Similar tests of anxiety-like behavior yield different results: comparison of the open field and free exploratory rodent procedures

Short chain fatty acids mediates complement C1q pathway alleviation of perioperative neurocognitive disorders

Perioperative neurocognitive disorders (PND) is one of the most common postoperative complications, which can lead to a harmful impact on self-dependence, longer hospital stays, increased medical costs, morbidity, and mortality amongst older adults. Microglia can modulate synapse elimination involved in the complement component protein 1q (C1q) pathway to induce cognitive dysfunction, which is significantly improved by short chain fatty acids (SCFAs) treatment. Here we investigate the effects of SCFAs treatment on PND via mediating C1q complement pathway. High-throughput sequencing of 16S rDNA from fecal samples of male SD rats was applied to assess the changes in gut microbiota. Fecal microbiota transplantation (FMT) was performed to investigate whether gut microbiota from PND rats could alter cognitive impairment. The blood from the rat tail vein was collected to measure the SCFAs concentrations. Hippocampal and brain tissue samples were obtained to perform Western blots, Golgi and immunofluorescence staining. Primary microglia treated with SCFAs or Histone deacetylase inhibitor were cultured to measure microglial activation states and the expression of acetylated histone. The 16S rDNA sequencing results showed that PND rats had the significant changes in the species diversity of the gut microbiota and the metabolite of specifc species. Gut microbiota from PND rats could alter spatial learning and memory, and meanwhile, the changed SCFAs concentrations in plasma were involved. The synapse elimination in PND rats was strikingly reversed by SCFAs treatment involved in modulation complement C1q via suppressing neuroinflammation. This suggests that a link between gut microbiota dysbiosis and cognitive function impairment is involved in synapse elimination via mediating complement C1q pathway. SCFAs treatment can alleviate PND, the mechanisms of which may be associated with regulating complement C1q pathway.

Sucrose binge-eating and increased anxiety-like behavior in Sprague-Dawley rats exposed to repeated LPS administration followed by chronic mild unpredictable stress

Exposure to persistent mild stress is a frequently encountered chronic challenge in a rapidly evolving society. Depending on various factors including sex, the response to stressors varies and is closely linked to the phenomenon of resilience. Depression and anxiety can be considered maladaptive responses to such stress. In this rat study, we investigated the sex-dependent effects of low-grade systemic inflammation during 1 week in combination with chronic unpredictable mild stress during the following 4 weeks on anxiety-like behavior and episodic feeding behavior. Increased anxiety-like behavior and increased sucrose intake were identified in stressed compared to control animals regardless of sex. Interestingly, two nearly equally distributed subpopulations were found in the stressed groups within each sex at the end of the 5-week protocol of combined stress exposure: the resistant and the susceptible, which were characterized by unchanged and increased sucrose intake, respectively. This difference in susceptibility to protracted combined mild stress and ensuing response to a sucrose eating binge demonstrates the complexity of the underlying regulatory mechanisms associated with emotional hyperreactivity. This model carries the potential for further investigation of the molecular basis of resilience and susceptibility to combined stressors and for testing treatments with potential preventive or therapeutic effects.

Caffeine intake during lactation has a sex-dependent effect on the hippocampal excitatory/inhibitory balance and pups' behavior

During early life, disruptions in glutamatergic and GABAergic synapse development in the hippocampus may contribute to several neurodevelopmental disorders, including cognitive deficits and psychiatric disorders. Caffeine is the most consumed psychoactive drug in the world, and previous work from our group has shown that caffeine disrupts visual system connections at different stages of development. This work aimed to investigate the effects of caffeine consumption during lactation in the glutamatergic and GABAergic synaptic markers in the hippocampus and on the behavior of rat offspring. We found that maternal caffeine intake significantly reduced GluN1 subunits of the NMDA receptor, increased the GluA1/GluA2 ratio of AMPA receptor in the dorsal hippocampus, and decreased GAD content in female pups' ventral hippocampus. On the other hand, an increase in GluN1/GluN2b subunits, a decrease in GAD content in the dorsal hippocampus, and a reduction of the GluA1 content in the ventral hippocampus were observed in male pups. In addition, changes in the behavior of the offspring submitted to indirect caffeine consumption were also sex-dependent, with females developing anxiety-like behavior and males showing anxiety-like behavior and hyper-locomotion. These results highlight that maternal caffeine intake promotes changes in the hippocampal excitatory and inhibitory balance and offspring behavior in a sex-dependent manner, suggesting that the population should be alerted to reduced caffeine consumption by breastfeeding mothers.

Social environment enrichment alleviates anxiety-like behavior in mice: Involvement of the dopamine system

Rearing environment plays a vital role in maintaining physical and mental health of both animals and humans. Plenty of studies have proved that physical environment enrichment in adolescence has protective effects on emotion, social behavior, learning and memory deficits. However, the following effects of social environment enrichment in adolescence remain largely elusive. Using the paradigm of companion rotation (CR), the present study found that social environment enrichment reduced anxiety-like behaviors of early adult male C57BL/6J mice. CR group also showed significantly higher expression of tyrosine hydroxylase in the ventral tegmental area and dopamine 1 receptor mRNA in the nucleus accumbens shell than control group. Taken together, these findings demonstrate that CR from adolescence to early adulthood can suppress the level of anxiety and upregulate dopaminergic neuron activity in early adult male C57BL/6J mice.

Recent advances in anxiety disorders: Focus on animal models and pathological mechanisms

Anxiety disorders have become one of the most severe psychiatric disorders, and the incidence is increasing every year. They impose an extraordinary personal and socioeconomic burden. Anxiety disorders are influenced by multiple complex and interacting genetic, psychological, social, and environmental factors, which contribute to disruption or imbalance in homeostasis and eventually cause pathologic anxiety. The selection of a suitable animal model is important for the exploration of disease etiology and pathophysiology, and the development of new drugs. Therefore, a more comprehensive understanding of the advantages and limitations of existing animal models of anxiety disorders is helpful to further study the underlying pathological mechanisms of the disease. This review summarizes animal models and the pathogenesis of anxiety disorders, and discusses the current research status to provide insights for further study of anxiety disorders.

Huperzine-A Improved Animal Behavior in Cuprizone-Induced Mouse Model by Alleviating Demyelination and Neuroinflammation

Huperzine A (HupA) is a natural acetylcholinesterase inhibitor (AChEI) with the advantages of high efficiency, selectivity as well as reversibility and can exhibit significant therapeutic effects against certain neurodegenerative diseases. It is also beneficial in reducing the neurological impairment and neuroinflammation of experimental autoimmune encephalomyelitis (EAE), a classic model for multiple sclerosis (MS). However, whether HupA can directly regulate oligodendrocyte differentiation and maturation and promote remyelination has not been investigated previously. In this study, we have analyzed the potential protective effects of HupA on the demylination model of MS induced by cuprizone (CPZ). It was found that HupA significantly attenuated anxiety-like behavior, as well as augmented motor and cognitive functions in CPZ mice. It also decreased demyelination and axonal injury in CPZ mice. Moreover, in CPZ mice, HupA increased mRNA levels of the various anti-inflammatory cytokines (Arg1, CD206) while reducing the levels of different pro-inflammatory cytokines (iNOS, IL-1β, IL-18, CD16, and TNF-α). Mecamylamine, a nicotinic acetylcholinergic receptor antagonist, could effectively reverse the effects of HupA. Therefore, we concluded that HupA primarily exerts its therapeutic effects on multiple sclerosis through alleviating demyelination and neuroinflammation.

The Anxiolytic Activity of Schinus terebinthifolia Leaf Lectin (SteLL) Is Dependent on Monoaminergic Signaling although Independent of the Carbohydrate-Binding Domain of the Lectin

The potential of plant lectins (carbohydrate-binding proteins) for the treatment of neurological disorders such as anxiety and depression has started to be reported in the last few years. Schinus terebinthifolia leaves contain a lectin called SteLL, which has displayed antimicrobial, immunomodulatory, antitumor, and analgesic activities. However, the effects of SteLL on the Central Nervous System (CNS) have not yet been determined. In this study, we investigated the in vivo anxiolytic effect of SteLL in mice using the open field (OF) and elevated plus maze (EPM) tests. In the OF, SteLL (1, 2, and 4 mg/kg, i.p.) did not interfere with the number of crossings but significantly reduced the number of rearings. In the EPM, SteLL 4 mg/kg and the combination SteLL (1 mg/kg) plus diazepam (1 mg/kg) significantly increased the time spent in the open arms while reducing the time spent in the closed arms. The anxiolytic effect of SteLL did not seem to be dependent on the carbohydrate-binding domain of the lectin. Nevertheless, the SteLL effect in the EPM was reversed by the pretreatment with the pharmacological antagonists of the α2-adrenoceptor, 5-HT2A/2C serotonin receptor, and the D1 dopamine receptor. Overall, our results suggest that the anxiolytic effect of SteLL is dependent on the monoaminergic signaling cascade.

Prefrontal cortical circuits in anxiety and fear: an overview

Pathological anxiety is among the most difficult neuropsychiatric diseases to treat pharmacologically, and it represents a major societal problem. Studies have implicated structural changes within the prefrontal cortex (PFC) and functional changes in the communication of the PFC with distal brain structures in anxiety disorders. Treatments that affect the activity of the PFC, including cognitive therapies and transcranial magnetic stimulation, reverse anxiety- and fear-associated circuit abnormalities through mechanisms that remain largely unclear. While the subjective experience of a rodent cannot be precisely determined, rodent models hold great promise in dissecting well-conserved circuits. Newly developed genetic and viral tools and optogenetic and chemogenetic techniques have revealed the intricacies of neural circuits underlying anxiety and fear by allowing direct examination of hypotheses drawn from existing psychological concepts. This review focuses on studies that have used these circuit-based approaches to gain a more detailed, more comprehensive, and more integrated view on how the PFC governs anxiety and fear and orchestrates adaptive defensive behaviors to hopefully provide a roadmap for the future development of therapies for pathological anxiety.

Dose Optimization of Anxiolytic Compounds Group in Valeriana jatamansi Jones and Mechanism Exploration by Integrating Network Pharmacology and Metabolomics Analysis

Anxiety disorder impacts the quality of life of the patients. The 95% ethanol extract of rhizomes and roots of Valeriana jatamansi Jones (Zhi zhu xiang, ZZX) has previously been shown to be effective for the treatment of anxiety disorder. In this study, the dose ratio of each component of the anxiolytic compounds group (ACG) in a 95% ethanol extract of ZZX was optimized by a uniform design experiment and mathematical modeling. The anxiolytic effect of ACG was verified by behavioral experiments and biochemical index measurement. Network pharmacology was used to determine potential action targets, as well as predict biological processes and signaling pathways, which were then verified by molecular docking analysis. Metabolomics was then used to screen and analyze metabolites in the rat hippocampus before and after the administration of ZZX-ACG. Finally, the results of metabolomics and network pharmacology were integrated to clarify the anti-anxiety mechanism of the ACG. The optimal dose ratio of ACG in 95% ethanol extract of ZZX was obtained, and our results suggest that ACG may regulate ALB, AKT1, PTGS2, CYP3A4, ESR1, CASP3, CYP2B6, EGFR, SRC, MMP9, IGF1, and MAPK8, as well as the prolactin signaling pathway, estrogen signaling pathway, and arachidonic acid metabolism pathway, thus affecting the brain neurotransmitters and HPA axis hormone levels to play an anxiolytic role, directly or indirectly.

Behavioral tests for evaluating the characteristics of brain diseases in rodent models: Optimal choices for improved outcomes (Review)

Behavioral assessment is the dominant approach for evaluating whether animal models of brain diseases can successfully mimic the clinical characteristics of diseases. At present, most research regarding brain diseases involves the use of rodent models. While studies have reported numerous methods of behavioral assessments in rodent models of brain diseases, each with different principles, procedures, and assessment criteria, only few reviews have focused on characterizing and differentiating these methods based on applications for which they are most appropriate. Therefore, in the present review, the representative behavioral tests in rodent models of brain diseases were compared and differentiated, aiming to provide convenience for researchers in selecting the optimal methods for their studies.

Chronic adolescent stress increases exploratory behavior but does not appear to change the acute stress response in adult male C57BL/6 mice

Chronic stress exposure in adolescence can lead to a lasting change in stress responsiveness later in life and is associated with increased mental health issues in adulthood. Here we investigate whether the Chronic Social Instability (CSI) paradigm influences the behavioral and molecular responses to novel acute stressors in mice, and whether it alters physiological responses influenced by the noradrenergic system. Using large cohorts of mice, we show that CSI mice display a persistent increase in exploratory behaviors in the open field test alongside small but widespread transcriptional changes in the ventral hippocampus. However, both the transcriptomic and behavioral responses to novel acute stressors are indistinguishable between groups. In addition, the pupillometric response to a tail shock, known to be mediated by the noradrenergic system, remains unaltered in CSI mice. Ultra-high performance liquid chromatography analysis of monoaminergic neurotransmitter levels in the ventral hippocampus also shows no differences between control or CSI mice at baseline or in response to acute stress. We conclude that CSI exposure during adolescence leads to persistent changes in exploratory behavior and gene expression in the hippocampus, but it does not alter the response to acute stress in adulthood and is unlikely to alter the function of the noradrenergic system.

Influence of HFD-induced precocious puberty on neurodevelopment in mice

BACKGROUND

Precocious puberty is frequently associated with obesity, which will lead to long-term effects, especially on growth and reproduction. However, the effect of precocious puberty on children's neurodevelopment is still unknown.

OBJECTIVES

Here we evaluated the effect of High fat diet (HFD)-induced precocious puberty on neurodevelopment and behaviors of animals.

METHODS

Ovaries sections were stained with hematoxylin-eosin (H&E) using standard techniques. Behavioral tests included elevated plus maze (EPM), open field exploration, Y-Maze, marble burying test, and novelty- suppressed feeding. The expression of genes related to puberty and neural development was detected by immunohistochemistry and Western blot.

RESULTS

Our results showed HFD-induced precocious puberty increased the risk-taking behavior and decreased memory of mice. The content of Tyrosine hydroxylase (TH) and Arginine vasopressin (AVP) in hypothalamus were higher in HFD group than control group. Although the recovery of normal diet will gradually restore the body fat and other physiological index of mice, the anxiety increases in adult mice, and the memory is also damaged.

CONCLUSIONS

These findings describe the sensitivity of mice brain to HFD-induced precocious puberty and the irrecoverability of neural damage caused by precocious puberty. Therefore, avoiding HFD in childhood is important to prevent precocious puberty and neurodevelopmental impairment in mice.

Objective and comprehensive re-evaluation of anxiety-like behaviors in mice using the Behavior Atlas

Various animal models of anxiety have been developed to evaluate anxiety and anxiolytic drugs. However, non-uniform measuring paradigms, variability in apparatus use and individual differences in animals confound study results. In this study, when all animals were included in the data analysis, we found no significant differences between control and stressed mice using standard behavioral paradigms for assessing anxiety (elevated plus maze and open field test). To provide a better assessment of anxiety, we therefore used a machine learning approach to analyze the behavioral patterns of each animal, and selected typical subjects in each group for use as a training set according to classical anxiety parameters. Spontaneous behaviors in these animals were captured by multi-view cameras and decomposed into sub-second modules using Behavior Atlas, and six behavioral features providing statistically significant difference between stressed and control mice were identified. Combined with low-dimensional embedding and clustering, new features were used to discriminate stressed mice from controls, in both the training set and all objects. Our results show Behavior Atlas is a powerful approach for identifying new potential biomarkers in an unbiased fashion. Our approach can complement classical measuring paradigms to objectively and comprehensively evaluate anxiety-like behaviors.