Assessing mouse behaviour throughout the light/dark cycle using automated in-cage analysis tools

Pharmacology and macrophage modulation of HPGDS inhibitor PK007 demonstrate reduced disease severity in DMD-affected muscles of the mdx mouse model

BACKGROUND

Duchenne Muscular Dystrophy (DMD) is an X-linked disease characterised by chronic inflammation, progressive muscle damage, and muscle loss. Typically, initial symptoms affect lower limb muscles, including the gastrocnemius (GA), tibialis anterior (TA), and extensor digitorum longus (EDL). During the acute phase of DMD, particularly in boys aged 2-8 years, muscle damage resulting in necrosis (myonecrosis) involves a complex immune-inflammatory response. Prostaglandin D2 (PGD2) is recognised for enhancing pro-inflammatory chemokine and interleukin signalling and recruiting infiltrating immune cells such as pro-inflammatory macrophages, exacerbating myonecrosis.

METHODS

To reduce levels of PGD2, a novel hematopoietic prostaglandin D2 synthase (HPGDS) inhibitor, PK007, was characterised (i) for potency and pharmacokinetic profiles and then tested in the mdx mouse model of DMD during the acute early onset of disease progression. Juvenile mdx and wild type (WT) C57Bl/10Scsn mice were orally treated with PK007 and control vehicle solution for 10 days, from postnatal day 18 to 28. This builds upon a previous study with PK007 with (ii) additional analyses of disease progression assessed for muscle grip strength, metabolic and locomotor activity, myonecrosis in a wide range of muscles (3 from hindlimb, diaphragm, heart, and tongue), macrophage infiltration and pro-inflammatory cytokines (TNF-α, IL-1β and iNOS).

RESULTS

PK007 exhibited high potency (17.23 ± 12 nM), a long half-life (3.0 ± 0.3 h), and good oral bioavailability (81%). Treatment with PK007 decreased serum PGD2 levels (33.36%) in mdx mice compared to control (vehicle-treated) mdx mice. In mdx mice (compared with controls), PK007 enhanced grip strength (69.05% increase) and improved locomotor activity (69.05% increase). Histological analysis revealed a significant reduction in the total myonecrotic area in PK007-treated GA (49.75%), TA (73.87%), EDL (60.31%), diaphragm (48.02%), and tongue (37.93%) muscles of mdx mice (compared with controls). Additionally, PK007 decreased macrophage cell area by 55.56% in GA and 47.83% in EDL muscles. Further expression of pro-inflammatory cytokines and enzymes such as TNF-α, IL-1β and iNOS were significantly reduced in PK007 treated mice. These results demonstrate that PK007 significantly reduces the inflammatory response, protects muscles from necrosis and increases strength in juvenile mdx mice.

CONCLUSION

This study lays a strong foundation for progressing the use of HPDGS inhibitors such as PK007, which specifically inhibit PGD2 and reduce inflammation, as a viable therapeutic approach for DMD. This approach protects dystrophic muscles from necrosis and reduces the severity of this debilitating disease, improving outcomes and quality of life.

Contactless monitoring of respiratory rate variability in rats under anesthesia with a compact 24GHz microwave radar sensor

Objective

The objective of this study was to develop and validate a noncontact monitoring system for respiratory rate variability in rats under anesthesia using a 24GHz microwave radar sensor. This study aimed to address the need for stress-free monitoring techniques that comply with the 3Rs principle (Reduction, Replacement, and Refinement) in laboratory animal settings.

Methods

Utilizing a 24GHz microwave radar sensor, this system detects subtle body surface displacements induced by respiratory movements in anesthetized rats. The setup includes a 24.05 to 24.25 GHz radar module coupled with a single-board computer, specifically Raspberry Pi, for signal acquisition and processing. The experiment involved four male Wistar rats tracking the variability in their respiratory rates at various isoflurane anesthesia depths to compare the radar system's performance with reference measurements.

Results

The radar system demonstrated high accuracy in respiratory rate monitoring, with a mean difference of 0.32 breaths per minute compared to laser references. The Pearson's correlation coefficient was high (0.89, p < 0.05), indicating a strong linear relationship between the radar and reference measurements. The system also accurately reflected changes in respiratory rates corresponding to different isoflurane anesthesia levels. Variations in respiratory rates were effectively mapped across different anesthesia levels, confirming the reliability and precision of the system for real-time monitoring.

Conclusion

The microwave radar-based monitoring system significantly enhanced the animal welfare and research methodology. This system minimizes animal stress and improves the integrity of physiological data in research settings by providing a non-invasive, accurate, and reliable means of monitoring respiratory rates.

Crimean-Congo hemorrhagic fever: Pathogenesis, transmission and public health challenges

The dangerous Crimean-Congo hemorrhagic fever virus (CCHFV), an encapsulated negative-sense RNA virus of the family Nairoviridae, is transmitted from person to person via ticks. With a case fatality rate between 10% to 40%, the most common ways that the disease may spread to humans are via tick bites or coming into touch with infected animals' blood or tissues. Furthermore, the transfer of bodily fluids between individuals is another potential route of infection. There is a wide range of symptoms experienced by patients throughout each stage, from myalgia and fever to extreme bruising and excess bleeding. Tick management measures include minimising the spread of ticks from one species to another and from people to animals via the use of protective clothing, repellents, and proper animal handling. In order to prevent the spread of illness, healthcare workers must adhere to stringent protocols. Despite the lack of an authorised vaccine, the main components of treatment now consist of preventative measures and supportive care, which may include the antiviral medicine ribavirin. We still don't know very much about the virus's mechanisms, even though advances in molecular virology and animal models have improved our understanding of the pathogenesis of CCHFV. A critical need for vaccination that is both safe and effective, as well as for quick diagnosis and efficient treatments to lessen the disease's impact in areas where it is most prevalent. Important steps towards lowering Crimean-Congo hemorrhagic fever mortality and morbidity rates were to anticipatethe future availability of immunoglobulin products.

The C1473G Mutation in the Mouse Tph2 Gene: From Molecular Mechanism to Biological Consequences

Tryptophan hydroxylase 2 (TPH2) hydroxylates L-tryptophan to L-5-hydroxy tryptophan-the key step of 5-HT synthesis in the mammalian brain. Some mutations in the human hTPH2 gene are associated with psychopathologies and resistance to antidepressant therapy. The C1473G polymorphism in the mouse Tph2 gene decreases the TPH2 activity in the mouse brain. In the present paper, B6-1473C and B6-1473G congenic mice that were different only in the C > G substitution were used. The molecular mechanism of decrease in the mutant enzyme activity and some physiological and behavioral traits affected by this mutation were revealed for the first time. Analysis of thermal denaturation curves in vitro revealed that the C > G substitution reduces the free energy of denaturation, stability and lifetime of mutant TPH2. Later, we evaluated the effect of the 1473G allele on the hierarchical state, competition for a sexual partner in adult mice, mouse embryos, hind legs dystonia and the response to LPS treatment in young mice. No effect of this mutation on the hierarchical state and competition for a female was observed in adult males. The C > G substitution does not affect survival, body mass or the TPH activity in the brain of 19-day-old mouse embryos. At the same time, we found that the 1473G allele causes hind legs dystonia in juvenile (3 weeks old) mice, which can affect their escape capability in threatening situations. Moreover, a significant increase in the vulnerability to LPS in juvenile B6-1473G males was shown: a single ip LPS administration killed about 40% of young mutant mice, but not wild-type ones. The body mass of mutant males was lower compared to wild-type ones, which also can indirectly decrease their concurrent and reproductive success.

Real-time behavioral monitoring of C57BL/6J mice during reproductive cycle

Introduction

The present study aims to identify differences in behavioral profiles in post-pubertal C57BL/6J males and female mice across distinct phases of the reproductive cycle in a home cage environment.

Methods

To reduce human bias, we used an automated behavioral analysis system HomeCageScan from CleverSys Inc. Mice were monitored continuously, and resulting data were summarized across 24-h, light, and dark cycles. Behavioral activities of each period were analyzed using hierarchical clustering, factor analysis, and principal component analysis.

Results

Females exhibited higher levels of physically demanding activities, including ambulatory and exploratory movements, particularly during estrus and metestrus, with estrus showing up to 30% more activity than males. In contrast, males consistently engaged in more sleep-related behaviors across all phases, with significantly higher engagement during the light cycle compared to females in proestrus and estrus (p < 0.0001); the extent of this sex difference was greater during proestrus and estrus than in metestrus and diestrus (p < 0.01). Notably, distinct patterns of sleep fragmentation were observed, with females experiencing greater disruptions during the light cycle, while males showed similar disruptions during the dark cycle. Feeding and resourcing behaviors were highest in males, showing up to 20% increase compared to cycling females, as well as significantly engaging in habituation-related behaviors such as feeding and digging. Interphase differences were observed within females, such as a significant increase of habituation-related activities during estrus compared to proestrus and diestrus (p < 0.05), while during the dark cycle, these activities peaked during the diestrus phase (p < 0.05). Female mice in the metestrus phase exhibited more sleep-related behaviors than those in proestrus.

Discussion

Our study has revealed prevalent behavioral differences due to sex, and inter-phase variations by employing a continuous monitoring approach designed to reduce bias. This methodology ensures a comprehensive understanding of natural behavioral patterns and strategies.

A new 2-hit model combining serine racemase deletion and maternal separation displays behavioral and cognitive deficits associated with schizophrenia

Schizophrenia (SCZ) is a multifactorial psychotic disorder characterized by positive and negative symptoms as well as cognitive impairments. To advance the current treatments, it is important to improve animal models by considering the multifactorial etiology, thus by combining different risk factors. The objective of our study was to explore in a new mouse model, the impact of genetic deletion of serine racemase (genetic vulnerability) combined with an early stress factor induced by maternal separation (early environmental exposure) in the context of SCZ development. The face validity of the model was assessed through a wide range of behavioral experiments. The 2-hit mice displayed an increased locomotor activity mimicking positive symptoms, working memory impairment, cognitive deficits and recognition memory alterations, which could reflect neophobia. This new multifactorial model therefore presents an interesting phenotype for modelling animal model with partial behavioral and cognitive deficits associated with SCZ.

Evaluation of the Digital Ventilated Cage® system for circadian phenotyping

The study of circadian rhythms has been critically dependent upon analysing mouse home cage activity, typically employing wheel running activity under different lighting conditions. Here we assess a novel method, the Digital Ventilated Cage (DVC®, Tecniplast SpA, Italy), for circadian phenotyping. Based upon capacitive sensors mounted under black individually ventilated cages with inbuilt LED lighting, each cage becomes an independent light-controlled chamber. Home cage activity in C57BL/6J mice was recorded under a range of lighting conditions, along with circadian clock-deficient cryptochrome-deficient mice (Cry1-/-, Cry2-/- double knockout). C57BL/6J mice exhibited a 24 h period under light/dark conditions, with a free-running period of 23.5 h under constant dark, and period lengthening under constant light. Animals displayed expected phase shifting responses to jet-lag and nocturnal light pulses. Sex differences in circadian parameters and phase shifting responses were also observed. Cryptochrome-deficient mice showed subtle changes in activity under light/dark conditions and were arrhythmic under constant dark, as expected. Our results show the suitability of the DVC system for circadian behavioural screens, accurately detecting circadian period, circadian disruption, phase shifts and mice with clock defects. We provide an evaluation of the strengths and limitations of this method, highlighting how the use of the DVC for studying circadian rhythms depends upon the research requirements of the end user.

Circadian patterns of behaviour change during pregnancy in mice

Food intake and activity adapt during pregnancy to meet the increased energy demands. In comparison to non-pregnant females, pregnant mice consume more food, eating larger meals during the light phase, and reduce physical activity. How pregnancy changes the circadian timing of behaviour was less clear. We therefore randomised female C57BL/6J mice to mating for study until early (n = 10), mid- (n = 10) or late pregnancy (n = 11) or as age-matched, non-pregnant controls (n = 12). Mice were housed individually in Promethion cages with a 12 h light-12 h dark cycle [lights on at 07.00 h, Zeitgeber (ZT)0] for behavioural analysis. Food intake between ZT10 and ZT11 was greater in pregnant than non-pregnant mice on days 6.5-12.5 and 12.5-17.5. In mice that exhibited a peak in the last 4 h of the light phase (ZT8-ZT12), peaks were delayed by 1.6 h in the pregnant compared with the non-pregnant group. Food intake immediately after dark-phase onset (ZT13-ZT14) was greater in the pregnant than non-pregnant group during days 12.5-17.5. Water intake patterns corresponded to food intake. From days 0.5-6.5 onwards, the pregnant group moved less during the dark phase, with decreased probability of being awake, in comparison to the non-pregnant group. The onset of dark-phase activity, peaks in activity, and wakefulness were all delayed during pregnancy. In conclusion, increased food intake during pregnancy reflects increased amplitude of eating behaviour, without longer duration. Decreases in activity also contribute to positive energy balance in pregnancy, with delays to all measured behaviours evident from mid-pregnancy onwards. KEY POINTS: Circadian rhythms synchronise daily behaviours including eating, drinking and sleep, but how these change in pregnancy is unclear. Food intake increased, with delays in peaks of food intake behaviour late in the light phase from days 6.5 to 12.5 of pregnancy, in comparison to the non-pregnant group. The onset of activity after lights off (dark phase) was delayed in pregnant compared with non-pregnant mice. Activity decreased by ∼70% in the pregnant group, particularly in the dark (active) phase, with delays in peaks of wakefulness evident from days 0.5-6.5 of pregnancy onwards. These behavioural changes contribute to positive energy balance during pregnancy. Delays in circadian behaviours during mouse pregnancy were time period and pregnancy stage specific, implying different regulatory mechanisms.

AI-powered home cage system for real-time tracking and analysis of rodent behavior

Researchers in animal behavior and neuroscience devote considerable time to observing rodents behavior and physiological responses, with AI monitoring systems reducing personnel workload. This study presents the RodentWatch (RW) system, which leverages deep learning to automatically identify experimental animal behaviors in home cage environments. A single multifunctional camera and edge device are installed inside the animal's home cage, allowing continuous real-time monitoring of the animal's behavior, position, and body temperature for extended periods. We investigated identifying the drinking and resting behaviors of rats, with recognition accuracy enhanced through contextual object labeling and modified non-maximum suppression (NMS) schemes. Two tests-a light cycle change test and a sucrose preference test-were conducted to evaluate the usability of this system in rat behavioral experiments. This system enables notable advancements in image-based behavior recognition for living rodents.

The Impact of LPS on Inflammatory Responses in Alpha-Tocopherol Deficient Mice

Background

To facilitate the evaluation of vitamin E (α-tocopherol, αT) status on health outcomes, the αT transfer protein knockout (Ttpa -/- ) mouse model has proved to be an effective tool for lowering αT body stores. Our previous study showed a further reduction in grip strength in LPS-treated Ttpa -/- compared with wild-type (WT) mice during a 9-wk αT-deficient diet feeding period but did not find a difference in LPS-induced inflammatory response markers. Further optimization of this mouse model is warranted to determine the appropriate depletion period and biomarkers endpoints.

Objectives

The objective was to examine whether 12 wk of an αT-deficient diet altered the inflammatory response 4 and/or 24 h after LPS injection in WT and Ttpa -/- mice.

Methods

WT and Ttpa -/- weanling littermates were fed an αT-deficient diet ad libitum for 12 wk. Mice were then injected with LPS (10 μg/mouse) or saline (control) intraperitoneally and killed 4 (Study 1) or 24 h (Study 2) later. Concentrations of αT in tissues were measured via HPLC. Grip strength and burrowing were evaluated to assess sickness behaviors before/after LPS injection. Expression of genes related to inflammatory responses was examined via RT-PCR.

Results

αT concentrations in the brain, liver, and serum of Ttpa -/- mice were notably lower or undetectable compared with WT mice in both studies. Hepatic αT concentrations were further decreased 24 h after LPS injection. Grip strength was reduced at 4 h post-injection but partially recovered to baseline values 24 h after LPS injection. The expression of genes related to inflammatory responses were altered by LPS. However, neither measure of sickness behavior nor gene expression markers differed between genotypes.

Conclusions

A 4-h LPS challenge reduced grip strength and resulted in an inflammatory response. At 24 h post-dosing, there was a partial, transitory recovery response in both Ttpa -/- and WT mice.

Astrocytic metabolic control of orexinergic activity in the lateral hypothalamus regulates sleep and wake architecture

Neuronal activity undergoes significant changes during vigilance states, accompanied by an accommodation of energy demands. While the astrocyte-neuron lactate shuttle has shown that lactate is the primary energy substrate for sustaining neuronal activity in multiple brain regions, its role in regulating sleep/wake architecture is not fully understood. Here we investigated the involvement of astrocytic lactate supply in maintaining consolidated wakefulness by downregulating, in a cell-specific manner, the expression of monocarboxylate transporters (MCTs) in the lateral hypothalamus of transgenic mice. Our results demonstrate that reduced expression of MCT4 in astrocytes disrupts lactate supply to wake-promoting orexin neurons, impairing wakefulness stability. Additionally, we show that MCT2-mediated lactate uptake is necessary for maintaining tonic firing of orexin neurons and stabilizing wakefulness. Our findings provide both in vivo and in vitro evidence supporting the role of astrocyte-to-orexinergic neuron lactate shuttle in regulating proper sleep/wake stability.

Clinicopathologic Dissociation: Robust Lafora Body Accumulation in Malin KO Mice Without Observable Changes in Home-Cage Behavior

Lafora disease (LD) is a syndrome of progressive myoclonic epilepsy and cumulative neurocognitive deterioration caused by recessively inherited genetic lesions of EPM2A (laforin) or NHLRC1 (malin). Neuropsychiatric symptomatology in LD is thought to be directly downstream of neuronal and astrocytic polyglucosan aggregates, termed Lafora bodies (LBs), which faithfully accumulate in an age-dependent manner in all mouse models of LD. In this study, we applied home-cage monitoring to examine the extent of neurobehavioral deterioration in a model of malin-deficient LD as a means to identify robust preclinical endpoints that may guide the selection of novel genetic treatments. At 6 weeks, ∼6-7 months, and ∼12 months of age, malin-deficient mice ("KO") and wild-type (WT) littermates underwent a standardized home-cage behavioral assessment designed to non-obtrusively appraise features of rest/arousal, consumptive behaviors, risk aversion, and voluntary wheel-running. At all timepoints, and over a range of metrics that we report transparently, WT and KO mice were essentially indistinguishable. In contrast, within WT mice compared across the same timepoints, we identified age-related nocturnal hypoactivity, diminished sucrose preference, and reduced wheel-running. Neuropathological examinations in subsets of the same mice revealed expected age-dependent LB accumulation, gliosis, and microglial activation in cortical and subcortical brain regions. At 12 months of age, despite the burden of neocortical LBs, we did not identify spontaneous seizures during an electroencephalographic (EEG) survey, and KO and WT mice exhibited similar spectral EEG features. However, in an in vitro assay of neocortical function, paroxysmal bursts of network activity (UP states) in KO slices were more prolonged at 3 and 6 months of age, but similar to WT at 12 months. KO mice displayed a distinct response to pentylenetetrazole, with a greater incidence of clonic seizures and a more pronounced postictal suppression of movement, feeding, and drinking behavior. Together, these results highlight the clinicopathologic dissociation in a mouse model of LD, where the accrual of LBs may latently modify cortical circuit function and seizure threshold without clinically meaningful changes in home-cage behavior. Our findings allude to a delay between LB accumulation and neurobehavioral decline in LD: one that may provide a window for treatment, and whose precise duration may be difficult to ascertain within the typical lifespan of a laboratory mouse.

Of Mice and Mates: Automated Classification and Modelling of Mouse Behaviour in Groups Using a Single Model Across Cages

Behavioural experiments often happen in specialised arenas, but this may confound the analysis. To address this issue, we provide tools to study mice in the home-cage environment, equipping biologists with the possibility to capture the temporal aspect of the individual's behaviour and model the interaction and interdependence between cage-mates with minimal human intervention. Our main contribution is the novel Global Behaviour Model (GBM) which summarises the joint behaviour of groups of mice across cages, using a permutation matrix to match the mouse identities in each cage to the model. In support of the above, we also (a) developed the Activity Labelling Module (ALM) to automatically classify mouse behaviour from video, and (b) released two datasets, ABODe for training behaviour classifiers and IMADGE for modelling behaviour.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11263-024-02118-3.

Ameliorative effect of Nyctanthes arbor-tristis L. by suppression of pentylenetetrazole-induced kindling in mice: An insight from EEG, neurobehavioral and in-silico studies

Epilepsy is an abiding condition associated with recurrent seizure attacks along with associated neurological and psychological emanation owing to disparity of excitatory and inhibitory neurotransmission. The current study encompasses the assessment of the Nyctanthes arbor-tristis L. methanolic extract (Na.Cr) in the management of convulsive state and concomitant conditions owing to epilepsy. The latency of seizure incidence was assessed using pentylenetetrazol (PTZ) kindling models along with EEG in Na.Cr pretreated mice, trailed by behavior assessment (anxiety and memory), biochemical assay, histopathological alterations, chemical profiling through GCMS, and molecular docking. The chronic assessment of PTZ-induced kindled mice depicted salvation in a dose-related pattern and outcomes were noticeable with extract at 400 mg/kg. The extract at 400 mg/kg defends the progress of kindling seizures and associated EEG. Co-morbid conditions in mice emanating owing to epileptic outbreaks were validated by behavioral testing and the outcome depicted a noticeable defense related to anxiety (P<0.001) and cognitive deficit (P<0.001) at 400 mg/kg. The isolated brains were evaluated for oxidative stress and the outcome demonstrated a noticeable effect in a dose-dependent pattern. Treatment with Na.Cr. also preserved the brain from PTZ induced neuronal damage as indicated by histopathological analysis. Furthermore, the GCMS outcome predicted 28 compounds abundantly found in the plant. The results congregated in the current experiments deliver valued evidence about the defensive response apportioned by Na.Cr which might be due to decline in oxidative stress, AChE level, and GABAergic modulation. These activities may contribute to fundamental pharmacology and elucidate some mechanisms behind the activities of Nyctanthes arbor-tristis.

Mice with deficiency in Pcdh15, a gene associated with bipolar disorders, exhibit significantly elevated diurnal amplitudes of locomotion and body temperature

Genetic factors significantly affect the pathogenesis of psychiatric disorders. However, the specific pathogenic mechanisms underlying these effects are not fully understood. Recent extensive genomic studies have implicated the protocadherin-related 15 (PCDH15) gene in the onset of psychiatric disorders, such as bipolar disorder (BD). To further investigate the pathogenesis of these psychiatric disorders, we developed a mouse model lacking Pcdh15. Notably, although PCDH15 is primarily identified as the causative gene of Usher syndrome, which presents with visual and auditory impairments, our mice with Pcdh15 homozygous deletion (Pcdh15-null) did not exhibit observable structural abnormalities in either the retina or the inner ear. The Pcdh15-null mice showed very high levels of spontaneous motor activity which was too disturbed to perform standard behavioral testing. However, the Pcdh15 heterozygous deletion mice (Pcdh15-het) exhibited enhanced spontaneous locomotor activity, reduced prepulse inhibition, and diminished cliff avoidance behavior. These observations agreed with the symptoms observed in patients with various psychiatric disorders and several mouse models of psychiatric diseases. Specifically, the hyperactivity may mirror the manic episodes in BD. To obtain a more physiological, long-term quantification of the hyperactive phenotype, we implanted nano tag® sensor chips in the animals, to enable the continuous monitoring of both activity and body temperature. During the light-off period, Pcdh15-null exhibited elevated activity and body temperature compared with wild-type (WT) mice. However, we observed a decreased body temperature during the light-on period. Comprehensive brain activity was visualized using c-Fos mapping, which was assessed during the activity and temperature peak and trough. There was a stark contrast between the distribution of c-Fos expression in Pcdh15-null and WT brains during both the light-on and light-off periods. These results provide valuable insights into the neural basis of the behavioral and thermal characteristics of Pcdh15-deletion mice. Therefore, Pcdh15-deletion mice can be a novel model for BD with mania and other psychiatric disorders, with a strong genetic component that satisfies both construct and surface validity.

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.

PAW, a cost-effective and open-source alternative to commercial rodent running wheels

Voluntary wheel running is a common measure of general activity in many rodent models across neuroscience and physiology. However, current commercial wheel monitoring systems can be cost-prohibitive to many investigators, with many of these systems requiring investments of thousands of dollars. In recent years, several open-source alternatives have been developed, and while these tools are much more cost effective than commercial system, they often lack the flexibility to be applied to a wide variety of projects. Here, we have developed PAW, a 3D Printable Arduino-based Wheel logger. PAW is wireless, fully self-contained, easy to assemble, and all components necessary for its production can be obtained for only $75 CAD. Furthermore, with its compact internal electronics, the 3D printed casing can be easily modified to be used with a wide variety of running wheel designs for a wide variety of rodent species. Data recorded with the PAW system shows circadian patterns of activity which is expected from mice and is consistent with results found in the literature. Altogether, PAW is a flexible, low-cost system that can be beneficial to a broad range of researchers who study rodent models.

Locomotor activity as an effective measure of the severity of inflammatory arthritis in a mouse model

OBJECTIVE

Mouse models are valuable in preclinical studies of inflammatory arthritis. However, current methods for measuring disease severity or responses to treatment are not optimal. In this study a smart cage system using multiple sensors to measure locomotor activity was evaluated in the K/BxN serum transfer model of inflammatory arthritis.

METHODS

Arthritis was induced in C57BL/6 mice with injections of K/BxN serum. Clinical index and ankle thickness were measured for 14 days. Locomotor activity was measured in smart cages for 23 h periods on Days 0, 7, and 13. The same measurements were taken in mice consuming diets supplemented or not with fish oil to evaluate a preventative treatment.

RESULTS

Initiation, peak and resolution phases of disease could be measured with the smart cages. Locomotor activity including speed, travel distance, number of active movements and rear movements were all significantly lower on Days 7-8 of illness (peak) compared to Days 0 and 13-14 (resolution) (one-way repeated measures analyses, p<0.05). The clinical index and ankle thickness measurements did not capture differences between dietary groups. Significantly increased activity was measured in most of the locomotor parameters in the fish oil group compared to the control mice at both Days 8 and 14 (2-way repeated measures ANOVA, p<0.05).

CONCLUSION

The measurement of locomotor activity provided a more detailed evaluation of the impact of inflammatory arthritis on animal well-being and mobility than that provided by measuring clinical index and ankle thickness, and could be a valuable tool in preclinical studies of inflammatory arthritis.

An in silico micro-multiphysics agent-based approach for simulating bone regeneration in a mouse femur defect model

Bone defects represent a challenging clinical problem as they can lead to non-union. In silico models are well suited to study bone regeneration under varying conditions by linking both cellular and systems scales. This paper presents an in silico micro-multiphysics agent-based (micro-MPA) model for bone regeneration following an osteotomy. The model includes vasculature, bone, and immune cells, as well as their interaction with the local environment. The model was calibrated by time-lapsed micro-computed tomography data of femoral osteotomies in C57Bl/6J mice, and the differences between predicted bone volume fractions and the longitudinal in vivo measurements were quantitatively evaluated using root mean square error (RMSE). The model performed well in simulating bone regeneration across the osteotomy gap, with no difference (5.5% RMSE, p = 0.68) between the in silico and in vivo groups for the 5-week healing period - from the inflammatory phase to the remodelling phase - in the volume spanning the osteotomy gap. Overall, the proposed micro-MPA model was able to simulate the influence of the local mechanical environment on bone regeneration, and both this environment and cytokine concentrations were found to be key factors in promoting bone regeneration. Further, the validated model matched clinical observations that larger gap sizes correlate with worse healing outcomes and ultimately simulated non-union. This model could help design and guide future experimental studies in bone repair, by identifying which are the most critical in vivo experiments to perform.

The Impact of Chronic Stress on Behavior and Body Mass in New Animal Models

(1) Background: Exposure to different sources of stress can have a significant effect on both psychological and physical processes. (2) Methods: The study took place over a period of 34 days and included a total of 40 animals. Regarding the exposure to chronic stressors, we opted for physiological, non-invasive stressors, e.g., running, swimming, and changes in the intensity of light. An unforeseen stress batch was also created that alternated all these stress factors. The animals were divided into five experimental groups, each consisting of eight individuals. In the context of conducting the open field test for behavioral assessment before and after stress exposure, we aimed to investigate the impact of stress exposure on the affective traits of the animals. We also monitored body mass every two days. (3) Results: The control group exhibited an average increase in weight of approximately 30%. The groups exposed to stress factors showed slower growth rates, the lowest being the running group, recording a rate of 20.55%, and the unpredictable stress group at 24.02%. The anxious behavior intensified in the group with unforeseen stress, in the one with light variations, and in the running group. (4) Conclusions: Our research validates the animal model of intermittent light exposure during the dark phase as a novel method of inducing stress. The modification of some anxiety parameters was observed; they vary according to the type of stress. Body mass was found to increase in all groups, especially in the sedentary groups, likely due to the absence of cognitive, spatial, and social stimuli except for cohabitation.

Local extracellular K+ in cortex regulates norepinephrine levels, network state, and behavioral output

Extracellular potassium concentration ([K+]e) is known to increase as a function of arousal. [K+]e is also a potent modulator of transmitter release. Yet, it is not known whether [K+]e is involved in the neuromodulator release associated with behavioral transitions. We here show that manipulating [K+]e controls the local release of monoaminergic neuromodulators, including norepinephrine (NE), serotonin, and dopamine. Imposing a [K+]e increase is adequate to boost local NE levels, and conversely, lowering [K+]e can attenuate local NE. Electroencephalography analysis and behavioral assays revealed that manipulation of cortical [K+]e was sufficient to alter the sleep-wake cycle and behavior of mice. These observations point to the concept that NE levels in the cortex are not solely determined by subcortical release, but that local [K+]e dynamics have a strong impact on cortical NE. Thus, cortical [K+]e is an underappreciated regulator of behavioral transitions.

Activity in Group-Housed Home Cages of Mice as a Novel Preclinical Biomarker in Oncology Studies

BACKGROUND

Improving experimental conditions in preclinical animal research is a major challenge, both scientifically and ethically. Automated digital ventilated cages (DVC®) offer the advantage of continuous monitoring of animal activity in their home-cage. The potential utility of this technology remains understudied and deserves investigation in the field of oncology.

METHODS

Using the DVC® platform, we sought to determine if the continuous assessment of locomotor activity of mice in their home cages can serve as useful digital readout in the monitoring of animals treated with the reference oncology compounds cisplatin and cyclophosphamide. SCID mice of 14 weeks of age were housed in DVC® cages in groups of four and followed with standard and digital examination before and after treatment over a 17-day total period.

RESULTS

DVC® detected statistically significant effects of cisplatin on the activity of mice in the short and long term, as well as trends for cyclophosphamide. The activity differences between the vehicle- and chemotherapy-treated groups were especially marked during the nighttime, a period when animals are most active and staff are generally not available for regular checks. Standard clinical parameters, such as body weight change and clinical assessment during the day, provided additional and complementary information.

CONCLUSION

The DVC® technology enabled the home cage monitoring of mice and non-invasive detection of animal activity disturbances. It can easily be integrated into a multimodal monitoring approach to better capture the different effects of oncology drugs on anti-tumor efficacy, toxicity, and safety and improve translation to clinical studies.

Clinicopathologic Dissociation: Robust Lafora Body Accumulation in Malin KO Mice Without Observable Changes in Home-cage Behavior

Lafora Disease (LD) is a syndrome of progressive myoclonic epilepsy and cumulative neurocognitive deterioration caused by recessively inherited genetic lesions of EPM2A (laforin) or NHLRC1 (malin). Neuropsychiatric symptomatology in LD is thought to be directly downstream of neuronal and astrocytic polyglucosan aggregates, termed Lafora bodies (LBs), which faithfully accumulate in an age-dependent manner in all mouse models of LD. In this study, we applied home-cage monitoring to examine the extent of neurobehavioral deterioration in a model of malin-deficient LD, as a means to identify robust preclinical endpoints that may guide the selection of novel genetic treatments. At 6 weeks, ~6-7 months and ~12 months of age, malin deficient mice ("KO") and wild type (WT) littermates underwent a standardized home-cage behavioral assessment designed to non-obtrusively appraise features of rest/arousal, consumptive behaviors, risk aversion and voluntary wheel-running. At all timepoints, and over a range of metrics that we report transparently, WT and KO mice were essentially indistinguishable. In contrast, within WT mice compared across timepoints, we identified age-related nocturnal hypoactivity, diminished sucrose preference and reduced wheel-running. Neuropathological examinations in subsets of the same mice revealed expected age dependent LB accumulation, gliosis and microglial activation in cortical and subcortical brain regions. At 12 months of age, despite the burden of neocortical LBs, we did not identify spontaneous seizures during an electroencephalographic (EEG) survey, and KO and WT mice exhibited similar spectral EEG features. Using an in vitro assay of neocortical function, paroxysmal increases in network activity (UP states) in KO slices were more prolonged at 3 and 6 months of age, but were similar to WT at 12 months. KO mice displayed a distinct response to pentylenetetrazole, with a greater incidence of clonic seizures and a more pronounced post-ictal suppression of movement, feeding and drinking behavior. Together, these results highlight a stark clinicopathologic dissociation in a mouse model of LD, where LBs accrue substantially without clinically meaningful changes in overall wellbeing. Our findings allude to a delay between LB accumulation and neurobehavioral decline: one that may provide a window for treatment, and whose precise duration may be difficult to ascertain within the typical lifespan of a laboratory mouse.

Enhanced maternal behaviors in a mouse model of congenital blindness

In mammals, mothering is one of the most important prosocial female behavior to promote survival, proper sensorimotor, and emotional development of the offspring. Different intrinsic and extrinsic factors can initiate and maintain these behaviors, such as hormonal, cerebral, and sensory changes. Infant cues also stimulate multisensory systems and orchestrate complex maternal responsiveness. To understand the maternal behavior driven by complex sensory interactions, it is necessary to comprehend the individual sensory systems by taking out other senses. An excellent model for investigating sensory regulation of maternal behavior is a murine model of congenital blindness, the ZRDBA mice, where both an anophthalmic and sighted mice are generated from the same litter. Therefore, this study aims to assess whether visual inputs are essential to driving maternal behaviors in mice. Maternal behaviors were assessed using three behavioral tests, including the pup retrieval test, the home cage maternal behavior test, and the maternal aggression test. Our results show that blind mothers (1) took less time to retrieve their offspring inside the nest, (2) spent more time nursing and licking their offspring in the second- and third-week postpartum, and (3) exhibited faster aggressive behaviors when exposed to an intruder male, compared to the sighted counterparts. This study provides evidence that congenitally blind mothers show more motivation to retrieve the pups, care, and protection towards their pups than sighted ones, likely due to a phenomenon of sensory compensation.

Long-term behavioural alterations in mice following transient cerebral ischemia

Ischemic stroke is one of the leading causes of disability and mortality worldwide. Acute and chronic post-stroke changes have variable effects on the functional outcomes of the disease. Therefore, it is imperative to identify what daily activities are altered after stroke and to what extent, keeping in mind that ischemic stroke patients often have long-term post-stroke complications. Translational studies in stroke have also been challenging due to inconsistent study design of animal experiments. The objective of this study was to clarify whether and to what extent mouse behaviour was altered during a 6 months period after cerebral stroke. Experimental stroke was induced in mice by intraluminal filament insertion into the middle cerebral artery (fMCAo). Neurological deficits, recovery rate, motor performance, and circadian activity were evaluated following ischemia. We observed severe neurological deficits, motor impairments, and delay in the recovery rate of mice during the first 14 days after fMCAo. Aberrant circadian activity and distorted space map were seen in fMCAo mice starting one month after ischemia, similarly to altered new and familiar cage activity and sucrose preference using the IntelliCage, and was still evident 60- and 180- days following stroke in the voluntary running wheel using the PhenoMaster system. A preference towards ipsilateral side turns was observed in fMCAo mice both acutely and chronically after the stroke induction. Overall, our study shows the importance of determining time-dependent differences in the long-term post-stroke recovery (over 180 days after fMCAo) using multiple behavioural assessments.

3D mouse pose from single-view video and a new dataset

We present a method to infer the 3D pose of mice, including the limbs and feet, from monocular videos. Many human clinical conditions and their corresponding animal models result in abnormal motion, and accurately measuring 3D motion at scale offers insights into health. The 3D poses improve classification of health-related attributes over 2D representations. The inferred poses are accurate enough to estimate stride length even when the feet are mostly occluded. This method could be applied as part of a continuous monitoring system to non-invasively measure animal health, as demonstrated by its use in successfully classifying animals based on age and genotype. We introduce the Mouse Pose Analysis Dataset, the first large scale video dataset of lab mice in their home cage with ground truth keypoint and behavior labels. The dataset also contains high resolution mouse CT scans, which we use to build the shape models for 3D pose reconstruction.

PiE: an open-source pipeline for home cage behavioral analysis

Over the last two decades a growing number of neuroscience labs are conducting behavioral assays in rodents. The equipment used to collect this behavioral data must effectively limit environmental and experimenter disruptions, to avoid confounding behavior data. Proprietary behavior boxes are expensive, offer limited compatible sensors, and constrain analysis with closed-source hardware and software. Here, we introduce PiE, an open-source, end-to-end, user-configurable, scalable, and inexpensive behavior assay system. The PiE system includes the custom-built behavior box to hold a home cage, as well as software enabling continuous video recording and individual behavior box environmental control. To limit experimental disruptions, the PiE system allows the control and monitoring of all aspects of a behavioral experiment using a remote web browser, including real-time video feeds. To allow experiments to scale up, the PiE system provides a web interface where any number of boxes can be controlled, and video data easily synchronized to a remote location. For the scoring of behavior video data, the PiE system includes a standalone desktop application that streamlines the blinded manual scoring of large datasets with a focus on quality control and assay flexibility. The PiE system is ideal for all types of behavior assays in which video is recorded. Users are free to use individual components of this setup independently, or to use the entire pipeline from data collection to analysis. Alpha testers have included scientists without prior coding experience. An example pipeline is demonstrated with the PiE system enabling the user to record home cage maternal behavior assays, synchronize the resulting data, conduct blinded scoring, and import the data into R for data visualization and analysis.

Bouts of rest and physical activity in C57BL/6J mice

The objective was to exploit the raw data output from a scalable home cage (type IIL IVC) monitoring (HCM) system (DVC®), to characterize pattern of undisrupted rest and physical activity (PA) of C57BL/6J mice. The system's tracking algorithm show that mice in isolation spend 67% of the time in bouts of long rest (≥40s). Sixteen percent is physical activity (PA), split between local movements (6%) and locomotion (10%). Decomposition revealed that a day contains ˜7100 discrete bouts of short and long rest, local and locomotor movements. Mice travel ˜330m per day, mainly during the dark hours, while travelling speed is similar through the light-dark cycle. Locomotor bouts are usually <0.2m and <1% are >1m. Tracking revealed also fits of abnormal behaviour. The starting positions of the bouts showed no preference for the rear over the front of the cage floor, while there was a strong bias for the peripheral (75%) over the central floor area. The composition of bouts has a characteristic circadian pattern, however, intrusive husbandry routines increased bout fragmentation by ˜40%. Extracting electrode activations density (EAD) from the raw data yielded results close to those obtained with the tracking algorithm, with 81% of time in rest (<1 EAD s-1) and 19% in PA. Periods ≥40 s of file when no movement occurs and there is no EAD may correspond to periods of sleep (˜59% of file time). We confirm that EAD correlates closely with movement distance (rs>0.95) and the data agreed in ˜97% of the file time. Thus, albeit EAD being less informative it may serve as a proxy for PA and rest, enabling monitoring group housed mice. The data show that increasing density from one female to two males, and further to three male or female mice had the same effect size on EAD (˜2). In contrast, the EAD deviated significantly from this stepwise increase with 4 mice per cage, suggesting a crowdedness stress inducing sex specific adaptations. We conclude that informative metrics on rest and PA can be automatically extracted from the raw data flow in near-real time (< 1 hrs). As discussed, these metrics relay useful longitudinal information to those that use or care for the animals.

Galactic Cosmic Irradiation Alters Acute and Delayed Species-Typical Behavior in Male and Female Mice

Exposure to space galactic cosmic radiation is a principal consideration for deep space missions. While the effects of space irradiation on the nervous system are not fully known, studies in animal models have shown that exposure to ionizing radiation can cause neuronal damage and lead to downstream cognitive and behavioral deficits. Cognitive health implications put humans and missions at risk, and with the upcoming Artemis missions in which female crew will play a major role, advance critical analysis of the neurological and performance responses of male and female rodents to space radiation is vital. Here, we tested the hypothesis that simulated Galactic Cosmic Radiation (GCRSim) exposure disrupts species-typical behavior in mice, including burrowing, rearing, grooming, and nest-building that depend upon hippocampal and medial prefrontal cortex circuitry. Behavior comprises a remarkably well-integrated representation of the biology of the whole animal that informs overall neural and physiological status, revealing functional impairment. We conducted a systematic dose-response analysis of mature (6-month-old) male and female mice exposed to either 5, 15, or 50 cGy 5-ion GCRSim (H, Si, He, O, Fe) at the NASA Space Radiation Laboratory (NSRL). Behavioral performance was evaluated at 72 h (acute) and 91-days (delayed) postradiation exposure. Specifically, species-typical behavior patterns comprising burrowing, rearing, and grooming as well as nest building were analyzed. A Neuroscore test battery (spontaneous activity, proprioception, vibrissae touch, limb symmetry, lateral turning, forelimb outstretching, and climbing) was performed at the acute timepoint to investigate early sensorimotor deficits postirradiation exposure. Nest construction, a measure of neurological and organizational function in rodents, was evaluated using a five-stage Likert scale 'Deacon' score that ranged from 1 (a low score where the Nestlet is untouched) to 5 (a high score where the Nestlet is completely shredded and shaped into a nest). Differential acute responses were observed in females relative to males with respect to species-typical behavior following 15 cGy exposure while delayed responses were observed in female grooming following 50 cGy exposure. Significant sex differences were observed at both timepoints in nest building. No deficits in sensorimotor behavior were observed via the Neuroscore. This study revealed subtle, sexually dimorphic GCRSim exposure effects on mouse behavior. Our analysis provides a clearer understanding of GCR dose effects on species typical, sensorimotor and organizational behaviors at acute and delayed timeframes postirradiation, thereby setting the stage for the identification of underlying cellular and molecular events.

Preclinical and translational models for delirium: Recommendations for future research from the NIDUS delirium network

Delirium is a common, morbid, and costly syndrome that is closely linked to Alzheimer's disease (AD) and AD-related dementias (ADRD) as a risk factor and outcome. Human studies of delirium have advanced our knowledge of delirium incidence and prevalence, risk factors, biomarkers, outcomes, prevention, and management. However, understanding of delirium neurobiology remains limited. Preclinical and translational models for delirium, while challenging to develop, could advance our knowledge of delirium neurobiology and inform the development of new prevention and treatment approaches. We discuss the use of preclinical and translational animal models in delirium, focusing on (1) a review of current animal models, (2) challenges and strategies for replicating elements of human delirium in animals, and (3) the utility of biofluid, neurophysiology, and neuroimaging translational markers in animals. We conclude with recommendations for the development and validation of preclinical and translational models for delirium, with the goal of advancing awareness in this important field.

Comparison of Toxicities among Different Bumped Kinase Inhibitor Analogs for Treatment of Cryptosporidiosis

Recent advances on the development of bumped kinase inhibitors for treatment of cryptosporidiosis have focused on the 5-aminopyrazole-4-carboxamide scaffold, due to analogs that have less hERG inhibition, superior efficacy, and strong in vitro safety profiles. Three compounds, BKI-1770, -1841, and -1708, showed strong efficacy in C. parvum infected mice. Both BKI-1770 and BKI-1841 had efficacy in the C. parvum newborn calf model, reducing diarrhea and oocyst excretion. However, both compounds caused hyperflexion of the limbs seen as dropped pasterns. Toxicity experiments in rats and calves dosed with BKI-1770 showed enlargement of the epiphyseal growth plate at doses only slightly higher than the efficacious dose. Mice were used as a screen to check for bone toxicity, by changes to the tibia epiphyseal growth plate, or neurological causes, by use of a locomotor activity box. These results showed neurological effects from both BKI-1770 and BKI-1841 and bone toxicity in mice from BKI-1770, indicating one or both effects may be contributing to toxicity. However, BKI-1708 remains a viable treatment candidate for further evaluation as it showed no signs of bone toxicity or neurological effects in mice.

Longitudinal home-cage automated assessment of climbing behavior shows sexual dimorphism and aging-related decrease in C57BL/6J healthy mice and allows early detection of motor impairment in the N171-82Q mouse model of Huntington's disease

Monitoring the activity of mice within their home cage is proving to be a powerful tool for revealing subtle and early-onset phenotypes in mouse models. Video-tracking, in particular, lends itself to automated machine-learning technologies that have the potential to improve the manual annotations carried out by humans. This type of recording and analysis is particularly powerful in objective phenotyping, monitoring behaviors with no experimenter intervention. Automated home-cage testing allows the recording of non-evoked voluntary behaviors, which do not require any contact with the animal or exposure to specialist equipment. By avoiding stress deriving from handling, this approach, on the one hand, increases the welfare of experimental animals and, on the other hand, increases the reliability of results excluding confounding effects of stress on behavior. In this study, we show that the monitoring of climbing on the wire cage lid of a standard individually ventilated cage (IVC) yields reproducible data reflecting complex phenotypes of individual mouse inbred strains and of a widely used model of neurodegeneration, the N171-82Q mouse model of Huntington's disease (HD). Measurements in the home-cage environment allowed for the collection of comprehensive motor activity data, which revealed sexual dimorphism, daily biphasic changes, and aging-related decrease in healthy C57BL/6J mice. Furthermore, home-cage recording of climbing allowed early detection of motor impairment in the N171-82Q HD mouse model. Integrating cage-floor activity with cage-lid activity (climbing) has the potential to greatly enhance the characterization of mouse strains, detecting early and subtle signs of disease and increasing reproducibility in preclinical studies.

Excessive rest time during active phase is reliably detected in a mouse model of myotonic dystrophy type 1 using home cage monitoring

Myotonic dystrophy type 1 (DM1) is a dominantly inherited neuromuscular disease caused by the abnormal expansion of CTG-repeats in the 3'-untranslated region of the Dystrophia Myotonica Protein Kinase (DMPK) gene, characterized by multisystemic symptoms including muscle weakness, myotonia, cardio-respiratory problems, hypersomnia, cognitive dysfunction and behavioral abnormalities. Sleep-related disturbances are among the most reported symptoms that negatively affect the quality of life of patients and that are present in early and adult-onset forms of the disease. DMSXL mice carry a mutated human DMPK transgene containing >1,000 CTGrepeats, modeling an early onset, severe form of DM1. They exhibit a pathologic neuromuscular phenotype and also synaptic dysfunction resulting in neurological and behavioral deficits similar to those observed in patients. Additionally, they are underweight with a very high mortality within the first month after birth presenting several welfare issues. To specifically explore sleep/rest-related behaviors of this frail DM1 mouse model we used an automated home cage-based system that allows 24/7 monitoring of their activity non-invasively. We tested male and female DMSXL mice and their wild-type (WT) littermates in Digital Ventilated Cages (DVCR) assessing activity and rest parameters on day and night for 5 weeks. We demonstrated that DMSXL mice show reduced activity and regularity disruption index (RDI), higher percentage of zero activity per each hour and longer periods of rest during the active phase compared to WT. This novel rest-related phenotype in DMSXL mice, assessed unobtrusively, could be valuable to further explore mechanisms and potential therapeutic interventions to alleviate the very common symptom of excessive daytime sleepiness in DM1 patients.

Neurochemical, histological, and behavioral profiling of the acute, sub-acute, and chronic MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is a heterogeneous multi-systemic disorder unique to humans characterized by motor and non-motor symptoms. Preclinical experimental models of PD present limitations and inconsistent neurochemical, histological, and behavioral readouts. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD is the most common in vivo screening platform for novel drug therapies; nonetheless, behavioral endpoints yielded amongst laboratories are often discordant and inconclusive. In this study, we characterized neurochemically, histologically, and behaviorally three different MPTP mouse models of PD to identify translational traits reminiscent of PD symptomatology. MPTP was intraperitoneally (i.p.) administered in three different regimens: (i) acute-four injections of 20 mg/kg of MPTP every 2 h; (ii) sub-acute-one daily injection of 30 mg/kg of MPTP for 5 consecutive days; and (iii) chronic-one daily injection of 4 mg/kg of MPTP for 28 consecutive days. A series of behavioral tests were conducted to assess motor and non-motor behavioral changes including anxiety, endurance, gait, motor deficits, cognitive impairment, circadian rhythm and food consumption. Impairments in balance and gait were confirmed in the chronic and acute models, respectively, with the latter showing significant correlation with lesion size. The sub-acute model, by contrast, presented with generalized hyperactivity. Both, motor and non-motor changes were identified in the acute and sub-acute regime where habituation to a novel environment was significantly reduced. Moreover, we report increased water and food intake across all three models. Overall, the acute model displayed the most severe lesion size, while across the three models striatal dopamine content (DA) did not correlate with the behavioral performance. The present study demonstrates that detection of behavioral changes following MPTP exposure is challenging and does not correlate with the dopaminergic lesion extent.

The prevention of home-cage grid climbing affects muscle strength in mice

Experimenters and treatment methods are the major contributors to data variability in behavioral neuroscience. However, home cage characteristics are likely associated with data variability. Mice housed in breeding cages spontaneously exhibit behavioral patterns such as biting into the wire grid and climbing on the grid lid. We aimed to clarify the effect of covering the stainless steel wire grid lid in commonly used home cage with Plexiglas to prevent climbing on muscle strength in mice. Furthermore, we investigated the effects of climbing prevention on activity and anxiety-like behavior, and the impact of climbing prevention during the postnatal development period and adulthood on muscle strength. Muscle strength, anxiety-like behavior, and locomotor activity were assessed by a battery of tests (wire hang, suspension, grip strength, rotarod, elevated-plus maze, and open field tests). Mice prevented from climbing the wire grid during postnatal development displayed lower muscle strength than those able to climb. Moreover, mice prevented from climbing for 3 weeks following maturity had weakened muscles. The muscle strength was decreased with 3 weeks of climbing prevention in even 1-year-old mice. In summary, the stainless steel wire grid in the home cage contributed to the development and maintenance of muscle strength in mice.

Home-cage behavior in the Stargazer mutant mouse

In many childhood-onset genetic epilepsies, seizures are accompanied by neurobehavioral impairments and motor disability. In the Stargazer mutant mouse, genetic disruptions of Cacng2 result in absence-like spike-wave seizures, cerebellar gait ataxia and vestibular dysfunction, which limit traditional approaches to behavioral phenotyping. Here, we combine videotracking and instrumented home-cage monitoring to resolve the neurobehavioral facets of the murine Stargazer syndrome. We find that despite their gait ataxia, stargazer mutants display horizontal hyperactivity and variable rates of repetitive circling behavior. While feeding rhythms, circadian or ultradian oscillations in activity are unchanged, mutants exhibit fragmented bouts of behaviorally defined "sleep", atypical licking dynamics and lowered sucrose preference. Mutants also display an attenuated response to visual and auditory home-cage perturbations, together with profound reductions in voluntary wheel-running. Our results reveal that the seizures and ataxia of Stargazer mutants occur in the context of a more pervasive behavioral syndrome with elements of encephalopathy, repetitive behavior and anhedonia. These findings expand our understanding of the function of Cacng2.

Optimization of Analysis of Circadian Rest-Activity Rhythm Using Cosinor Analysis in Mice

OBJECTIVE

Data processing in analysis of circadian rhythm was performed in various ways. However, there was a lack of evidence for the optimal analysis of circadian rest-activity rhythm. Therefore, we aimed to perform mathematical simulations of data processing to investigate proper evidence for the optimal analysis of circadian rest-activity rhythm.

METHODS

Locomotor activities of 20 ICR male mice were measured by infrared motion detectors. The data of locomotor activities was processed using data summation, data average, and data moving average methods for cosinor analysis. Circadian indices were estimated according to time block, respectively. Also, statistical F and p-values were calculated by zero-amplitude test.

RESULTS

The data moving average result showed well-fitted cosine curves independent of data processing time. Meanwhile, the amplitude, MESOR, and acrophase were properly estimated within 800 seconds in data summation and data average methods.

CONCLUSION

These findings suggest that data moving average would be an optimal method for data processing in a cosinor analysis and data average within 800-second data processing time might be adaptable. The results of this study can be helpful to analyze circadian restactivity rhythms and integrate the results of the studies using different data processing methods.

Challenges of a small world analysis for the continuous monitoring of behavior in mice

Documenting a mouse's "real world" behavior in the "small world" of a laboratory cage with continuous video recordings offers insights into phenotypical expression of mouse genotypes, development and aging, and neurological disease. Nevertheless, there are challenges in the design of a small world, the behavior selected for analysis, and the form of the analysis used. Here we offer insights into small world analyses by describing how acute behavioral procedures can guide continuous behavioral methodology. We show how algorithms can identify behavioral acts including walking and rearing, circadian patterns of action including sleep duration and waking activity, and the organization of patterns of movement into home base activity and excursions, and how they are altered with aging. We additionally describe how specific tests can be incorporated within a mouse's living arrangement. We emphasize how machine learning can condense and organize continuous activity that extends over extended periods of time.

Translational relevance of forward genetic screens in animal models for the study of psychiatric disease

Psychiatric disorders represent a significant burden in our societies. Despite the convincing evidence pointing at gene and gene-environment interaction contributions, the role of genetics in the etiology of psychiatric disease is still poorly understood. Forward genetic screens in animal models have helped elucidate causal links. Here we discuss the application of mutagenesis-based forward genetic approaches in common animal model species: two invertebrates, nematodes (Caenorhabditis elegans) and fruit flies (Drosophila sp.); and two vertebrates, zebrafish (Danio rerio) and mice (Mus musculus), in relation to psychiatric disease. We also discuss the use of large scale genomic studies in human populations. Despite the advances using data from human populations, animal models coupled with next-generation sequencing strategies are still needed. Although with its own limitations, zebrafish possess characteristics that make them especially well-suited to forward genetic studies exploring the etiology of psychiatric disorders.

Antioxidant and Antiaging Properties of Agar Obtained from Brown Seaweed Laminaria digitata (Hudson) in D-Galactose-Induced Swiss Albino Mice

The present paper explores the antioxidant and antiaging properties of agar extracted from Laminaria digitata (L. digitata) on a D-galactose (D-Gal)-induced mouse model. Experimental mice were divided into four groups: group I comprised of control nontreated mice, group II comprised of D-Gal-induced mice, group III mice were treated with extracted agar after D-Gal induction, and group IV mice were given ascorbic acid as a positive control. Antioxidant enzymes and aging marker proteins declined significantly in group II, whereas they were normal in group III and group IV mice. Expressions of interleukin-1β (IL-1β) in D-Gal-induced mice were significantly enhanced in the liver and brain of the experimental mice, which were otherwise normal in agar-treated mice. Also, IL-6 levels were significantly increased in the liver and reversed in the brain of D-gal mice, while it was regularly in the agar-treated mice. The histopathological analysis of D-Gal-induced mice showed spongiosis and tangles in brain cells, increased fat and decreased collagen contents in the skin, and few dilated sinuses in the hepatic cells. The changes were under control in group III and group IV mice, suggesting the protective effects of agar extracted from L. digitata and ascorbic acid.

Voluntary wheel running behaviour as a tool to assess the severity in a mouse pancreatic cancer model

Laboratory animals frequently undergo routine experimental procedures such as handling, restraining and injections. However, as a known source of stress, these procedures potentially impact study outcome and data quality. In the present study, we, therefore, performed an evidence-based severity assessment of experimental procedures used in a pancreatic cancer model including surgical tumour induction and subsequent chemotherapeutic treatment via repeated intraperitoneal injections. Cancer cell injection into the pancreas was performed during a laparotomy under general anaesthesia. After a four-day recovery phase, mice received either drug treatment (galloflavin and metformin) or the respective vehicle substances via daily intraperitoneal injections. In addition to clinical scoring, an automated home-cage monitoring system was used to assess voluntary wheel running (VWR) behaviour as an indicator of impaired well-being. After surgery, slightly elevated clinical scores and minimal body weight reductions, but significantly decreased VWR behaviour were observed. During therapy, body weight declined in response to chemotherapy, but not after vehicle substance injection, while VWR activity was decreased in both cases. VWR behaviour differed between treatment groups and revealed altered nightly activity patterns. In summary, by monitoring VWR a high impact of repeated injections on the well-being of mice was revealed and substance effects on well-being were distinguishable. However, no differences in tumour growth between treatment groups were observed. This might be due to the severity of the procedures uncovered in this study, as exaggerated stress responses are potentially confounding factors in preclinical studies. Finally, VWR was a more sensitive indicator of impairment than clinical scoring in this model.

Creating Detailed Metadata for an R Shiny Analysis of Rodent Behavior Sequence Data Detected Along One Light-Dark Cycle

Automated mouse phenotyping through the high-throughput analysis of home cage behavior has brought hope of a more effective and efficient method for testing rodent models of diseases. Advanced video analysis software is able to derive behavioral sequence data sets from multiple-day recordings. However, no dedicated mechanisms exist for sharing or analyzing these types of data. In this article, we present a free, open-source software actionable through a web browser (an R Shiny application), which performs an analysis of home cage behavioral sequence data, which is designed to spot differences in circadian activity while preventing p-hacking. The software aligns time-series data to the light/dark cycle, and then uses different time windows to produce up to 162 behavior variables per animal. A principal component analysis strategy detected differences between groups. The behavior activity is represented graphically for further explorative analysis. A machine-learning approach was implemented, but it proved ineffective at separating the experimental groups. The software requires spreadsheets that provide information about the experiment (i.e., metadata), thus promoting a data management strategy that leads to FAIR data production. This encourages the publication of some metadata even when the data are kept private. We tested our software by comparing the behavior of female mice in videos recorded twice at 3 and 7 months in a home cage monitoring system. This study demonstrated that combining data management with data analysis leads to a more efficient and effective research process.

Automated Home-Cage Monitoring During Acute Experimental Colitis in Mice

For ethical and legal reasons it is necessary to assess the severity of procedures in animal experimentation. To estimate the degree of pain, suffering, distress or lasting harm, objective methods that provide gradebale parameters need to be tested and validated for various models. In this context, automated home-cage monitoring becomes more important as a contactless, objective, continuous and non-invasive method. The aim of this study was to examine a recently developed large scale automated home-cage monitoring system (Digital Ventilated Cage, DVC^®) with regard to the applicability and added value for severity assessment in a frequently used acute colitis mouse model. Acute colitis was induced in female C57BL/6J mice by varying doses of DSS (1.5 and 2.5%), matched controls received water only (0%). Besides DVC^® activity monitoring and nest scoring, model specific parameters like body weight, clinical colitis score, and intestinal histo-pathology were used. In a second approach, we questioned whether DVC^® can be used to detect an influence of different handling methods on the behavior of mice. Therefore, we compared activity patterns of mice that underwent tunnel vs. tail handling for routine animal care procedures. In DSS treated mice, disease specific parameters confirmed induction of a graded colitis. In line with this, DVC^® revealed reduced activity in these animals. Furthermore, the system displayed stress-related activity changes due to the restraining procedures necessary in DSS-treatment groups. However, no significant differences between tunnel vs. tail handling procedures were detected. For further analysis of the data, a binary classifier was applied to categorize two severity levels (burdened vs. not burdened) based on activity and body weight. In all DSS-treatment groups data points were allocated to the burdened level, in contrast to a handling group. The fraction of "burdened" animals reflected well the course of colitis development. In conclusion, automated home-cage monitoring by DVC^® enabled severity assessment in a DSS-induced colitis model equally well as gold standard clinical parameters. In addition, it revealed changes in activity patterns due to routine handling procedures applied in experimental model work. This indicates that large scale home-cage monitoring can be integrated into routine severity assessment in biomedical research.

Apparatus design and behavioural testing protocol for the evaluation of spatial working memory in mice through the spontaneous alternation T-maze

Spatial working memory can be assessed in mice through the spontaneous alternation T-maze test. The T-maze is a T-shaped apparatus featuring a stem (start arm) and two lateral goal arms (left and right arms). The procedure is based on the natural tendency of rodents to prefer exploring a novel arm over a familiar one, which induces them to alternate the choice of the goal arm across repeated trials. During the task, in order to successfully alternate choices across trials, an animal has to remember which arm had been visited in the previous trial, which makes spontaneous alternation T-maze an optimal test for spatial working memory. As this test relies on a spontaneous behaviour and does not require rewards, punishments or pre-training, it represents a particularly useful tool for cognitive evaluation, both time-saving and animal-friendly. We describe here in detail the apparatus and the protocol, providing representative results on wild-type healthy mice.

Zfhx3-mediated genetic ablation of the SCN abolishes light entrainable circadian activity while sparing food anticipatory activity

Circadian rhythms persist in almost all organisms and are crucial for maintaining appropriate timing in physiology and behaviour. Here, we describe a mouse mutant where the central mammalian pacemaker, the suprachiasmatic nucleus (SCN), has been genetically ablated by conditional deletion of the transcription factor Zfhx3 in the developing hypothalamus. Mutants were arrhythmic over the light-dark cycle and in constant darkness. Moreover, rhythms of metabolic parameters were ablated in vivo although molecular oscillations in the liver maintained some rhythmicity. Despite disruptions to SCN cell identity and circuitry, mutants could still anticipate food availability, yet other zeitgebers - including social cues from cage-mates - were ineffective in restoring rhythmicity although activity levels in mutants were altered. This work highlights a critical role for Zfhx3 in the development of a functional SCN, while its genetic ablation further defines the contribution of SCN circuitry in orchestrating physiological and behavioral responses to environmental signals.

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Deletion of Zfhx3 in developing hypothalamus leads to behavioral arrhythmicity

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SCN cell identity is absent while other retinal targets and visual functions remain

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Rhythms in metabolic functions are lost while some molecular rhythms in liver persist

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Conditional mutants can respond to food availability and other environmental cues

Advances in mouse genetics for the study of human disease

The mouse is the pre-eminent model organism for studies of mammalian gene function and has provided an extraordinarily rich range of insights into basic genetic mechanisms and biological systems. Over several decades, the characterization of mouse mutants has illuminated the relationship between gene and phenotype, providing transformational insights into the genetic bases of disease. However, if we are to deliver the promise of genomic and precision medicine, we must develop a comprehensive catalogue of mammalian gene function that uncovers the dark genome and elucidates pleiotropy. Advances in large-scale mouse mutagenesis programmes allied to high-throughput mouse phenomics are now addressing this challenge and systematically revealing novel gene function and multi-morbidities. Alongside the development of these pan-genomic mutational resources, mouse genetics is employing a range of diversity resources to delineate gene-gene and gene-environment interactions and to explore genetic context. Critically, mouse genetics is a powerful tool for assessing the functional impact of human genetic variation and determining the causal relationship between variant and disease. Together these approaches provide unique opportunities to dissect in vivo mechanisms and systems to understand pathophysiology and disease. Moreover, the provision and utility of mouse models of disease has flourished and engages cumulatively at numerous points across the translational spectrum from basic mechanistic studies to pre-clinical studies, target discovery and therapeutic development.

Experimental considerations for the assessment of in vivo and in vitro opioid pharmacology

Morphine and other mu-opioid receptor (MOR) agonists remain the mainstay treatment of acute and prolonged pain states worldwide. The major limiting factor for continued use of these current opioids is the high incidence of side effects that result in loss of life and loss of quality of life. The development of novel opioids bereft, or much less potent, at inducing these side effects remains an intensive area of research, with multiple pharmacological strategies being explored. However, as with many G protein-coupled receptors (GPCRs), translation of promising candidates from in vitro characterisation to successful clinical candidates still represents a major challenge and attrition point. This review summarises the preclinical animal models used to evaluate the key opioid-induced behaviours of antinociception, respiratory depression, constipation and opioid-induced hyperalgesia and tolerance. We highlight the influence of distinct variables in the experimental protocols, as well as the potential implications for differences in receptor reserve in each system. Finally, we discuss how methods to assess opioid action in vivo and in vitro relate to each other in the context of bridging the translational gap in opioid drug discovery.

Male-Female Differences In The Effects Of Age On Performance Measures Recorded For 23 Hours In Mice

Functional independence is an important aspect of successful aging and differs with age and by sex in humans. Physical performance often declines earlier than other age-associated functional impairments. Rodent models are used to study pharmacological/toxicological effects of human therapies. However, physical outcomes in mice are usually assessed for short periods, with limited information on the influence of age and sex. Here, we investigated how age and sex affected murine physical performance over 23 hours of continuous observation. Young (3 months) and old (22 months) C57BL/6JArc male and female mice were assessed using the Laboratory Animal Behavior Observation, Registration, and Analysis System. Mice were individually housed for recording of distance travelled, mean gait speed, and durations of different physical activities. Compared to young mice of the same sex, old mice travelled significantly shorter distances with slower gait speeds, shorter durations of locomotion, rearing, climbing and immobility. Older mice groomed significantly more than young mice. Old females reared more during the light cycle than old males. Young females climbed substantially more than young males. Significant age*sex interactions were detected for rearing and climbing, whereby an age-related decline was greater in males than females. Our results suggest that old age reduces exploratory activities and increases grooming in mice. Age-related declines vary between sexes and tend to be greater in males. This non-invasive assessment can be applied to investigate how different interventions affect rodents of different ages and sexes, through the day-night cycle.