Analytical strategies for the marble burying test: avoiding impossible predictions and invalid p-values

Sigma-1 receptor modulation by fluvoxamine ameliorates valproic acid-induced autistic behavior in rats: Involvement of chronic ER stress modulation, enhanced autophagy and M1/M2 microglia polarization

Autism spectrum disorder (ASD) is a neurodevelopmental disorder. While, fluvoxamine (FVX) is an antidepressant and widely prescribed to ASD patients, clinical results are inconclusive and the mechanism of FVX in the management of ASD is unclear. This study determined the potential therapeutic impact of FVX, a sigma-1 receptor (S1R) agonist, against the valproic acid (VPA)-induced model of autism. On gestational day 12.5, Wistar pregnant rats were given a single intraperitoneal (i.p.) injection of either VPA (600 mg/kg) or normal saline (10 mL/kg, vehicle-control). Starting on postnatal day (PND) 21 to PND 50, FVX (30 mg/kg, P·O. daily) and NE-100, (S1R) antagonist, (1 mg/kg, i.p. daily) were given to male pups. Behavior tests and histopathological changes were identified at the end of the experiment. In addition, the cerebellum biomarkers of endoplasmic reticulum (ER) stress and autophagy were assessed. Microglial cell polarization to M1 and M2 phenotypes was also assessed. FVX effectively mitigated the histopathological alterations in the cerebellum caused by VPA. FVX enhanced sociability and stereotypic behaviors in addition to its noteworthy impact on autophagy enhancement, ER stress deterioration, and controlling microglial cell polarization. The current investigation confirmed that the S1R agonist, FVX, can lessen behavioral and neurochemical alterations in the VPA-induced rat model of autism.

Methodological approach: using a within-subjects design in the marble burying assay

In 2016, the National Institutes of Health mandated the use of both male and female mice in funded research. The use of both sexes is an important variable to consider; however, it comes with negative consequences such as increased animal expenses. One way to combat these negatives is to explore the option of using a within-subjects design (repeated measures) in behavioral assays that historically use a between-subjects design. Our study aimed to determine if a within-subjects design can be utilized in the marble burying assay. The marble burying assay is used as a tool for screening putative anxiolytic compounds as the assay is thought to measure obsessive-compulsive disorder- or anxiety-like behaviors. First, we compared the effects of sex and digging medium (corn cob or Sani Chip) on the number of marbles buried using CD-1 mice. Second, we determined if mice would continue to bury marbles after repeated exposures to the test arena. Lastly, we tested three positive controls (buspirone, ketamine, and fluoxetine). We found that mice buried significantly more marbles within Sani Chip digging medium, and no sex differences were observed. Next, the number of marbles buried and locomotor activity remained consistent across four test sessions. The positive controls buspirone (3.2-10 mg/kg) ketamine (32 mg/kg), and fluoxetine (10 mg/kg) decreased the number of marbles buried using the within-subjects design. These data suggest that a within-subjects design is optimal for the marble burying assay as it will reduce the number of animals and increase statistical power.

Canagliflozin Ameliorates Oxidative Stress and Autistic-like Features in Valproic-Acid-Induced Autism in Rats: Comparison with Aripiprazole Action

Based on their proven anti-inflammatory and antioxidant effects, recent studies have examined the therapeutic potential of the sodium-glucose cotransporter 2 (SGLT2) inhibitors in neurodevelopmental disorders such as autism spectrum disorder (ASD). Therefore, the aim of this study is to assess the effects of subchronic systemic treatment with intraperitoneal (i.p.) canagliflozin (20, 50, and 100 mg/kg) compared to aripiprazole (ARP) (3 mg/g, i.p.) in a valproic acid (VPA)-induced rat model of autism. The behavioral characteristics of ASD, oxidative stress, and acetylcholinesterase (AChE) activity in rats with ASD-like behaviors, which were induced by prenatal exposure to VPA, were evaluated. The behavioral assessment methods used for this study were the open field test (OFT), the marble-burying test (MBT), and the nestlet-shredding test (NST) to examine their exploratory, anxiety, and compulsiveness-like actions, while the biochemical assessment used for this study was an ELISA colorimetric assay to measure ASD biomarker activity in the hippocampus, prefrontal cortex, and cerebellum. Rats that were pretreated with 100 mg/kg of canagliflozin displayed a significantly lower percentage of shredding (1.12 ± 0.6%, p < 0.01) compared to the ARP group (3.52 ± 1.6%). Pretreatment with (20 mg/kg, 50 mg/kg, and 100 mg/kg) canagliflozin reversed anxiety levels and hyperactivity and reduced hyper-locomotor activity significantly (161 ± 34.9 s, p < 0.05; 154 ± 44.7 s, p < 0.05; 147 ± 33.6 s, p < 0.05) when compared with the VPA group (303 ± 140 s). Moreover, canagliflozin and ARP mitigated oxidative stress status by restoring levels of glutathione (GSH) and catalase (CAT) and increasing the levels of malondialdehyde (MDA) in all tested brain regions. The observed results propose repurposing of canagliflozin in the therapeutic management of ASD. However, further investigations are still required to verify the clinical relevance of canagliflozin in ASD.

Prophylactic Effect of Bovine Colostrum on Intestinal Microbiota and Behavior in Wild-Type and Zonulin Transgenic Mice

The microbiota-gut-brain axis (MGBA) involves bidirectional communication between intestinal microbiota and the gastrointestinal (GI) tract, central nervous system (CNS), neuroendocrine/neuroimmune systems, hypothalamic-pituitary-adrenal (HPA) axis, and enteric nervous system (ENS). The intestinal microbiota can influence host physiology and pathology. Dysbiosis involves the loss of beneficial microbial input or signal, diversity, and expansion of pathobionts, which can lead to loss of barrier function and increased intestinal permeability (IP). Colostrum, the first milk from mammals after birth, is a natural source of nutrients and is rich in oligosaccharides, immunoglobulins, growth factors, and anti-microbial components. The aim of this study was to investigate if bovine colostrum (BC) administration might modulate intestinal microbiota and, in turn, behavior in two mouse models, wild-type (WT) and Zonulin transgenic (Ztm)-the latter of which is characterized by dysbiotic microbiota, increased intestinal permeability, and mild hyperactivity-and to compare with control mice. Bioinformatics analysis of the microbiome showed that consumption of BC was associated with increased taxonomy abundance (p = 0.001) and diversity (p = 0.004) of potentially beneficial species in WT mice and shifted dysbiotic microbial community towards eubiosis in Ztm mice (p = 0.001). BC induced an anxiolytic effect in WT female mice compared with WT female control mice (p = 0.0003), and it reduced anxiogenic behavior in Ztm female mice compared with WT female control mice (p = 0.001), as well as in Ztm male mice compared with WT BC male mice (p = 0.03). As evidenced in MGBA interactions, BC supplementation may well be applied for prophylactic approaches in the future. Further research is needed to explore human interdependencies between intestinal microbiota, including eubiosis and pathobionts, and neuroinflammation, and the potential value of BC for human use. The MGH Institutional Animal Care and Use Committee authorized the animal study (2013N000013).

Neonatal immune challenge influences the microbiota and behaviour in a sexually dimorphic manner

There is comorbidity between anxiety disorders and gastrointestinal disorders, with both linked to adverse early life events. The microbiome gut-brain-axis, a bidirectional communication system, is plastic throughout the neonatal period and is a possible mediator of this relationship. Here, we used a well-established neonatal rodent immune activation model to investigate the long-term effect of neonatal lipopolysaccharide (LPS) exposure on adult behaviour and the relationship to microbiome composition. Wistar rats were injected with LPS (0.05 mg/kg) or saline (equivolume) on postnatal days 3 and 5. In adulthood, behavioural tests were performed to assess anxiety-like behaviour, and microbiota sequencing was performed on stool samples. There were distinctly different behavioural phenotypes for LPS-exposed males and females. LPS-exposed males displayed typical anxiety-like behaviours with significantly decreased social interaction (F_(1,22) = 7.576, p = 0.009) and increased defecation relative to saline controls (F_(1,23) = 8.623, p = 0.005). LPS-exposed females displayed a different behavioural phenotype with significantly increased social interaction (F_(1,22) = 6.094, p = 0.018), and exploration (F_(1,24) = 6.359, p = 0.015), compared to saline controls. With respect to microbiota profiling data, Bacteroidota was significantly increased for LPS-exposed females (F_(1,14) = 4.931p = 0.035) and Proteobacteria was decreased for LPS-exposed rats of both sexes versus controls (F_(1,30) = 4.923p = 0.035). Furthermore, alterations in predicted functional pathways for neurotransmitters in faeces were observed with a decrease in the relative abundance of D-glutamine and D-glutamate metabolism in LPS exposed females compared to control females (p < 0.05). This suggests that neonatal immune activation alters both later life behaviour and adult gut microbiota in sex-specific ways. These findings highlight the importance of sex in determining the impact of neonatal immune activation on social behaviour and the gut microbiota.

In pursuit of biomarkers for predicting susceptibility to activity-based anorexia in adolescent female rats

OBJECTIVE

Identifying risk factors that contribute to the development of anorexia nervosa (AN) is critical for the implementation of early intervention strategies. Anxiety, obsessive-compulsive behavior, and immune dysfunction may be involved in the development of AN; however, their direct influence on susceptibility to the condition remains unclear. Here, we used the activity-based anorexia (ABA) model to examine whether activity, anxiety-like behavior, compulsive behavior, and circulating immune markers predict the subsequent development of pathological weight loss.

METHOD

Female Sprague-Dawley rats (n = 44) underwent behavioral testing before exposure to ABA conditions after which they were separated into susceptible and resistant subpopulations. Blood was sampled before behavioral testing and after recovery from ABA to screen for proinflammatory cytokines.

RESULTS

Rats that were vulnerable to pathological weight loss differed significantly from resistant rats on all key ABA parameters. While the primary measures of anxiety-like or compulsive behavior were not shown to predict vulnerability to ABA, increased locomotion and anxiety-like behavior were both associated with the extent of weight loss in susceptible but not resistant animals. Moreover, the change in expression of proinflammatory markers IL-4 and IL-6 evoked by ABA was associated with discrete vulnerability factors. Intriguingly, behavior related to risk assessment was shown to predict vulnerability to ABA.

DISCUSSION

We did not find undisputable behavioral or immune predictors of susceptibility to pathological weight loss in the ABA rat model. Future research should examine the role of cognition in the development of ABA, dysfunction of which may represent an endophenotype linking anorectic, anxiety-like and compulsive behavior.

PUBLIC SIGNIFICANCE

Anorexia nervosa (AN) has among the highest mortality rates of all psychiatric disorders and treatment options remain limited in their efficacy. Understanding what types of risk factors contribute to the development of AN is essential for implementing early intervention strategies. This study describes how some of the most common psychological features of AN could be used to predict susceptibility to pathological weight loss in a well-established animal model.

Sex-Dependent Signatures, Time Frames and Longitudinal Fine-Tuning of the Marble Burying Test in Normal and AD-Pathological Aging Mice

The marble burying (MB) test, a classical test based on the natural tendency of rodents to dig in diverse substrates and to bury small objects, is sensitive to some intrinsic and extrinsic factors. Here, under emerging neuroethological quantitative and qualitative analysis, the MB performance of 12-month-old male and female 3xTg-AD mice for Alzheimer’s disease and age-matched counterparts of gold-standard C57BL6 strain with normal aging unveiled sex-dependent signatures. In addition, three temporal analyses, through the (1) time course of the performance, and (2) a repeated test schedule, identified the optimal time frames and schedules to detect sex- and genotype-dependent differences. Besides, a (3) longitudinal design from 12 to 16 months of age monitored the changes in the performance with aging, worsening in AD-mice, and modulation through the repeated test. In summary, the present results allow us to conclude that (1) the marble burying test is responsive to genotype, sex, aging, and its interactions; (2) the male sex was more sensitive to showing the AD-phenotype; (3) longitudinal assessment shows a reduction in females with AD pathology; (4) burying remains stable in repeated testing; (5) the time-course of marbles burying is useful; and (6) burying behavior most likely represents perseverative and/or stereotyped-like behavior rather than anxiety-like behavior in 3xTg-AD mice.

Functional and epigenetic phenotypes of humans and mice with DNMT3A Overgrowth Syndrome

Germline pathogenic variants in DNMT3A were recently described in patients with overgrowth, obesity, behavioral, and learning difficulties (DNMT3A Overgrowth Syndrome/DOS). Somatic mutations in the DNMT3A gene are also the most common cause of clonal hematopoiesis, and can initiate acute myeloid leukemia (AML). Using whole genome bisulfite sequencing, we studied DNA methylation in peripheral blood cells of 11 DOS patients and found a focal, canonical hypomethylation phenotype, which is most severe with the dominant negative DNMT3AR882H mutation. A germline mouse model expressing the homologous Dnmt3aR878H mutation phenocopies most aspects of the human DOS syndrome, including the methylation phenotype and an increased incidence of spontaneous hematopoietic malignancies, suggesting that all aspects of this syndrome are caused by this mutation.

Impaired hypothalamic feedback dysregulates brain glucocorticoid signaling in genetically-selected Marchigian Sardinian alcohol-preferring rats

Genetically-selected Marchigian Sardinian alcohol-preferring (msP) rats display comorbid symptoms of increased alcohol preference and elevated anxiety-like behavior. Heightened stress sensitivity in msPs is influenced by genetic polymorphisms of the corticotropin-releasing factor receptor in the central nucleus of the amygdala (CeA), as well as reduced influence of anti-stress mechanisms that normally constrain the stress response. Given this propensity for stress dysregulation, in this study, we expand on the possibility that msPs may display differences in neuroendocrine processes that normally terminate the stress response. We utilized behavioral, biochemical, and molecular assays to compare basal and restraint stress-induced changes in the hypothalamic-pituitary-adrenal (HPA) axis of male and female msPs relative to their nonselected Wistar counterparts. The results showed that msPs display deficits in marble-burying behavior influenced by environmental factors and procedures that modulate arousal states in a sex-dependent manner. Whereas male msPs display evidence of dysregulated neuroendocrine function (higher adrenocorticotropic hormone levels and subthreshold reductions in corticosterone), females display restraint-induced elevations in corticosterone levels that were persistently higher in msPs. A dexamethasone challenge reduced the circulation of these stress hormones, although the reduction in corticosterone was generally attenuated in msP versus Wistar rats. Finally, we found evidence of diminished stress-induced glucocorticoid receptor (GR) phosphorylation in the hypothalamic paraventricular nucleus of msPs, as well as innate increases in phosphorylated GR levels in the CeA of male msPs. Collectively, these findings suggest that negative feedback processes regulating HPA responsiveness are diminished in msP rats, possibly underlying differences in the expression of anxiety-like behaviors.

The Chronic Treatment With 5-HT2A Receptor Agonists Affects the Behavior and the BDNF System in Mice

Serotonin 5-HT2A receptors and the brain-derived neurotrophic factor (BDNF) are involved in the pathophysiology and treatment of many psychiatric diseases. However, the interaction between 5-HT2A and BDNF is still poorly understood. In the present paper, the effects of chronic treatment with mixed 5-HT2A/2C receptor agonist DOI, highly selective 5-HT2A agonists TCB-2 and 25CN-NBOH on behavior and the BDNF system have been investigated. Chronic treatment of males of C57Bl/6 mice with DOI, TCB-2 and 25CN-NBOH (1 mg/kg, i.p., 14 days) resulted in desensitization of 5-HT2A receptors. Treatment with 25CN-NBOH significantly increased startle amplitude. At the same time all used drugs failed to affect anxiety, exploratory and stereotyped behavior as well as spatial memory and learning. TCB-2 and 25CN-NBOH increased the BDNF mRNA level. All 5-HT2A agonists increased the proBDNF level but failed to alter the mature BDNF protein level. TrkB and p75NTR mRNA levels were affected by all utilized agonists. All drugs decreased the total level as well as membrane TrkB protein one indicating downregulation of TrkB receptors. All agonists decreased the membrane p75NTR protein level. Thus, we have shown for the first time that the chronic activation of the 5-HT2A receptor with agonists has affected the BDNF system almost on all levels-transcription, proBDNF production, TrkB and p75NTR receptors' level. The obtained data suggested possible suppression in BDNF-TrkB signaling under chronic treatment with 5-HT2A agonists.

DNMT3A Haploinsufficiency Results in Behavioral Deficits and Global Epigenomic Dysregulation Shared across Neurodevelopmental Disorders

Mutations in DNA methyltransferase 3A (DNMT3A) have been detected in autism and related disorders, but how these mutations disrupt nervous system function is unknown. Here, we define the effects of DNMT3A mutations associated with neurodevelopmental disease. We show that diverse mutations affect different aspects of protein activity but lead to shared deficiencies in neuronal DNA methylation. Heterozygous DNMT3A knockout mice mimicking DNMT3A disruption in disease display growth and behavioral alterations consistent with human phenotypes. Strikingly, in these mice, we detect global disruption of neuron-enriched non-CG DNA methylation, a binding site for the Rett syndrome protein MeCP2. Loss of this methylation leads to enhancer and gene dysregulation that overlaps with models of Rett syndrome and autism. These findings define the effects of DNMT3A haploinsufficiency in the brain and uncover disruption of the non-CG methylation pathway as a convergence point across neurodevelopmental disorders.

Ethologically based behavioural and neurochemical characterisation of mice with isoform-specific loss of dysbindin-1A in the context of schizophrenia

Dysbindin-1 is implicated in several aspects of schizophrenia, including cognition and both glutamatergic and dopaminergic neurotransmission. Targeted knockout of dysbindin-1A (Dys-1A KO), the most abundant and widely expressed isoform in the brain, is associated with deficits in delay/interference-dependent working memory. Using an ethologically based approach, the following behavioural phenotypes were examined in Dys-1A KO mice: exploratory activity, social interaction, anxiety and problem-solving ability. Levels of monoamines and their metabolites were measured in striatum, hippocampus and prefrontal cortex using high-performance liquid chromatography with electrochemical detection. The ethogram of initial exploration in Dys-1A KO mice was characterised by increased rearing from a seated position; over subsequent habituation, stillness was decreased relative to wildtype. In a test of dyadic social interaction with an unfamiliar conspecific in a novel environment, female KO mice showed an increase in investigative social behaviours. Marble burying behaviour was unchanged. Using the puzzle-box test to measure general problem-solving performance, no effect of genotype was observed across nine trials of increasing complexity. Dys-1A KO demonstrated lower levels of 5-HT in ratio to its metabolite 5-HIAA in the prefrontal cortex. These studies elaborate the behavioural and neurochemical phenotype of Dys-1A KO mice, revealing subtle genotype-related differences in non-social and social exploratory behaviours and habituation of exploration in a novel environment, as well as changes in 5-HT activity in brain areas related to schizophrenia.

Marble-burying behavior test as a murine model of compulsive-like behavior

Object burying by rodents is a popular screening tool for anxiolytic agents. However, modulation of marble-burying by serotonin reuptake inhibitors prompted its link to obsessive-compulsive disorder/compulsive-like behavior. The Marble-burying behavior test is an acute test; however, some investigators incorporate the sub-acute treatment regimen as an essential component for screening anti-compulsive agents. The test exhibits between-laboratory methodological differences and demonstrates positive treatment responses to an array of pharmacotherapies, creating doubts about its predictive validity and construct validity. Numerous reviews are available on marble-burying behavior test, which incorporates the test as a part of anti-compulsive behavior-like screens, but none has made it a sole subject-matter for discussion. This review attempts to provide a comprehensive account of the marble-burying test as a model of compulsive-like disorders. It envisages the model's scientific origins, the preclinical research done and its correlation with the clinical research outcomes, and a detailed discussion about its validity. In conclusion, there appears a need to address the issue of construct and predictive validity of the model authoritatively; or the paradigm may remain squandered in the field of obsessive-compulsive disorder research.

Persistent central inflammation and region specific cellular activation accompany depression- and anxiety-like behaviours during the resolution phase of experimental colitis

Depression and anxiety-related psychological symptoms are increasingly recognised as important co-morbidities in patients with inflammatory bowel disease (IBD). Dextran sulfate sodium (DSS) -induced colitis is an animal model of IBD in which afferent activation of the gut-brain axis can be assessed and explored as a source of behavioural change. Exposure of adult male Wistar rats to DSS (5%) in drinking water induced distal colitis. In parallel to local inflammatory responses in the gut wall, increased expression of IL-6 and iNOS was found in the cerebral cortex and an increase in ventricular volume. Immunoreactivity of immediate early gene FosB/ΔFosB activation was measured as an index of cellular activation and was increased in the nucleus accumbens and dorsal raphe nucleus in acutely colitic animals. Following resolution of the acute colitic response, sustained anhedonia in the saccharin preference test, immobility in the forced swim test, reduced burying behaviour in the marble burying test, and mild signs of anxiety in the elevated plus maze and light/dark box were observed. Central increases in iNOS expression persisted during the recovery phase and mapped to reactive microglia, particularly those found in the parenchyma surrounding circumventricular regions. Evidence of associated nitration was also found. Sustained increases in ventricular volume and reduced T2 magnetic resonance relaxometry time in cortical regions were observed during the recovery period. FosB/ΔFosB activation was evident in the dorsal raphe during recovery. Persistent central inflammation and cellular activation may underpin the emergence of symptoms of depression and anxiety in experimental colitis.

Periconceptional folate deficiency leads to autism-like traits in Wistar rat offspring

BACKGROUND

Folates in their role as key one carbon donors, are essential for two major pathways: the synthesis of DNA and RNA precursors and DNA methylation. A growing body of evidence from epidemiological studies indicates a possible association between nutritional and functional deficiency in folates and Autism Spectrum Disorders (ASD). However, there are no available behavioral animal studies on periconceptional one‑carbon donor deficiency during gestation and the autistic phenotype.

OBJECTIVE

The objective of this study was to determine if the periconceptional alteration of one‑carbon metabolism induced with a folate deficient diet would affect the behaviour of rat offspring.

METHODS

Female Wistar rats were divided in two groups: control (basal diet, in compliance with standards of regular laboratory diets), or exposed during one month before breeding until Gestational Day 15 to a modified diet with no added folic acid (0.2mg/kg of food), reduced choline (750mg/kg of food), and added 1% SST (a non-absorbable antibiotic used to inhibit folate synthesis by gut bacteria). We administered behavioral tests to offspring, i.e., open field (P20), social interactions (P25), marble burying (P30), elevated plus maze (P35), and prepulse inhibition of the acoustic startle reflex (sensorimotor gating) (P45). Blood homocysteine levels were used to confirm the deficit in one‑carbon donors.

RESULTS

Compared to controls, offspring with the periconceptional deficit in folate showed: (i) congenital body malformations; (ii) reduced social interactions, with a ~30% decrease in social sniffing behavior; (iii) reduced exploration of the open arm by 50% in the elevated plus maze test, indicating increased anxiety; (iv) a ~160% increased number of marbles buried, indicating repetitive behaviors; and (v) altered sensorimotor gating, with a global 50% decrease in startle inhibition.

CONCLUSION

Maternal periconceptional deficit in folate provokes alterations in the behavior of offspring relevant to the autistic-like phenotype.

A comparison of methods for the analysis of binomial clustered outcomes in behavioral research

BACKGROUND

In behavioral research, data consisting of a per-subject proportion of "successes" and "failures" over a finite number of trials often arise. This clustered binary data are usually non-normally distributed, which can distort inference if the usual general linear model is applied and sample size is small. A number of more advanced methods is available, but they are often technically challenging and a comparative assessment of their performances in behavioral setups has not been performed.

METHOD

We studied the performances of some methods applicable to the analysis of proportions; namely linear regression, Poisson regression, beta-binomial regression and Generalized Linear Mixed Models (GLMMs). We report on a simulation study evaluating power and Type I error rate of these models in hypothetical scenarios met by behavioral researchers; plus, we describe results from the application of these methods on data from real experiments.

RESULTS

Our results show that, while GLMMs are powerful instruments for the analysis of clustered binary outcomes, beta-binomial regression can outperform them in a range of scenarios. Linear regression gave results consistent with the nominal level of significance, but was overall less powerful. Poisson regression, instead, mostly led to anticonservative inference.

COMPARISON WITH EXISTING METHODS

GLMMs and beta-binomial regression are generally more powerful than linear regression; yet linear regression is robust to model misspecification in some conditions, whereas Poisson regression suffers heavily from violations of the assumptions when used to model proportion data.

CONCLUSIONS

We conclude providing directions to behavioral scientists dealing with clustered binary data and small sample sizes.