvenile (PND60) and adult (PND95) male offspring rats. BPA increased anxiety-like behavior while decreasing sucrose preference and sociability on a choice task between novel conspecific male rats and enhanced immobility on the forced swim test. Perinatal exposure to BPA causes thyroid insult by overproducing ROS, increasing iNOS, and NF-κB levels-these effects, in turn, down-regulate Nrf-2/HO-1 signaling, resulting in DNA fragmentation within thyroid tissues. Furthermore, perinatal BPA exposure for 60 and 95 days resulted in a significant fold decrease in TPO mRNA levels in the thyroid tissues, with an insignificant fold rise in TPO expression levels in BPA 50-60. In conclusion, the present study found that perinatal BPA exposure induced thyroid allostasis-adaptive response by inhibiting the NF-κB/Nrf-2/HO-1/iNOS signaling pathway and altering the transcriptional expression of TPO, where TSH reinforced a possible association with TPO activity, disrupting thyroid hormone synthesis in juvenile rats and gradual deterioration reaching the adult stage.

Paroxetine Loaded Nanostructured Lipid Carriers Based In-situ Gel for Brain Delivery via Nasal Route for Enhanced Anti-Depressant Effect: In Vitro Prospect and In Vivo Efficacy

This study focused on developing a thermosensitive gel with nanostructured lipid carriers (NLCs) loaded with paroxetine (PAR) to enhance the treatment and management of depression via nasal administration. Micro emulsion technique was utilized for the PAR-NLCs preparation. The acetyl alcohol and oleic acid were used in the ratio of 76:24. In the NLCs Tween 40, Span40 and Myrj 52 were used as a surfactant. The NLCs were then added into Poloxamer mixture to get thermosensitive NLCs based gel. Characterization, in vitro and in vivo studies were performed to check the efficiency of formulation in drug delivery. The entrapment efficiency of optimized PAR-NLCs was about 90%. The particle size, zeta potential and PDI were 155 ± 1.4 nm, -25.9 ± 0.5 mV, and 0.12 ± 0.01 respectively. The optimized gel showed a gelling temperature of 31.50 ± 0.50°C and a gelling time of 1 ± 0.12 s with a pH of 6, suitable for nasal administration. The in vitro release assay of PAR-NLC-gel showed a cumulative release of about 59% in the first 6 h after comparison with PAR-NLCs which showed almost 100%release. In vivo studies included forced swim test and tail suspension tests showed significant potential for treating depression when compared to PAR-NLCs. PAR-NLCs and NLCs based gel enhanced the tissue architecture and suppressed the expression of TNF-α in brain cortex from histological and immunohistochemical analysis. PAR- NLCs gel-based delivery system can prove to be an effective delivery system for brain targeting through nose for the better management of depression.

Chronic stress in adulthood results in microvascular dysfunction and subsequent depressive-like behavior

Depression is a prevalent mental disorder characterized by unknown pathogenesis and challenging treatment. Recent meta-analyses reveal an association between cardiovascular risk factors and an elevated risk of depression. Despite this, the precise role of vascular injury in depression development remains unclear. In this investigation, we assess vascular system function in three established animal models of depression- chronic unpredictable mild stress (CUMS), chronic social defeat stress (CSDS) and maternal separation (MS)-utilizing ultrasonography and laser Doppler measurement. All three model animals exhibit anhedonia and despair-like behavior. However, significant microvascular dysfunction (not macrovascular) is observed in animals subjected to CUMS and CSDS models, while such dysfunction is absent in the MS model. Statistical analysis further indicates that microcirculation dysfunction is not only associated with depression-like behavior but is also intricately involved in the development of depression in the CUMS and CSDS models. Furthermore, our study has proved for the first time that endothelial nitric oxide synthase-deficient (eNOS+/-) mice, which is a classic model of vascular endothelial injury, showed depression-like behavior which occurred two months later than microvascular dysfunction. Notably, the mitigation of microvascular dysfunction successfully reverses depression-like behavior in eNOS+/- mice by enhancing nitric oxide production. In conclusion, this study unveils the pivotal role of microvascular dysfunction in the onset of depression induced by chronic stress in adulthood and proposes that modulating microvascular function may serve as a potential intervention in the treatment of depression.

Neurobehavioral Impairments Predict Specific Cerebral Damage in Rat Model of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a severe form of stroke that can cause unpredictable and diffuse cerebral damage, which is difficult to detect until it becomes irreversible. Therefore, there is a need for a reliable method to identify dysfunctional regions and initiate treatment before permanent damage occurs. Neurobehavioral assessments have been suggested as a possible tool to detect and approximately localize dysfunctional cerebral regions. In this study, we hypothesized that a neurobehavioral assessment battery could be a sensitive and specific method for detecting damage in discrete cerebral regions following SAH. To test this hypothesis, a behavioral battery was employed at multiple time points after SAH induced via an endovascular perforation, and brain damage was confirmed via postmortem histopathological analysis. Our results demonstrate that impairment of sensorimotor function accurately predict damage in the cerebral cortex (AUC 0.905; sensitivity 81.8%; specificity 90.9%) and striatum (AUC 0.913; sensitivity 90.1%; specificity 100%), while impaired novel object recognition is a more accurate indicator of damage to the hippocampus (AUC 0.902; sensitivity 74.1%; specificity 83.3%) than impaired reference memory (AUC 0.746; sensitivity 72.2%; specificity 58.0%). Tests for anxiety-like and depression-like behaviors predict damage to the amygdala (AUC 0.900; sensitivity 77.0%; specificity 81.7%) and thalamus (AUC 0.963; sensitivity 86.3%; specificity 87.8%), respectively. This study suggests that recurring behavioral testing can accurately predict damage in specific brain regions, which could be developed into a clinical battery for early detection of SAH damage in humans, potentially improving early treatment and outcomes.

Antidepressant effects of selective adenosine receptor antagonists targeting the A1 and A2A receptors administered jointly with NMDA receptor ligands: behavioral, biochemical and molecular investigations in mice

BACKGROUND

The objective of the study was to ascertain the antidepressant potential of the co-administration of NMDA receptor ligands and selective adenosine A1 and A2A receptor antagonists.

METHODS

The forced swim test (FST) and spontaneous locomotor activity test were carried out in adult male naïve mice. Before the behavioral testing, animals received DPCPX (a selective adenosine A1 receptor antagonist, 1 mg/kg) or istradefylline (a selective adenosine A2A receptor antagonist, 0.5 mg/kg) in combination with L-701,324 (a potent NMDA receptor antagonist, 1 mg/kg), D-cycloserine (a partial agonist at the glycine recognition site of NMDA receptor, 2.5 mg/kg), CGP 37849 (a competitive NMDA receptor antagonist, 0.3 mg/kg) or MK-801 (a non-competitive NMDA receptor antagonist, 0.05 mg/kg). Additionally, serum BDNF level and the mRNA level of the Adora1, Comt, and Slc6a15 genes in the murine prefrontal cortex were determined.

RESULTS

The obtained results showed that DPCPX and istradefylline administered jointly with NMDA receptor ligands (except for DPCPX + D-cycloserine combination) produced an antidepressant effect in the FST in mice without enhancement in spontaneous motility of animals. An elevation in BDNF concentration was noted in the D-cycloserine-treated group. Adora1 expression increased with L-701,324, DPCPX + D-cycloserine, and DPCPX + CGP 37849, while D-cycloserine, CGP 37849, and MK-801 led to a decrease. Comt mRNA levels dropped with DPCPX + L-701,324, istradefylline + L-701,324/CGP 37849 but increased with D-cycloserine, MK-801, CGP 37849 and DPCPX + MK-801/ CGP 37849. Slc6a15 levels were reduced by D-cycloserine, DPCPX + L-701,324 but rose with DPCPX + CGP 37849/MK-801 and istradefylline + D-cycloserine/MK-801/CGP 37849.

CONCLUSION

Our study suggests that selective antagonists of adenosine receptors may enhance the antidepressant efficacy of NMDA receptor ligands highlighting a potential synergistic interaction between the adenosinergic and glutamatergic systems. Wherein, A2A receptor antagonists are seen as more promising candidates in this context. Given the intricate nature of changes in BDNF levels and the expression of Adora1, Comt, and Slc6a15 seen after drug combinations exerting antidepressant properties, further research and integrative approaches are crucial understand better the mechanisms underlying their antidepressant action.

The role of 5-HTergic neuron activation in the rapid antidepressant-like effects of hypidone hydrochloride (YL-0919) in mice

Introduction

Major depressive disorder (MDD) is a common and disabling mental health condition; the currently available treatments for MDD are insufficient to meet clinical needs due to their limited efficacy and slow onset of action. Hypidone hydrochloride (YL-0919) is a sigma-1 receptor agonist and a novel fast-acting antidepressant that is currently under clinical development.

Methods

To further understand the fast-acting antidepressant activity of YL-0919, this study focused on the role of 5-HTergic neurons in the dorsal raphe nucleus (DRN) in mice. Using fiber photometry to assess neural activity in vivo and two behavioral assays (tail suspension test and forced swimming test) to evaluate antidepressant-like activity.

Results

It was found that 3 or 7 days of YL-0919 treatment significantly activated serotonin (5-HT) neurons in the DRN and had significant antidepressant-like effects on mouse behaviors. Chemogenetic inhibition of 5-HTergic neurons in the DRN significantly blocked the antidepressant-like effect of YL-0919. In addition, YL-0919 treatment significantly increased the 5-HT levels in the prefrontal cortex (PFC). These changes were drastically different from those of the selective serotonin reuptake inhibitor (SSRI) fluoxetine, which suggested that the antidepressant-like effects of the two compounds were mechanistically different.

Conclusion

Together, these results reveal a novel role of 5-HTergic neurons in the DRN in mediating the fast-acting antidepressant-like effects of YL-0919, revealing that these neurons are potential novel targets for the development of fast-acting antidepressants for the clinical management of MDD.

Linalool-rich rosewood essential oil (Aniba rosaeodora Ducke) mitigates emotional and neurochemical impairments induced by ethanol binge-like exposure during adolescence in female rats

Linalool-rich Rosewood oil (Aniba rosaeodora Ducke) is a natural compound widely used in perfumery industry. Evidence suggests that linalool exerts antidepressant and anxiolytic effects. Conversely, ethanol binge drinking (i.e., intermittent and episodic consumption) during adolescence elicits neurobehavioral alterations associated with brain damage. Here, we investigated whether linalool-rich Rosewood oil administration can improve the emotional and molecular impairments associated with ethanol binge-like exposure during adolescence in female rats. Rosewood oil was obtained by hydrodistillation and posteriorly analyzed. Adolescent female Wistar rats received four-cycles of ethanol binge-like pattern (3 g/kg/day, 3 days on/4 days off) and daily Rosewood oil (35 mg/kg, intranasally) for 28 days. Twenty-four hours after treatments, it was evaluated the impact of ethanol exposure and Rosewood oil treatment on the putative emotional impairments assessed on the splash and forced swimming tests, as well as the levels of brain-derived neurotrophic factor (BDNF), S100B, oxidative parameters, and inflammatory cytokines in prefrontal cortex and hippocampus. Results indicated that Rosewood oil intranasal administration mitigated emotional impairments induced by ethanol exposure accompanied by a marked increase in BDNF, S100B, glutathione (GSH), and antioxidant activity equivalent to Trolox (TEAC) levels in brain areas. Rosewood oil treatment also prevented the ethanol-induced increase of interleukin-1β, interleukin-6, tumor necrosis factor α (TNF-α), and neurofilament light chain (NFL) levels. These findings provide the first evidence that Rosewood oil intranasal administration exerts protective effects against emotional and molecular impairments associated with adolescent ethanol binge-like exposure, possibly due to linalool actions triggering neurotrophic factors, rebalancing antioxidant status, and attenuating proinflammatory process.

Corticosterone disrupts spatial working memory during retention testing when highly taxed, which positively correlates with depressive-like behavior in middle-aged, ovariectomized female rats

Major Depressive Disorder affects 8.4 % of the U.S. population, particularly women during perimenopause. This study implemented a chronic corticosterone manipulation (CORT, a major rodent stress hormone) using middle-aged, ovariectomized female rats to investigate depressive-like behavior, anxiety-like symptoms, and cognitive ability. CORT (400 μg/ml, in drinking water) was administered for four weeks before behavioral testing began and continued throughout all behavioral assessments. Compared to vehicle-treated rats, CORT significantly intensified depressive-like behaviors: CORT decreased sucrose preference, enhanced immobility on the forced swim test, and decreased sociability on a choice task between a novel conspecific female rat and an inanimate object. Moreover, CORT enhanced anxiety-like behavior on a marble bury task by reducing time investigating tabasco-topped marbles. No effects were observed on novelty suppressed feeding or the elevated plus maze. For spatial working memory using an 8-arm radial arm maze, CORT did not alter acquisition but disrupted performance during retention. CORT enhanced the errors committed during the highest working memory load following a delay and during the last trial requiring the most items to remember; this cognitive metric positively correlated with a composite depressive-like score to reveal that as depressive-like symptoms increased, cognitive performance worsened. This protocol allowed for the inclusion of multiple behavioral assessments without stopping the CORT treatment needed to produce a MDD phenotype and to assess a battery of behaviors. Moreover, that when middle-age was targeted, chronic CORT produced a depressive-like phenotype in ovariectomized females, who also comorbidly expressed aspects of anxiety and cognitive dysfunction.

Effects of sleep deprivation on anxiety-depressive-like behavior and neuroinflammation

BACKGROUND

Depression is defined by a persistent low mood and disruptions in sleep patterns, with the WHO forecasting that major depression will rank as the third most prevalent contributor to the global burden of disease by the year 2030. Sleep deprivation serves as a stressor that triggers inflammation within the central nervous system, a process known as neuroinflammation. This inflammatory response plays a crucial role in the development of depression by upregulating the expression of inflammatory mediators that contribute to symptoms such as anxiety, hopelessness, and loss of pleasure.

METHODS

In this study, sleep deprivation was utilized as a method to induce anxiety and depressive-like behaviors in mice. The behavioral changes in the mice were then evaluated using the EZM, EPM, TST, FST, and SPT. H&E staining and Nissl staining was used to detect morphological changes in the medial prefrontal cortical (mPFC) regions. Elisa to assess serum CORT levels. Detection of mRNA levels and protein expression of clock genes, high mobility genome box-1 (Hmgb1), silent message regulator 6 (Sirt6), and pro-inflammatory factors by RT-qPCR, Western blotting, and immunofluorescence techniques.

RESULTS

Sleep deprivation resulted in decreased exploration of unfamiliar territory, increased time spent in a state of despair, and lower sucrose water intake in mice. Additionally, sleep deprivation led to increased secretion of serum CORT and upregulation of clock genes, IL6, IL1β, TNFα, Cox-2, iNOS, Sirt6, and Hmgb1. Sleep.

CONCLUSIONS

Sleep deprivation induces anxiety-depressive-like behaviors and neuroinflammation in the brain. Transcription of clock genes and activation of the Sirt6/Hmgb1 pathway may contribute to inflammatory responses in the mPFC.

Repetitive transcranial magnetic stimulation (rTMS) for depressive-like symptoms in rodent animal models

Repetitive transcranial magnetic stimulation (rTMS) emerged as a non-invasive brain stimulation technique in the treatment of psychiatric disorders. Both preclinical and clinical studies as well as systematic reviews provide a heterogeneous picture, particularly concerning the stimulation protocols used in rTMS. Here, we present a review of rTMS effects in rodent models of depressive-like symptoms with the aim to identify the most relevant factors that lead to an increased therapeutic success. The influence of different factors, such as the stimulation parameters (stimulus frequency and intensity, duration of stimulation, shape and positioning of the coil), symptom severity and individual characteristics (age, species and genetic background of the rodents), on the therapeutic success are discussed. Accumulating evidence indicates that rTMS ameliorates a multitude of depressive-like symptoms in rodent models, most effectively at high stimulation frequencies (≥5 Hz) especially in adult rodents with a pronounced pathological phenotype. The therapeutic success of rTMS might be increased in the future by considering these factors and using more standardized stimulation protocols.

Environmental enrichment enhances the antidepressant effect of ketamine and ameliorates spatial memory deficits in adult rats

Ketamine is a rapid-acting antidepressant associated with various cognitive side effects. To mitigate these side effects while enhancing efficacy, it can be co-administered with other antidepressants. In our study, we adopted a similar strategy by combining ketamine with environmental enrichment, a potent sensory-motor paradigm, in adult male Wistar rats. We divided the animals into four groups based on a combination of housing conditions and ketamine versus vehicle injections. The groups included those housed in standard cages or an enriched environment for 50 days, which encompassed a 13-day-long behavioral testing period. Each group received either two doses of ketamine (20 mg/kg, IP) or saline as a vehicle. We tested the animals in the novel object recognition test (NORT), forced swim test (FST), open field test (OFT), elevated plus maze (EPM), and Morris water maze (MWM), which was followed by ex vivo c-Fos immunohistochemistry. We observed that combining environmental enrichment with ketamine led to a synergistic antidepressant effect. Environmental enrichment also ameliorated the spatial memory deficits caused by ketamine in the MWM. There was enhanced neuronal activity in the habenula of the enrichment only group following the probe trial of the MWM. In contrast, no differential activity was observed in enriched animals that received ketamine injections. The present study showed how environmental enrichment can enhance the antidepressant properties of ketamine while reducing some of its side effects, highlighting the potential of combining pharmacological and sensory-motor manipulations in the treatment of mood disorders.

Multisensory Fusion Training and 7, 8-Dihydroxyflavone Improve Amyloid-β-Induced Cognitive Impairment, Anxiety, and Depression-Like Behavior in Mice Through Multiple Mechanisms

Background

There is growing interest in the role of physical activity in patients with of Alzheimer's disease (AD), particularly regarding its impact of cognitive function, gut microbiota, metabolites, and neurotrophic factors.

Objective

To investigate the impact of multisensory fusion training (MSFT) combined with 7, 8-dihydroxyflavone (DHF) on the behavioral characteristics, protein expression, microbiome, and serum metabolome using the AD model in mice induced with amyloid-β (Aβ).

Methods

We assessed cognitive ability, anxiety-like and depression-like behaviors in Aβ mice using behavioral measures. Western blotting was employed to detect the expression of relevant proteins. The 16S rRNA gene sequencing and metabolomics were used to analyze changes in the intestinal microbial composition and serum metabolic profile, respectively, of Aβ mice.

Results

The behavioral outcomes indicated that a 4-week intervention combining DHF and MSFT yielded remarkable improvements in cognitive function and reduced anxiety and depression-like behaviors in Aβ mice. In the hippocampus of Aβ mice, the combined intervention increased the levels of BDNF, VGF, PSD-95, Nrf2, p-GSK3β and p-CREB proteins. Analyses of sequence and metabolomic data revealed that Bacteroides and Ruminococcaceae were remarkably more abundant following the combined intervention, influencing the expression of specific metabolites directly linked to the maintenance of neuronal and neurobehavioral functions. These metabolites play a crucial role in vital processes, such as amino acid metabolism, lipid metabolism, and neurotransmitter metabolism in mice.

Conclusion

Our study highlighted that MSFT combined with DHF improves cognitive impairment, anxiety, and depression-like behavior in Aβ mice through multiple mechanisms, and further validated the correlation between the gut microbiome and serum metabolome. These findings open up a promising avenue for future investigations into potential treatment strategies for AD.

Antidepressant-like effects of hyperoside on chronic stress-induced depressive-like behaviors in mice: Gut microbiota and short-chain fatty acids

BACKGROUND

The antidepressant effect of hyperoside (HYP), which is the main component of Hypericum perforatum, is not established. This study aimed to determine the effects of HYP on depression.

METHODS

The antidepressant-like effect of HYP was studied in mice induced by chronic restraint stress (CRS). The effects of HYP on behavior, inflammation, neurotransmitters, gut microbiota, and short-chain fatty acids (SCFAs) were studied in CRS mice.

RESULTS

HYP improved depressive-like behavior in mice induced by CRS. Nissl staining analysis showed that HYP improved neuronal damage in CRS mice. Western blot (WB) analysis showed that HYP increased the expression levels of BDNF and PSD95 in the hippocampus of CRS mice. The results of ELISA showed that HYP down-regulated the expression levels of IL-6, IL-1β, TNF-α, and CORT in the hippocampus, blood, and intestinal tissues of mice and up-regulated the expression levels of 5-HT and BDNF. Hematoxylin and eosin (HE) staining results indicate that HYP can improve the intestinal histopathological injury of CRS mice. The results of 16S rRNA demonstrated that HYP attenuated the dysbiosis of the gut microbiota of depressed mice, along with altering the concentration of SCFAs.

LIMITATIONS

In the present study, direct evidence that HYP improves depressive behaviors via gut microbiota and SCFAs is lacking, and only female mice were evaluated, which limits the understanding of the effects of HYP on both sexes.

CONCLUSIONS

HYP can improve CRS-induced depressive-like behaviors in mice, which is associated with regulating the gut microbiota and SCFAs concentration.

Adolescent male rats show altered gut microbiota composition associated with depressive-like behavior after chronic unpredictable mild stress: Differences from adult rats

Accumulating evidence reveals the metabolism and neurotransmitter systems are different in major depressive disorder (MDD) between adolescent and adult patients; however, much is still unknown from the gut microbiome perspective. To minimize confounding factors such as geographical location, ethnicity, diet, and drugs, we investigated the gut microbial differences between adolescent and adult male Sprague-Dawley rats. We exposed the adolescent rats to chronic unpredictable mild stress (CUMS) for 3 weeks and assessed their behavior using the sucrose preference test (SPT), open field test (OFT), and forced swimming test (FST). We collected and sequenced fecal samples after the behavioral tests and compared them with our previous data on adult rats. Both adolescent and adult CUMS rats exhibited reduced sucrose preference in SPT, reduced total distance in OFT, and increased immobility time in FST. Moreover, compared to their respective controls, the adolescent CUMS rats had distinct amplicon sequence variants (ASVs) mainly in the Muribaculaceae family, Bacteroidetes phylum, while the adult CUMS rats had those in the Lachnospiraceae family, Firmicutes phylum. In the adolescent group, the Muribaculaceae negatively correlated with FST and positively correlated with SPT and OFT. In the adult group, the different genera in the Lachnospiraceae showed opposite correlations with FST. Furthermore, the adolescent CUMS rats showed disrupted microbial functions, such as "Xenobiotics biodegradation and metabolism" and "Immune system", while the adult CUMS rats did not. These results confirmed the gut microbiota differences between adolescent and adult rats after CUMS modeling and provided new insight into the age-related influence on depression models.

Relationships between trace elements and cognitive and depressive behaviors in sprague dawley and wistar albino rats

Introduction: This study investigates the effects of social isolation on mental health and cognitive functions in Sprague Dawley (SD) and Wistar Albino (WIS) rat strains, prompted by the heightened awareness of such impacts amid the COVID-19 pandemic. This study aims to explore the impact of social isolation on memory, learning, and behavioral changes in middle-aged SD and WIS rat strains and to investigate cortical trace element levels, seeking potential correlations between these levels and the observed behavioral responses to social isolation. Methods: Four groups of 14-month-old male rats were established: control and isolated SDs and WIS rats (CONT-SD, ISO-SD, CONT-WIS, ISO-WIS). Morris Water Maze and Porsolt Forced Swimming tests were conducted for behavioral assessment. Following behavioral tests, rats were sacrificed under general anesthesia, and cortices were isolated for analysis of macro and trace element levels (ICP/MS). Results: In behavioral tests, CONT-SD rats exhibited superior performance in the Morris Water Maze test compared to CONT-WIS rats, but displayed increased depressive behaviors following social isolation, as evident in the Porsolt Forced Swimming test (p < 0.05). ISO-SD rats showed elevated levels of Co and Cu, along with reduced levels of Cs and As, compared to ISO-WIS rats. Moreover, isolation resulted in decreased Cu and Mo levels but increased Rb levels in WIS rats. Comparison of trace element levels in naïve groups from different strains revealed lower Zn levels in the WIS group compared to SD rats. Discussion: The findings suggest that the SD strain learns faster, but is more susceptible to depression after isolation compared to the WIS strain. Increased Co and Cu levels in ISO-SD align with previous findings, indicating potential trace element involvement in stress responses. Understanding these mechanisms could pave the way for preventive treatment strategies or therapeutic targets against the consequences of stressors, contributing to research and measures promoting a balanced diet to mitigate neurobehavioral abnormalities associated with social isolation in the future.

Rodent tests of depression and anxiety: Construct validity and translational relevance

Behavioral testing constitutes the primary method to measure the emotional states of nonhuman animals in preclinical research. Emerging as the characteristic tool of the behaviorist school of psychology, behavioral testing of animals, particularly rodents, is employed to understand the complex cognitive and affective symptoms of neuropsychiatric disorders. Following the symptom-based diagnosis model of the DSM, rodent models and tests of depression and anxiety focus on behavioral patterns that resemble the superficial symptoms of these disorders. While these practices provided researchers with a platform to screen novel antidepressant and anxiolytic drug candidates, their construct validity-involving relevant underlying mechanisms-has been questioned. In this review, we present the laboratory procedures used to assess depressive- and anxiety-like behaviors in rats and mice. These include constructs that rely on stress-triggered responses, such as behavioral despair, and those that emerge with nonaversive training, such as cognitive bias. We describe the specific behavioral tests that are used to assess these constructs and discuss the criticisms on their theoretical background. We review specific concerns about the construct validity and translational relevance of individual behavioral tests, outline the limitations of the traditional, symptom-based interpretation, and introduce novel, ethologically relevant frameworks that emphasize simple behavioral patterns. Finally, we explore behavioral monitoring and morphological analysis methods that can be integrated into behavioral testing and discuss how they can enhance the construct validity of these tests.

Cajanus cajan (L) Millsp seeds extract prevents rotenone-induced motor- and non-motor features of Parkinson disease in mice: Insight into mechanisms of neuroprotection

ETHNOPHARMACOLOGICAL RELEVANCE

Cajanus cajan (L) Millsp (Fabaceae) seed decoction is used by traditional healers in Nigeria as nerve tonic, hence, could be beneficial in the treatment of Parkinson's disease (PD), a progressive and debilitating neurodegenerative disease that imposes great burden on the healthcare system globally.

AIM OF THE STUDY

This study aimed at investigating the neuroprotective effect of ethanol seed extract of Cajanus cajan (CC) in the treatment of rotenone-induced motor symptoms and non-motor symptoms associated with PD.

MATERIALS AND METHODS

To assess the protective action of CC on rotenone-induced motor- and non-motor symptoms of PD, mice were first pretreated with CC (50, 100 or 200 mg/kg, p.o.) an hour before oral administration of rotenone (1 mg/kg, p.o, 0.5% in carboxyl-methylcellulose) for 28 consecutive days and weekly behavioural tests including motor assessment (open field test (OFT), rotarod, pole and cylinder tests) and non-motor assessment (novel object recognition (NOR), Y-maze test (YM), forced swim and tail suspension, gastric emptying and intestinal fluid accumulation tests) were carried out. The animals were euthanized on day 28 followed by the collection of brain for assessment of oxidative stress, inflammatory markers and immunohistochemical analysis of the striatum (STR) and substantia nigra (SN). Phytochemicals earlier isolated from CC were docked with protein targets linked with PD pathology such as; catechol-O-methyltransferase (COMT), tyrosine hydroxylase (TH) and Leucine rich receptor kinase (LRRK).

RESULTS

this study showed that CC significantly reduced rotenone-induced spontaneous motor impairment in OFT, pole, cylinder and rotarod tests in mice as well as significant improvement in non-motor features (significant reversal of rotenone-induced deficits discrimination index and spontaneous alternation behaviour in NORT and YM test, respectively, reduction in immobility time in forced swim/tail suspension test, gastrointestinal disturbance in intestinal transit time in mice. Moreso, rotenone-induced neurodegeneration, oxidative stress and neuroinflammation were significantly attenuated by CC administration. In addition, docking analysis showed significant binding affinity of CC phytochemicals with COMT, TH and LRRK2 receptors.

CONCLUSION

Cajanus cajan seeds extract prevented both motor and non-motor features of Parkinson disease in mice through its antioxidant and anti-inflammatory effects. Hence, could be a potential phytotherapeutic adjunct in the management of Parkinson disease.

Assessment of the anxiolytic, antidepressant, and antioxidant potential of Parquetina nigrescens (Afzel.) Bullock in Wistar rats

ETHNOPHARMACOLOGICAL RELEVANCE

The recent growing concerns about the multisystemic nature of mental health conditions in the global population are facilitating a new paradigm involving alternative natural, nutritional, and complementary therapies. Herbal remedies despite accounts in literature of their ethnobotanical as alternative remedies for diverse ailments, remain underexplored for psychiatric disorders like anxiety, depression, and insomnia.

AIM OF THE STUDY

Hence, the anxiolytic, antidepressant, and antioxidant properties of a hydro-ethanolic leaf extract of Parquetina nigrescens (PN) in male Wistar rats were investigated.

MATERIALS AND METHODS

The sedative effect was evaluated using the Diazepam sleeping time test while anxiety was induced with a single intraperitoneal injection of 20 mg/kg pentylenetetrazol (PTZ). This was after pre-treatment with 100, 150, and 250 mg/kg of PN or the standard drugs (1 mg/kg diazepam and 30 mg/kg imipramine) for 14 consecutive days. Behavioral tests (Open Field test, Elevated Plus-Maze test, and Forced Swim test) were performed on days 1 and 14, to evaluate the antidepressant and anxiolytic activities of PN. Oxidative stress and neurochemical markers were determined in the brain homogenates of the animals.

RESULTS

The duration of sleep was significantly (p < 0.001) increased in the PN-administered group compared to the control. The behavioral models showed that PN exhibited antidepressant and anxiolytic properties in PTZ-induced animals. Significant reductions were observed in GSH level and SOD activity while MDA, nitrite, and GPx levels were significantly increased in PTZ-induced rats. However, treatment with PN significantly improved brain antioxidant status by ameliorating the PTZ-induced oxidative stress. Dopamine, cortisol, and acetylcholine esterase activity levels were significantly (p < 0.05) elevated while serotonin and brain-derived neurotrophic factors were reduced in PTZ-induced rats compared with the control.

CONCLUSION

The PN demonstrated neurotransmitter modulatory ability by ameliorating the PTZ-induced neurochemical dysfunction. Findings from this study showed that PN exhibited sedative, antidepressant, and anxiolytic activities in rats.

Litter reduction-induced obesity promotes early depressive-like behavior and elevated prefrontal cortex GFAP expression in male offspring

AIMS

The present study was developed to investigate how litter reduction-induced obesity promotes early depressive-related behaviors in rodent offspring.

MAIN METHODS

We employed a standardized litter size reduction protocol, dividing litters into groups: normal litters (NL), consisting of six males and six females pups and small litters (SL), comprising two males and two females pups. Maternal behavior was monitored during the initial week of lactation. Subsequently, we assessed the pups for weight gain, locomotor activity, social play behavior, and performance in forced swimming test. We further evaluated the weights of retroperitoneal and perigonadal fat tissues, along with the expression of glial fibrillary acidic pprotein (GFAP) in the hippocampus and prefrontal cortex of the offspring.

KEY FINDINGS

Our results indicated that litter size reduction led to an increased the maternal behavior. In contrast, offspring from the SL group displayed greater weight gain and increased, retroperitoneal and perigonadal fat. Both male and female rodents in the SL group exhibited decreased social play behavior, and male offspring spent more time immobile during the forced swimming test, suggesting a depressive-like phenotype. Notably, we observed an increase in the GFAP expression in the prefrontal cortex of male rodents, with a trend toward increased expression in the hippocampus.

SIGNIFICANCE

Obesity may facilitate the development of early depressive-like behaviors, potentially associated with elevated GFAP expression in the prefrontal cortex.

A rate-limiting step in antidepressants onset: Excitation of glutamatergic pyramidal neurons in medial prefrontal cortex of rodents

Although clinical antidepressants have varied mechanisms of action, it remains unclear whether they may have a common mechanism underlying their antidepressant effects. We investigated the behavioral effects of five different antidepressants (differing in target, chemical structure, and rate of onset) and their effects on the firing activities of glutamatergic pyramidal neurons in the medial prefrontal cortex (mPFC) using the forced swimming test (FST) and electrophysiological techniques (in vivo). We employed fiber photometry recordings to validate the effects of antidepressants on the firing activity of pyramidal neurons. Additionally, multichannel electrophysiological recordings were conducted in mice exhibiting depressive-like behaviors induced by chronic restraint stress (CRS) to investigate whether antidepressants exert similar effects on pyramidal neurons in depressed mice. Behavioral tests were utilized for evaluating the depression model. We found that fluoxetine, duloxetine, vilazodone, YL-0919, and ketamine all increase the firing activities of glutamatergic pyramidal neurons (at least 57%) while exerting their initial onset of antidepressant effects. Fiber photometry revealed an increase in the calcium activity of pyramidal neurons in the mPFC at the onset of antidepressant effects. Furthermore, a significant reduction was observed in the firing activity of pyramidal neurons in the mPFC of CRS-exposed mice, which was reversed by antidepressants. Taken together, our findings suggested that five pharmacologically distinct classes of antidepressants share the common ability to increase the firing activity of pyramidal neurons, just different time, which might be a rate-limiting step in antidepressants onset. The study contributes to the body of knowledge of the mechanisms underlying antidepressant effects and paves the way for developing rapid-acting antidepressants.

Intravenous Reelin rescues despair-like behavior, Reelin cells in the dentate sub-granular zone, and spleen atrophy in the cyclic corticosterone model of recurring depressive episodes

Novel antidepressants are predominantly evaluated preclinically in rodent models of chronic stress in which animals experience a single prolonged exposure to chronic stress prior to treatment. Rodent models of a single episode of chronic stress translate poorly to human depressive disorders, which are commonly marked by recurring depressive episodes. Intravenous administration of Reelin has previously been shown to resolve immobility in the forced swim test of rats exposed to a single prolonged exposure to chronic stress. To determine whether Reelin has antidepressant-like properties in a model of recurring depressive episodes, Long-Evans rats (N = 57) were exposed to multiple cycles of chronic stress and stress-free periods before the administration of a single injection of Reelin during the final cycle of chronic stress. The animals then performed in the forced swim test and open field test before the post-mortem evaluation of Reelin cell counts in the sub-granular zone of the dentate gyrus to determine the impact of treatment on hippocampal Reelin levels and spleen white pulp to evaluate the role of Reelin treatment in peripheral inflammation. The results show a single Reelin injection reversed elevated levels of immobility in the forced swim test in both male and female subjects exposed to the cyclic chronic stress model of recurring depressive episodes. Treatment with Reelin also restored Reelin-positive cell counts in the dentate gyrus sub-granular zone and reversed atrophy of spleen white pulp. The results shown here indicate that treatment with Reelin could effectively resolve alterations in forced swim test behavior caused by the cyclic corticosterone model of recurring depressive episodes and that Reelin homeostasis is important for regulating stress-related inflammation. Future preclinical antidepressant research should incorporate models of multiple depressive episodes to improve the translation of preclinical rodent research to human depressive disorders.

Effects of housing conditions on stress, depressive like behavior and sensory-motor performances of C57BL/6 mice

BACKGROUND

The effects of housing conditions on animal physiology, behavior or stress are still debated. The aim of this study was to investigate the effects of three different housing systems, individually ventilated cages (IVC), classical small cages with floor surface area of 500 cm2 (CC500) and classical large cages with floor surface area of 800 cm2 (CC800) on body weight, sensory-motor performances, depression-like behavior, plasma corticosterone and brain oxidative stress parameters in C57BL/6 mice. The mice housed in one of the cages from birth to 6 months of age. Hang wire and adhesive removal tests were performed to evaluate somatosensory and motor performances. The extent of depression was determined by the forced swim test. Blood corticosterone levels were measured. In addition, brain malondialdehyde (MDA), total antioxidant status (TAS) and total oxidant status (TOS) levels were analyzed.

RESULTS

The depression-like behavior of the groups was similar. Although there were no significant differences in hang wire test among groups, CC500 group required longer durations in adhesive removal test. The body weight and plasma corticosterone levels of CC800 group were significantly higher than other groups. The oxidative stress parameters were highest in CC500 cage.

CONCLUSIONS

Our study showed that the least stressful housing condition was IVC cage systems. Interestingly, the number of mice in the classical cages had a significant effect on stress levels and sensory-motor performance.

Early life stress enhances the susceptibility to depression and interferes with neuroplasticity in the hippocampus of adolescent mice via regulating miR-34c-5p/SYT1 axis

Early life events are major risk factors for the onset of depression and have long-term effects on the neurobiological changes and behavioral development of rodents. However, little is known about the specific mechanisms of early life adversity in the susceptibility to subsequent stress exposure in adolescence. This study characterized the effect of maternal separation (MS), an animal model of early life adversity, on the behavioral responses to restraint stress in mice during adolescence and investigated the molecular mechanism underlying behavioral vulnerability to chronic stress induced by MS. Our results showed that MS exposure could further reinforce the depressive vulnerability to restraint stress in adolescent mice. In addition, miR-34c-5p expression was obviously up-regulated in the hippocampi of MS mice at postnatal day (P) 14 and P42. Further, synaptotagmin-1 (SYT1) was deemed as a target gene candidate of miR-34c-5p on the basis of dual luciferase assay. It was found that the downregulation of miR-34c-5p expression in the hippocampi of MS mice could ameliorate dysfunction of synaptic plasticity by targeting molecule SYT1, effects which were accompanied by alleviation of depressive and anxious behaviors in these mice. The results demonstrated that the miR-34c-5p/SYT1 pathway was involved in the susceptibility to depression induced by MS via regulating neuroplasticity in the hippocampi of mice.